Propagation of High Permeable Planar Inclusions in Weakly Cemented Formations

Abstract

A well system for installing highly permeable inclusions at multiple azimuths in anelastic weakly cemented formations. The well system includes a wellbore device interconnected to a tubular string for initiating and propagating of planar inclusions at multiple azimuths into a formation surrounding the wellbore. The well device radially expands to seal against the formation, with the device having multiple openings in its sidewall at differing azimuths for the initiation and propagating of inclusions into the formation by controlled injection of a viscous non-penetrating fluid. The viscous propagating fluid carries proppant to the extremities of the inclusions, creating highly permeable planes at multiple azimuths from the wellbore. The well device is particularly well suited for use in conjunction with anelastic weakly cemented formations.

Description

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

This invention claims priority from U.S. Provisional Patent Application No. 63/252,400, filed Oct. 5, 2021, which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides for the planar propagation of multiple inclusions of differing azimuths for increased permeability planes in weakly cemented formations.

BACKGROUND OF THE INVENTION

Recent advancements have been made in the art of forming increased permeability drainage planes in weakly cemented formations. These advancements are particularly useful for enhancing and maximizing injection and production flow rates of supercritical carbon dioxide in depleted petroleum reservoirs for subsurface carbon energy storage to enable the carbon electric grid to meet supply and demand needs both daily and seasonal, achieving a zero carbon grid, whilst utilizing renewable energy to its maximum potential, and assisted by gravity drainage to produce additional hydrocarbons from the pressure depleted petroleum reservoirs, etc., and also assist hydrocarbon recovery from heavy oil and oil sand formations; although the advancements have other uses, as well.

In many circumstances, it is desirable to complete such wells “open hole,” i.e., without using a cemented casing to install the high permeable inclusions at multiple azimuths and coalesce the respective inclusions at differing depths. Following installation of the multiple azimuth permeable inclusions, the well is completed with a production tubing to inject and produce fluids from the wells.

Therefore, it will be appreciated that improvements are needed in the art of improving injection and production flow rate control in wells.

SUMMARY OF THE INVENTION

In carrying out the principles of the present invention, well systems and associated devices and methods are provided which solve at least one problem in the art. One example is described below in which multiple azimuth permeable inclusions are installed in a formation from a downhole tool device in an “open hole” wellbore configuration with the multiple azimuth inclusions coalesced with their respective azimuth inclusions at differing depths, enabling high injection and production flow rates of fluids into and from the well. The downhole device seals against the formation, and at particular azimuths the device circumferentially opens and an initial slot is created by various means; explosive shape charges, mechanical slotting, fluid jetting, a combination of mechanical and fluid insertion of a wedge into the formation, etc. or by additional expansion of the downhole tool to exceed the passive Rankine effective pressure of the formation, all of which initial methods are individually followed by the injection of a highly viscous non-penetrating fluid enabling the planar propagation of an inclusion in the formation and it being maintained on azimuth during propagation. The device is particularly well suited for use in conjunction with anelastic weakly cemented formations.

In one aspect, a well system is provided which includes a downhole tool expansion device interconnected to a tubular string for initiating and propagating of at least one inclusion into a formation. The expansion tool device has at least one opening in a sidewall for fluid communication between the inclusion and an interior of the tool and tubular string. A flow control device controls the flow of highly viscous non-penetrating fluid into the formation from the tubular string.

These and other features, advantages, benefits and objects will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention hereinbelow and the accompanying drawings, in which similar elements are indicated in the various figures using the same reference numbers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic partially cross-sectional view of a well system in the unexpanded state and associated method in accordance with the present invention

FIG. 1B is a schematic partially cross-sectional view of the well system in the expanded state and associated method with the down hole tool device expanded and initial slots formed in the formation in accordance with the present invention.

FIG. 2A is an enlarged scale schematic vertical sectional view of the down hole expanded tool and initial slot on a particular azimuth in the formation in accordance with the present invention.

FIG. 2B is a schematic partially cross-sectional view of the well system and associated method showing the propagated inclusion on the same azimuth as FIG. 2A in accordance with the present invention.

FIG. 2C is a schematic cross-section view of the well system and associated method showing an initiation sequence of the inclusions into the formation for six multiple azimuth inclusions through an expansion down hole tool device in the open hole well system in accordance with the present invention.

FIG. 3A is a schematic cross-sectional view of the expansion device for the installation of three azimuth inclusions in accordance with the present invention.

FIG. 3B is a schematic cross-sectional view of the expansion device showing the down hole tool rotated sixty degrees for the formation of three additional inclusions at differing azimuths in accordance with the present invention.

FIG. 4A is a schematic isometric view of six inclusions installed in the formation at differing azimuths at a particular depth in accordance with the present invention.

FIG. 4B is a schematic isometric view showing the coalescence of an inclusion formed at a shallower depth coalesced with its respective azimuth inclusion at a deeper depth in accordance with the present invention.

FIG. 5 is a schematic isometric view of six inclusions installed in the formation at differing azimuths at a particular depth coalesced with their respective inclusion formed at a shallower depth in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present invention. The embodiments are described merely as examples of useful applications of the principles of the invention, which is not limited to any specific details of these embodiments.

In the following description of the representative embodiments of the invention, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used for convenience in referring to the accompanying drawings. In general, “above”, “upper”, “upward” and similar terms refer to a direction toward the earth's surface along a wellbore, and “below”, “lower”, “downward” and similar terms refer to a direction away from the earth's surface along the wellbore.

Representatively illustrated in FIG. 1A is a formation 1 with an open hole wellbore 2 and associated device 3 which embody principles of the present invention. In the system, a wellbore 2 has been drilled intersecting a subterranean formation 1. Although the wellbore 2 is depicted in FIG. 1 as being substantially vertical, the wellbore in other embodiments could be horizontal, inclined, deviated or otherwise oriented.

The formation 1 includes several zones penetrated by the wellbore 2, and, one or more of these zones could be in separate formations, part of other reservoirs, etc.

An open hole tool device 3 is inserted in the wellbore 2 as depicted in FIG. 1A. The tool device 3 has three circumferential locations, 4, 5 and 6, that open circumferentially as the tool radially expands to contact the formation 1, as shown in FIG. 1B. The downhole device 3 seals against the formation 1, and at three azimuths, the device circumferentially opens, 4, 5 and 6 and an initial slot is created by various means; either explosive shape charges, mechanical slotting, fluid jetting, or a combination of mechanical and fluid insertion of a wedge into the formation, etc. or by additional expansion of the downhole tool to exceed the passive Rankine effective pressure of the formation, as denoted by 7, 8 and 9 in FIG. 1B. The downhole device 3 is in contact with the formation 1, to act as a circumferential and vertical seal of the individual slots 7, 8 and 9 from each other and the wellbore 2 above and below the down hole tool 3. The initiation method to form slots 7, 8 and 9 is followed by the injection of a highly viscous non-penetrating fluid into each slot either independently or injected in sequence.

FIG. 2A shows the initial slot 7 from the down hole device 3 in a formation 1, with the injection of a viscous non-penetrating fluid propagating the inclusion 10 on azimuth from the initial slot 7 into the formation. The other two inclusions on differing azimuths are injection in sequence following the completion of injection of the planar inclusion 10. The injection viscous fluid injected to form the inclusion 10 contains sand or manufactured proppants, and an enzyme breaker to enable a clean highly permeable inclusion to be placed in the formation 1. In the case of supercritical carbon dioxide energy storage applications, the proppant could be either a garnet sand or manufactured ceramic. Following the completion of the planar propagation of the inclusion 10 in the formation 1, the sequence of injecting the other azimuth inclusions is illustrated in FIG. 2C for six inclusions on six differing azimuths. The device is particularly well suited for use in conjunction with weakly cemented formations.

FIG. 3A shows a cross-section view at the completion of the first inclusion 10, and in FIG. 3B at the completion of the second and third inclusions 11 and 12, with the tool contracted, rotated sixty degrees counter clockwise, expanded to seal with the formation 1, and three additional slots, 13, 14 and 15 are created on three differing azimuths, with the device ready for the independent injection and installation of three remaining inclusions on the azimuths of the initial slots, 13, 14 and 15 respectively. It is not necessary for the inclusions 10, 11 and 12 to be formed independently as they could be created simultaneously, provided they are each individually flow controlled or they could be formed in any other combination to that shown.

FIG. 4A shows six inclusions 10, 11, 12, 16, 17 and 18 formed in the formation 1 at multiple azimuths at a particular depth from a vertical wellbore 2. The open hole tool device 3 is then raised in the wellbore 2 to a shallower depth and inclusions are subsequentially installed at a shallower depth as shown in FIG. 4B, with inclusion denoted as 19 constructed first. Inclusion 19 is coalesced with its earlier constructed on-azimuth inclusion 10 by the process of pore pressure relief. At the time of injecting and propagating inclusion 19, the inclusion 10 viscous fluid has been enzyme degraded into water and sugars, such that inclusion 10 is now a highly permeable sand propped inclusion. By reducing the fluid pressure in inclusion 10 while propagating inclusion 19 ensures that inclusion 19 coalesces with inclusion 10. The open hole tool device 3 has control of fluid pressure at depth and thus the system and method can thus ensure that the inclusions are coalesced with their respective deeper on azimuth inclusions, as shown in FIG. 4B coalescence of inclusions on a single azimuth, and in FIG. 5 for all six azimuth inclusions constructed at two differing depths. Thus, the system and method can install vertically coalesced inclusions on azimuth over considerable vertical height and throughout the vertical extent required in the formation 1, or any combination of formation sequences.

The system and method could be used to install inclusion on azimuth in formations comprised of relatively strong rock, but the system and method find especially beneficial application in ductile rock formations made up of weakly cemented sediments, in which it is typically very difficult to obtain directional or geometric control over inclusions as they are being formed. In particular, the system and method are applicable to anelastic formations, having a formation Quality factor of less than 20, in which pressurizing a wellbore with a non-penetrating fluid in such formations has a poor to low efficiency in generating circumferential tensile stresses in such formations.

Weakly cemented sediments are primarily frictional materials since they have minimal cohesive strength. An uncemented sand having no inherent cohesive strength (i.e., no cement bonding holding the sand grains together) cannot contain a stable crack within its structure and cannot undergo brittle fracture. Such materials are categorized as frictional materials which fail under shear stress, whereas brittle cohesive materials, such as strong rocks, fail under normal stress.

The term “cohesion” is used in the art to describe the strength of a material at zero effective mean stress. Weakly cemented materials may appear to have some apparent cohesion due to suction or negative pore pressures created by capillary attraction in fine grained sediment, with the sediment being only partially saturated. These suction pressures hold the grains together at low effective stresses and, thus, are often called apparent cohesion.

The suction pressures are not true bonding of the sediment's grains, since the suction pressures would dissipate due to complete saturation of the sediment. Apparent cohesion is generally such a small component of strength that it cannot be effectively measured for strong rocks, and only becomes apparent when testing very weakly cemented sediments.

Geological strong materials, such as relatively strong rock, behave as brittle materials at normal petroleum reservoir depths, but at great depth (i.e. at very high confining stress) or at highly elevated temperatures, these rocks can behave like ductile frictional materials. Weakly cemented sands and weakly cemented formations behave as ductile frictional materials from shallow to deep depths, and the behavior of such materials are fundamentally different from rocks that exhibit brittle fracture behavior. Ductile frictional materials fail under shear stress and consume energy due to frictional sliding, rotation and displacement.

Conventional hydraulic dilation of weakly cemented sediments is conducted extensively on petroleum reservoirs as a means of sand control. The procedure is commonly referred to as “Frac-and-Pack.” In a typical operation, the casing is perforated over the formation interval intended to be fractured and the formation is injected with a treatment fluid of low gel loading without proppant, in order to form the desired two winged structure of a fracture. Then, the proppant loading in the treatment fluid is increased substantially to yield tip screen-out of the fracture. In this manner, the fracture tip does not extend further, and the fracture and perforations are backfilled with proppant.

The process assumes a two winged fracture is formed as in conventional brittle hydraulic fracturing. However, such a process has not been duplicated in the laboratory or in shallow field trials. In laboratory experiments and shallow field trials what has been observed is chaotic geometries of the injected fluid, with many cases evidencing cavity expansion growth of the treatment fluid around the well and with deformation or compaction of the host formation.

Weakly cemented sediments behave like a ductile frictional material in yield due to the predominantly frictional behavior and the low cohesion between the grains of the sediment. Such materials do not “fracture” and, therefore, there is no inherent fracturing process in these materials as compared to conventional hydraulic fracturing of strong brittle rocks.

Linear elastic fracture mechanics is not applicable to the behavior of anelastic formations either weakly or strongly cemented sediments. The knowledge base of propagating viscous planar inclusions in anelastic formations is primarily from recent experience over the past twenty years and much is still not known regarding the process of viscous fluid propagation in these formations.

However, the present disclosure provides information to enable those skilled in the art of hydraulic fracturing, soil and rock mechanics to practice a method and system to initiate and control the propagation of a viscous fluid in weakly cemented sediments. The viscous fluid propagation process in these sediments involves the unloading of the formation 1 in the vicinity of the tip of the propagating viscous fluid, causing dilation of the formation, which generates pore pressure gradients towards this dilating zone. As the formation 1 dilates at the tips of the advancing viscous dilation fluid, the pore pressure decreases dramatically at the tips, resulting in increased pore pressure gradients surrounding the tips.

The pore pressure gradients at the tips of the inclusions result in the liquefaction, cavitation (degassing) or fluidization of the formation 1 immediately surrounding the propagating tips. That is, the formation 1 in the dilating zone about the tips acts like a fluid since its strength, fabric and in situ stresses have been destroyed by the fluidizing process, and this fluidized zone in the formation immediately ahead of the viscous fluid propagating tip is a planar path of least resistance for the viscous fluid to propagate further. In at least this manner, the system and associated method provide for directional and geometric control over the advancing propagating inclusions 10, 11 and 12.

The behavioral characteristics of the viscous fluid are preferably controlled to ensure the propagating viscous fluid does not overrun the fluidized zone and lead to a loss of control of the propagating process. Thus, the viscosity of the fluid and the volumetric rate of injection of the fluid should be controlled to ensure that the conditions described above persist while the inclusions are being propagated through the formation 1.

For example, the viscosity of the fluid to propagate the inclusions is preferably greater than approximately 100 centipoise at the respective shear rate of inclusion propagation. However, if a foamed propagated fluid is used in the system and method, a greater range of viscosity and injection rate may be permitted while still maintaining directional and geometric control over the inclusions.

The system and associated method are applicable to formations of weakly cemented sediments with low cohesive strength compared to the vertical overburden stress prevailing at the depth of interest. Low cohesive strength is defined herein as no greater than 400 pounds per square inch (psi) plus 0.4 times the mean effective stress (p′) at the depth of propagation.

c<400 psi+0.4 p′  (1)

where c is cohesive strength and p′ is mean effective stress in the formation 1.

Examples of such weakly cemented sediments are sand and sandstone formations, mudstones, shales, and siltstones, all of which have inherent low cohesive strength. Critical state soil mechanics assists in defining when a material is behaving as a cohesive material capable of brittle fracture or when it behaves predominantly as a ductile frictional material.

Weakly cemented sediments are also characterized as having a soft skeleton structure at low effective mean stress due to the lack of cohesive bonding between the grains. On the other hand, hard strong stiff rocks will not substantially decrease in volume under an increment of load due to an increase in mean stress.

In the art of poroelasticity, the Skempton B parameter is a measure of a sediment's characteristic stiffness compared to the fluid contained within the sediment's pores. The Skempton B parameter is a measure of the rise in pore pressure in the material for an incremental rise in mean stress under undrained conditions.

In stiff rocks, the rock skeleton takes on the increment of mean stress and thus the pore pressure does not rise, i.e., corresponding to a Skempton B parameter value of at or about 0. But in a soft soil, the soil skeleton deforms easily under the increment of mean stress and, thus, the increment of mean stress is supported by the pore fluid under undrained conditions (corresponding to a Skempton B parameter of at or about 1).

The following equations illustrate the relationships between these parameters:

Δu=B Δp   (2)

B=(Ku−K)/(αKu)   (3)

α=1−(K/Ks)   (4)

where Δu is the increment of pore pressure, B the Skempton B parameter, Δp the increment of mean stress, Ku is the undrained formation bulk modulus, K the drained formation bulk modulus, α is the Biot-Willis poroelastic parameter, and Ks is the bulk modulus of the formation grains. In the system and associated method, the bulk modulus K of the formation 14 is preferably less than approximately 750,000 psi.

For use of the system and method in weakly cemented sediments, preferably the Skempton B parameter is as follows:

B>0.95 exp(−0.04 p′)+0.008 p′  (5)

The system and associated method are applicable to formations of weakly cemented sediments (such as tight gas sands, turbidite reservoirs, mudstones and shales) where large extensive propped vertical permeable drainage planes are desired to intersect thin sand lenses and provide drainage paths for greater gas production from the formations. In weakly cemented formations containing heavy oil (viscosity >100 centipoise) or bitumen (extremely high viscosity >100,000 centipoise), generally known as oil sands, propped vertical permeable drainage planes provide drainage paths for cold production from these formations, and access for steam, solvents, oils, and heat to increase the mobility of the petroleum hydrocarbons and thus aid in the extraction of the hydrocarbons from the formation. In highly permeable weak sand formations, permeable drainage planes of large lateral length result in lower drawdown of the pressure in the reservoir, which reduces the fluid gradients acting towards the wellbore, resulting in less drag on fines in the formation, resulting in reduced flow of formation fines into the wellbore.

Although the present invention contemplates the formation of permeable drainage paths which generally extend laterally away from a vertical or near vertical wellbore penetrating an earth formation 1 and generally in a vertical plane in opposite directions from the wellbore, those skilled in the art will recognize that the invention may be carried out in earth formations wherein the permeable drainage paths can extend in directions other than vertical, such as in inclined or horizontal directions. Furthermore, it is not necessary for the planar inclusions to be used for drainage, since in some circumstances it may be desirable to use the planar inclusions exclusively for injecting fluids into the formation 1, or for forming an impermeable barrier in the formation, etc.

Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the invention, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to these specific embodiments, and such changes are within the scope of the principles of the present invention. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents.

The following U.S. patent documents are incorporated by reference in their entirety as background and to assist in the understanding of the foregoing disclosure of the invention.

• • U.S. Pat. No. 7,640,975 Flow control for increased permeability planes in unconsolidated formations
  • U.S. Pat. No. 7,640,982 Method of injection plane initiation in a well
  • U.S. Pat. No. 7,647,966 Method for drainage of heavy oil reservoir via horizontal wellbore
  • U.S. Pat. No. 7,814,978 Casing expansion and formation compression for permeability plane orientation
  • U.S. Pat. No. 7,832,477 Casing deformation and control for inclusion propagation
  • U.S. Pat. No. 7,918,269 Drainage of heavy oil reservoir via horizontal wellbore
  • U.S. Pat. No. 7,950,456 Casing deformation and control for inclusion propagation
  • U.S. Pat. No. 8,122,953 Drainage of heavy oil reservoir via horizontal wellbore
  • U.S. Pat. No. 8,151,874 Thermal recovery of shallow bitumen through increased permeability inclusions
  • U.S. Pat. No. 8,863,840 Thermal recovery of shallow bitumen through increased permeability inclusions
  • U.S. Pat. No. 8,955,585 Forming inclusions in selected azimuthal orientations from a casing section
  • U.S. Pat. No. 10,119,356 Forming inclusions in selected azimuthal orientations from a casing section
  • U.S. Pat. No. 10,704,367 Forming inclusions in selected azimuthal orientations from casing section

Claims

1. A wellbore completion system, comprising:

an open hole expansion tool device connected to a tubular string for initiating and propagating at least one inclusion into a formation surrounding the wellbore, the device expanding and sealing against the wellbore, having at least one opening in a sidewall, forming an initiating slot in the sidewall of the wellbore at the opening, and propagating a planar inclusion from the slot by injection of a viscous non-penetrating fluid into the formation; and the initiating slot is formed in the formation by either mechanical cutting, fluid jetting, explosive shape or perforating charges, or a combination of either.

2. The well system of claim 1, wherein the initiating slot is formed by a combination of mechanical and fluid insertion of a wedge into the formation at the sidewall opening of the device.

3. The well system of claim 1, wherein the initiating slot is formed by additional expansion of the downhole tool against the sidewall of the wellbore to exceed the passive Rankine effective pressure of the formation.

4. The well system of claim 1, wherein the number of device sidewall openings is greater than one, with each sidewall opening in fluid isolation of each other, and each initiating slot at each sidewall opening are independently flow controlled for the injection of the propagating viscous non-penetrating fluid.

5. The well system of claim 1, wherein the propagating viscous non-penetrating fluid contains an enzyme breaker and carries proppant, either quartz sand, garnet sand or a manufactured ceramic proppant to the extremities of the inclusion.

6. The well system of claim 1, wherein the device after installing multiple azimuth inclusions, is then radially contracted, rotated, radially expanded to seal with the wellbore sidewall and further multiple azimuth inclusions are formed and propagated into the formation at differing azimuths, with each inclusion having independent flow control of its propagating viscous fluid.

7. The well system of claim 1, wherein the formation comprises an anelastic weakly cemented sediment, with a formation Quality factor of less than 20.

8. The well system of claim 1, wherein multiple azimuth permeable inclusions are formed at a depth in the wellbore, the well device is radially contracted and raised to a shallower depth in the wellbore, expanded to the wellbore sidewall and multiple azimuth inclusions are installed, with the wellbore fluid pressure below the well device is controlled by the device to ensure that inclusions propagating at the shallower depth coalesce to their respective azimuth deeper inclusion by pore pressure relief.