Device and method for improving accuracy of core water permeability measurement

Abstract

The present invention provides a device and method for improving the accuracy of core water permeability measurement, belonging to the technical field of reservoir development. The device provided by the present invention utilizes the principle of simulating the density difference between water and displacement fluid, and uses two different intermediate containers to test the flow friction resistance of simulated water and displacement fluid in a pipeline of unit length, which can reduce the influence brought by the flow friction resistance; by setting four pressure gauges to measure the pressure difference at different heights, the driving force generated by the instrument and equipment at different spatial positions can be determined, so as to facilitate the elimination of these errors in subsequent calculation of core water permeability measurement, and achieve the goal of improving the accuracy of core water permeability measurement. The results of the embodiments show that using the device provided by the present invention to test and calculate the core water permeability can effectively reduce the experimental error of the previous test method and ensure the accuracy of the core water permeability experiment.

Description

Technical Field

[0001] The present invention relates to the technical field of reservoir development, and particularly relates to a device and a method for improving the accuracy of core water permeability measurement. Background Art

[0002] Reservoir rocks are porous media. Permeability is the property that indicates the ability of a rock to allow fluids (oil, gas, water) to pass through under a certain pressure difference. The magnitude of permeability is represented by permeability, which is one of the physical properties of the reservoir. The permeability of the rock directly affects the production of oil and gas wells and is the basic data for oil and gas migration, accumulation, and oil and gas field development. Permeability can evaluate the difficulty and effect of oil and gas extraction. In different geological reservoirs, the permeability varies greatly. Accurate permeability is crucial for reservoir understanding, reservoir analysis, and reservoir evaluation in the process of oil and gas field development.

[0003] Currently, petroleum scientists and technicians use the conventional displacement process and combine it with the petroleum and natural gas industry standard (SY / T5336 - 2006) to measure the core water permeability. However, due to problems such as pressure differences and frictional resistances generated by the height differences between pipelines and various instruments in the experimental process, the test results do not match well with each other, the error of the measured core water permeability is relatively large, and the calculation results are uncertain, thus greatly affecting reservoir understanding, reservoir analysis, and reservoir evaluation in the process of oil and gas field development.

[0004] Therefore, how to overcome the problem of experimental errors caused by inconsistent test processes in the existing core water permeability measurement methods and improve the accuracy of core water permeability measurement has become an urgent technical problem in this field. Summary of the Invention

[0005] The purpose of the present invention is to provide a device and a method for improving the accuracy of core water permeability measurement. The method provided by the present invention eliminates problems such as pressure differences and frictional resistances generated by the height differences between pipelines and various instruments in the experimental process, and ensures the accuracy of core water permeability measurement.

[0006] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a device for improving the accuracy of core water permeability measurement, including a core holder;

[0008] One end of the core holder is connected to the bottom of a pressure gauge 4, a pressure gauge 3, and an intermediate container I in sequence through pipelines;

[0009] The pressure gauge 3 is connected to a support base;

[0010] The top of the intermediate container I is connected to the top of an intermediate container II through a pipeline;

[0011] The top end of the intermediate container I is connected to the pressure gauge 2;

[0012] The top end of the intermediate container II is connected to the pressure gauge 1;

[0013] The bottom of the intermediate container II is connected to a constant flow pump through a pipeline.

[0014] Preferably, the other end of the core holder is connected to a collector through a pipeline;

[0015] The middle and upper part of the core holder is connected to a hand pump and a liquid storage cup through a pipeline.

[0016] The present invention provides a method for improving the accuracy of core water permeability measurement. The test is carried out using the device described in the above technical solution, including the following steps:

[0017] (1) Respectively test the flow friction resistance f1 of the simulated water in the pipeline per unit length and the flow friction resistance f2 of the displacement fluid in the pipeline per unit length;

[0018] (2) Calculate the injection-production end pressure difference ΔP of the core holder by using the flow friction resistances f1 and f2 obtained in the step (1);

[0019] (3) Calculate the core water permeability K by using the injection-production end pressure difference ΔP of the core holder obtained in the step (2).

[0020] Preferably, the simulated water in the step (1) is any one of distilled water, deionized water, formation water, and oilfield simulated injection water.

[0021] Preferably, the displacement fluid in the step (1) is any one of white oil and aviation kerosene.

[0022] Preferably, the test method for the flow friction resistance of the simulated water and the displacement fluid in the pipeline per unit length in the step (1) includes the following steps:

[0023] 1) Place the core in the core holder, then connect the constant flow pump, the intermediate container of the simulated water, the intermediate container of the displacement fluid, the hand pump, and the core holder, and then adjust each valve to obtain the installed experimental equipment;

[0024] 2) Increase the confining pressure of the core holder in the installed experimental equipment obtained in the step 1) to 3 MPa, and then ensure that the confining pressure of the core holder and the injection pressure are not lower than 1.5 MPa during the test to obtain the device before displacement;

[0025] 3) Inject simulated water and displacement fluid into the device before displacement in step 2) at an injection rate of 0.5 - 1 mL / min respectively for displacement. After the outlet flow rate is stable, record the readings of pressure gauges 1 - 4 and the flow rate, and calculate the flow friction resistance f1 of the simulated water per unit length of the pipeline and the flow friction resistance f2 of the displacement fluid per unit length of the pipeline through the pressure difference of the pressure gauges.

[0026] Preferably, the calculation method of the flow friction resistance f1 of the simulated water per unit length of the pipeline in step 3) is shown in Equation I:

[0027] f1 = (P3 - P4 - ρ1gh1) / L1 Equation I;

[0028] In Equation I, f1 is the flow friction resistance of the simulated water per unit length of the pipeline, with the unit of MPa / m; P3 is the pressure reading of pressure gauge 3, with the unit of MPa; P4 is the pressure reading of pressure gauge 4, with the unit of MPa; ρ1 is the density of the simulated water, with the unit of g / cm 3 ; g is the acceleration due to gravity; h1 is the height difference between pressure gauges 3 and 4, with the unit of m; L1 is the length of the pipeline between pressure gauges 3 and 4, with the unit of m.

[0029] Preferably, the calculation method of the flow friction resistance f2 of the displacement fluid per unit length of the pipeline in step 3) is shown in Equation II:

[0030] f2 = (P1 - P2 - ρ2gh2) / L2 Equation II;

[0031] In Equation II, f2 is the flow friction resistance of the displacement fluid per unit length of the pipeline, with the unit of MPa / m; P1 is the pressure reading of pressure gauge 1, with the unit of MPa; P2 is the pressure reading of pressure gauge 2, with the unit of MPa; ρ2 is the density of the displacement fluid, with the unit of g / cm 3 ; g is the acceleration due to gravity; h2 is the height difference between pressure gauges 1 and 2, with the unit of m; L2 is the length of the pipeline between pressure gauges 1 and 2, with the unit of m.

[0032] Preferably, the calculation method of the pressure difference ΔP at the injection and production ends of the core holder in step (2) is shown in Equation III:

[0033] ΔP = P2 + g[ρ2h5 + ρ1h3 - (ρ1 - ρ2)h i - ρ1h4] - f1s1 - f2s2 Equation III;

[0034] In Equation III, ΔP is the pressure difference at the injection and production ends of the core holder, with the unit of 10 -1 MPa; P2 is the pressure reading of pressure gauge 2, with the unit of MPa; g is the acceleration due to gravity; ρ1 is the density of the simulated water, with the unit of g / cm3 ; ρ2 is the density of the displacement fluid, with the unit of g / cm 3 ; h i is the cumulative injection height of the displacement fluid, with the unit of m; h3 is the height of the intermediate container of the simulated water, with the unit of m; h4 is the height difference between the discharge end of the intermediate container of the simulated water and the injection end of the core holder, with the unit of m; h5 is the height difference between the injection end of the pressure gauge 2 and the intermediate container of the simulated water, with the unit of m; f1 is the flow friction resistance of the simulated water in the pipeline per unit length, with the unit of MPa / m; s1 is the length of the pipeline containing the simulated water between the pressure gauge 2 and the core injection end, with the unit of m; f2 is the flow friction resistance of the displacement fluid in the pipeline per unit length, with the unit of MPa / m; s2 is the length of the pipeline containing the displacement fluid between the pressure gauge 2 and the core injection end, with the unit of m.

[0035] Preferably, the calculation method of the core water permeability K in the step (3) is shown in Equation IV:

[0036] K = QμL / AΔP Equation IV;

[0037] In Equation IV, K is the core water permeability, with the unit of μm 2 ; Q is the flow rate through the core, with the unit of cm 3 / s; μ is the viscosity of the simulated water, with the unit of mPa·s; L is the length of the core, with the unit of cm; A is the cross-sectional area of the core, with the unit of cm 2 ; ΔP is the pressure difference between the injection and production ends of the core holder, with the unit of 10 -1 MPa.

[0038] The present invention provides a device for improving the accuracy of core water permeability measurement, including a core holder; one end of the core holder is connected to the bottom of the pressure gauge 4, the pressure gauge 3 and the intermediate container I in sequence through pipelines; the pressure gauge 3 is connected to the support base; the top end of the intermediate container I is connected to the top end of the intermediate container II through a pipeline; the top end of the intermediate container I is connected to the pressure gauge 2; the top end of the intermediate container II is connected to the pressure gauge 1; the bottom of the intermediate container II is connected to a constant flow pump through a pipeline. The device provided by the present invention utilizes the principle of the density difference between the simulated water and the displacement fluid, and uses two different intermediate containers to measure the flow friction resistance of the simulated water and the displacement fluid in the pipeline per unit length, which can reduce the influence brought by the flow friction resistance; by setting four pressure gauges to measure the pressure differences at different heights, the driving forces generated by the instrument and equipment at different spatial positions can be determined, so as to facilitate the elimination of these errors when calculating the core water permeability subsequently, and achieve the goal of improving the accuracy of core water permeability measurement. The results of the embodiments show that using the device provided by the present invention to test and calculate the core water permeability can effectively reduce the experimental errors of the previous test methods and ensure the accuracy of the core water permeability experiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the experimental equipment for improving the accuracy of core water permeability measurement provided by the present invention;

[0040] Figure 2 Schematic diagram of the experimental equipment for conventional core water permeability measurement. DETAILED DESCRIPTION

[0041] The present invention provides a device for improving the accuracy of core water permeability measurement, comprising a core holder;

[0042] One end of the core holder is connected to the pressure gauge 4, the pressure gauge 3 and the bottom of the intermediate container 1 in sequence through pipelines;

[0043] The pressure gauge 3 is connected to the bracket base;

[0044] The top of the intermediate container I is connected to the top of the intermediate container II through a pipeline;

[0045] The top of the intermediate container 1 is connected to the pressure gauge 2;

[0046] The top of the intermediate container II is connected to the pressure gauge 1;

[0047] The bottom of the intermediate container II is connected to a constant flow pump through a pipeline.

[0048] like Figure 1 As shown, the device for improving the accuracy of core water permeability measurement provided by the present invention includes a core holder. The present invention has no special restrictions on the specific size and structure of the core holder, as long as it can stabilize the core.

[0049] like Figure 1 As shown, in the present invention, one end of the core holder is connected to a pressure gauge 4, a pressure gauge 3, and the bottom of the intermediate container 1 in sequence through pipelines. The present invention has no particular limitation on the specific sources of the pressure gauges 4 and 3; any pressure gauge familiar to those skilled in the art that can accurately display pressure can be used.

[0050] In one embodiment of the present invention, the height of the pressure gauge 4 is higher than that of the pressure gauge 3. The present invention has no particular limitation on the specific heights of the pressure gauges 4 and 3, and they can be determined according to the technical common sense of those skilled in the art.

[0051] The present invention has no particular limitation on the specific structure of the intermediate container 1, and any intermediate container well known to those skilled in the art can be used. In one embodiment of the present invention, the intermediate container 1 is an intermediate container for holding simulated water.

[0052] In the present invention, the pressure gauge 3 is connected to the bracket base.

[0053] In the present invention, the top end of the intermediate container I is connected to the top end of the intermediate container II through a pipeline.

[0054] In the present invention, the top end of the intermediate container I is connected to the pressure gauge 2. In the present invention, the top end of the intermediate container II is connected to the pressure gauge 1. In an embodiment of the present invention, the height of the pressure gauge 2 is higher than that of the pressure gauge 1. The present invention does not have special limitations on the specific heights of the pressure gauge 1 and the pressure gauge 2, and they can be determined according to the technical common sense of those skilled in the art.

[0055] In the present invention, the bottom of the intermediate container II is connected to a constant flow pump through a pipeline.

[0056] In the present invention, the other end of the core holder is connected to a collector through a pipeline. By setting the collector in the present invention, the liquid flowing out of the core can be collected.

[0057] In the present invention, the middle upper part of the core holder is connected to a hand pump and a liquid storage cup through a pipeline. The present invention uses the hand pump to transport the liquid in the liquid storage cup to the core holder through the pipeline.

[0058] The device provided by the present invention utilizes the principle of simulating the density difference between water and displacement fluid, and uses two different intermediate containers to test the flow friction resistance of simulated water and displacement fluid in a pipeline of unit length, which can reduce the influence brought by the flow friction resistance; by setting four pressure gauges to measure the pressure difference at different heights, the driving force generated by the instrument and equipment at different spatial positions can be determined, so as to facilitate the subsequent elimination of these errors when calculating the water permeability of the core by water measurement, and achieve the goal of improving the accuracy of the water permeability measurement of the core by water measurement.

[0059] The present invention also provides a method for improving the accuracy of water permeability measurement of the core. Using the device described in the above technical solution for testing, it includes the following steps:

[0060] (1) Respectively test the flow friction resistance f1 of simulated water in a pipeline of unit length and the flow friction resistance f2 of displacement fluid in a pipeline of unit length;

[0061] (2) Calculate the injection-production end pressure difference ΔP of the core holder by using the flow friction resistances f1 and f2 obtained in the step (1);

[0062] (3) Calculate the water permeability K of the core by water measurement by using the injection-production end pressure difference ΔP of the core holder obtained in the step (2).

[0063] The present invention respectively tests the flow friction resistance f1 of simulated water in a pipeline of unit length and the flow friction resistance f2 of displacement fluid in a pipeline of unit length.

[0064] In the present invention, the simulated water is preferably any one of distilled water, deionized water, formation water, and simulated injection water for oilfields, more preferably any one of formation water and simulated injection water for oilfields; the displacement fluid is preferably any one of white oil and aviation kerosene, more preferably white oil. The present invention does not have special limitations on the specific sources of the simulated water and the displacement fluid, and commercially available products well-known to those skilled in the art can be used. By separately testing the flow friction resistance f1 of the simulated water in a pipeline per unit length and the flow friction resistance f2 of the displacement fluid in a pipeline per unit length, the present invention can eliminate the errors caused by the flow friction resistance of the simulated water and the displacement fluid through subsequent calculation processes, thereby ensuring the accuracy of the water permeability measurement of the core.

[0065] In the present invention, the test method for the flow friction resistance of the simulated water and the displacement fluid in a pipeline per unit length preferably includes the following steps:

[0066] 1) Place the core in a core holder, then connect a constant flow pump, an intermediate container for the simulated water, an intermediate container for the displacement fluid, a hand pump, and the core holder. Then adjust each valve to obtain the installed experimental equipment;

[0067] 2) Increase the confining pressure of the core holder in the installed experimental equipment obtained in step 1) to 3 MPa, and then ensure that the confining pressure of the core holder and the injection pressure are not less than 1.5 MPa during the test to obtain the device before displacement;

[0068] 3) Inject the simulated water and the displacement fluid into the device before displacement obtained in step 2) at an injection rate of 0.5 - 1 mL / min for displacement. After the outlet flow rate is stable, record the readings and flow rates of pressure gauges 1 - 4, and calculate the flow friction resistance f1 of the simulated water in a pipeline per unit length and the flow friction resistance f2 of the displacement fluid in a pipeline per unit length respectively through the pressure differences of the pressure gauges.

[0069] The present invention preferably places the core in a core holder, then connects a constant flow pump, an intermediate container for the simulated water, an intermediate container for the displacement fluid, a hand pump, and the core holder. Then adjust each valve to obtain the installed experimental equipment. The present invention does not have special limitations on the specific sources of the equipment, and commercially available products well-known to those skilled in the art can be used.

[0070] In the present invention, the core is preferably a natural core or an artificial core; the shape of the core is preferably a cylinder; the diameter of the core is preferably 2 - 3 cm, more preferably 2.5 cm; the length of the core is preferably 5 - 15 cm, more preferably 10 cm.

[0071] The schematic diagram of the experimental equipment for improving the accuracy of water permeability measurement of the core provided by the present invention is as Figure 1 shown. As Figure 1It can be seen that, first, the core saturated with water is placed in the core holder. Then, the constant flow pump, the intermediate container for simulated water, the intermediate container for displacement fluid, the hand pump, and the core holder are connected. Next, each valve is adjusted. Finally, the simulated water and the displacement fluid are injected at an injection rate of 0.5 - 1 mL / min for displacement. After the outlet flow rate stabilizes, the readings of pressure gauges 1 - 4 and the flow rate are recorded. By using the above experimental equipment, the present invention utilizes the principle of the density difference between the simulated water and the displacement fluid. The distilled water in the constant flow pump displaces the displacement fluid in intermediate container II, and the displacement fluid enters intermediate container I through the pipeline, displacing the simulated water in intermediate container I into the core holder. The water permeability of the core is calculated through Darcy's law, reducing the experimental error of the previous testing methods and ensuring the accuracy of the core water permeability experiment.

[0072] In the present invention, before placing the core in the core holder, it is preferred to first calculate the volume of the core saturated with simulated water and the porosity of the core.

[0073] In the present invention, the method for calculating the volume of the core saturated with simulated water and the porosity of the core is preferably as follows: First, measure the geometric dimensions of the core. Then, weigh the dry weight of the core. Next, evacuate and saturate the core with simulated water. Then, weigh the wet weight of the core. Finally, calculate the volume of the core saturated with simulated water and the porosity of the core based on the obtained parameters. By calculating the volume of the core saturated with simulated water and the porosity of the core, the present invention can facilitate the control of subsequent experimental parameters.

[0074] After obtaining the installed experimental equipment, the present invention preferably raises the confining pressure of the core holder in the installed experimental equipment to 3 MPa, and then ensures that the confining pressure of the core holder and the injection pressure are not lower than 1.5 MPa during the test to obtain the device before displacement. By controlling the confining pressure and the injection pressure, the present invention can ensure the smooth injection of the simulated water and the displacement fluid in the device.

[0075] After obtaining the device before displacement, the present invention preferably injects the simulated water and the displacement fluid at an injection rate of 0.5 - 1 mL / min for displacement. After the outlet flow rate stabilizes, the readings of pressure gauges 1 - 4 and the flow rate are recorded, and the flow friction resistance f1 of the simulated water in the pipeline per unit length and the flow friction resistance f2 of the displacement fluid in the pipeline per unit length are calculated respectively through the pressure difference of the pressure gauges.

[0076] In the present invention, the calculation method of the flow friction resistance f1 of the simulated water in the pipeline per unit length is preferably as shown in Equation I:

[0077] f1 = (P3 - P4 - ρ1gh1) / L1 Equation I;

[0078] In Formula I, f1 is the flow friction resistance of the simulated water per unit length of the pipeline, with the unit of MPa / m; P3 is the pressure indication of Pressure Gauge 3, with the unit of MPa; P4 is the pressure indication of Pressure Gauge 4, with the unit of MPa; ρ1 is the density of the simulated water, with the unit of g / cm 3 ; g is the acceleration of gravity; h1 is the height difference between Pressure Gauge 3 and Pressure Gauge 4, with the unit of m; L1 is the length of the pipeline between Pressure Gauge 3 and Pressure Gauge 4, with the unit of m.

[0079] In the present invention, the calculation method of the flow friction resistance f2 of the displacement fluid per unit length of the pipeline is preferably as shown in Formula II:

[0080] f2 = (P1 - P2 - ρ2gh2) / L2 Formula II;

[0081] In Formula II, f2 is the flow friction resistance of the displacement fluid per unit length of the pipeline, with the unit of MPa / m; P1 is the pressure indication of Pressure Gauge 1, with the unit of MPa; P2 is the pressure indication of Pressure Gauge 2, with the unit of MPa; ρ2 is the density of the displacement fluid, with the unit of g / cm 3 ; g is the acceleration of gravity; h2 is the height difference between Pressure Gauge 1 and Pressure Gauge 2, with the unit of m; L2 is the length of the pipeline between Pressure Gauge 1 and Pressure Gauge 2, with the unit of m.

[0082] The calculation method of the flow friction resistance of the simulated water and the displacement fluid per unit length of the pipeline provided by the present invention fully considers the influence brought by the density and gravity of the simulated water and the displacement fluid, can improve the accuracy of the flow friction resistance, and thus further improve the accuracy of the core water permeability measured by using the flow friction resistance subsequently.

[0083] After obtaining the flow friction resistance f1 of the simulated water per unit length of the pipeline and the flow friction resistance f2 of the displacement fluid per unit length of the pipeline, the present invention uses the flow friction resistances f1 and f2 to calculate the injection-production end pressure difference ΔP of the core holder.

[0084] In the present invention, the calculation method of the injection-production end pressure difference ΔP of the core holder is preferably as shown in Formula III:

[0085] ΔP = P2 + g[ρ2h5 + ρ1h3 - (ρ1 - ρ2)h i - ρ1h4] - f1s1 - f2s2 Formula III;

[0086] In Formula III, ΔP is the injection-production end pressure difference of the core holder, with the unit of 10 -1 MPa; P2 is the pressure indication of Pressure Gauge 2, with the unit of MPa; g is the acceleration of gravity; ρ1 is the density of the simulated water, with the unit of g / cm 3 ; ρ2 is the density of the displacement fluid, with the unit of g / cm3 ; h i where h is the cumulative injection height of the displacement fluid, in m; h3 is the height of the intermediate container of the simulated water, in m; h4 is the height difference between the discharge end of the intermediate container of the simulated water and the injection end of the core holder, in m; h5 is the height difference between the pressure gauge 2 and the injection end of the intermediate container of the simulated water, in m; f1 is the flow friction resistance of the simulated water in the pipeline per unit length, in MPa / m; s1 is the length of the pipeline containing the simulated water between the pressure gauge 2 and the core injection end, in m; f2 is the flow friction resistance of the displacement fluid in the pipeline per unit length, in MPa / m; s2 is the length of the pipeline containing the displacement fluid between the pressure gauge 2 and the core injection end, in m.

[0087] After obtaining the pressure difference ΔP between the injection and production ends of the core holder, the present invention calculates the core water permeability K using the pressure difference ΔP between the injection and production ends of the core holder.

[0088] In the present invention, the calculation method of the core water permeability K is preferably as shown in Equation IV:

[0089] K = QμL / AΔP Equation IV;

[0090] In Equation IV, K is the core water permeability, in μm 2 ; Q is the flow rate through the core, in cm 3 / s; μ is the viscosity of the simulated water, in mPa·s; L is the length of the core, in cm; A is the cross-sectional area of the core, in cm 2 ; ΔP is the pressure difference between the injection and production ends of the core holder, in 10 -1 MPa. The present invention calculates the core water permeability using Darcy's law, which can further improve the accuracy of the core water permeability.

[0091] The method provided by the present invention first tests the flow friction resistance of the simulated water and the displacement fluid in the pipeline per unit length, then tests the displacement force generated by the instrument and equipment at different spatial positions, and finally comprehensively calculates the core water permeability, which can improve the accuracy of the core water permeability experiment; the method provided by the present invention optimizes the experimental process design, solves the problem of experimental error caused by the inconsistent test process in the existing core water permeability test method, reduces the experimental error of the previous test method, achieves the goal of improving the accuracy of the core water permeability, and provides theoretical guidance for the laboratory water permeability experiment.

[0092] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0093] Embodiment 1

[0094] A device for improving the accuracy of core water permeability measurement includes a core holder;

[0095] One end of the core holder is connected to the bottom of a pressure gauge 4, a pressure gauge 3, and an intermediate container I in sequence through pipelines;

[0096] The pressure gauge 3 is connected to a support base;

[0097] The top of the intermediate container I is connected to the top of an intermediate container II through a pipeline;

[0098] The top of the intermediate container I is connected to a pressure gauge 2;

[0099] The top of the intermediate container II is connected to a pressure gauge 1;

[0100] The bottom of the intermediate container II is connected to a constant flow pump through a pipeline.

[0101] Embodiment 2

[0102] A device for improving the accuracy of core water permeability measurement includes a core holder;

[0103] One end of the core holder is connected to the bottom of a pressure gauge 4, a pressure gauge 3, and an intermediate container I in sequence through pipelines; the height of the pressure gauge 4 is higher than that of the pressure gauge 3;

[0104] The pressure gauge 3 is connected to a support base;

[0105] The top of the intermediate container I is connected to the top of an intermediate container II through a pipeline;

[0106] The top of the intermediate container I is connected to a pressure gauge 2;

[0107] The top of the intermediate container II is connected to a pressure gauge 1;

[0108] The height of the pressure gauge 2 is higher than that of the pressure gauge 1;

[0109] The bottom of the intermediate container II is connected to a constant flow pump through a pipeline;

[0110] The other end of the core holder is connected to a collector through a pipeline;

[0111] The middle and upper part of the core holder is connected to a hand pump and a liquid storage cup through pipelines.

[0112] Example 3

[0113] A method for improving the accuracy of core water permeability measurement uses the device provided in Example 2 for testing, specifically the following steps:

[0114] (1) First, measure the geometric dimensions of the core, then weigh the dry weight of the core, then evacuate and saturate it with simulated water, then weigh the wet weight of the core, and finally calculate the saturated simulated water volume and core porosity based on the obtained parameters. Then, respectively test the flow friction resistance f1 of the simulated water in the pipeline per unit length and the flow friction resistance f2 of the displacement fluid in the pipeline per unit length; the simulated water is the simulated injection water in the oilfield, and the composition of the simulated injection water in the oilfield is shown in Table 1. The density of the simulated water is 0.996 g / cm 3 ; the displacement fluid is white oil, and the density of the displacement fluid is 0.816 g / cm 3 ;

[0115] (2) Calculate the injection-production end pressure difference ΔP of the core holder according to the different spatial positions of the experimental equipment using the flow friction resistances f1 and f2 obtained in step (1); the different spatial positions are respectively the position of the pressure gauge, the position of the core holder, and the position of the pipeline. Many parameters such as L1, L2, and h1 - 5 are shown in Table 2;

[0116] (3) Calculate the core water permeability K using the injection-production end pressure difference ΔP of the core holder obtained in step (2);

[0117] The specific test method for the flow friction resistance of the simulated water and the displacement fluid in the pipeline per unit length in step (1) is specifically the following steps:

[0118] 1) Place the core in the core holder, then connect the constant flow pump, the intermediate container of the simulated water, the intermediate container of the displacement fluid, the hand pump, and the core holder. Then, adjust each valve to obtain the installed experimental equipment; the core is a quartz sand epoxy resin cemented artificial core, and the external geometric dimensions of the core are: Φ2.5 cm × 10 cm, and the gas permeability K of the core g = 200×10 -3 μm 2 ;

[0119] 2) Increase the confining pressure of the core holder in the installed experimental equipment obtained in step 1) to 3 MPa, and then ensure that the confining pressure of the core holder and the injection pressure are not lower than 1.5 MPa during the test to obtain the device before displacement;

[0120] 3) Inject simulated water and displacement fluid into the device before displacement in step 2) at an injection rate of 0.5 mL / min for displacement. After the outlet flow rate is stable, record the readings of pressure gauges 1 - 4 and the flow rate. Calculate the flow friction resistance f1 of the simulated water per unit length of the pipeline and the flow friction resistance f2 of the displacement fluid per unit length of the pipeline through the pressure difference of the pressure gauges;

[0121] The calculation method of the flow friction resistance f1 of the simulated water per unit length of the pipeline is shown in Equation I:

[0122] f1 = (P3 - P4 - ρ1gh1) / L1 = 0.0027 (MPa / m) Equation I;

[0123] In Equation I, f1 is the flow friction resistance of the simulated water per unit length of the pipeline, with the unit of MPa / m; P3 is the pressure reading of pressure gauge 3, with the unit of MPa; P4 is the pressure reading of pressure gauge 4, with the unit of MPa; ρ1 is the density of the simulated water, with the unit of g / cm 3 ; g is the acceleration due to gravity; h1 is the height difference between pressure gauges 3 and 4, with the unit of m; L1 is the length of the pipeline between pressure gauges 3 and 4, with the unit of m;

[0124] The calculation method of the flow friction resistance f2 of the displacement fluid per unit length of the pipeline is shown in Equation II:

[0125] f2 = (P1 - P2 - ρ2gh2) / L2 = 0.0018 (MPa / m) Equation II;

[0126] In Equation II, f2 is the flow friction resistance of the displacement fluid per unit length of the pipeline, with the unit of MPa / m; P1 is the pressure reading of pressure gauge 1, with the unit of MPa; P2 is the pressure reading of pressure gauge 2, with the unit of MPa; ρ2 is the density of the displacement fluid, with the unit of g / cm 3 ; g is the acceleration due to gravity; h2 is the height difference between pressure gauges 1 and 2, with the unit of m; L2 is the length of the pipeline between pressure gauges Ⅰ and Ⅱ, with the unit of m;

[0127] The calculation method of the injection - production end pressure ΔP of the core holder is shown in Equation III, and the calculation results are shown in Table 3 and Table 4:

[0128] ΔP = P2 + g[ρ2h5 + ρ1h3 - (ρ1 - ρ2)h i - ρ1h4] - f1s1 - f2s2 Equation III;

[0129] In Equation III, ΔP is the injection - production end pressure difference of the core holder, with the unit of -1MPa; P2 is the pressure indication of pressure gauge 2, with the unit of MPa; g is the acceleration of gravity; ρ1 is the density of the simulated water, with the unit of g / cm 3 ; ρ2 is the density of the displacement fluid, with the unit of g / cm 3 ; h i is the cumulative injection height of the displacement fluid, with the unit of m; h3 is the height of the intermediate container of the simulated water, with the unit of m; h4 is the height difference between the discharge end of the intermediate container of the simulated water and the injection end of the core holder, with the unit of m; h5 is the height difference between pressure gauge 2 and the injection end of the intermediate container of the simulated water, with the unit of m; f1 is the flow friction resistance of the simulated water in the pipeline per unit length, with the unit of MPa / m; s1 is the length of the pipeline containing the simulated water, with the unit of m; f2 is the flow friction resistance of the displacement fluid in the pipeline per unit length, with the unit of MPa / m; s2 is the length of the pipeline containing the displacement fluid, with the unit of m.

[0130] The core water permeability is calculated using Darcy's law. The calculation method of the core water permeability K is shown in Equation IV, and the calculation results are shown in Table 3:

[0131] K = QμL / AΔP Equation IV;

[0132] In Equation IV, K is the core water permeability, with the unit of μm 2 ; Q is the flow rate through the core, with the unit of cm 3 / s; μ is the viscosity of the simulated water, with the unit of mPa·s; L is the length of the core, with the unit of cm; A is the cross-sectional area of the core, with the unit of cm 2 ; ΔP is the pressure difference between the injection and production ends of the core holder, with the unit of 10 -1 MPa.

[0133] Example 4

[0134] The difference from Example 3 is that in step 3), simulated water and displacement fluid are respectively injected into the displacement pre-device in step 2) at an injection rate of 0.8 mL / min for displacement, and other conditions are the same as those in Example 3.

[0135] Example 5

[0136] The difference from Example 3 is that in step 3), simulated water and displacement fluid are respectively injected into the displacement pre-device in step 2) at an injection rate of 1 mL / min for displacement, and other conditions are the same as those in Example 3.

[0137] Comparative Example 1

[0138] Use Figure 2 The specific test process for testing the core water permeability using the device shown:

[0139] First, place the core saturated with water in the core holder. Then, connect the bottom of the piston-type intermediate container to the constant flow pump through a pipeline. Next, connect the injection end of the core holder to a pressure gauge and the top of the piston-type intermediate container through pipelines respectively. Connect the production end of the core holder to the collector through a pipeline. Then, connect the middle and upper parts of the core holder to a hand pump and a liquid storage cup through pipelines. Finally, displace with simulated water and displacement fluid at an injection rate of 0.5 mL / min respectively. The simulated water and displacement fluid are the same as those in Example 3. After the outlet flow rate stabilizes, record the readings of the pressure gauge and the flow rate.

[0140] Comparative Example 2

[0141] The difference from Comparative Example 1 is that: displace with simulated water and displacement fluid at an injection rate of 0.8 mL / min respectively. After the outlet flow rate stabilizes, record the readings of the pressure gauge and the flow rate. Other conditions are the same as those in Comparative Example 1.

[0142] Comparative Example 3

[0143] The difference from Comparative Example 1 is that: displace with simulated water and displacement fluid at an injection rate of 1 mL / min respectively. After the outlet flow rate stabilizes, record the readings of the pressure gauge and the flow rate. Other conditions are the same as those in Comparative Example 1.

[0144] Test Examples 3 - 5 and Comparative Examples 1 - 3, and the test results obtained are shown in Table 3:

[0145] Table 1 Composition of the simulated injection water in Oilfield in Examples 3 - 5 and Comparative Examples 1 - 3

[0146]

[0147] Table 2 Basic parameter data in Examples 3 - 5

[0148] Basic parameters Unit (cm) <![CDATA[h1]]> 10 <![CDATA[h2]]> 10 <![CDATA[h3]]> 30 <![CDATA[h4]]> 20 <![CDATA[h5]]> 5 <![CDATA[h i > 225 <![CDATA[L1]]> 55 <![CDATA[L2]]> 50 <![CDATA[s1]]> 130 <![CDATA[s2]]> 55

[0149] Table 3 Test results obtained from Examples 3 - 5 and Comparative Examples 1 - 3

[0150]

[0151] As can be seen from Table 3, the core water permeability was measured through three groups of different flow rate experiments using the conventional method (i.e., Comparative Examples 1-3) and the method provided by the present invention. By comparing the test results of the two methods with the gas permeability of the core, it can be found that the test results of the method provided by the present invention can effectively reduce the experimental error and ensure the accuracy of the core water permeability experiment. Through multiple groups of flow rate experiments, the error caused by randomness is avoided, and the obtained test results are more persuasive; at the same time, it can be seen that it is not that the faster the displacement injection speed, the higher the accuracy. When the displacement injection speed is 0.5-1 mL / min, it has higher test accuracy.

[0152] Example 6

[0153] The difference from Example 4 is that the core is a quartz sand epoxy resin cemented artificial core, and the appearance geometric dimensions of the core are: Φ2.5 cm × 10 cm, and the gas permeability K of the core g = 2000×10 -3 μm 2 ; other conditions are the same as those in Example 4.

[0154] Example 7

[0155] The difference from Example 5 is that the core is a quartz sand epoxy resin cemented artificial core, and the appearance geometric dimensions of the core are: Φ2.5 cm × 10 cm, and the gas permeability K of the core g = 2000×10 -3 μm 2 ; other conditions are the same as those in Example 5.

[0156] Comparative Example 4

[0157] The difference from Comparative Example 2 is that the core is a quartz sand epoxy resin cemented artificial core, and the appearance geometric dimensions of the core are: Φ2.5 cm × 10 cm, and the gas permeability K of the core g = 2000×10 -3 μm 2 ; other conditions are the same as those in Comparative Example 2.

[0158] Comparative Example 5

[0159] The difference from Comparative Example 3 is that the core is a quartz sand epoxy resin cemented artificial core, and the appearance geometric dimensions of the core are: Φ2.5 cm × 10 cm, and the gas permeability K of the core g = 2000×10 -3 μm 2 ; other conditions are the same as those in Comparative Example 3.

[0160] The core water permeability of Examples 6 - 7 and Comparative Examples 4 - 5 was tested, and the test results of the core water permeability are shown in Table 4:

[0161] Table 4 Test Results of Core Water Permeability Obtained from Examples 6 - 7 and Comparative Examples 4 - 5

[0162]

[0163] As can be seen from Table 4, the flow friction resistance of the simulated water and the displacement fluid in the pipeline per unit length and the displacement force generated by the instrument and equipment at different spatial positions have an impact on the core water permeability. The core water permeability obtained by calculation is about 50% of the gas permeability, which conforms to the industry understanding, reduces the experimental error of the previous test method, and ensures the accuracy of the core water permeability experiment.

[0164] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A device for improving the accuracy of water permeability measurement of rock cores, comprising a rock core holder; One end of the core holder is connected to the pressure gauge 4, the pressure gauge 3 and the bottom of the intermediate container 1 in sequence through pipelines; The pressure gauge 3 is connected to the bracket base; The top of the intermediate container I is connected to the top of the intermediate container II through a pipeline; The top of the intermediate container 1 is connected to the pressure gauge 2; The top of the intermediate container II is connected to the pressure gauge 1; The bottom of the intermediate container II is connected to a constant flow pump through a pipeline; The height of the pressure gauge 4 is higher than that of the pressure gauge 3; The height of the pressure gauge 2 is higher than that of the pressure gauge 1 .

2. The device according to claim 1, characterized in that The other end of the core holder is connected to the collector through a pipeline; The middle and upper part of the core holder is connected to the hand pump and the liquid storage cup through a pipeline.

3. A method for improving the accuracy of water permeability measurement of core rock, using the device according to any one of claims 1 to 2 for testing, comprising the following steps: (1) Test the simulated water flow friction resistance f1 and displacement fluid flow friction resistance f2 per unit length of pipeline respectively; (2) Calculating the pressure difference ΔP at the injection and production ends of the core holder using the flow friction resistances f1 and f2 obtained in step (1); (3) Calculating the water permeability K of the core using the injection-production end pressure difference ΔP of the core holder obtained in step (2).

4. The method according to claim 3, characterized in that The simulated water in step (1) is any one of distilled water, deionized water, formation water and oilfield simulated injection water.

5. The method according to claim 3, characterized in that The displacement fluid in step (1) is any one of white oil and aviation kerosene.

6. The method according to claim 3, characterized in that The test method for simulating the flow friction resistance of water and displacement fluid in a unit length pipeline in step (1) comprises the following steps: 1) Place the core in the core holder, then connect the constant flow pump, the intermediate container for simulated water, the intermediate container for displacement fluid, the hand pump, and the core holder. Then adjust the valves to obtain the assembled experimental equipment. 2) increasing the annular pressure of the core holder in the installed experimental equipment obtained in step 1) to 3 MPa, and then ensuring that the annular pressure of the core holder and the injection pressure are not less than 1.5 MPa during the test process, to obtain a pre-displacement device; 3) Simulated water and displacement fluid were respectively introduced into the pre-displacement device in step 2) at an injection rate of 0.5 to 1 mL / min for displacement. After the outlet flow rate stabilized, the readings and flow rates of pressure gauges 1 to 4 were recorded. The flow friction resistance f1 of the simulated water per unit length of the pipeline and the flow friction resistance f2 of the displacement fluid per unit length of the pipeline were calculated based on the pressure difference of the pressure gauges.

7. The method according to claim 6, characterized in that The calculation method of the friction resistance f1 of the simulated water flow in the unit length pipeline in step 3) is shown in formula I: f1=(P3-P4-ρ1gh1) / L1Formula I; In formula I, f1 is the friction resistance of simulated water flow in unit length pipeline, unit is MPa / m; P3 is the pressure reading of pressure gauge 3, unit is MPa; P4 is the pressure reading of pressure gauge 4, unit is MPa; ρ1 is the density of simulated water, unit is g / cm 3 ; g is the acceleration of gravity; h1 is the height difference between pressure gauge 3 and pressure gauge 4, in m; L1 is the length of the pipeline between pressure gauge 3 and pressure gauge 4, in m.

8. The method according to claim 6, characterized in that The calculation method of the flow friction resistance f2 of the displacement fluid per unit length of the pipeline in step 3) is shown in Formula II: f2=(P1-P2-ρ2gh2) / L2Formula II; In formula II, f2 is the flow friction resistance of the displacement fluid in the unit length of the pipeline, in MPa / m; P1 is the pressure reading of pressure gauge 1, in MPa; P2 is the pressure reading of pressure gauge 2, in MPa; ρ2 is the density of the displacement fluid, in g / cm 3 ; g is the acceleration due to gravity; h2 is the height difference between pressure gauge 1 and pressure gauge 2, in meters; L2 is the length of the pipeline between pressure gauge 1 and pressure gauge 2, in meters.

9. The method according to claim 3, characterized in that The calculation method of the pressure difference ΔP at the injection and production ends of the core holder in step (2) is shown in Formula III: ΔP = P2 + g[ρ2h5 + ρ1h3 - (ρ1 - ρ2)h i - ρ1h4] - f1s1 - f2s2 Equation III; In formula III, ΔP is the pressure difference between the injection and production ends of the core holder, in units of 10-1 MPa; P2 is the pressure reading of pressure gauge 2, in units of MPa; g is the acceleration of gravity; ρ1 is the density of simulated water, in units of g / cm 3 ; ρ2 is the density of the displacement fluid, in g / cm 3 ;h i is the cumulative injection height of the displacement fluid, in meters; h3 is the height of the intermediate container for simulating water, in meters; h4 is the height difference between the discharge end of the intermediate container for simulating water and the injection end of the core holder, in meters; h5 is the height difference between the pressure gauge 2 and the injection end of the intermediate container for simulating water, in meters; f1 is the flow friction resistance of simulated water in the pipeline per unit length, in MPa / m; s1 is the length of the pipeline containing simulated water between pressure gauge 2 and the core injection end, in m; f2 is the flow friction resistance of the displacement fluid in the unit length of the pipeline, in MPa / m; s2 is the length of the pipeline containing the displacement fluid between pressure gauge 2 and the core injection end, in m.

10. The method according to claim 3, characterized in that The calculation method of the core water permeability K in step (3) is shown in Formula IV: K = Q μL / AΔP Formula IV; In formula IV, K is the core water permeability, unit is μm 2 ; Q is the flow rate through the core, in cm 3 / s; μ is the viscosity of simulated water, in mPa·s; L is the length of the core, in cm; A is the cross-sectional area of the core, in cm 2 ; ΔP is the pressure difference between the injection and production ends of the core holder, unit is 10 -1 MPa.

Images