Device for determining phase permeabilities

Abstract

FIELD: measurement technology.SUBSTANCE: invention relates to studying phase permeabilities of oil and gas reservoirs and can be used in solving a large number of geotechnical problems, in particular for the development of technologies for increasing oil recovery. A device for determining phase permeabilities comprises a core holder with a test sample installed in it, a thermostat that ensures the maintenance of a constant temperature in the test sample, plunger pumps for feeding working fluids into the test sample at reservoir pressure, an intermediate gas tank with a piston, a check valve installed on the gas supply pipeline, a pump for creating a crimping pressure, pipelines for feeding and removing working fluids with valves, a backpressure regulator, containers with working fluids, a measuring flask for measuring the liquid level at the outlet of the core holder, pressure sensors, a differential pressure gauge for measuring the pressure drop on the test sample and a gas cylinder. Additionally, the device includes a vessel equipped with a temperature sensor, a pressure gauge and a valve, which is connected to a pipeline for removing working fluids directly behind the core holder, as well as a valve installed on the pipeline for supplying a three-phase mixture directly in front of the core holder.EFFECT: ability to construct phase diagrams of the dependence of the permeability of a sample for gas, water and oil on the gas saturation of the pore space.3 cl, 1 dwg

Description

[0001] Technical area

[0002] The technical solution relates to the field of studying phase permeabilities of oil and gas reservoirs and can be used to solve a large number of geotechnical problems, including the development of technologies for enhancing oil recovery.

[0003] Prior Art

[0004] A device is known for determining phase permeabilities in a porous medium with its three-phase saturation [RU 2822821], comprising a core holder with a test sample of the porous medium installed in it, a three-phase measuring separator equipped with ultrasonic sensors that control the separation boundaries of the media in it, a dry-air thermostat that ensures the maintenance of a constant temperature in the core holder and the measuring three-phase separator, as well as an automatic control system, wherein the internal volume of the three-phase measuring separator is divided into an upper, middle and lower communicating sections, the upper section is filled with a first fluid, the middle section is filled with a second fluid having a density higher than the first fluid, and the lower section is filled with a third fluid having a density higher than the second fluid, in addition, the core holder is equipped with a system for creating and monitoring rock pressure, a differential pressure gauge with pressure sensors,a system for measuring the saturation of a sample of a porous medium with a first or second fluid, receiving information from ultrasonic sensors monitoring the level of the boundary of the media in the measuring separator, and a system for measuring the saturation of a sample of a porous medium with a third fluid, wherein the automatic control system includes an automatic control system and a controller that records data coming from the system for measuring the saturation of a sample of a porous medium with a third fluid and from the system for measuring the saturation of a sample of a porous medium with the first or second fluid, as well as data on the pressure drop on the differential pressure gauge, in addition, the outlet of the core holder is connected via a branch pipeline to the inlet of a three-phase measuring separator, the outlet from the lower section of the three-phase measuring separator is connected to the first inlet of the core holder via a pipeline in which the first recirculation pump is installed,which is connected via feedback to a system for measuring the saturation of a sample of a porous medium with a third fluid, the outlet from the middle section of the three-phase measuring separator is connected to the second input of the core holder via a pipeline in which a second recirculation pump is installed, the outlet from the upper section of the three-phase measuring separator is connected to the third input of the core holder via a pipeline in which a third recirculation pump is installed.

[0005] The device operates based on gravity separation of three phases in a density separator (upper, middle, and lower fluids), which requires a sufficiently large density difference and stable, well-separated systems. In real oil-water-gas reservoir systems (especially in the presence of emulsions, surfactants, and condensate), this condition is often violated, reducing the reliability of saturation and permeability determinations.

[0006] A device is known comprising a core holder with a test sample installed therein [RU 2660772 C1], a dry-air thermostat maintaining a constant temperature in the sample, recirculation pumps providing a filtration process by feeding fluids of specified phase systems into the sample at a constant specified flow rate, a crimping device for creating formation pressure on the sample, a pipeline system for feeding and removing working fluids, equipped with shut-off valves, a differential pressure gauge with pressure sensors for determining the pressure drop across the sample. A measuring separator consisting of a container for separating incoming fluids based on the difference in their densities, equipped with a system for monitoring and measuring the interface level of the media in a state of thermodynamic equilibrium.The pipeline system also includes a bypass line for flushing the pipeline at the core holder outlet with a predetermined fluid ratio to mitigate any unaccounted for changes in the working fluids. Furthermore, all of the above equipment, including the pipeline system with the bypass line, is housed in a single dry-air thermostat, creating a closed thermodynamic system that eliminates the cooling of the working fluids during their recirculation during the filtration process.

[0007] The device is designed for oil and gas (excluding water). The separator separates only by the difference in density of the two fluids, without supporting three-phase oil-water-gas filtration. There is no vessel for "discharging" gas from the core, which reduces accuracy in pores. The entire circuit (pumps, bypass line, separator) in a large dry-air thermostat complicates core replacement and calibration. It requires long-term stabilization (2-3 times the separator volume) and bypass flushing to eliminate mass transfer.

[0008] Devices for determining phase permeabilities in reservoir conditions are known (Instructions for the operation of the automated software and measuring complex for petrophysical study of cores PIK-OFP / EP-3. - Novosibirsk: ZAO Geologika, 2008. - 33 p.; patent RU 108105, IPC E21B 47 / 00, G01N 15 / 08, published 10.09.2011, bulletin No. 25), containing plunger pumps for feeding oil and water into the test sample at reservoir pressure, a core holder with the test sample installed in it in a rubber cuff, a pump for creating rock pressure, pipelines for supplying and discharging working fluids with valves, containers with working fluids, a backpressure regulator, a measuring flask for measuring the liquid level at the outlet from core holder, thermostat to maintain a constant temperature in the test sample, differential pressure gauge to measure the pressure drop across the test sample.The specified devices allow one to determine the phase permeability of the test sample when filtering two-phase mixtures through it.

[0009] The disadvantage of the described devices is the impossibility of determining phase permeabilities during three-phase filtration of oil, water and gas.

[0010] A device for determining phase permeabilities is known (patent RU 166252, IPC G01N 15 / 08, published 20.11.2016, bulletin No. 32), comprising a core holder with a test sample installed in it in a rubber cuff, a thermostat that ensures the maintenance of a constant temperature in the test sample, plunger pumps for feeding working fluids (oil and water) into the test sample at reservoir pressure, a pump for creating rock pressure, pipelines for feeding and removing working fluids with valves, a backpressure regulator, containers with working fluids, a measuring flask for measuring the liquid level at the outlet of the core holder, pressure sensors, a differential pressure gauge for measuring the pressure drop on the test sample and a gas cylinder. The specified device allows for three-phase filtration of fluids through a rock sample.

[0011] The disadvantage of this device is the uneven flow of gas into the inlet line when pumping gas and liquids together, as well as limitations on gas pressure due to the current value of gas pressure in the cylinder.

[0012] A device for determining phase permeabilities is known (patent RU 2803430, IPC G01N 15 / 08, published 13.09.2023, bulletin No. 26), taken as a prototype, which contains a core holder with a test sample installed in it, a thermostat that ensures maintaining a constant temperature in the test sample, plunger pumps for feeding working fluids into the test sample at reservoir pressure, an intermediate gas tank with a piston, a check valve installed on the gas supply pipeline, a pump for creating crimping pressure, pipelines for feeding and removing working fluids with valves, a backpressure regulator, containers with working fluids, a measuring flask for measuring the liquid level at the outlet of the core holder, pressure sensors, a differential pressure gauge for measuring the pressure drop on the test sample and a gas cylinder.

[0013] This device allows for three-phase filtration through a rock sample.

[0014] A disadvantage of this device is the inability to determine the gas saturation of the pore space of a rock sample during combined gas and liquid flow. During prolonged simultaneous filtration of gas, oil, and water through a rock sample, a steady state is reached, where the ratio of these phases in the pore space reaches equilibrium. Reaching a steady state is indicated by a constant differential pressure gauge reading, measuring the pressure drop across the sample, as well as by a constant electrical resistance. The lack of information on the gas saturation of a rock sample during steady-state filtration prevents the construction of phase diagrams of the sample's permeability to gas, water, and oil versus the gas saturation of the pore space, as well as the calculation of oil saturation.

[0015] Brief Summary of the Invention

[0016] The technical task is to measure the gas saturation of the pore space of a rock sample during the combined pumping of gas and liquids.

[0017] The technical result consists in providing the possibility of constructing phase diagrams of the dependence of the permeability of a sample for gas, water and oil on the gas saturation of the pore space, which expands the possibilities of analyzing and predicting hydrocarbon production modes in oil and gas and gas condensate fields, including when using methods of enhancing oil recovery, gas and condensate production during three-phase filtration in the reservoir.

[0018] The technical result is achieved in that the device for determining phase permeabilities includes a core holder with a test sample installed in it, a thermostat that ensures maintaining a constant temperature in the test sample, plunger pumps for feeding working fluids into the test sample at reservoir pressure, an intermediate gas tank with a piston, a check valve installed on the gas supply pipeline, a pump for creating a crimping pressure, pipelines for feeding and removing working fluids with valves, a backpressure regulator, containers with working fluids, a measuring flask for measuring the liquid level at the outlet of the core holder, pressure sensors, a differential pressure gauge for measuring the pressure drop on the test sample and a gas cylinder, is characterized in that it includes a vessel with a temperature sensor, a pressure gauge and a valve connected to the pipeline for removing working fluids immediately after the core holder, and a valve,installed on the pipeline for supplying a three-phase mixture directly in front of the core holder,

[0019] The above set of features allows us to solve the stated problem and ensures the stated technical result.

[0020] This device measures the gas saturation of the pore space of a rock sample while simultaneously filtering three phases (water, oil, and gas) through the sample. It also calculates oil saturation using the difference between the initial pore volume, gas saturation, and water saturation, determined using the standard method of measuring the sample's electrical resistance. This makes it possible to determine the dependence of rock permeability for each phase on the saturation of each phase. This expands the capabilities of analyzing and predicting hydrocarbon production modes at oil and gas and gas condensate fields using enhanced oil recovery (EOR) and gas and condensate production methods.

[0021] The device allows determining the gas saturation of the pore space of the core during three-phase filtration.

[0022] The technical solution is explained by this description and a drawing, which depicts a hydraulic diagram of the proposed device, explaining the essence of the claimed technical solution.

[0023] Implementation of technical solution

[0024] The device for determining phase permeabilities includes a core holder 1 with a rock sample being tested installed in it, a thermostat 2 that maintains a constant temperature in the sample being tested, plunger pumps 3-5 for feeding working fluids to the sample being tested at reservoir pressure, a pump for creating confining pressure 6, a gas cylinder 7, pipelines for feeding working fluids 8 with valves 13, 14, a pipeline for feeding gas 9 with valves 15, 16, a pipeline for feeding a three-phase mixture 10 to the input of core holder 1, a pipeline for removing a three-phase mixture 11 with a valve 18, a pipeline for removing working fluids 12 with a valve 17, containers with working fluids 19, a backpressure regulator 20, a measuring flask 21 for measuring the liquid level at the outlet of the core holder, pressure sensors 22-25, differential pressure gauge 26 for measuring the pressure drop on the test sample, check valve 27, intermediate tank 28 for gas with piston 29, vessel 31,temperature sensor 34 for measuring the temperature of the medium in vessel 31, pressure gauge 32 for measuring the pressure of the medium in vessel 31, valve 30 for feeding fluids into vessel 31 and valve 33 on the pipeline for feeding a three-phase mixture to the input of the core holder.

[0025] Vessel 31 is connected via valve 30 to pipeline for removing working fluids 11 at the point between core holder 1 and pressure sensor 25. Pressure gauge 32 is connected to vessel 31 at the top point of the vessel, temperature sensor 34 is mounted with its measuring part in the inner space of vessel 31.

[0026] Vessel 31 with pressure gauge 32, temperature sensor 34, and valve 30 allows for gas saturation measurements using the Mendeleev-Clapeyron equation after filtration stops: the gas expands in the vessel, and the pressure and temperature determine the gas mass in the core pores. Valve 33 in front of the core holder stabilizes the three-phase mixture (water-oil-nitrogen), ensuring uniform flow and a steady-state regime for accurate calculations. according to Darcy.

[0027] Plunger pumps 3-5, gas cylinder 7, intermediate gas tank 28 with piston 29, pipelines for supplying working fluids 8 with valves 13, 14 and with containers with working fluids 19, pipeline for supplying three-phase mixture 10, pipeline for supplying gas 9 with valves 15, 16, pressure sensors 23, 24, check valve 27 and valve 33 form an input line.

[0028] The pipeline for removing working fluids 11 with the valve 18, the vessel 31, the pressure gauge 32, the temperature sensor 34, the valve 30, the backpressure regulator 20, the measuring flask 21 and the pressure sensor 25 form the outlet line.

[0029] A pump for creating crimping pressure 6, a pipeline for supplying working fluids 8 with a valve 14, a pressure sensor 22, a pipeline for removing working fluids 12 with a valve 17 and with a container with working fluid 19 form a crimping line.

[0030] The working fluid for plunger pumps 3 and 5 is water, for plunger pump 4 it is oil, and for plunger pump 6 it is mineral oil. Gas cylinder 7 is filled with nitrogen, helium, or another gas specified for the experiment. Vessel 31 is evacuated.

[0031] The device for determining phase permeabilities works as follows.

[0032] Using thermostat 2, set the temperature of core holder 1 with a rock sample inside.

[0033] The crimping pressure in core holder 1 is set by supplying oil using pump 6 to create crimping pressure. Valve 14 on pipeline 8 for supplying working fluids is open, and valve 17 on pipeline 12 for removing working fluids is closed. The crimping pressure is monitored using pressure sensor 22. When the set crimping pressure value is reached, valve 14 is closed.

[0034] Working fluids (water and oil) are drawn into plunger pumps 3-5 from containers with working fluids 19 through pipelines for supplying working fluids 8. In this case, valves 13 on pipelines for supplying working fluids 8, connecting containers with working fluids 19 with plunger pumps 3-5 are open, and valves 14 on pipelines for supplying working fluids 8 from plunger pumps 3-5 are closed.

[0035] At the same time, intermediate tank 28 is filled with gas from gas cylinder 7. In this case, valve 15 on gas supply pipeline 9, connecting gas cylinder 7 and intermediate tank 28 is open, and valve 16 on gas supply pipeline 9, connecting intermediate tank 28 with check valve 27, is closed.

[0036] Vessel 31 is evacuated, while valve 30 connecting the vessel to the pipeline for removing working fluids 11 is closed.

[0037] The gas pressure in the intermediate tank 28 is increased to the required working pressure value, for which purpose the working fluid (water) is supplied to the intermediate tank 28 by the plunger pump 5, moving the piston 29 and compressing the gas. In this case, the valve 14 on the pipeline for supplying working fluids 8, connecting the plunger pump 5 with the intermediate tank 28 is open, and the valve 13 on the pipeline for supplying working fluids 8, connecting the plunger pump 5 with the container with working fluids 19, the valve 15, connecting the intermediate tank 28 with the gas cylinder 7 and the valve 16 on the pipeline for supplying gas 9 are closed. The pressure value in the intermediate tank 28 is monitored using the pressure sensor 23.

[0038] Working fluids are fed by plunger pumps 3 and 4 through pipelines for supplying working fluids 8 into the pipeline for supplying a three-phase mixture 10 and then to the input of the core holder 1. In this case, valves 13 on pipelines for supplying working fluids 8, connecting containers with working fluids 19 with plunger pumps 3 and 4, are closed, and valves 14, connecting pumps 3 and 4 with pipelines for supplying working fluids 8, are open.

[0039] Using the counterpressure regulator 20, the required working pressure is set in the pores of the rock sample being tested, placed in the core holder 1, and controlled by the pressure sensor 25.

[0040] Gas is supplied from the intermediate tank 28 to the gas supply pipeline 9. For this purpose, the working fluid (water) is supplied to the intermediate tank 28 by the plunger pump 5, moving the piston 29. In this case, the valve 14 on the pipeline for supplying working fluids 8, connecting the intermediate tank 28 with the plunger pump 5, and the valve 16 on the pipeline for supplying gas 9, connecting the intermediate tank 28 with the check valve 27 are open, and the valve 13 on the pipeline for supplying working fluids 8, connecting the container with the working fluid 19 with the plunger pump 5, and the valve 15 on the pipeline for supplying gas 9, connecting the intermediate tank 28 with the gas cylinder 7, are closed.

[0041] The gas flow rate from the intermediate tank 28 corresponds to the specified flow rate of the working fluid of the plunger pump 5.

[0042] Gas flows from the intermediate tank 28 through the gas supply pipeline 9 into the three-phase mixture supply pipeline 10 through the check valve 27. The check valve 27 prevents working fluids from flowing into the gas supply pipeline 9 from the working fluid supply pipeline 10.

[0043] By mixing the 10 components entering the three-phase mixture supply pipeline, a three-phase mixture of water, oil and gas is formed at the entrance to the core holder 1.

[0044] A three-phase mixture of water, oil and gas enters a core holder 1 through a pipeline for supplying a three-phase mixture 10, passes through the rock sample being tested and enters a measuring flask 21 for measuring the liquid level through a pipeline for removing working fluids 11 through a backpressure regulator 20.

[0045] Achieving a steady-state filtration mode is recorded by the constancy of the readings of the differential pressure gauge 26 connected to the core holder, and also, additionally, by the constancy of the readings of the sample electrical resistance meter (not shown in the diagram).

[0046] The determination of phase permeability during stationary filtration of oil, water and gas in a given ratio is determined based on the flow rate of each phase, the pressure difference on the sample, the viscosity of the fluid, the length and cross-sectional area of ​​the sample according to the Darcy equation:

[0047] ,

[0048] where i is the mode (water, oil and gas consumption);

[0049] j - phase (water, oil, gas);

[0050] Q - fluid flow rate, ml / s;

[0051] µ - fluid viscosity, mPa⋅s;

[0052] L - sample length, m;

[0053] Δp - pressure difference on the sample (differential pressure), kPa;

[0054] F - cross-sectional area of ​​the sample, m 2 .

[0055] When the steady-state three-phase filtration mode is reached, determined by the stability of the pressure drop (the readings of the differential pressure gauge 26) and electrical resistance, the value of the pressure difference on the sample is recorded, then pumps 3, 4 and 5 are stopped, valve 33 in front of the core holder and valve 18 between the core holder and the counter-pressure unit are closed, and valve 30 between the core holder and vessel 31 of known volume is opened , while three fluids from the pore space of the sample rush into vessel 31, in which pressure is formed In this case, due to the volumetric expansion of the gas, the temperature of the gas in the vessel becomes equal to , which is recorded using temperature sensor 34. Part of the vessel's volume is filled with liquid , however, due to the fact that the volumetric expansion of gas is many times greater than the volumetric expansion of liquid, it can be assumed that the gas occupies the entire volume of vessel 31. The volume of liquid can then be taken into account by adjusting , the volume of gas in the pipeline between core holder 1 and vessel 31 can be calculated based on the length of the pipeline and its internal diameter, and taken into account by the correction to Taking these assumptions into account, it is assumed that the mass of gas in the vessel after opening valve 30 is equal to the mass of gas in the pores of the sample before opening valve 30.

[0056] Gas mass in vessel 31 can be expressed from the Mendeleev-Clapeyron equation:

[0057]

[0058] where - pressure in the vessel, Pa;

[0059] - vessel volume, m 3 ;

[0060] - temperature in the vessel after filling with gas, K;

[0061] - mass of gas in the vessel, g;

[0062] µ - molar mass of gas, g / mol;

[0063] R is the universal gas constant, 8.314 J / (mol⋅K).

[0064] If we take into account the compressibility coefficient of real gases ZP,T, then the equation will take the form:

[0065]

[0066] where compressibility coefficient of real gases at temperature and pressure , fractions of a unit;

[0067] Then the volume of gas that it occupied in the pores of the sample under pressure and temperature before opening valve 30 was equal to:

[0068]

[0069] where - volume of gas in the pores of the sample, ml;

[0070] - pressure in the pores of the sample, Pa;

[0071] - sample temperature, K;

[0072] - the compressibility coefficient of real gases at temperature and pressure , fractions of a unit.

[0073] Thus, the initial gas saturation in the sample, before opening valve 30, is determined by the formula:

[0074]

[0075] where - initial gas saturation of the sample, fractions of a unit;

[0076] V П - volume of open pores in a rock sample, ml.

[0077] The water saturation SB of the sample before opening valve 30 is determined by a known method by measuring the electrical resistance of the sample (OST 39-235-89. Oil. Method for determining phase permeabilities under laboratory conditions during joint stationary filtration).

[0078] Oil saturation sample before opening valve 30 is determined by known values and the pore volume, in dimensionless form equal to one:

[0079]

[0080] Where SB is the initial water saturation of the sample, fractions of a unit;

[0081] - initial oil saturation of the sample, fractions of a unit;

[0082] Additionally, oil saturation can be clarified in the Zacks apparatus.

[0083] When filtering multiple phases (oil, water, gas) through a rock sample simultaneously, the permeability of each phase will depend on the saturation of the sample with the other phases; i.e., the permeability of each phase will be determined by the ratio of the mixture components. Accordingly, accurately measuring the sample permeability for each phase and the sample saturation with each phase will allow us to predict the recovery rate and volumes of each phase from the reservoir under field production conditions, including the volumes of oil, water, and gas that will remain unrecovered during production.

[0084] Test conditions must ensure the preservation or reproduction of the natural physicochemical characteristics of the rock-formation fluid system, and the maintenance of temperature and pressure values ​​corresponding to those in the formation during the experiment. The combined fluid flow rate during the test is selected based on the field displacement front velocities.

[0085] Using the proposed device will allow one to measure the gas saturation of the pore space of a rock sample with the simultaneous filtration of three phases (water, oil, gas) through the sample, and then calculate the oil saturation through the difference between the initial pore volume, gas saturation, and water saturation determined in a standard way by measuring the electrical resistance of the sample, and thereby establish the dependence of the rock permeability for each phase on the saturation of each phase.

[0086] A vessel with a temperature sensor and pressure gauge, connected immediately downstream of the core holder on a branch, records the volume and pressure of the gas phase at the outlet, calculating gas saturation using the equation of state for material balance, where the gas volume in the vessel corrects the data from the volumetric flask. This provides data for phase diagrams in steady-state mode (by stabilizing ΔP and resistance). A valve upstream of the core holder ensures uniform mixing of gas and liquids, minimizing turbulence and pulsations, which improves the reproducibility of experiments by 10-15% for phase flow rates. The device expands its application in enhanced oil recovery applications by calculating residual oil saturation and modeling reservoir processes with a gas-oil ratio without additional calibrations.

Claims

1. A device for determining phase permeabilities, comprising a core holder with a test sample installed therein, a thermostat that maintains a constant temperature in the test sample, plunger pumps for feeding working fluids into the test sample at reservoir pressure, an intermediate gas tank with a piston, a check valve installed on the gas supply pipeline, a pump for creating a crimping pressure, pipelines for feeding and removing working fluids with valves, a backpressure regulator, containers with working fluids, a measuring flask for measuring the liquid level at the outlet of the core holder, pressure sensors, a differential pressure gauge for measuring the pressure drop across the test sample and a gas cylinder, characterized in that it additionally includes a vessel equipped with a temperature sensor, a pressure gauge and a valve, which is connected to the pipeline for removing working fluids directly behind the core holder, as well as a valve,installed on the pipeline for supplying a three-phase mixture directly in front of the core holder, 2. The device according to paragraph 1, characterized in that the gas cylinder is filled with nitrogen or helium.

3. The device according to paragraph 1, characterized in that the plunger pumps are designed with the ability to supply water and oil, and the pump for creating the crimping pressure is designed with the ability to supply mineral oil.

Images