METHODS AND APPARATUS FOR WELL PRODUCTIVITY
A system and method for drilling a formation and a method for computing expected production from a wellbore in a formation and/or hydrocarbon reserves associated with the formation, the formation having a plurality of naturally-occurring fractures, the method including computationally modelling the formation; computing one or more wellbore positions intersecting some or all of the fractures; and computing an expected production from the wellbore at least partially based on an expected wellbore damage associated with a particular type of drilling technique.
The invention relates to the field of well productivity and in particular, but not exclusively, well productivity from oil and gas reservoirs. The invention also relates to apparatus, systems and methods for well development and production such as, but not exclusively, systems and apparatus for drilling hydrocarbon reservoirs.
In some examples, the invention relates to well productivity from, development of and/or production from so-called unconventional reservoirs, including shale oil/gas, coal seam gas, etc., although the invention may apply to conventional reservoirs also.
BACKGROUNDSignificant innovation and technological development has occurred in recent years in relation to the development and testing of wells in the oil and gas industry. The ability to drill the most effective wellbore in the most appropriate position for optimum field development can be important to the commercial success, or failure, of the well.
Typically, data are collected prior to any drilling operation in order to try to determine the quality and properties of any subterranean formation (e.g. seismic data). This permits an a priori assessment of appropriate well trajectories, etc. However, regardless of the extent of data collection, uncertainties still remain and this can lead to poorer performance of the well than expected.
A significant cost in establishing production from unconventional reservoirs, both in terms of time and materials, can be attributed to chemical and/or hydraulic fracturing of the rock formation in order to permit production. Further costs are incurred when, due to a reduction in production, there is a requirement to re-fracture any formation. At present, little consideration is given to these matters.
When developing from so-called unconventional reservoirs, such as those having a low permeability (e.g. shale formations), it is expected that some form of chemical and/or hydraulic fracturing of the rock formation is required in order to permit production.
However, the process of hydraulic or chemical fracturing can introduce further uncertainties due to the lack of predictability of the hydraulic or chemical fracturing process. In addition, hydraulic or chemical fracturing can significantly increase the cost in establishing production from such unconventional reservoirs, both in terms of time and materials. Further costs are incurred when, due to a reduction in production, there is a requirement to re-fracture any formation.
At present, little consideration is given to these matters, and so successful development and production from a particular formation, particularly low permeability formations, cannot be guaranteed. There remains a desire to reduce the uncertainties and risk associated with developing reservoirs, and in particular so-called unconventional reservoirs, as well as improving the commercial viability of such reservoirs.
This background serves only to set a scene to allow a skilled reader to better appreciate the following description. Therefore, none of the above discussion should necessarily be taken as an acknowledgement that that discussion is part of the state of the art or is common general knowledge.
SUMMARYThe invention relates to methods and apparatus to assist with well productivity, for example, well productivity from oil and gas reservoirs, and/or systems, apparatus and methods for well development and production, and in particular systems and methods for improving the commercial viability of reservoirs. In some examples, the invention relates specifically to so-called unconventional reservoirs or formations, and provides a solution to effectively produce from such formations without using hydraulic fracturing, or at least only fracturing to a minimal extent. The invention may find particular applicability in relation to shale formations or coal beds.
In some aspects of the invention, there is provided a method for computing expected production from a wellbore in a formation and/or hydrocarbon reserves associated with the formation. This method may be used in exploration and/or appraisal of a formation, field or potential field.
That method may comprise computationally modelling a formation, for example, having a plurality of naturally-occurring fractures. The formation may be considered to be a low permeability formation, such as a shale formation. In such cases, the naturally-occurring fractures may be spaced from one another, roughly at intervals, in the formation. The formation may comprise a plurality of micro-fractures, between the naturally-occurring fractures.
The method may comprise computing one or more wellbore positions, such as appropriate, calculated and/or optimal wellbore positions, intersecting some or all of the fractures. The method may comprise computing the one or more wellbore positions at least partially based on expected production from the wellbore. The expected production and/or reserves may be based on an expected wellbore damage associated with a particular type of drilling technique, such as reverse-circulation drilling. The one or more wellbore positions may be computed using and/or based on the model of the formation. The computed expected production of the wellbore may be for the wellbore in the one or more computed wellbore positions. The expected production and/or reserves may be at least partially based on the inflow from naturally-occurring fractures, e.g. together with inflow from micro-fractures (e.g. micro-fractures that may have been minimally damaged by the particular type of drilling technique).
The method may comprise subsequently deciding to drill and produce from a wellbore based on the expected production and/or reserves. The method may comprise subsequently deciding to alter the initially-computed wellbore positions based on the expected production. The method may comprise determining the need to fracture a near-wellbore formation surrounding the wellbore based on the expected production and/or reserves. The method may comprise re-computing one or more of the wellbore positions, intersecting some or all of the fractures, in order to reduce, or eliminate, the need for hydraulic or chemical fracturing.
In other words, the method may comprise computing one or more of the wellbore positions in order to provide a particular (e.g. maximum) recovery from the formation, without hydraulic or chemical fracturing.
The method may comprise computing an expected production from a wellbore in a formation and/or hydrocarbon reserves associated with a formation by,
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- computationally modelling a formation having a plurality of naturally occurring fractures;
- computing one or more wellbore positions, intersecting some or all of the fractures; and
- computing an expected production from the wellbore and/or hydrocarbon reserves associated with a formation, based on an expected wellbore damage associated with the particular type of drilling technique, for example, reverse-circulation drilling.
The expected production and/or reserves may be based on the inflow from naturally-occurring fractures together with micro-fractures.
The method may comprise obtaining data, such as core data, from appraisal wells drilled specifically using the particular type of drilling technique, e.g. reverse-circulation drilling, for the purposes of modelling the formation.
The data may be reviewed, and the formation potential may be re-appraised by computationally modelling the formation, e.g. using or based on at least some of the data.
Since the above method better models the contribution from natural fractures and/or micro-fractures, it may more accurately determine the full extent of any exploration/appraisal well to be used for the hydrocarbon reservoir to be calculated. In addition, the impact of the natural fractures and matrix mobility of hydrocarbons through input into the reservoir model may be calculated, which may potentially improve the reserves booking of the asset owner, and/or may provide a determination of the number of wells required for the development phase.
According to another aspect of the invention, there is a method of drilling a wellbore in a formation, for example, during exploration and/or appraisal of a formation, field or potential field.
The method may comprise drilling one or more wellbores into a formation having a plurality of naturally-occurring fractures. The wellbores may be drilled so as to intersect some or all of the fractures (e.g. where each fracture is spaced from the other). The drilling may provide an expected wellbore damage.
The method may include monitoring the drilling (or production) at the wellbore intersecting the fractures. The method may comprise choosing not to fracture the wellbore based on the observed drilling/production.
According to a further aspect of the invention, there may be provided a method of forming a wellbore in a formation, for example, during exploration and/or appraisal of a formation, field or potential field.
The method may comprise using or determining parameters associated with a formation. The method may comprise computationally modelling the formation, for example, using the parameters. The method may comprise computing one or more wellbore positions, such as appropriate, calculated and/or optimal wellbore positions. The wellbore positions may be based on drilling the formation, for example, using reverse-circulation drilling or other advanced drilling techniques.
The method may comprise drilling one or more of the wellbore positions. The method may comprise using data associated with the drilling operation to confirm one or both of the parameters associated with the formation and the computed model of the formation.
The method may comprise the method described in relation to any of the other aspects described herein. For example, the one or more wellbore positions may be wellbore positions associated with a particular, optimum or maximum recovery from the formation, e.g. as determined using any of the above methods for computing expected production from a wellbore according to one or more of the other aspects.
The method may additionally include altering, or modifying, one or more of
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- (i) the determined parameters
- (ii) the computed model; and
- (iii) the wellbore positions,
based on an identified difference between data associated with drilling, and expected data associated with the parameters or model.
The method may include real-time monitoring of data while drilling, for example, by using measurement/logging while drilling, and/or observing cuttings from a drilled location.
The method may be considered to be an integrated drilling solution.
According to a further aspect of the invention, there is provided a method of forming a wellbore in a formation, the method comprising;
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- determining parameters associated with a formation;
- computationally modelling the formation, and computing one or more wellbore positions, e.g. appropriate, calculated and/or optimal wellbore positions;
- drilling one or more of the wellbore positions, and
- using data associated with the drilling operation to confirm one or both of the parameters associated with the formation and the computed model of the formation.
In some aspects of the invention, there is provided a drilling system. The drilling system may comprise drilling apparatus, for example, reverse-circulation drilling apparatus.
The drilling system may comprise data-acquisition apparatus. That data-acquisition apparatus may be in communication with the drilling apparatus, and may be configured to determine formation parameters, for example, when drilling using the drilling apparatus.
The system may additionally comprise formation-modelling apparatus. The formation-modelling apparatus may be configured to at least partially perform the method according to any of the above aspects and/or at least one feature or method step described in relation thereto. The formation-modelling apparatus may be configured to determine to expected production from a wellbore in a formation and/or hydrocarbon reserves associated with the formation. The formation-modelling apparatus may be configured to compute one or more wellbore positions, such as appropriate, calculated and/or optimal wellbore positions, intersecting at least some or all fractures in the formation. The formation-modelling apparatus may be configured to compute the one or more wellbore positions based on expected production from the wellbore, which may be based on an expected wellbore damage associated with a particular type of drilling technique, such as reverse-circulation drilling and/or may be based on the inflow from naturally-occurring fractures, e.g. together with inflow from micro-fractures.
The formation modelling apparatus may be in communication with the data acquisition apparatus, and may be configured to use the, or any, determined formation parameters with a simulated model of the formation. For example, the formation modelling apparatus may be configured to use determined formation parameters in order to verify a simulated model of the formation (e.g. verify an a priori simulated model). The formation modelling apparatus may be configured to use determined formation parameters in order to generate a simulated model of the formation (e.g. generate an a posteriori simulated model). In any case, this may allow for control of the drilling apparatus based on the simulated model of the formation.
The system may be configured for use with low permeability formations, such as shale formations (e.g. shale gas and/or oil formation). The system may be configured for use with coal-seam-gas formations (e.g. coal-bed methane).
The drilling apparatus may be configured to drill formations without unduly affecting a near wellbore formation (e.g. without causing damage, or significant damage, to the wellbore). In other words, the drilling apparatus may be configured to reduce the extent to which the formation (or near wellbore) is damaged during a drilling process, when compared with conventional drilling techniques.
The drilling apparatus may be configured to pass drilling fluid to and from any drill bit, via an annulus of a drill string (e.g. rather than between the drill string and a bore wall). The drilling apparatus may be configured such that drilling fluid, having been returned to surface, may have been in contact only with the formation at a specific location (e.g. at, or around, the drill bit). The drilling apparatus may be configured to use compressed gas as a drilling fluid. The drilling fluid (e.g. gas) may be inert, or substantially inert, to the formation.
The drilling apparatus may comprise at least one flow control device. The least one flow control device may be configured to prevent any undesired flow of hydrocarbons, or other fluids or gases, from uncontrollably reaching the surface (e.g. when drilling through overpressured zones in the formation). In some examples, at least one shut-off valve (e.g. blowout preventer) is provided as a flow control device. One, some or all flow control devices may be configured as downhole devices, and optionally may be provided at or near a drill bit of the drilling apparatus.
In some examples, one, or some of the flow control device(s) are used to regulate the flow of fluids or gases from the formation to the data acquisition apparatus. The flow control device(s) may be used to control the fluid/gas flow so as to permit the data-acquisition apparatus to determine formation parameters at the region of the formation being drilled. Such flow control devices may permit isolation and testing of selected zones in the formation.
The data-acquisition apparatus may be configured to sample materials, including produced liquids, gases and/or cuttings provided during drilling in order to determine formation parameters. The acquisition apparatus may be configured to compute or determine the location of natural fractures in the rock formation, based on sampled materials from the well. For example, the data acquisition apparatus may be configured to determine hydrocarbon production, or liberation, at a particular drilling region or position. A determined change (e.g. increase) in hydrocarbon production may indicate the presence of a natural fracture at the drilling location. Similarly, a determined change (e.g. decrease) in hydrocarbon production at a drilling location may indicate that the drill bit is no longer at a natural fracture.
The data acquisition apparatus may also comprise apparatus for other data measurements or analysis when drilling (e.g. measurements-while-drilling; logging-while-drilling, etc.). Formation parameters may include pressures, rock materials, inflow, hydrocarbon compositions, etc. The data acquisition apparatus may comprise, for example, mass spectrometers, densitometers, liquid chromatographers, etc., in a known manner.
The data acquisition apparatus may be configured to determine formation parameters in real time (e.g. at the time of drilling), or relevant time (e.g. around the time of drilling). The acquisition apparatus may be configured to communicate determined parameters to the formation-modelling apparatus in real time, or relevant time (e.g. at the time or drilling, or around the time of drilling, for example, while drilling continues).
The formation-modelling apparatus may be configured to use computational fluid dynamics, for example using finite volumes, to model the formation being drilled.
The formation-modelling apparatus may be configured to use (e.g. verify and confirm) a simulated model of the formation based on determined formation parameters (e.g. confirm formation parameters are the same or similar to those modelled prior to drilling, or at least prior to drilling at that particular location). The formation modelling apparatus may be configured to use, for example generate and/or revise, the simulated model of the formation based on determined formation parameters (e.g. when the determined formation parameters are newly collected, or differ from, from modelled formation parameters).
The formation modelling apparatus may be configured to model wellbore inflow. The formation modelling apparatus may be configured to assume little or no damage to the formation during drilling (e.g. based on use of the drilling apparatus). In other words, the modelling apparatus may use the determined formation parameters as accurately representing the quality or properties of the formation at a particular drilling location. This may be achieved when the drilling apparatus uses reverse circulation drilling.
The system may be configured to use the determined formation parameters in order to verify/generate/revise a simulated model of the formation and then control the drilling apparatus based on the simulated model of the formation.
Control of the drilling apparatus may include adjustment to expected trajectory of a drilled wellbore. Control may include adjustment to the length of a wellbore. Control may include drilling of side branches, or the like, from a wellbore. Control may include deviation of the wellbore in order to increase natural fracture intersection, or area of exposure of natural fracture.
Control may include drilling a primary wellbore, for example, using reverse circulation drilling. Control may include drilling one or more secondary wellbores from the primary wellbore, for example, during development of an existing field or wellbore or after an exploration appraisal of the formation. In some cases, each secondary wellbore may be drilled in order to intersect one or more natural fractures in the formation. For example, the one or more secondary wellbores may be arranged to maximise a number of natural fractures intersected by the wellbores, e.g. by optimizing orientation or the secondary wellbore in terms of azimuth and/or deviation angle. In this way, the requirement for hydraulic fracturing may be minimised and/or the number of surface locations to be developed may be minimised.
The formation-modelling apparatus may be configured to update and/or optimise the model or simulated model based on core data acquired for the primary and/or secondary well bore(s). This may provide data for the formation in which the natural fractures and hydrocarbons are present. The coring procedures used to collect the core data may be known in the art, e.g. using the best existing operational standards to protect the integrity of the data collected as an industry standard.
In some aspects of the invention, there is provided a drilling system comprising:
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- reverse-circulation drilling apparatus;
- data-acquisition apparatus in communication with the drilling apparatus, and configured to determine formation parameters when drilling using the drilling apparatus; and
- formation-modelling apparatus, in communication with the data acquisition apparatus, and configured to use the determined formation parameters with a simulated model of the formation so as to allow for control of the drilling apparatus based on the simulated model of the formation.
In other aspects of the invention, there is provided a method of drilling a wellbore. The method may comprise drilling, such as using reverse-circulation drilling apparatus, to drill a wellbore. The method may comprise acquiring data from drilling in order to determine formation parameters. The method may additionally comprise using the formation parameters with, or to verify, a simulated model of the formation, e.g. so as to allow for control of the drilling apparatus based on the simulated model of the formation. In some examples, the method may comprise additionally controlling the drilling based on the verification.
According to a further aspect of the invention, there is provided a method of drilling a formation.
The method may comprise drilling a primary wellbore using reverse-circulation drilling apparatus. The method may comprise drilling one or more secondary wellbores from the primary wellbore, for example, during development of an existing field or wellbore or after an exploration/appraisal of the formation. Each secondary wellbore may be drilled in order to intersect one or more natural fractures in the formation. For example, the one or more secondary wellbores may be arranged to maximise a number of natural fractures intersected by the wellbores, e.g. by optimizing orientation or the secondary wellbore in terms of azimuth and/or deviation angle. In this way, the requirement for hydraulic fracturing may be minimised and/or the number of surface locations to be developed may be minimised.
The or each secondary wellbore may be drilled using reverse-circulation drilling apparatus.
The method may comprise permitting the well to flow during drilling of the primary wellbore. The method may comprise permitting the well to flow during drilling of the or each secondary wellbore.
The method may comprise determining the well and reservoir potential during drilling (e.g. determining hydrocarbon content and/or composition from wellbore inflow during drilling).
The method may comprise isolating one or more of the secondary wellbore from the primary wellbore during drilling. Isolation may be provided mechanically and/or chemically.
The method may be used in unconventional hydrocarbon reservoirs such as a shale formation (e.g. gas or oil type shale reservoirs). In such examples, gas may be accessible from low permeability sedimentary layers and natural fractures. The method may be used in coal bed methane or coal seam gas type reservoirs where gas is accessed in coal deposits and the natural fractures and cleats in the coal.
The method may comprise acquiring data from drilling in order to determine formation parameters. The method may additionally comprise using the formation parameters in order to verify a simulated model of the formation so as to allow for control of the drilling apparatus based on the simulated model of the formation. In some examples, the method may comprise additionally controlling the drilling based on the verification, for example, in order to drill secondary wellbores.
In some examples, the method may comprise determining the location of natural fractures in the rock formation, based on sampled materials from a well in order to determine desired location(s) for secondary wellbores. The method may comprise determining hydrocarbon production, or liberation, at a particular drilling region or location in order to determine the location of natural fractures (e.g. wherein a determined relative increase in hydrocarbon production indicates the presence of a natural fracture at that drilling region or location).
According to a further aspect of the invention, there is provided a method of drilling a formation, comprising:
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- drilling a primary wellbore using reverse-circulation drilling apparatus, and
- drilling one or more secondary wellbores from the primary wellbore, each secondary wellbore being drilled in order to intersect one or more natural fractures in the formation.
The invention includes one or more corresponding aspects, embodiments or features in isolation or in various combinations whether or not specifically stated (including claimed) in that combination or in isolation. For example, any of the features or combinations of features described above in relation to any of the above aspects may be applicable individually or in combination to any of the other aspects. As will be appreciated, features associated with particular recited embodiments relating to methods, may be equally appropriate as features of embodiments relating specifically to apparatus, and vice versa.
It will also be appreciated that one or more embodiments/aspects may be useful or improving well productivity, and/or reducing costs.
The above summary is intended to be merely exemplary and non-limiting.
A description is now given, by way of example only, with reference to the accompanying drawings, in which: —
The following examples are given in relation to what may commonly be considered to be an unconventional reservoir. However, it will be appreciated that the invention need not be so limited, and may be applied to many different types of reservoirs.
Within the formation 100 there may be present a number of naturally-occurring fractures 120. Those fractures 120, depending on the geology, may be typically spaced from one another by particular intervals. Between those intervals, there may additionally be numerous micro-fractures, formed in the formation 100. The naturally-occurring fractures 120 have been greatly simplified for ease of understanding, and the micro-fractures have not been included in the figure for the same reasons.
Typically, when the existence of such a formation 100 is suspected, further analytical data is accumulated, such as lithography assessments, structural geological characteristics, as well as potential drilling data from the local area, and other such data. This cumulative data can be used to estimate a suitable location for a well, and approximate the potential recovery from any such drilled well.
This information is then passed to a drilling contractor who is responsible for drilling wellbores into the formation, using the suitable locations for the wellbores. During such drilling operations, it is common for the formation 100 (e.g. that formation extending around a wellbore) to become damaged, for example due to egress of drilling fluids or the like, into the near-wellbore formation (i.e. the formation surrounding the wellbore). Further, if the permeability of the formation 100 is expected to be comparatively low, such as one might expect in a shale formation, or the like, then the drilled well may subsequently be fractured, for example hydraulically, in order to increase the recovery from the reservoir. In some cases, the location of the wellbore may be selected based on the orientation of the naturally-occurring fractures 120 or to ensure it passes through brittle rock such that, when fractured hydraulically, production from the formation 100 can be increased, or at least initially increased. In other words, where the formation 100 is expected to be unconventional, or of low permeability, the location of the wellbores are selected with an a priori understanding that the well will be fractured subsequently.
By way of an example,
While such hydraulic or chemical fracturing may indeed increase the initial production from the formation 100, the use of fracturing fluid may significantly increases the overall costs of drilling the well in the formation 100. Further, wells that have been developed by initially hydraulic or chemical fracturing the formation can require some amount of re-fracturing later in the lifecycle of the well. Without being bound by theory, this may be due to the formations propensity to return to original natural state, after hydraulic or chemical fracturing is complete. Any such re-fracturing of the well again increases costs.
Development of well using existing techniques, and relying on hydraulic or chemical fracturing to maximise potential production, can be ineffective and overly costly. There remains a desire to reduce the uncertainties and risk associated with developing reservoirs, and in particular so-called unconventional reservoirs, as well as improving the commercial viability of such reservoirs.
The above-described process is represented by
There is a need to improve the above described process in order to reduce, mitigate, or entirely obviate the need to fracture a well. Further, there is need to improve the ability with which the properties of a formation 100 are understood, and the formation drilled, in order to maximise production from each particular well.
To achieve this, the following described example of data accumulation and drilling may be considered. This is also generally shown in
In a first step 210, properties of the formation 100, or reservoir, may be assessed. This may be considered to be a data review. Here, data accumulated regarding the formation 100 may include one or more of data from lithography assessments, structural geological characteristics, as well as potential drilling data from the local area. This may include other data such as one or more of data from initial drilling reports, logging data, well tests, etc.
Simply by way of an example, the data may be derived from one or more of: core data, reservoir-rock distribution data; Borehole Image Data (BHI) data; Petrophysical Data (e.g. TOC determination); data associated with Interpreted Depth Structure and Faults; Fracture Characterisation data; and/or geomechanical analysis data, etc.
The accumulation of the formation properties may permit the assessment of the overall anticipated reservoir quality.
In a second step 220, an optimised well design may be created. This may be achieved by initially creating a reservoir and well design using finite volumes and computational fluid dynamics, specifically for modelling subterranean regions. An example of such a method is described in U.S. Ser. No. 12/788,166 (Method of Modelling Production from a Subterranean Region), which is incorporated herein by reference in its entirety. The use of such methodology allows for the modelling of the formation 100 as a single fluid flow system, making no physical distinction between reservoir, or near-wellbore, inflow and well flow. This method may be considered more accurate than other inflow predictions and requires no correction, connection, fudge or skin factors. It enables evaluation of the optimum well geometry.
During the modelling process, drilling techniques, including reverse-circulation drilling, are considered when selecting the suitable locations for wellbores. Reverse-circulation drilling may be considered to operate differently from conventional drilling techniques because, broadly speaking, drilling fluid flows to and from any drill bit, via the annulus of a drill string, rather than between drilling string and the bore wall. An example of reverse-circulation drilling is disclosed in U.S. Pat. No. 6,892,829B2 (Two String Drilling System), which is incorporated here in its entirety.
The use of reverse-circulation drilling techniques may reduce the extent to which any formation 100 is damaged during the drilling process, when compared with conventional drilling techniques. Further, given that drilling fluid returned to surface is likely to have been in contact only with the formation 100 at a specific location (e.g. at the drill bit), then accurate measurements can be made as to formation 100 properties at that drill bit, when assessing that drilling fluid at surface (e.g. assessing cuttings). This may be used in addition to other data measurements or analysis when drilling (e.g. measurements-while-drilling; logging-while-drilling, etc.), as will be further explained.
The model may include potential completion designs, diagrams and geometry, together with potential well options and trajectories.
The method of modelling may allow for an expected production from a wellbore in formation 100 and/or hydrocarbon reserves associated with the formation to be computed. This may be achieved by computationally modelling, as above, the formation 100 in which a plurality of naturally-occurring fractures 120 are present, together with one or more wellbores intersecting those fractures 120. In exemplary formations 100, those fractures 120 will be spaced from each other and consideration may be given to the potential for inflow from micro-fractures, existing in addition to the naturally-occurring fractures 120. For example, given use of reverse-circulation drilling in which the formation 100 may be damaged only to a limited (or no) extent, an approximate inflow from micro-fractures existing between natural fractures 120 may be computed. This may be based on the position of one or more appropriate wellbores, intersecting some or all of the fractures. In some examples, the well trajectory may be selected to maximise the potential inflow from the naturally-occurring fractures 120 together with the micro-fractures. This may include deviated wellbores at between 30 and 60 degrees from vertical (e.g. 45 degrees).
Expected production from the wellbore 130 and/or hydrocarbon reserves associated with the formation may then be computed, based on an expected wellbore damage associated with reverse-circulation drilling (and other parameters associated with the wellbore 130). This may allow for an optimised well design to be achieved. Optimising the well design in this manner may obviate or at least mitigate the need for subsequent hydraulic or chemical fracturing of the wellbore 130. In other words, what may be considered to be unconventional reservoirs may be exploited without the need for subsequent hydraulic or chemical fracturing of the wells in order to achieve suitable production and recovery rates. This may be achieved by the use of reverse-circulation drilling together with exploitation of natural fracture and micro-fractures at the wellbore 130.
In some examples, the method may include the recovery of core data from appraisal wells drilled specifically using reverse-circulation drilling. In those examples, such data may be reviewed, and the formation potential may be re-appraised. In those cases, a model for those re-appraised wells may be generated based on the data from the reappraisal.
In a third step 330, the optimised wells may be drilled using recommended well trajectories derived from the computational modelling process. The drilling may use reverse-circulation drilling techniques, as expected in the model. To assist with successful drilling, downhole shut off valves may used with reverse-circulation drilling, which are known in the art.
For example, the reverse-circulation drilling may make use of flow-control means, or downhole blow-out preventers (downhole BOP). An example of such a BOP for use with reverse-circulation drilling is described in U.S. Pat. No. 8,408,337B2 (Downhole Blowout Preventor), which is incorporated here by reference in its entirety. Such a device may be useful in preventing hydrocarbons or indeed other fluids uncontrollably reaching the surface (e.g. in overpressured horizons).
Other reverse circulation techniques may be used, such as those disclosed in U.S. Pat. No. 7,343,983B2 (Method and Apparatus for Isolating and Testing Zones During Reverse Circulating Drilling), which is incorporated herein by reference in its entirety.
In addition, the drilling may include cementing, for example, specifically cementing used for reverse-circulation drilling. Such cementing may enable drilling though water and loss zones (e.g. of low permeability or pressure), whereby the reverse-circulating cementing is can be used to isolate a particular region of the formation, such as a shallow aquifer or other water bearing or loss zones. This may allow for the development of wells in sensitive, populated areas without impacting on, for example, the shallow water zones. Examples of reverse-circulation drilling using cementing are describing in U.S. Pat. No. 7,540,325B2 (Well Cementing Apparatus and Methods), which is incorporated here in it entirety.
It will be appreciated that the above isolation of water zones, etc. may be incorporated into the model.
During the drilling process, parameters associated with a formation 100 may be determined. This may be achieved by assessing cutting, measurement-while-drilling, logging-while-drilling, etc. Data derived from the drilling operation may be used to confirm one or both of the parameters associated with the formation (e.g. step 310) and the computed model of the formation 100 (e.g. step 320).
In some examples, that data may be accumulated and used in real time. In other words, data may be accumulated and the model may be updated to ensure that the appropriate location of each well is still being provided. For example, the method may include altering, or modifying, one or more of: the determined parameters: the computed model; and the wellbore positions, based on an identified difference, or significant difference, between data associated with drilling, and expected data associated with the parameters or the generated model (e.g. 310 and/or 320). Further, the method may allow drilling data interpretation in real time to allow improvement in operational decisions. That data may include pore pressure, wellbore stability, tool failure risks, and other drilling problems, which may prompt a change in optimised well design, and so a change to expected drilling.
The above described methods, and as shown in
It will be appreciated that the above methodology may find particular application in older formations, or what may be considered to be more fractured formations. Further, it will be appreciated that, when using the above methodology, the most appropriate wellbore may be drilled in the formation for that given low permeability formation, reducing or entirely eliminating any need to fracture or indeed re-fracture the well.
In some examples, the method may comprise an initial data review of an expected formation 100, and then initial modelling of an approximation of location of wellbores (e.g. using reverse circulation drilling). Subsequently, validation and confirmation may be obtained that drilling and production may occur, cost-effectively, without the need for hydraulic or chemical fracturing of the formation. This may be considered to be a feasibility study. Subsequently, a full model may be generated and drilling can occur.
The following example provides a manner in which the above integrated workflow may be implemented:
Phase One—Data Review
- A review of the available data may be conducted to include one or more of the following:
- Review of the core data
- Review of the core reservoir rock distribution
- Review of Borehole Image Data (BHI)
- Review of Available Petrophysical Data in the Well(s)—total organic carbon (TOC) calculation, etc.
- Review of Interpreted Depth Structure and Faults
- Review of Fracture Characterisation Studies
- Review of geomechanical analysis (or do a fit for purpose analysis)
Data, such as seismic data, may help to characterise the reservoirs, such as shale gas reserves, in terms of structural features, formation heterogeneity, rock properties, and stress, etc.
Application of one or more of the following seismic attributes may allow for identification of appropriate location for well placement in order to optimize well placement, reduce the drilling risk and minimize/mitigate or eliminate any need for hydraulic fracture operation:
-
- Post-stack seismic amplitudes
- Structural attributes such as 3D curvature and coherency
- Physical attributes like spectral decomposition
- Attributes based on trace shape similarity. This may be useful in detecting changes in facies, lithology, and rock properties.
Appropriate locations for wellbore may include areas where the shale is brittle. Those areas also respond favourably to hydraulic fracturing. Areas that are already folded and faulted increase the likelihood of naturally-occurring fractures.
-
- Modelling and mapping shale brittleness using seismic inversion and well data available to identify these wellbore locations and estimate their properties distribution, for example, in 3D.
The rock physics feasibility study can be performed using key wells with the best well log information available and any existing post-stack and pre-stack information available around the well locations. This activity may include one or more of the following:
-
- Definition and validation of the rock physics model to use. Possibility to test different methodologies available.
- Elastic property estimation and crossplot analysis. Consistent multi-well elastic moduli analysis will help determine correlations with the reservoir properties such as lithology, porosity and fluids, which allow an efficient Amplitude Variation with Offset/Amplitude Variation with Azimuth (AVO/AVAZ) based reservoir description.
- Resolution analysis to examine the minimum resolvable thickness in seismic analysis.
- Fluid Substitution and AVO modelling. Different realistic fluid saturation scenarios will be produced at the well locations and we will produce synthetic gathers for each case.
- Seismic data quality analysis to screen any seismic pre-conditioning process that may help to reduce the uncertainty and increase the resolution.
Data useful for this analysis includes: existing well database and existing seismic volumes, CRP gathers at well locations if available.
Full Field Extension 1. Azimuthal Seismic AnalysisAnalysis of either amplitude, velocity/impedance or coherence/curvature variations with azimuth, which may give an indication of anisotropy/fractures. Existing azimuthal processing (all existing azimuth stacks) may be helpful in order to perform this work. This includes:
a. Pre-Stack Depth Migration (PSDM) Migrated Azimuth Stacks
b. PSDM Migrated gathers
c. PSDM Angle stacks
d. Interpreted horizons
e. Acquisition and Processing reports
f. Well logs particularly P and S velocities (cross diapole sonic if exists) and density logs
g. Petrophysics database interval velocity from PSDM
2. Simultaneous AVO InversionExisting migrated PSDM gathers may be used to estimate elastic properties that can be used to describe the lateral extension of petrophysical properties such as porosity, lithology, etc, as defined during the feasibility stage.
Pre-stack information may be helpful for this process, and Central Reference Point (CRP) gathers if they exist are also helpful for this process. This includes
-
- PSDM Full Azimuth Angle Stacks
- PSDM Migrated gathers
- Interpreted horizons
- Acquisition and Processing reports
- Well logs. Particularly P and S velocities (cross diapole sonic if exists) and density logs
- Petrophysics database
- Interval velocity from PSDM
Subsequent to the above assessments, drilling and production may occur, cost-effectively, without the need for hydraulic or chemical fracturing of the formation. Data generated from drilling may be used to update the model and/or data parameters in order to optimise well location and ultimate production.
Consider now
The system 1200 of
Here, the drilling system 1200 comprises drilling apparatus 1210, which in this example is shown as reverse-circulation drilling apparatus 1210. The drilling apparatus 1210 is configured to drill a formation without unduly affecting a near wellbore formation (e.g. without causing damage, or significant damage to the wellbore). In other words, the drilling apparatus 1210 is configured to reduce the extent to which the formation 100 (or near wellbore formation) is damaged during a drilling process, when compared with conventional drilling techniques.
As is shown in
In this particular example, the drilling apparatus 1210 is configured to use compressed gas as a drilling fluid. That drilling fluid (e.g. gas) may be inert to the formation 100.
Here, the drilling apparatus 1210 further comprises at least one flow control device 1220. As is shown in
Of course, in alternative examples, the flow control device may be provided additionally or alternatively at surface.
Here, the least one flow control device 1220 can be configured to prevent any undesired flow of hydrocarbons, or other fluids or gases, from uncontrollably reaching the surface (e.g. in when drilling through overpressured zones in the formation). In some examples, at least one shut-off valve (e.g. blowout preventer) is comprised with the, or each, flow control device 1220. Such flow control devices 1220 are known in the art.
In some examples, one, or some of the flow control device(s) 1220 can be used to regulate the flow of fluids or gases from the formation to data acquisition apparatus 1230 of the system 1200 (as explained in more detail below). In such a manner, the flow control device(s) 1220 may be used to control the fluid/gas flow so as to permit data-acquisition apparatus 1230 to determine formation parameters at the region of the formation 100 being drilled. Such flow control devices 1220 can permit isolation and testing of selected zones in the formation 100.
Here, the data-acquisition apparatus 1230 of the drilling system 1200 is specifically configured to determine formation parameters in real time, or at least relevant time, when drilling the formation 100. Relevant time may be considered to be within a time frame that permits drilling decisions based on determined formation parameters that, although not instantaneous, are nevertheless applicable given the rate of change of drilling or rate of change of formation 100.
While shown for ease here as apparatus 1230 provided at a drill rig 1235 (e.g. at surface), it will readily be appreciated that some or all of the data acquisition apparatus 1230 may be provided downhole (e.g. logging-while-drilling apparatus, measuring-while-drilling apparatus, etc.). In such a manner, the data-acquisition apparatus may be provided downhole and/or at surface. The data acquisition apparatus may comprise, for example, mass spectrometers, densitometers, liquid chromatographers, etc., in a known manner. A skilled reader will readily be able to implement the various embodiments accordingly.
Here, that data-acquisition apparatus 1230 is in communication with the drilling apparatus 1210 so as to determine formation parameters, for example, when drilling using the drilling apparatus 1210. Formation parameters may include pressures, rock materials, inflow, hydrocarbon compositions, etc. In “communication” can include “fluid communication” (e.g. when determining composition of fluids, cuttings, etc., produced from the drilling location), as well as “signalling communication” (e.g. electrical, electromagnetic, optical, acoustic, etc.), when determining formation parameters using one or more sensors associated with the drilling apparatus 1210.
In such a manner, the data-acquisition apparatus 1230 can be configured to sample materials, including produced liquids, gases and/or cuttings provided during drilling in order to determine formation parameters. In this example, the acquisition apparatus 1230 is specifically configured to compute or determine hydrocarbon production, or liberation, at a particular drilling region or position. In such a manner, it is possible to determine the location of natural fractures in the rock formation, based on sampled materials from the drilled well. For example, a determined change (e.g. increase) in hydrocarbon production may indicate the presence of a natural fracture at the drilling location. Similarly, a determined change (e.g. decrease) in hydrocarbon production at a drilling location may indicate that the drill bit 1212 is no longer at a natural fracture.
As is shown in
Here, the formation-modelling apparatus 1240 is provided on a computer, comprising a processor and memory in a known manner, together with (in this example) a user interface 1245 (shown here as a keyboard 1246 and graphical interface 1247). Of course, it will readily be appreciated that the formation-modelling apparatus 1240 may be provided on a dedicated hardware, such as field programmable gate arrays, system-on-chips, or even across a network of computers (e.g. within a network cloud).
In this example, formation-modelling apparatus 1240 is configured to use computational fluid dynamics, for example using finite volumes, to model the formation 100 being drilled.
In some examples, a well design may have been created prior to drilling. In other examples, the model may be generated during drilling. Either way, the model may be generated by initially creating a reservoir and well design using finite volumes and computational fluid dynamics, specifically for modelling subterranean regions. An example of such a method is described in U.S. Ser. No. 12/788,166 (Method of Modelling Production from a Subterranean Region), which in incorporated herein by reference in its entirety. The use of such methodology allows for the modelling of the formation 100 as a single fluid flow system, making no physical distinction between reservoir, or near-wellbore, inflow and well flow. This method may be considered more accurate than other inflow predictions and requires no correction, connection, fudge or skin factors. It enables evaluation of the optimum well geometry.
In this example, the formation-modelling apparatus 1240 is configured to use (e.g. verify and confirm) a simulated model of the formation 100 based on determined formation parameters received from the data-acquisition apparatus (e.g. confirm formation parameters are the same or similar to those modelled prior to drilling, or at least prior to drilling at that particular location). In some examples, the formation-modelling apparatus 1240 is additionally or alternatively configured to generate and/or revise the simulated model of the formation based on determined formation parameters (e.g. when the determined formation parameters are newly collected from, or differ from, the modelled formation parameters.
Here, the formation-modelling apparatus 1240 is configured to model wellbore inflow. That wellbore inflow can be modelled based on, for example, determined hydrocarbon production from natural fractures. Those natural fractures can be modelled within any simulation in order to allow for maximisation of production from those fractures.
In certain examples, the formation-modelling apparatus 1240 implements the method described above, e.g. in relation to
The formation-modelling apparatus 1240 is specifically configured to assume little or no damage to the formation during to drilling (e.g. based on the use of the drilling apparatus). As such, the modelling apparatus 1240 can use the determined formation parameters as accurately representing the quality or properties of the formation at a particular drilling location, and so can be used to control the drill bit 1212 accordingly.
Here, the system 1200 is configured to use the determined formation parameters in order to verify/generate/revise a simulated model of the formation 100, which in turn can then be used to control the drilling apparatus based on the simulated model of the formation 100.
Control of the drilling apparatus 1210 may include adjustment to expected trajectory of a drilled wellbore. Control may include adjustment to the length of a wellbore. Control may include drilling of side branches, or the like, from a wellbore. Control may include deviation of the wellbore in order to increase natural fracture intersection, or area of exposure of natural fracture.
In other words, because of the use of the particular drilling apparatus 1210 no, or at least very little, formulation damage has occurred. As such, a simulation model can be used to permit the accurate representation of the formation in real or relevant time, based on data acquisition (e.g. the identification of natural fractures), which in turn can be used so as to accurately control the drill bit 1212 and thus maximise the potential production. In such cases, no hydraulic or chemical fracturing of the well bore is required, and any poor initial data for low permeability reservoirs can be accommodated. In addition, collected data and simulation can be used to determine appropriate completion of a wellbore for optimum production.
Therefore, rather than the use of conventional data collection, drilling techniques together with conventional hydraulic or chemical fracturing methods, development and production from formations, and particularly low permeability formations, can be improved using a combination of reverse-circulation drilling apparatus, data acquisition apparatus together with formation modelling apparatus. The use of drilling techniques that do not unduly affect the formation 100 permit the use of simulated models together in a combined system 1200 that accurately depicts low permeability formations, and natural fractures, and thus allow for optimum drilling trajectories, without the need for hydraulic or chemical fracturing.
In addition, and as suggested, data collected (e.g. during drilling and/or post drilling) and models used by the above system 1200 may be employed to determine appropriate casing points or completion intervals. In some examples, data acquired and corresponding modelling may be used to determine a desire for hydraulic or chemical fracturing at a particular location. The above described system 1200 may be additionally used for such purposes (e.g. when identifying the absence of appropriate levels of hydrocarbon production from a natural fracture).
In some examples, when drilling such wells, the use of reverse-circulation drilling apparatus 1210 may allow for complex well trajectories to be considered, which may be particularly useful when developing and producing from shale formations, or the like, that comprise natural fractures 120.
For example, and with particular reference to
During such processes, the well may be permitted to flow during drilling of the primary wellbore 1300. In addition, the well may be permitted to flow during drilling of the or each secondary wellbore 1310. During drilling of each secondary wellbore 1310, well and reservoir potential may be determined (e.g. determining hydrocarbon content and/or composition from wellbore inflow during drilling) in order to optimise well design, and ultimately production.
In some examples, isolating one or more of the secondary wellbores 1310 from the primary wellbore 1300 during drilling may be desired. In such cases, isolation may be provided mechanically and/or chemically.
It will readily be appreciated that while the system of
While in the above examples, shale formations (e.g. gas or oil type shale reservoirs) have been described (e.g. accessible gas from low permeability sedimentary layers and natural fractures), the above systems, methods and apparatus may equally be used in coal bed methane or coal seam gas type reservoirs where gas is accessed in coal deposits and the natural fractures and cleats in the coal.
The applicant discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.
Claims
1. A method for computing expected production from a wellbore in a formation and/or hydrocarbon reserves associated with a formation, the formation having a plurality of naturally-occurring fractures, the method comprising:
- computationally modelling the formation;
- computing one or more wellbore positions intersecting some or all of the fractures;
- computing an expected production from the wellbore and/or reserves at least partially based on an expected wellbore damage associated with a particular type of drilling technique.
2. The method of claim 1; wherein the one or more wellbore positions are computed using and/or based on the model of the formation; and/or the computed expected production of the wellbore is for the wellbore in the one or more wellbore positions.
3. The method of claim 1 or claim 2, wherein:
- the expected production and/or reserves is/are at least partially based on the inflow from the naturally-occurring fractures; and/or
- the formation comprises a plurality of micro-fractures between the naturally-occurring fractures and the expected production and/or reserves is/are at least partially based on the inflow from naturally-occurring fractures together with inflow from micro-fractures.
4. The method according to any preceding claim, wherein the method comprises subsequently deciding to drill and produce from a wellbore based on the expected production and/or reserves.
5. The method according to any preceding claim, wherein the method comprises subsequently deciding to alter the initially-computed wellbore positions based on the expected production and/or reserves.
6. The method according to any preceding claim, wherein the method comprises determining the need to fracture a near-wellbore formation surrounding the wellbore based on the expected production.
7. The method according to any preceding claim, wherein the method comprises re-computing one or more of the wellbore positions, intersecting some or all of the fractures, in order to reduce, or eliminate, the need for hydraulic or chemical fracturing.
8. The method according to claim 7, wherein the method comprises computing one or more of the wellbore positions in order to provide a particular or maximum recovery from the formation, without hydraulic or chemical fracturing.
9. The method according to any preceding claim, wherein the particular technique is or comprises reverse-circulation drilling.
10. The method according to any preceding claim, wherein the method comprises obtaining data, such as core data, from appraisal wells drilled specifically using the particular type of drilling technique for the purposes of modelling the formation.
11. The method of claim 10, wherein the data is reviewed, and the formation potential re-appraised, by computationally modelling the formation using or based on at least some of the data.
12. A method of forming a wellbore in a formation; the method comprising:
- using or determining parameters associated with a formation;
- computationally modelling the formation using the parameters;
- computing one or more wellbore positions, e.g. using the computed model, based on the type of drilling to be used for the formation; and
- drilling one or more of the wellbore positions.
13. The method according to claim 12, the method comprising using data associated with the drilling operation to confirm at least one or each of the parameters associated with the formation and the computed model of the formation.
14. The method of any of claim 12 or 13, comprising the method of any of claims 1 to 11, wherein the one or more wellbore positions are wellbore positions associated with a particular, optimum or maximum recovery from the formation.
15. The method according to any of claims 12 to 14, wherein the method includes altering, or modifying, one or more of: based on an identified difference between data associated with drilling, and expected data associated with the parameters or model.
- (i) the determined parameters
- (ii) the computed model; and
- (iii) the wellbore positions,
16. The method according to any of claims 12 to 15, the method comprising real-time monitoring of data while drilling.
17. A drilling system comprising:
- reverse-circulation drilling apparatus;
- data-acquisition apparatus in communication with the drilling apparatus, the data acquisition apparatus being configured to determine formation parameters when drilling using the drilling apparatus; and
- formation-modelling apparatus, in communication with the data acquisition apparatus, and configured to use the determined formation parameters with a simulated model of the formation so as to allow for control of the drilling apparatus based on the simulated model of the formation.
18. The system according to claim 17, wherein the formation modelling apparatus is configured to implement the method of any of claims 1 to 11 and/or the system is configured to implement the method of any of claims 12 to 16.
19. The system according to claim 18, wherein the system is configured for use with low permeability formations, such as shale-rock formations.
20. The system according to any of claims 17 to 19, wherein the drilling apparatus comprises at least one flow control device, the flow control device configured to prevent or inhibit undesired flow of fluids from uncontrollably reaching a surface.
21. The system according to claim 20, wherein the flow control device is configured to regulate the flow of fluids from a formation to the data acquisition apparatus.
22. The system according to any of the claim 20 or 21, wherein the flow control device permits isolation and testing of selected zones in the formation.
23. The system according to any of the claims 17 to 22, wherein the data-acquisition apparatus is configured to sample materials, including liquids, gases and/or cuttings provided during drilling, in order to determine formation parameters.
24. The system according to claim 23, wherein the data-acquisition apparatus is configured to compute or determine the location of natural fractures in the rock formation, based on sampled materials from a well.
25. A system according to claim 24, wherein the data-acquisition apparatus is configured to determine hydrocarbon production, or liberation, at a particular drilling region or location, and wherein a determined relative increase in hydrocarbon production indicates the presence of a natural fracture at that drilling region or location.
26. A system according to any of claims 17 to 25, wherein the data-acquisition apparatus is configured to determine formation parameters in real time and is configured to communicate determined parameters to the formation-modelling apparatus in real time.
27. A system according to any of claims 17 to 26, wherein the formation-modelling apparatus is configured to use computational fluid dynamics using finite volumes to model a formation being drilled.
28. A system according to any of claims 17 to 27, wherein the formation-modelling apparatus is configured to verify, generate and/or revise a simulated model of the formation based on determined formation parameters.
29. A system according to any of claims 17 to 28, wherein the formation modelling apparatus is configured to model wellbore inflow, assuming little or no damage to the formation during to drilling.
30. A system according to any of claims 17 to 29, wherein the system is additionally configured to control the drilling apparatus based on the simulated model of the formation.
31. A system according to claim 30, wherein control comprises one or more of: adjustment to expected trajectory of a drilled wellbore; adjustment to the length of a wellbore; drilling of side branches; deviation of the wellbore, in order to increase natural fracture intersection.
32. A system according to claim 30 or 31, wherein control includes drilling a primary wellbore and drilling one or more secondary wellbores from the primary wellbore, each secondary wellbore being drilled in order to intersect one or more natural fractures in the formation.
33. A system according to claim 32, wherein the one or more secondary wellbores are arranged to maximise a number of natural fractures intersected by the wellbores by optimizing orientation or the secondary wellbore(s) in terms of azimuth and/or deviation angle.
34. A system according to claim 32 or claim 33, wherein the formation-modelling apparatus is configured to update and/or optimise the model based on core data acquired for the primary and/or secondary well bore(s).
35. A method of drilling a formation comprising:
- drilling a primary wellbore using reverse-circulation drilling apparatus, and
- drilling one or more secondary wellbores from the primary wellbore, each secondary wellbore being drilled in order to intersect one or more natural fractures in the formation.
36. The method according to claim 35, wherein the or each secondary wellbore is drilled using reverse-circulation drilling apparatus.
37. The method according to claim 35 or claim 36, wherein at least the one or more secondary wellbores are drilled during development of an existing field or wellbore or after an exploration/appraisal of the formation.
38. The method according to any of claims 35 to 37, wherein the one or more secondary wellbores are arranged to maximise a number of natural fractures intersected by the wellbores by optimizing orientation or the secondary wellbore in terms of azimuth and/or deviation angle.
39. The method according to any of claims 35 to 38, comprising permitting the well to flow during drilling of the primary wellbore.
40. The method according to any of claims 35 to 39, comprising permitting the well to flow during drilling of the or each secondary wellbore.
41. The method according to any of the claims 35 to 40, comprising determining well and reservoir potential during drilling by determining hydrocarbon content and/or composition from wellbore inflow during drilling.
42. The method according to any of the claims 35 to 41, comprising isolating one or more of the secondary wellbores from the primary wellbore during drilling, wherein such isolation is provided mechanically and/or chemically.
43. The method according to any of the claims 35 to 42 comprising determining the location of natural fractures in rock formation, based on sampled materials from a well, in order to determine desired location(s) for secondary wellbores.
44. The method according to claim 43, comprising determining hydrocarbon production, or liberation, at a particular drilling region or location in order to determine the location of natural fractures in order to determine desired location for secondary wellbores.
45. The method according to claim 44, wherein a determined relative increase in hydrocarbon production during drilling indicates the presence of a natural fracture at that drilling region or location.
46. The method according to any of the claims 35 to 45, comprising acquiring data from drilling in order to determine formation parameters, and using the formation parameters with a simulated model of the formation so as to allow for control of the drilling apparatus based on the simulated model of the formation.
47. The method according to claim 46, wherein the formation parameters are used to verify, generate and/or revise the simulated model of the formation.
48. The method according to any of the claims 35 to 47, wherein the method is used in shale-rock formation.
49. The method according to any of claims 35 to 48, comprising acquiring core data for the primary and/or secondary well bore(s) to collect data for the formation in which the natural fractures and hydrocarbons are present and optionally updating the simulated model based on the data and/or core data.
50. An unconventional hydrocarbon reservoir comprising:
- a primary wellbore having been drilled using reverse-circulation drilling apparatus, and
- one or more secondary wellbores having been drilled from the primary wellbore, the or each secondary wellbore intersecting one or more natural fractures in the formation.
51. The unconventional hydrocarbon reservoir according to claim 50, wherein the unconventional hydrocarbon reservoir is or comprises or is comprised in a shale rock formation.
Type: Application
Filed: Aug 8, 2014
Publication Date: Jun 30, 2016
Inventors: Joost DE BAKKER (Aberdeen), Michael BYRNE (Aberdeen), Ali GHOLIPOUR (Aberdeen), Peter PAVY (Aberdeen), Tom FIELDER (Aberdeen)
Application Number: 14/910,897
