Abstract: A reservoir sampling apparatus (20) is described having at least one probe (26) adapted to provide a fluid flow path between a formation and the inner of the apparatus with the flow path being sealed from direct flow of fluids from the borehole annulus with a heating projector (251) adapted to project heat into the formation surrounding the probe and a controller (253) to maintain the temperature in the formation below a threshold value.

Abstract: A borehole formation testing system that measures resistivity of near borehole formation in situ rather than the measuring resistivity of fluid drawn into a formation tester tool. A radially extendable probe assembly contacts and forms a hydraulic seal with the wall of a borehole using a pad. Electrode contacts are disposed on the contact surface of the pad and electrically contact the near borehole formation. Response of the electrode contacts are used to determine resistivity of the near borehole formation. This resistivity is with a deeper formation resistivity measurement to determine if virgin formation fluid is at or in the vicinity of the pad. Alternately, a plurality of resistivity measurements is made at the formation tester pad and virgin formation fluid at or near the pad is determined from the rate of change of the plurality of resistivity measurements.

Abstract: Methods and apparatus to control a formation testing operation based on a mudcake leakage are disclosed. A disclosed example method for use with a downhole tool disposed in a wellbore comprises measuring a property of a mudcake layer at a first location in a wellbore, determining a value representative of an estimated leakage through the mudcake layer based on the property, and determining, based on the value, whether to continue a formation testing operation.

Abstract: A technique usable with a well includes disposing a retractable line in a conduit having an open end located above a region of interest in the well. The retractable line comprises a sensing portion that, when the line is deployed, extends from the open end of the conduit and into the region of interest. Information observed by the sensing portion in the region of interest is communicated to the surface. When further well operations are to be performed in the region of interest, the retractable line is retracted until the sensing portion is located above the region of interest and below the surface. After the well operation is completed, the retractable line may be re-deployed such that the sensing portion again extends through the open end of the conduit and into the region of interest to continue observing characteristics associated with the well.

Abstract: A method includes calculating a correction factor that uses a tool component volume change model to estimate a system volume change resulting from a change in the tool component. An apparatus includes a carrier conveyable into a well borehole, a formation test tool coupled to the carrier, the formation test tool including a tool component. A measurement device to estimate a change in the tool component during operation, and a compensator uses an estimated system volume change resulting at least in part from the change in the tool component during a downhole operation, the compensator compensating for the system volume change and wherein the estimated system volume change is estimated at least in part using a volume change model.

Abstract: Fluid tests may be performed to determine suitability of an additive for a production enhancement treatment. In one aspect, a measuring device is used to determine a result of adding a sample of solid material to a test fluid that includes an additive. The result may include, for example, a change in surface tension, a change in contact angle, and/or another result. The measured result is used to determine the suitability of the additive for use in a stimulation treatment for a subterranean formation. For example, the additive may be determined suitable for use during a pad phase of a fracture treatment, during a proppant-laden phase of a fracture treatment, and/or for other phases and/or types of stimulation treatments.

Abstract: This application relates to various methods and apparatus for rapidly obtaining accurate formation property data from a drilled earthen borehole. Quickly obtaining accurate formation property data, including formation fluid pressure, is vital to beneficially describing the various formations being intersected. For example, methods are disclosed for collecting numerous property values with a minimum of downhole tools, correcting and calibrating downhole measurements and sensors, and developing complete formation predictors and models by acquiring a diverse set of direct formation measurements, such as formation fluid pressure and temperature. Also disclosed are various methods of using of accurately and quickly obtained formation property data.

Abstract: Example methods and apparatus to determine the compressibility of a fluid are disclosed. A disclosed example method includes capturing a fluid in a chamber, pressurizing the captured fluid to first and second pressures, measuring first and second values representative of first and second densities of the fluid while pressurized at respective ones of the first and second pressures, and computing a third value representative of a compressibility of the fluid using the first and second values.

Abstract: A method of sampling fluid from a rock formation penetrated by a borehole includes positioning a downhole tool having a flow line in the borehole, establishing an inlet port through which fluid passes from a first point in the formation into the flow line, establishing an outlet port through which fluid passes from the flow line into a second point in the formation, and passing fluid between the formation and the flow line through the inlet and outlet ports.

Abstract: A formation fluid sampling tool is provided with a drill which drills into the formation in a manner perpendicular or oblique to the borehole wall. The tool comprises a mechanism for enhancing the mobility of the reservoir fluid, such as a heating element on the drill, hot fluid which is generated in the tool and injected into the drilled hole, or a solvent which is stored in the tool and injected by the tool into the drilled hole.

Abstract: A method of retrieving a formation fluid from a formation adjacent a borehole wall includes estimating at least one of a permeability of the formation and a viscosity of the formation fluid. A first tool is selected based on the estimation, the first tool being selected from one of a heating and sampling tool, an injection and sampling tool, and a coring tool. An attempt to retrieve a formation fluid sample from the formation is then made with the first tool, and a formation fluid sample is retrieved from the formation. A second retrieval process may then be initiated, in which the second retrieval process includes increasing the mobility of the formation fluid.

Abstract: A system for testing a subterranean formation penetrated by a well includes a downhole tool configured to be coupled to a work string that includes a tool body having a longitudinal bore for circulating a fluid and at least one aperture configured to receive at least one module. The system further includes a plurality of modules that are each configured to engage the at least one aperture and at least one cavity configured for receiving a probe, and a plurality of probes that each include at least one orifice configured for testing the formation, wherein a first of the plurality of probes has a first configuration and a second of the plurality of probes has a second configuration.

Abstract: Methods and apparatus to use multiple sensors to measure downhole fluid properties are described. An example method of measuring a property of a downhole fluid involves obtaining a plurality of measurements for each of a plurality of sensors. Each of the measurements corresponds to a same property of the downhole fluid, and each of the sensors is differently configured to measure the property. Additionally, the example method involves obtaining a plurality of weighting values, each of which corresponds to one of the sensors. The example method also involves applying the weighting values to the respective measurements obtained by each of the corresponding sensors to generate a weight-corrected measurement for each of the sensors. Further still, the example method involves generating a value representative of a measurement of the property of the downhole fluid based on the weight-corrected measurements and outputting the value representative of the measurement of the property.

Abstract: Example microfluidic methods and apparatus to perform in situ chemical detection are disclosed. A disclosed example downhole apparatus comprises a microfluidic chamber to introduce a microfluidic-scale drop of a reagent into a formation fluid to form a mixed fluid, a flowline to fluidly couple the formation fluid from a geologic formation to the microfluidic chamber, and a detector to measure a property of the mixed fluid, the property representative of a presence of a chemical in the formation fluid.

Abstract: A method for conducting a formation test includes providing a volume change model for a tool component, and providing a control program that uses the volume change model to estimate a system volume change resulting from a change in the tool component during a downhole operation. An apparatus for conducting a formation test includes a carrier, a formation test tool, a measurement device that estimates a change in a tool component during operation, and a processor that uses a volume change model to estimate a system volume change resulting at least in part from the change in the tool component during a downhole operation.

Abstract: A method of retrieving a formation fluid from a formation adjacent a borehole wall includes estimating at least one of a permeability of the formation and a viscosity of the formation fluid. A first tool is selected based on the estimation, the first tool being selected from one of a heating and sampling tool, an injection and sampling tool, and a coring tool. An attempt to retrieve a formation fluid sample from the formation is then made with the first tool, and a formation fluid sample is retrieved from the formation. A second retrieval process may then be initiated, in which the second retrieval process includes increasing the mobility of the formation fluid.

Abstract: The present invention provides a downhole spectrometer for determination of dew point pressure to determine an associated optimal pumping rate during sampling to avoid precipitation of asphaltenes in a formation sample. A sample is captured at formation pressure in a controlled volume. The pressure in the controlled volume is reduced. Initially the formation fluid sample appears dark and allows less light energy to pass through a sample under test. The sample under test, however, becomes lighter and allows more light energy to pass through the sample as the pressure is reduced and the formation fluid sample becomes thinner or less dense under the reduced pressure. At the dew point pressure, however, the sample begins to darken and allows less light energy to pass through it as asphaltenes begin to precipitate out of the sample. Thus, the dew point is that pressure at which peak light energy passes through the sample.

Abstract: A reservoir sampling apparatus (20) is described having at least one probe (26) adapted to provide a fluid flow path between a formation and the inner of the apparatus with the flow path being sealed from direct flow of fluids from the borehole annulus with a heating projector (251) adapted to project heat into the formation surrounding the probe and a controller (253) to maintain the temperature in the formation below a threshold value.

Abstract: Apparatus and methods for collecting a downhole sample are provided. The method may include monitoring a flow path parameter, introducing a sealant to a borehole wall when the flow path parameter satisfies a first predetermined condition, and collecting a downhole sample when the flow path parameter satisfies a second predetermined condition. An apparatus may include a formation sampling tool having a flow path, an inhibitor coupled to the formation sampling tool, a sampler coupled to the formation sampling tool, and a selector that selects one or more of the inhibitor and the sampler when a parameter of the flow path satisfies a predetermined condition.

Abstract: A system for testing a subterranean formation penetrated by a well includes a downhole tool configured to be coupled to a work string that includes a tool body having a longitudinal bore for circulating a fluid and at least one aperture configured to receive at least one module. The system further includes a plurality of modules that are each configured to engage the at least one aperture and at least one cavity configured for receiving a probe, and a plurality of probes that each include at least one orifice configured for testing the formation, wherein a first of the plurality of probes has a first configuration and a second of the plurality of probes has a second configuration.

Abstract: A formation evaluation tool positionable in a wellbore penetrating a subterranean formation is provided. The formation evaluation tool includes a cooling system adapted to pass a cooling fluid through electronics in the formation evaluation tool whereby heat is dissipated therefrom, the electronics has at least one gauge, a fluid communication device having an inlet adapted to receive the formation fluid and a flowline operatively connected to the fluid communication device and the gauge for placing the formation fluid in fluid communication therewith whereby properties of the formation fluid are determined.

Abstract: A method of sampling fluid from a rock formation penetrated by a borehole includes positioning a downhole tool having a flow line in the borehole, establishing an inlet port through which fluid passes from a first point in the formation into the flow line, establishing an outlet port through which fluid passes from the flow line into a second point in the formation, and passing fluid between the formation and the flow line through the inlet and outlet ports.

Abstract: A method includes acquiring formation fluid sample information including pressure, volume, and temperature. Monotonic formation fluid information is extracted from the formation fluid sample information and a pressure, volume, temperature information set is constructed. A curvature sequence is estimated using a first partial derivative and a second partial derivative of pressure with respect to volume. A first maxima is estimated from the curvature sequence, and the formation fluid property is estimated using the estimated first maxima. A method may include a volume acceleration sequence estimated using a first partial derivative and a second partial derivative of the volume with respect to pressure. A first maxima is estimated from the volume acceleration sequence, and the formation fluid property is estimated at least in part by using the estimated first maxima. A method may include establishing a first linear regression model and predicting a confidence interval.

Abstract: A system for testing a subterranean formation penetrated by a well includes a downhole tool configured to be coupled to a work string that includes a tool body having a longitudinal bore for circulating a fluid and at least one aperture configured to receive at least one module. The system further includes a plurality of modules that are each configured to engage the at least one aperture and at least one cavity configured for receiving a probe, and a plurality of probes that each include at least one orifice configured for testing the formation, wherein a first of the plurality of probes has a first configuration and a second of the plurality of probes has a second configuration.

Abstract: The present application is directed to a method and apparatus for monitoring soil hydraulic properties, and for collecting soil pore-water samples, in relatively undisturbed soil conditions, by means of a vadose zone probe (10) adapted to be mounted on an inflatable sleeve (18) for installation in a borehole (14) formed in the vadose zone, said vadose zone probe comprises a fluid cell (15) having one or more conduits (13a, 13b, 13c) connected thereto for externally accessing its interior, and a porous medium (11) installed in, or formed on, one of its walls for allowing passage of liquid between the interior of said fluid cell and the borehole soil, wherein said vadose zone probe is made from an elongated body having a front (10f) and rear (10r) sides, and wherein said rear side is substantially flat and said front side is made from a deformable and permeable material, or having a curvature corresponding to the curvature of said borehole.

Abstract: A formation evaluation tool positionable in a wellbore penetrating a subterranean formation is provided. The formation evaluation tool includes a cooling system adapted to pass a cooling fluid near electronics in the formation evaluation tool whereby heat is dissipated therefrom, the electronics has at least one gauge, a fluid communication device having an inlet adapted to receive the formation fluid and a flowline operatively connected to the fluid communication device and the gauge for placing the formation fluid in fluid communication therewith whereby properties of the formation fluid are determined. The formation evaluation tool may also be provided with a plurality of sample chambers operatively connected to the flowline for collecting at least a portion of the formation fluid and a pressure compensator in fluid communication with the wellbore and operatively connected to the plurality of sample chambers for applying pressure to the sample chambers whereby pressure is balanced therebetween.

Abstract: An apparatus and method for use in determining pressure at a formation of interest in-situ. A carrier carrying a tool is conveyed in a borehole. The tool includes a sealing member and a port exposable to the formation of interest. A formation fluid sampling chamber is separated from a hydraulic fluid chamber by a flexible member that allows pressure communication from the fluid sampling chamber to the hydraulic fluid chamber. A sensor senses pressure in the hydraulic fluid for determining pressure in the sampling chamber.

Abstract: A method and apparatus for of determining a formation parameter of interest. The method includes placing a tool into communication with the formation to test the formation and drawing down a test volume at an increasing draw rate during a first draw period and decreasing the draw rate during a second draw period to create a smooth draw down cycle. The draw down can be step-wise or continuous. The formation parameter is determined using formation rate analyis and characteristics determined during the draw down cycle.

Abstract: An apparatus and method for characterizing a subsurface formation is provided. The apparatus includes a tool body, a probe assembly carried by the tool body for sealing off a region of the borehole wall, an actuator for moving the probe assembly between a retracted position for conveyance of the tool body and a deployed position for sealing off a region of the borehole wall and a perforator extending through the probe assembly for penetrating a portion of the sealed-off region of the borehole wall. The tool may be provided with first and second drilling shafts with bits for penetrating various surfaces. The method involves sealing off a region of a wall of an open borehole penetrating the formation, creating a perforation through a portion of the sealed-off region of the borehole wall and testing the formation.

Abstract: Embodiments of the present invention relate to systems and methods for real-time management of formation fluid sampling down a wellbore using a guarded probe. More specifically, but not by way of limitation, embodiments of the present invention provide for management of downhole fluid sampling by sensing properties of fluids collected by a downhole-fluid-sampling-device, modeling the fluid sampling process from these sensed properties and using the modeling of the fluid sampling process to manage in real-time the fluid sampling process.

Abstract: A system for testing a subterranean formation penetrated by a well includes a downhole tool configured to be coupled to a work string that includes a tool body having a longitudinal bore for circulating a fluid and at least one aperture configured to receive at least one module. The system further includes a plurality of modules that are each configured to engage the at least one aperture and at least one cavity configured for receiving a probe, and a plurality of probes that each include at least one orifice configured for testing the formation, wherein a first of the plurality of probes has a first configuration and a second of the plurality of probes has a second configuration.

Abstract: A method for testing petroleum or water wells. A tool is secured to a tubing and run into the well and to the reservoir zone to be explored. An upper and a lower seal isolate the reservoir zone. A piston is run into the tubing and pumped down to the tool. When sampling is to take place, a valve is opened and the reservoir fluid, together with drilling fluid filling the well, is allowed to enter the tool while displacing the piston. At the same time, measuring is carried out to identify a tracer added to the drilling fluid. When the tracer no longer can be traced, the drilling fluid contaminated reservoir fluid is displaced out of the tool by the piston and clean reservoir fluid is allowed to enter the tool. The invention also relates to an apparatus for practising the method.

Abstract: A sampling tool for retrieving one or more samples from a wellbore drilled in a subterranean formation includes a coring device retrieving a core from a wellbore wall, wellbore isolation devices that isolate an annular region proximate to the coring device; and a flow device that flows fluid out of the isolated region. During operation, the sampling tool is positioned adjacent a formation of interest. The isolation device is activated to isolate an annular region proximate to the sampling tool. Decentralizing arms can be used to position the coring device next to the wellbore wall. Thereafter, the flow device flows fluid out of the isolated annular region. When the isolated region includes mostly formation fluid, the coring device is activated to retrieve a core from a wall of the wellbore in the isolated annular region and store it in formation fluid.

Abstract: A method of retrieving a formation fluid from a formation adjacent a borehole wall includes estimating at least one of a permeability of the formation and a viscosity of the formation fluid. A first tool is selected based on the estimation, the first tool being selected from one of a heating and sampling tool, an injection and sampling tool, and a coring tool. An attempt to retrieve a formation fluid sample from the formation is then made with the first tool, and a formation fluid sample is retrieved from the formation. A second retrieval process may then be initiated, in which the second retrieval process includes increasing the mobility of the formation fluid.

Abstract: Methods for performing downhole fluid compatibility tests include obtaining an downhole fluid sample, mixing it with a test fluid, and detecting a reaction between the fluids. Tools for performing downhole fluid compatibility tests include a plurality of fluid chambers, a reversible pump and one or more sensors capable of detecting a reaction between the fluids.

Abstract: The present invention provides a chemometric equation to estimate fluid density, viscosity, dielectric constant and resistivity for a formation fluid sample downhole. The chemometric estimates can be used directly as estimated values for fluid density, viscosity, dielectric constant and resistivity for a formation fluid sample downhole. The chemometric estimates can also be plugged into a Levenberg-Marquardt (LM) non-linear least squares fit, as an initial estimate of the parameter to be estimated by the LM fit. If the initial parameter estimate is too far from the actual parameter values, the LM algorithm may take a long time to converge or even fail to converge entirely. The present invention estimates an initial value of a parameter that provides a high probability that the LM algorithm will converge to a global minimum.

Abstract: A downhole, extendable testing apparatus and methods of use are described and claimed herein. In one embodiment, an extendable sample device is connected to a draw down piston assembly. A position indicator may be used to show the position of the draw down piston during movement, and the draw down piston may be stopped and re-started, and moved at different rates. A filter may be used to clean fluids drawn into the extendable sample device. In another embodiment, the extendable sample device may connected to a hydraulic circuit. The hydraulic circuit may include accumulators for accumulating fluid pressures and operating the apparatus. Further apparatus and methods are disclosed herein.

Abstract: A sample module is provided for use in a downhole tool to obtain fluid from a subsurface formation penetrated by a wellbore. The sample module includes a sample chamber carried by the module for collecting a sample of formation fluid obtained from the formation via the downhole tool, and a validation chamber carried by the module for collecting a substantially smaller sample of formation fluid than the sample chamber. The validation chamber is removable from the sample module at the surface without disturbing the sample chamber. A sample chamber is also provided that includes a substantially cylindrical body capable of safely withstanding heating at the surface, following collection of a formation fluid sample via the downhole tool and withdrawal of the sample chamber from the wellbore, to temperatures necessary to promote recombination of the sample components within the chambers. Additionally, the body is equipped so as to be certified for transportation.

Abstract: The present invention provides a down hole spectrometer for determination of dew point pressure to determine an associated optimal pumping rate during sampling to avoid precipitation of asphaltenes in a formation sample. A sample is captured at formation pressure in a controlled volume. The pressure in the controlled volume is reduced. Initially the formation fluid sample appears dark and allows less light energy to pass through a sample under test. The sample under test, however, becomes lighter and allows more light energy to pass through the sample as the pressure is reduced and the formation fluid sample becomes thinner or less dense under the reduced pressure. At the dew point pressure, however, the sample begins to darken and allows less light energy to pass through it as apshaltenes begin to precipitate out of the sample. Thus, the dew point is that pressure at which peak light energy passes through the sample.

Abstract: A viscometer for a down hole tool positionable in a well bore penetrating a subterranean formation is described. The formation contains at least one fluid therein. The down hole tool is adapted to convey at least a portion of the fluid to the viscometer. The viscometer comprises a sensor unit, and at least one magnet. The sensor unit is positionable within the down hole tool and comprises at least two spatially disposed clamps and a wire suspended in tension between the at least two clamps such that the wire is available for interaction with the fluid when the viscometer is positioned within the down hole tool and the down hole tool is positioned within the subterranean formation and receives the fluid from the subterranean formation.

Abstract: An apparatus and method for determining at least one downhole formation property is disclosed. The apparatus includes a probe and a pretest piston positionable in fluid communication with the formation, and a series of flowlines pressure gauges, and valves configured to selectively draw into the apparatus for measurement of one of formation fluid and mud; The method includes performing a first pretest to determine an estimated formation parameter; using the first pretest to design a second pretest and generate refined formation parameters whereby formation properties may be estimated.

Abstract: A method and apparatus for sampling formation fluid includes drawing formation fluid from the subterranean formation into the downhole tool and collecting the formation fluid in a sample chamber. An exit flow line is operatively connected to the sample chamber for selectively removing a contaminated and/or clean portion of the formation fluid from the sample chamber whereby contamination is removed from the sample chamber. For example, a clean portion of the formation fluid may be passed to another sample chamber for collection, or a contaminated portion may be dumped into the borehole.

Abstract: A viscometer-densimeter for a down hole tool positionable in a well bore penetrating a subterranean formation is described. The formation contains at least one fluid therein. The down hole tool is adapted to convey at least a portion of the fluid to the viscometer-densimeter. The viscometer-densimeter comprises a sensor unit, and at least one magnet. The sensor unit is positionable within the down hole tool and comprises at least two spatially disposed connectors and a wire suspended in tension between the at least two connectors such that the wire is available for interaction with the fluid when the viscometer-densimeter is positioned within the down hole tool and the down hole tool is positioned within the subterranean formation and receives the fluid from the subterranean formation. The connectors and the wire are constructed so as to provide a frequency oscillator.

Abstract: The present invention provides a downhole method and apparatus using a flexural mechanical resonator, for example, a tuning fork to provide real-time direct measurements and estimates of the viscosity, density and dielectric constant of formation fluid or filtrate in a hydrocarbon producing well. The present invention additionally provides a method and apparatus for monitoring cleanup from a leveling off of viscosity or density over time, measuring or estimating bubble point for formation fluid, measuring or estimating dew point for formation fluid, and determining the onset of asphaltene precipitation. The present invention also provides for intercalibration of plural pressure gauges used to determine a pressure differential downhole. A hard or inorganic coating is placed on the flexural mechanical resonator (such as a tuning fork) to reduce the effects of abrasion from sand particles suspended in the flowing fluid in which the flexural mechanical resonator is immersed.

Abstract: A method and apparatus for testing formations surrounding an earth borehole. The method includes the following steps: providing a tool movable through the borehole; providing a flow line in the tool; establishing fluid communication between the formations and the flow line of the tool; and providing a sand trap in communication with the flow line of the tool for trapping sand flowing with fluid from the formations.

Abstract: A formation testing tool and method for providing pressure controlled sampling is provided. A flow line delivers formation fluid to a sample chamber in the testing tool. A first valve controls the flow of formation fluid from the flow line to the sample chamber. A piston is slidably disposed in the sample chamber to define a sample cavity and a actuation cavity having variable volumes determined by movement of the piston. An actuator is also provided to move the piston in a first direction to increase the volume of the sample cavity and a second direction to decrease the volume of the sample cavity whereby formation fluid may be drawn into the sample cavity and pressurized therein using the actuator and the first valve.

Abstract: An apparatus and method for determining at least one downhole formation property is disclosed. The apparatus includes a probe and a pretest piston positionable in fluid communication with the formation, and a series of flowlines pressure gauges, and valves configured to selectively draw into the apparatus for measurement of one of formation fluid and mud. The method includes performing a first pretest to determine an estimated formation parameter; using the first pretest to design a second pretest and generate refined formation parameters whereby formation properties may be estimated.

Abstract: The apparatuses and methods herein relate to techniques for extracting fluid from a subsurface formation. A downhole sampling tool is provided with a probe having an internal wall capable of selectively diverting virgin fluids into virgin flow channels for sampling, while diverting contaminated fluids into contaminated flow channels to be discarded. The characteristics of the fluid passing through the channels of the probe may be measured. The data generated during sampling may be sent to a controller capable of generating data, communicating and/or sending command signals. The flow of fluid into the downhole tool may be selectively adjusted to optimize the flow of fluid into the channels by adjusting the internal wall within the probe and/or by adjusting the flow rates through the channels. The configuration of the internal wall and/or the flow rates may be automatically adjusted by the controller and/or manually manipulated to further optimize the fluid flow.

Abstract: An apparatus and method for determining at least one downhole formation property is disclosed. The apparatus includes a probe and a pretest piston positionable in fluid communication with the formation, and a series of flowlines pressure gauges, and valves configured to selectively draw into the apparatus for measurement of one of formation fluid and mud. The method includes performing a first pretest to determine an estimated formation parameter; using the first pretest to design a second pretest and generate refined formation parameters whereby formation properties may be estimated.

Abstract: Disclosed is a method for transporting blended crude oils comprising the steps of; (a) admixing a first crude oil with a second, different crude oil to form a crude oil admixture; (b) determining a first value representing the content of unprecipitated asphaltenes in the admixture; (c) holding the admixture for a period of time at standard conditions; (d) determining a second value representing the content of unprecipitated asphaltenes in the admixture; and (e) either: (i) transporting the admixture if the second value is the same as or within a predetermined range of the first value; or (ii) taking remedial action to prevent asphaltene precipitation prior to transporting if the second value is outside a predetermined range from the first value. Also disclosed is a method for estimating the storage stability of stored crude oils and crude oil admixtures.