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DE60305816T2 - Method for measuring formation properties with time-limited formation test - Google Patents

Method for measuring formation properties with time-limited formation test Download PDF

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Publication number
DE60305816T2
DE60305816T2DE2003605816DE60305816TDE60305816T2DE 60305816 T2DE60305816 T2DE 60305816T2DE 2003605816 DE2003605816 DE 2003605816DE 60305816 TDE60305816 TDE 60305816TDE 60305816 T2DE60305816 T2DE 60305816T2
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pressure
formation
phase
flow line
test
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DE60305816D1 (de
Inventor
Jean-Marc Follini
Jean-Michel Hache
Julian J. Pop
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Schlumberger Technology BV
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Schlumberger Technology BV
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Priority to US434923priority
Priority to US10 / 434,923 priority patent / US7263880B2 / en
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Classifications

    • E — FIXED CONSTRUCTIONS
    • E21-EARTH DRILLING; MINING
    • E21B-EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B49 / 00 — Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
    • E21B49 / 008 — Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells by injection test; by analyzing pressure variations in an injection or production test, e.g. for estimating the skin factor
    • E — FIXED CONSTRUCTIONS
    • E21-EARTH DRILLING; MINING
    • E21B-EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B49 / 00 — Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
    • E21B49 / 08 — Obtaining fluid samples or testing fluids, in boreholes or wells
    • E21B49 / 10 — Obtaining fluid samples or testing fluids, in boreholes or wells using side-wall fluid samplers or testers

Description

  • BACKGROUND OF THE INVENTION
  • The present invention relates to the field of oil and gas exploration. More particularly, the invention relates to methods of determining at least one property of a subterranean formation penetrated by a borehole using a formation tester.
  • In the past few decades, state-of-the-art techniques have been developed to identify and extract hydrocarbons, commonly referred to as oil and gas, from subterranean formations. These techniques facilitate the discovery, assessment and production of hydrocarbons from subterranean formations.
  • Typically, when it is believed that a subterranean formation containing an economically recoverable amount of hydrocarbons has been discovered, a borehole is drilled from the surface of the earth to the desired subterranean formation and tests are performed on the formation to determine if the Formation hydrocarbons with commercial value can be produced. The tests performed on subterranean formations typically include interrogating infiltrated formations to determine the presence of hydrocarbons and to assess the amount of recoverable hydrocarbons contained therein. These preliminary tests are carried out using formation testing tools, often referred to as formation testers. Formation testers are typically lowered into a wellbore by a conduit, casing, drill string, or the like, and can be used to determine various formation characteristics that aid in determining the quality, quantity, and conditions of the hydrocarbons or other fluids contained therein . Other formation test equipment may be part of a drilling tool, such as a drill string, to measure formation parameters during the drilling process.
  • Formation testing equipment typically includes slimline tools designed to be lowered into a borehole and positioned at a depth in the borehole adjacent the subterranean formation from which data is desired. Once positioned in the wellbore, these tools are fluidly connected to the formation to collect data from the formation. Typically, a probe, snorkel, or other device is sealed into engagement with the borehole wall to establish such fluid communication.
  • Formation testers are typically used to measure downhole parameters such as downhole pressures, formation pressures and formation mobilities, and others. They can also be used to collect samples from a formation so that the types of fluid contained in the formation and other fluid properties can be determined. The formation properties, as determined during a formation test, are important factors in determining the commercial value of a production well and the manner in which hydrocarbons can be recovered from the production well.
  • The operation of formation testers can be more easily understood by referring to the construction of a conventional line-based formation tester shown in FIGS. As shown in Fig. 4, the piped tester is lowered from a derrick into an open borehole filled with a fluid commonly referred to in the industry as "mud". The borehole is lined with a filter cake which is deposited on the wall of the borehole during the drilling operations. The borehole penetrates a formation.
  • The operation of a conventional, modular, line-based formation tester having multiple interconnected modules is described in U.S. Patent Nos. 4,860,581 and 4,936,139 issued to Zimmerman et al. issued, are described in more detail. Figure 11 is a graph of a pressure versus time measured by the formation tester during operation of a conventional line-based formation tester used to measure parameters such as the formation tester. B. to determine the formation pressure.
  • In Figures 13 and 14, in the operation of a conventional line-based formation tester, a formation tester is lowered into a borehole by a conduit cable. After lowering the formation tester to the desired position in the wellbore, the pressure in the flow line in the formation tester can be equalized to the hydrostatic pressure of the fluid in the wellbore by opening a compensation valve (not shown). A pressure sensor or measuring device is used to measure the hydrostatic pressure of the fluid in the borehole. The pressure measured at this point is shown graphically along the line in FIG. The formation tester can then be "set up" by anchoring the tester in place with hydraulically actuated pistons, thereby positioning the probe on the side wall of the wellbore to establish fluid communication with the formation, and by closing the relief valve to remove the Isolate the interior of the tool from the downhole fluids. The point at which a seal is formed between the probe and the formation and fluid communication is established, referred to as the "tool set" point, is graphically shown in FIG. Fluid from the formation is then drawn into a preliminary test chamber by withdrawing a piston into the formation tester to create a pressure drop in the flow line below formation pressure. This volume expansion cycle, referred to as a "depressurization" cycle, is graphed along the line in FIG.
  • When piston retraction is halted (shown at dot in FIG. 6), fluid from the formation continues to enter the probe until, after a sufficient time, the pressure in the flow line equals the pressure in the formation, as shown at reference number in FIG. This cycle, referred to as a "pressurize" cycle, is shown along the line in FIG. As shown in Figure 12, it is commonly believed that the final build-up pressure at the numeral, often referred to as the "sand face" pressure, is a good approximation of the formation pressure.
  • The shape of the curve and the corresponding data generated by the pressure history can be used to determine various formation characteristics. For example, pressures measured during depressurization (in) and pressure build-up (in) can be used to determine formation mobility, which is the ratio of formation permeability to formation fluid viscosity. When the formation tester probe is detached from the borehole wall, the pressure in the flow line increases rapidly until the pressure in the flow line equals the pressure of the borehole, as shown in FIG. After the formation measurement cycle has been completed, the formation tester can be detached and repositioned at a different depth, with the formation test cycle repeated if necessary.
  • During this type of wireline tool test operation, pressure data collected downhole is typically electronically transmitted to the surface via the pipeline communication system. On the surface, an operator typically monitors the pressure in the flow line at a console and the pipeline recording system records the pressure data in real time. Data recorded during the depressurization and build-up cycles of the test can be analyzed either on the downhole computer in real time or later in a data processing center to determine critical formation parameters such as formation fluid pressure, mud overpressure, e.g. H. determine the difference between the wellbore pressure and the formation pressure, and the mobility of the formation.
  • Wired formation test facilities enable rapid data transfers for real-time monitoring and control of the test and tool through the use of wired telemetry. This type of communication system enables field engineers to assess the quality of test measurements as they arise and, if necessary, take immediate action to abort a test procedure or set pre-test parameters before attempting further measurements. By observing the data as it is collected during the pre-test depressurization, an engineer can e.g. B. have the option of changing the initial pre-test parameters, such as the rate and extent of depressurization, to better match the formation characteristics before attempting another test. Examples of line-based formation test equipment and / or formation test methods of the prior art are e.g. See, for example, U.S. Patents No. 3,934,468 issued to Brieger, No. 4,860,581 and No. 4,936,139 issued to Zimmerman et al. and No. 5,969,241 issued to Auzerais. These patents are assigned to the assignee of the present invention.
  • Formation testers can also be used during drilling operations. One such downhole tool suitable for collecting data from a subterranean formation during drilling operations is e.g. See, for example, U.S. Patent No. 6,230,557 B1 issued to Ciglenec et al. assigned to the assignee of the present invention.
  • Various techniques have been developed to carry out specific formation test operations or preliminary tests. U.S. Patents 5,095,745 and 5,233,866, both issued to Des Brandes, describe e.g. B. a method of determining formation parameters by analyzing the point at which the pressure deviates from a linear pressure drop.
  • Despite the advantages made in developing methods for performing pre-tests, there remains a need to eliminate delays and errors in the pre-test process and to improve the accuracy of the parameters derived from such tests. Since formation testing operations are used throughout the drilling operations, the duration of testing and the lack of real-time connectivity with the tools are significant limitations that must be considered.The problems associated with real-time connectivity for these operations arise primarily from the current limitations of telemetry typically used during pre-operations, such as mud pulse telemetry. Limitations such as rates of telemetry data in the uplink and downlink mostly for logging while drilling or measuring tools while drilling result in slow information exchange between the downhole tool and the surface. A simple process of sending a preliminary pressure history to the surface, whereupon an engineer sends a command downhole to retract the probe based on the transmitted data, can cause significant delays that adversely affect drilling operations.
  • Delays also increase the possibility that the tools will get stuck in the wellbore. To reduce the possibility of getting stuck, drilling operation specifications are often established based on the prevailing formation and drilling conditions to determine how long a drill string can be immobile in a borehole. According to these specifications, a drill string is only allowed to be immobile for a limited period of time in order to use a measuring head and take a pressure measurement. Due to the limitations of current real-time communications between some tools and the surface, it may be desirable for the tool to be able to perform nearly all operations in an automatic mode.
  • Therefore, what is desired is a method which enables a formation tester to be used to take formation test measurements in a wellbore in a specified period of time and which can be easily implemented using line-assisted tools or drilling tools that require minimal interference from the surface system Have consequence.
  • SUMMARY OF THE INVENTION
  • A method of determining formation parameters using a downhole tool positioned in a borehole adjacent a subterranean formation is provided. The method includes the steps of: establishing fluid communication with the formation; Performing a first preliminary test to determine an initial estimate of the formation parameters; Designing pre-test criteria to perform a second pre-test based on the initial estimate of the formation parameters; and performing a second pre-test in accordance with the designed pre-test criteria, thereby determining a refined estimate of the formation parameters.
  • Methods are also provided for determining formation properties using a formation tester.
  • Methods are also provided for determining a condition for terminating a depressurization operation during a pre-test.
  • Methods for determining formation fluid mobilities are provided.
  • Methods are provided for estimating formation pressures from drawdown operations during preliminary tests.
  • In another aspect, the invention relates to a method of determining wellbore parameters using a downhole tool positioned in a wellbore adjacent a subterranean formation. The method comprises the steps of: establishing fluid communication between a pilot chamber in the downhole tool and the formation via a flow line (with an initial pressure in the flow line); Moving a pre-test piston positioned in the pre-test chamber in a controlled manner to reduce the initial pressure to a down pressure; Stopping the movement of the piston to allow the descent pressure to be adjusted to a stabilized pressure; and repeating the steps until a difference between the stabilized pressure and the initial pressure is substantially less than a predetermined pressure drop. One or more wellbore parameters can then be determined from an analysis of one or more of the pressures. An initial estimate of the formation parameters from an analysis of one or more of the pressures and pre-test criteria to perform a second pre-test based on the initial estimate of the formation parameters can be determined and a pre-test of the formation in accordance with the designed pre-test criteria can be carried out, whereby a refined estimate of the formation parameters is determined .
  • In another aspect, the invention relates to a method of estimating formation pressure using a formation tester located in a wellbore penetrating a formation. The method includes the steps of: measuring a first pressure in a flow line in fluid communication with the subterranean formation; Moving a pilot piston in a controlled manner in a pilot chamber to create a predetermined pressure drop in the flow conduit; Stopping the pilot piston after a selected movement of the pilot piston; Allow the pressure in the flow line to stabilize; and repeating the steps until a difference between the stabilized pressure in the flow line and the first pressure in the flow line is substantially less than a predetermined pressure drop. The formation pressure can then be determined from a final stabilized pressure in the flow line.
  • Other aspects and advantages of the invention will become apparent from the following description and the appended claims.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • Figure 12 shows a conventional conducted formation tester located in a borehole;
  • FIG. 13 is a sectional view of the modular conventional wired formation tester of FIG.
  • Figure 12 is a graph of the pressure measurement as a function of time for a typical prior art pre-test sequence performed using a conventional formation tester;
  • Figure 12 shows a flow chart of steps involved in a pre-test according to an embodiment of the invention;
  • Figure 13 shows a schematic of components of a module of a formation tester suitable for practicing embodiments of the invention;
  • FIG. 13 is a graph of a pressure measurement as a function of time for performing the pre-test of FIG.
  • FIG. 14 is a flow chart detailing the steps involved in carrying out the exploration phase of the flow chart of FIG.
  • FIG. 14 is a detailed view of the investigation phase portion of the illustration showing the completion of the depressurization; FIG.
  • FIG. 13 is a detailed view of the investigation phase portion of the diagram of FIG. 14 depicting the determination of the termination of pressure build-up; FIG.
  • FIG. 14 is a flow chart detailing the steps involved in performing the measurement phase of the flow chart of FIG.
  • Figure 12 shows a flow chart of steps involved in a pre-test according to an embodiment of the invention that includes a mud compressibility phase;
  • FIG. 13 is a graph of a pressure measurement as a function of time for performing the pre-test of FIG.
  • shows the corresponding rate of volume change;
  • FIG. 14 is a flow chart detailing the steps involved in performing the mud compressibility phase of the flow chart of FIG.
  • Figure 12 shows a flow chart of steps involved in a pre-test including a sludge filtering phase in accordance with an embodiment of the invention;
  • FIG. 13 is a graph of one of pressure measurements as a function of time for performing the pre-test of FIG.
  • shows the corresponding rate of volume change;
  • FIG. 14 shows the modified sludge compressibility phase of FIG. 4 modified for use with the sludge filtering phase;
  • Figures 10-C show a flow chart detailing the steps involved in performing the mud filtering phase of the flow chart of Figure 14, showing a mud filtering phase, showing a modified mud filtering phase with a repetitive compression cycle, and showing a modified mud filtering phase with a decompression cycle;
  • Figure 3 shows a graph of pressure measurements as a function of time for performing a pre-test that includes a modified test phase in accordance with an embodiment of the invention;
  • shows the corresponding rate of volume change;
  • FIG. 13 is a flow chart detailing the steps involved in performing the modified exploration phase of FIG.
  • Figure 3 shows a graph of pressure measurements as a function of time for performing a pre-test including a modified test phase, according to an embodiment of the invention;
  • shows the corresponding rate of volume change;
  • FIG. 14 is a flow chart detailing the steps involved in performing the modified exploration phase of FIG. and
  • Figure 12 shows a fluid compressibility correction list that can be used to provide corrected mud compressibility when the original mud compressibility is performed at a different temperature and / or pressure.
  • An embodiment of the present invention relating to a method for estimating formation properties (e.g., formation pressures and mobilities) is shown in the block diagram of FIG. As shown in FIG. 4, the method includes an investigation phase and a measurement phase.
  • The method can be carried out with any formation tester known in the art, such as the tester described with reference to FIGS. Other formation testers may also be used and / or adapted to embodiments of the invention, such as the conducted formation testers of U.S. Patent Nos. 4,860,581 and 4,936,139 issued to Zimmerman et al. and the downhole drilling tool of U.S. Patent No. 6,230,557 B1 issued to Ciglenec et al. was granted.
  • One version of a probe module that can be used with such formation testers is shown in FIG. The module includes a probe, a sealing device surrounding the probe, and a flow line extending from the probe into the module. The flow line extends from the measuring sensor to the measuring sensor isolating valve and has a pressure measuring device. A second flow line extends from the probe isolation valve to the sample line isolation valve and to the equalization valve and has a pressure measuring device. A reversible pre-test piston in a pre-test chamber also extends from the flow line. The outlet conduit extends from the equalization valve and out of the wellbore and has a pressure gauge. The sample flow line extends from the sample line isolation valve and through the tool. Fluid whose sample is in the flow line can be stored, flushed, or used for other purposes.
  • The probe isolation valve separates fluid in the flow line from fluid in the flow line. The sample line isolation valve separates fluid in the flow line from fluid in the sample line. The equalization valve separates fluid in the wellbore from fluid in the tool. By operating the valves to selectively isolate fluid in the fluid lines, the pressure measuring device and can be used to determine various pressures. For example, by closing the valve, formation pressure can be measured by the gauge when the probe is in fluid communication with the formation, minimizing the tool volume associated with the formation.
  • In a further example, when the equalizing valve is open, mud can be drawn from the borehole into the tool with the aid of the pilot piston. Upon closing the equalization valve, probe isolation valve, and sample line isolation valve, fluid in the tool can become trapped between these valves and the pilot piston. The pressure gauge can be used to continuously monitor the downhole fluid pressure during operation of the tool and can be used in conjunction with the pressure gauges and / or to directly measure the pressure drop across the filter cake and the transmission of borehole disturbances through the filter cake for later use monitor for these disturbances in correcting the measured sand surface pressure.
  • One of the functions of the pilot piston is to draw or introduce fluid into the formation, or to compress or expand fluid trapped between the probe isolation valve, sample line isolation valve, and the equalization valve. The Vorprüfkolben preferably has the possibility, at low rates, z. B. 0.01 cm3/ s and at high rates, e.g. B. 10 cm3/ s and has the ability to handle large volumes in a single stroke, e.g. B. 100 cm3 to suck in. If it is necessary, more than 100 cm3 Also, to prime from the formation without retracting the probe, the pilot piston can be reused. The position of the pilot piston can preferably be continuously monitored and positively controlled, and its position can be "locked" when it is in a rest position. In some embodiments, the probe may further include a filter valve (not shown) and a filter piston (not shown).
  • Various actuations of the valves, the pre-test piston and the measuring sensor enable the tool to be operated in accordance with the methods described. While these specifications define a preferred probe module, one skilled in the art will recognize that other specifications can be used without departing from the scope of the invention. While a module is of the probe type, it will be appreciated that either a probe tool or a sealing tool may be used with some modifications. In the following description, it is assumed that a probe tool is used. However, one skilled in the art will appreciate that similar procedures can be used with sealing tools.
  • The techniques disclosed herein can also be used with other devices that include a flow conduit. As used herein, the term "flow conduit" is intended to refer to a conduit, cavity, or other passage for providing fluid communication between the formation and the pilot piston and / or for allowing fluid to flow between them. Other such devices can be, for. B. contain a device in which the probe and the preliminary test piston are integrally formed. An example of such a device is shown in US Patent No. 6,230,557 B1 and in US Patent Application Serial No. 10 / 248,782 assigned to the assignee of the present invention.
  • As shown in Figure 10, the exploration phase involves obtaining initial estimates of formation parameters, such as formation pressure and formation mobility. These initial estimates can then be used to design the measurement phase. If so desired and allowed, a measurement phase is then carried out according to these parameters in order to produce a refined estimate of the formation parameters. FIG. 12 represents a corresponding pressure curve which illustrates the changes in pressure as a function of time when the method of FIG. While the pressure history of FIG. 14 can be obtained by the apparatus of FIG. 10, it will be appreciated that it can also be obtained by other downhole tools such as the test equipment of FIGS.
  • The investigation phase is shown in more detail in. The investigation phase includes the triggering of the pressure reduction after the tool at time t3 for the duration Ti has been set up, the execution of the pressure reduction, the termination of the pressure reduction, the execution of the pressure build-up and the end of the pressure build-up. To begin the exploration phase of step 11, the probe is placed in fluid communication with the formation and anchored in place with the interior of the tool separated from the borehole. The pressure reduction is carried out by advancing the piston into the pre-test chamber. To stop the pressure reduction, the piston is stopped. The pressure begins to build up in the flow line until the pressure build-up at the reference symbol is ended. The investigation phase has a duration TIP. The investigation phase can also be carried out as described above with reference to FIGS. 12 and 14, with the depressurization flow rate and the depressurization termination point being defined in advance before the investigation phase is initiated.
  • The pressure curve of the examination phase is shown in more detail in.Parameters such as the formation pressure and the formation mobility can be determined from an analysis of the data derived from the pressure curve of the investigation phase. The termination point represents e.g. B. A tentative estimate of the formation pressure. Alternatively, formation pressures can be estimated more accurately by extrapolating the pressure trend obtained during pressure build-up using techniques known to one skilled in the art, the extrapolated pressure corresponding to the pressure that would be obtained if the Pressure build-up continues indefinitely. Such procedures may require additional processing to preserve the formation pressure.
  • The formation mobility (K / μ)1 can also be determined from the pressure build-up phase represented by the line. Techniques known to one skilled in the art can be used to estimate formation mobility from the rate of pressure change as a function of time during pressure build-up. Such procedures may require additional processing to obtain formation mobility estimates.
  • The work presented in a publication by Goode et al. entitled "Multiple Probe Formation Testing and Vertical Reservoir Continuity," SPE 22738 and is available for presentation at the 1991 Society of Petroleum Engineers Annual Technical Conference and Exhibition, held in Dallas, Texas October 6-9, 1991 alternatively, implies that the area of ​​the graph which is represented by the hatched area and identified by the reference symbol and is indicated here with A can be used for a prediction of the formation mobility. This area is indicated by a line extending horizontally from the termination point (representing the estimated formation pressure P.350 at termination), delimits the pressure decrease line and the pressure build-up line. This area can be determined and related to an estimate of formation mobility using the following equation:
    where (K / μ)1 is the first estimate of the formation mobility (D / cP), where K is the formation permeability (Darcy, denoted by D) and μ is the formation fluid viscosity (cP) (since the quantity determined by the formation testers is the ratio of the formation permeability to the formation fluid viscosity, i.e. the Mobility, the explicit value of viscosity is not needed); V1 (cm3) is the volume extracted from the formation during the preliminary survey, V1 = V (t7 + T1) - V (t7 - T0) = V (t7) - V (t7 - T0), where V is the volume of the pre-test chamber, rp is the probe radius (cm), and εK is an error term that is typically small (less than a few percent) for formations with a mobility greater than 1 mD / cP.
  • The variable ΩS., which accounts for the effect of a finite size borehole on the pressure behavior of the probe, can be determined by the following equation found in a paper by FJ Kuchuk entitled "Multiprobe Wireline Formation Tester Pressure Behavior in Crossflow-Layered Reservoirs," In Situ , (1996) 20, 1, 1: where rp and rw represent the radius of the probe and the radius of the borehole, respectively; ρ = rp/ rw, η = Kr/ Kz; ϑ = 0.58 + 0.078logη + 0.26logρ + 0.8ρ2; and Kr and Kz represent the radial permeability and the vertical permeability, respectively.
  • In obtaining the result presented in Equation 1, it was assumed that the formation permeability is isotropic; H. Kr = Kz = K, the flow regime is "spherical" during the test and the conditions that ensure the validity of the Darcy relationship apply.
  • Furthermore, the pressure reduction step of the examination phase can be analyzed in order to determine the pressure drop as a function of time in order to determine various characteristics of the pressure curve. A best fit line derived from points along the drawdown line is shown and extends from the trigger point. A point of deviation can be determined along the curve which represents the point at which the curve has a minimum deviation δ0 Reached from the best adapted line. The point of departure can be used as an estimate of the "onset of flow", the point at which fluid is delivered from the formation into the tool during the depressurization of the survey phase.
  • The point of deviation can be determined by known techniques, such as the techniques disclosed in U.S. Patent Nos. 5,095,745 and 5,233,866, both issued to Desbrandes. Desbrandes teaches a technique for estimating formation pressure from the point of departure from a best-fit line generated using data points from the depressurization phase of the pre-test. Alternatively, the point of deviation may be determined by examining the most recently acquired point to see if it sticks to the linear trend representing the extent of the flow line as successive pressure data is acquired. If this is not the case, the pressure reduction can be stopped and the pressure can be allowed to stabilize. The point of deviation can also be determined using the time derivative of the pressure recorded during. If the derivative changes by 2 to 5% (it is likely to be smaller), the appropriate point is used to represent the beginning of a flow out of the formation. To confirm, if necessary, that the diversion from the expansion line represents flow from the formation, additional small volume preliminary tests may be performed.