CN108896599A - A kind of system and method for testing Gas And Water Relative Permeability curve - Google Patents

Abstract

The invention discloses a system and method for testing gas-water relative permeability curves. The system includes a core holder, a first back pressure valve and a working medium connected in series between the confining pressure outlet end of the rock core holder and the confining pressure inlet end. bottle, circulation pump, heater, and the inlet of the core holder are provided with No. 1 parallel pipeline, No. 2 parallel pipeline, and No. 3 parallel pipeline. Humidifier, pressure stabilizer, pressure reducing valve, gas cylinder; No. 3 parallel pipeline is provided with a vent valve; the outlet end of the core holder is provided with a first parallel pipeline and a second parallel pipeline, the first parallel pipeline is connected to a vacuum pump, and the second parallel pipeline The pipeline is connected with the second back pressure valve and metering device. The method includes: S1, preparation; S2, core saturated with formation water; S3, measurement of gas-phase effective permeability in the state of core bound water; S4, measurement of gas-water relative permeability; S5, measurement of water-phase effective permeability in the state of core residual gas; S6 , Air-water relative permeability curve drawing.

Description

A system and method for testing gas-water relative permeability curve

technical field

The invention relates to the field of oil and natural gas, in particular to a system and method for testing gas-water relative permeability curves.

Background technique

The gas-water relative permeability curve is an indispensable data in the water drive gas reservoir development project. It is used to calculate the water drive gas efficiency, predict the gas reservoir development index, analyze the gas reservoir It is an important basis for numerical simulation research.

At present, the laboratory test of my country's gas-water relative permeability curve is mainly based on the current People's Republic of China oil and gas industry standard (SY/T5345-2007 "Measurement method for relative permeability of two-phase fluid in rock") and the national standard of the People's Republic of China (GB /T28912-2012 "Method for Determination of Relative Permeability of Two-phase Fluid in Rock"). In the aforementioned standards, the test methods for gas-water relative permeability curves mainly include the steady-state method and the unsteady-state gas-drive-water method. in:

The basic principle of the steady-state method is one-dimensional Darcy flow. The experimental process requires that a large displacement pressure difference must be adopted under the condition of ensuring no turbulent flow to eliminate the influence of the end effect during the experimental process. The standard stipulates that it is The gas permeability of the tested core must be greater than 0.5mD, so its scope of application is limited. In addition, the steady-state method also has the disadvantages of a long experimental test period and a relatively complicated determination process of fluid saturation.

The theoretical basis of the unsteady gas flooding water method is Buckley-Leverett's water flooding oil front advancement theory. During the experimental test, the fluid distribution in the porous medium is a function of time and space, resulting in constant changes in the recorded data at the outlet. The reliability of the relative permeability curve test results is greatly affected by the calculation method and the accuracy of the calculation process. And there is a shortage of complex data processing. At the same time, the assumptions of the theory require that the compressibility of the fluid is not considered, which is feasible for slightly compressible fluids such as oil and water, but not feasible for compressible fluids such as gas. In addition, in the actual gas reservoir development process, water drives gas, not gas drives water, and the gas-water relative permeability curve is greatly affected by the fluid saturation sequence. It has little guiding significance for the development of actual water drive gas reservoirs.

Contents of the invention

The invention provides a system and method for testing the gas-water relative permeability curve. The invention not only conforms to the actual development process of water drive gas reservoirs, but also effectively overcomes the shortcomings of the existing methods.

The purpose of the present invention is achieved like this:

A system for testing the gas-water relative permeability curve by the unsteady water driving method, including a core holder and a nuclear magnetic resonance device, the nuclear magnetic resonance device is used to detect the core in the core holder, and the core holder The device has an inlet port, an outlet port, a confining pressure inlet port, and a confining pressure outlet port. Valves are provided at the inlet port and the outlet port of the core holder. Under normal conditions, the valves at the inlet port and the outlet port of the rock core holder is closed,

The first back pressure valve, working medium bottle, circulating pump and heater are connected in series between the confining pressure outlet end and the confining pressure inlet end of the core holder to form a loop. The first back pressure valve is connected with For the first back pressure pump controlling the pressure of the first back pressure valve, the working fluid bottle is equipped with a liquid working medium for applying confining pressure in the nuclear magnetic resonance displacement experiment;

No. 1 parallel pipeline, No. 2 parallel pipeline, and No. 3 parallel pipeline are set at the inlet end of the core holder, and the No. 1 parallel pipeline is connected with an intermediate container and a constant-speed constant-pressure pump in turn, and the intermediate container is equipped with Experimental formation water; the No. 2 parallel pipeline is sequentially connected with a humidifier, a voltage stabilizer, a pressure reducing valve, and a gas cylinder; the No. 3 parallel pipeline is provided with a vent valve;

The outlet end of the core holder is provided with a first parallel pipeline and a second parallel pipeline, the first parallel pipeline is connected to a vacuum pump, and the second parallel pipeline is sequentially connected to a second back pressure valve and a metering device for metering liquid , the metering device is connected with a gas flow meter, and the second back pressure valve is connected with a second back pressure pump for controlling the pressure of the second back pressure valve.

Preferably, a computer control terminal is also included, and the computer control terminal is connected with the nuclear magnetic resonance device, the constant speed and constant pressure pump, the circulation pump, the heater, the first back pressure pump, the second back pressure pump, and the metering device.

Preferably, the experimental formation water in the intermediate container is configured according to the mineral composition of the actual gas reservoir experimental formation water.

A method for testing the gas-water relative permeability curve by the unsteady-state water-driven gas method, including a system for testing the gas-water relative permeability curve by the unsteady-state water-driven gas method, the method includes the following steps:

S1. Experiment preparation

S2. Formation water in core saturation experiment

S21, put the rock core into the rock core holder, start the circulation pump, heater and the first back pressure pump, set the displacement pressure of the circulation pump, the pressure of the first back pressure valve and the temperature of the heater, the displacement pressure of the circulation pump is higher than The pressure of the back pressure valve to establish the temperature and pressure conditions required for the test;

S22. Open the vent valve, start the constant-speed constant-pressure pump for constant-pressure displacement, the displacement pressure is lower than the confining pressure, use the experimental formation water to empty the air in the pipeline at the outlet end of the constant-speed constant-pressure pump, and then close the vent valve to make constant After the fluid pressure in the pipeline at the outlet end of the constant-speed and constant-pressure pump reaches the displacement pressure of the constant-speed and constant-pressure pump, the constant-speed and constant-pressure pump is turned off;

S23, open the valve at the outlet end of the rock core holder, start the vacuum pump, vacuumize the rock core, then close the valve at the outlet end, and turn off the vacuum pump;

S24. Start the constant speed and constant pressure pump, drive at the same pressure and constant pressure, open the valve at the inlet end of the core holder to saturate the core with the experimental formation water, then close the valve at the inlet end of the core holder, and turn off the constant speed and constant pressure pump;

S25, using nuclear magnetic resonance to detect the T2 spectrum of the rock core in a saturated water state;

S3. Determination of gas phase effective permeability in the state of core irreducible water

S31, open the vent valve and the gas cylinder, use gas to exhaust the experimental formation water in the pipeline at the outlet end of the gas cylinder, then close the vent valve, and after the fluid pressure in the pipeline at the outlet end of the gas cylinder is stable, open the valve at the inlet end of the core holder and The valve at the outlet end of the core holder is displaced by constant pressure until the result displayed by the metering device does not change;

S32. Using nuclear magnetic resonance to detect the T2 spectrum of the rock core in the state of irreducible water, and calculate the irreducible water saturation of the rock core;

S33, using a gas flow meter to record the gas flow rate under the current displacement pressure difference, and calculate the gas phase effective permeability of the core in the irreducible water state;

S34, closing the valve at the inlet end of the core holder, the valve at the outlet end of the rock core holder, the gas cylinder and the gas flowmeter;

S4. Determination of air-water relative permeability

S41. Start the constant speed and constant pressure pump and the second back pressure pump, set the displacement pressure of the constant speed and constant pressure pump and the pressure of the second back pressure valve, and use water to drive the gas until the core holder with a constant displacement pressure difference Air bubbles are no longer generated at the outlet end of the core holder, the pressure at the inlet end of the core holder and the outlet end of the core holder at different time nodes, the experimental formation water flow rate and the T2 spectrum of the core are recorded, and the water saturation of the core at different time nodes and the corresponding Water phase effective permeability;

S42. According to the change of water saturation of the core at different time points, calculate the rate of change of gas volume in the core at different time points, so as to calculate the gas flow rate and gas phase effective permeability at different time points;

S5. Determination of water phase effective permeability in the state of core residual gas

S51. Detect the T2 spectrum of the core in the state of residual gas, and calculate the residual gas saturation of the core;

S52. Displacing the experimental formation water with a constant pressure, measuring the flow rate of the experimental formation water under the current displacement pressure difference, and calculating the effective permeability of the water phase of the core in the state of residual gas;

S6. Drawing of gas-water relative permeability curve

Taking the water saturation of the core as the abscissa and the relative permeability as the ordinate, a Cartesian coordinate system is established, and smooth curves are used to draw the gas phase relative permeability curves and water phase relative permeability curves corresponding to different core water saturations.

Preferably, in S33, the gas-phase effective permeability of the core in the irreducible water state is continuously calculated three times, and the relative error is less than 3%.

Preferably, in S52, the water phase effective permeability of the core in the state of residual gas is continuously calculated three times, and the relative error is less than 3%.

Due to the adoption of the above technical scheme, the present invention has high test precision, simple method, short test cycle and wide application range.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Detailed ways

Referring to Fig. 1, a system for testing the gas-water relative permeability curve by the unsteady-state water-driven gas method includes a core holder and a nuclear magnetic resonance device, and the nuclear magnetic resonance device is used to detect the rock core in the rock core holder, and the rock core The structure and working method of the holder and the nuclear magnetic resonance device are the same as the invention patent application with the patent application number: 201510392019.X. The core holder has an inlet port, an outlet port, a confining pressure inlet port, and a confining pressure outlet port. The inlet end and the outlet end of the core holder are provided with valves, and under normal conditions, the valves at the inlet end and the outlet end of the rock core holder are in a closed state.

The first back pressure valve (represented as a back pressure valve in the figure), a working medium bottle, a circulation pump, and a heater are connected in series between the confining pressure outlet end and the confining pressure inlet end of the core holder, and a loop is formed. For providing confining pressure and nuclear magnetic resonance, the first back pressure valve is connected to a first back pressure pump (represented as a back pressure pump in the figure) for controlling the pressure of the first back pressure valve, and the working medium bottle is equipped with a Liquid working fluid under confining pressure in NMR displacement experiments.

No. 1 parallel pipeline, No. 2 parallel pipeline, and No. 3 parallel pipeline are set at the inlet end of the core holder, and the No. 1 parallel pipeline is connected with an intermediate container and a constant-speed constant-pressure pump in turn, and the intermediate container is equipped with Experimental formation water, the experimental formation water in the intermediate container is configured according to the mineral composition of the actual gas reservoir experimental formation water. The constant speed and constant pressure pump adopts a high precision constant speed and constant pressure pump. The No. 2 parallel pipeline is sequentially connected with a humidifier, a voltage stabilizer, a pressure reducing valve, and a gas cylinder. In this embodiment, a nitrogen cylinder is used; the No. 3 parallel pipeline is provided with a vent valve;

The outlet end of the core holder is provided with a first parallel pipeline and a second parallel pipeline, the first parallel pipeline is connected to a vacuum pump, and the second parallel pipeline is sequentially connected to the second circuit for controlling the pressure of the second back pressure valve. A pressure valve and a metering device, the metering device is connected to a gas flow meter, and the back pressure end of the second back pressure valve is connected to a second back pressure pump (shown as a back pressure pump in the figure).

A computer control terminal is also included, and the computer control terminal is connected with the nuclear magnetic resonance device, the constant speed and constant pressure pump, the circulation pump, the heater, the first back pressure pump, the second back pressure pump, and the metering device. The computer control terminal obtains the information of each device, and controls each device according to the test needs.

A method for testing the gas-water relative permeability curve by the unsteady-state water-driven gas method, including a system for testing the gas-water relative permeability curve by the unsteady-state water-driven gas method, the method includes the following steps:

S1. Experiment preparation

S11. Prepare the core, clean and dry it, measure the diameter and length of the core, measure the porosity and absolute permeability of the core by gas; in particular, according to the standard, the gas permeability of the experimental core must be greater than 0.01mD before it can be used to test the relative permeability of gas and water rate curve;

S12, configure the experimental formation water, and transfer it into the intermediate container; in particular, the experiment uses high-purity nitrogen instead of natural gas;

S13. Connect relevant experimental equipment according to the experimental flow chart, and check the connection of the experimental equipment to ensure that there is no leakage throughout the experiment;

S14. Set the NMR test parameters according to the Petroleum and Natural Gas Industry Standard of the People's Republic of China (SY/T6490-2007 "Code for Laboratory Measurement of Rock Sample NMR Parameters");

S2. Formation water in core saturation experiment

S21, put the rock core into the rock core holder, start the circulation pump, heater and the first back pressure pump, set the displacement pressure of the circulation pump, the pressure of the first back pressure valve and the temperature of the heater, the displacement pressure of the circulation pump is higher than The pressure of the back pressure valve to establish the temperature and pressure conditions required for the test;

S22. Open the vent valve, start the constant-speed constant-pressure pump for constant-pressure displacement, the displacement pressure is lower than the confining pressure, use the experimental formation water to empty the air in the pipeline at the outlet end of the constant-speed constant-pressure pump, and then close the vent valve to make constant After the fluid pressure in the pipeline at the outlet end of the constant-speed and constant-pressure pump reaches the displacement pressure of the constant-speed and constant-pressure pump, the constant-speed and constant-pressure pump is turned off;

S23, open the valve at the outlet end of the rock core holder, start the vacuum pump, vacuumize the rock core, then close the valve at the outlet end, and turn off the vacuum pump;

S24. Start the constant speed and constant pressure pump, drive at the same pressure and constant pressure, open the valve at the inlet end of the core holder to saturate the core with the experimental formation water, then close the valve at the inlet end of the core holder, and turn off the constant speed and constant pressure pump;

S25, using nuclear magnetic resonance to detect the T2 spectrum of the rock core in a saturated water state _;

S3. Determination of gas phase effective permeability in the state of core irreducible water

S31. Open the vent valve and the gas cylinder, exhaust the experimental formation water in the pipeline at the outlet end of the gas cylinder with nitrogen, then close the vent valve, and after the fluid pressure in the pipeline at the outlet end of the gas cylinder stabilizes, open the valve at the inlet end of the core holder and The valve at the outlet end of the core holder is displaced with constant pressure until the metering device shows that the result does not change, indicating that the gas drive water is over, which means that the core irreducible water has been established during the experiment;

S32, using nuclear magnetic resonance to detect the T2 spectrum of the rock core under the irreducible water state, and calculating the irreducible water saturation of the rock core _;

S33, using a gas flow meter to record the gas flow rate under the current displacement pressure difference, and calculate the gas phase effective permeability of the rock core in the irreducible water state; continuously calculate the gas phase effective permeability of the rock core in the irreducible water state for three times, and make the relative error less than 3%.

S34, closing the valve at the inlet end of the core holder, the valve at the outlet end of the rock core holder, the gas cylinder and the gas flow meter;

S4. Determination of air-water relative permeability

S41. Start the constant speed and constant pressure pump and the second back pressure pump, set the displacement pressure of the constant speed and constant pressure pump and the back pressure of the second back pressure pump, and use water to displace gas until the core is clamped with a constant displacement pressure difference Air bubbles are no longer generated at the outlet end of the core holder, the pressure at the inlet end of the core holder and the outlet end of the core holder at different time nodes, the experimental formation water flow rate and the _T2 spectrum of the rock core are recorded, and the water saturation of the rock core at different time nodes is calculated and Corresponding water phase effective permeability;

S42. According to the changes in the water saturation of the core at different time points, the principle of material balance is adopted, that is, the pore volume of the core is constant, and the gas volume change rate in the core at different time points is calculated, thereby calculating the gas flow rate and gas phase effective permeability at different time points .

S5. Determination of water phase effective permeability in the state of core residual gas

S51, detecting the T2 spectrum of the rock core under the state of residual gas, and calculating the residual gas saturation of the rock core _;

S52. Displace the experimental formation water with a constant pressure, measure the experimental formation water flow rate under the current displacement pressure difference, and calculate the effective permeability of the water phase of the core in the state of residual gas; continuously calculate the effective water phase of the core in the state of residual gas for three times Permeability, and make the relative error less than 3%.

S6. Drawing of gas-water relative permeability curve

Taking the water saturation of the core as the abscissa and the relative permeability as the ordinate, a Cartesian coordinate system is established, and smooth curves are used to draw the gas phase relative permeability curves and water phase relative permeability curves corresponding to different core water saturations.

Referring to Fig. 1, each parallel pipeline of the present invention is provided with a valve at one end connected to the core holder, and the valves are all gate valves. There are pressure gauges where pressure needs to be measured, and thermometers where temperature needs to be measured.

Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that it can be described in terms of form and Various changes may be made in the details without departing from the scope of the invention defined by the claims.

Claims (6)

1. a kind of system of unstable state water drive gas method test Gas And Water Relative Permeability curve, including core holding unit, nuclear magnetic resonance Device, the nuclear magnetic resonance device are used to detect the rock core in core holding unit, and the core holding unit has arrival end, outlet End, confining pressure arrival end, confining pressure outlet end, the arrival end of the core holding unit, outlet end are equipped with valve, described under normality Core holding unit arrival end, outlet end valve be in close state, it is characterised in that：

The confining pressure outlet end of the core holding unit to be sequentially connected in series between confining pressure arrival end the first back-pressure valve, working medium bottle, circulation Pump, heater, and loop is formed, the first back-pressure valve connection is for controlling the first backpressure pump of the first back-pressure valve pressure, institute State working medium bottle be provided in nuclear magnetic resonance displacement test apply confining pressure liquid working substance；

Arrival end setting No.1 parallel connection pipeline, No. two parallel connection pipelines, No. three pipelines in parallel of the core holding unit, the No.1 Pipeline in parallel is connected with intermediate receptacle, constant speed and constant pressure pump in turn, and experiment water flooding is housed in the intermediate receptacle；Described No. two simultaneously Union line is connected with humidifier, voltage-stablizer, pressure reducing valve, gas cylinder in turn；Described No. three pipeline installation of relief valve in parallel；

The pipeline in parallel of outlet end setting first, the second pipeline in parallel of the core holding unit, the described first pipeline connection in parallel Vacuum pump, the described second pipeline in parallel are sequentially connected the second back-pressure valve, the metering device for metering liquid, the metering device It is connected with gas flowmeter, the second back-pressure valve connection is for controlling the second backpressure pump of the second back-pressure valve pressure.

2. a kind of system of unstable state water drive gas method test Gas And Water Relative Permeability curve according to claim 1, special Sign is, further includes computer controlling terminal, the computer controlling terminal and nuclear magnetic resonance device, constant speed and constant pressure pump, circulation Pump, heater, the first backpressure pump, the second backpressure pump, metering device connection.

3. a kind of system of unstable state water drive gas method test Gas And Water Relative Permeability curve according to claim 1, special Sign is that the experiment water flooding in the intermediate receptacle is tested water flooding mineral constituent according to practical gas reservoir and configured.

4. a kind of method of unstable state water drive gas method test Gas And Water Relative Permeability curve, which is characterized in that including claim A kind of system of any unstable state water drive gas method test Gas And Water Relative Permeability curve of 1-3, method include the following steps：

S1, Preparatory work of experiment

S2, rock core saturation experiments water flooding

S21, rock core is packed into core holding unit, circulating pump displacement pressure is arranged in starting circulating pump, heater and the first backpressure pump Power, the first back-pressure valve pressure and heter temperature, the displacement pressure of circulating pump are slightly above back-pressure valve pressure, establish needed for test Temperature, pressure condition；

S22, blow valve is opened, starting constant speed and constant pressure pumps constant pressure displacement, and displacement pressure is lower than confining pressure, permanent with experiment water flooding emptying Air in the pipeline of fast constant pressure pump outlet end, is then shut off blow valve, reaches constant speed and constant pressure pump discharge end pipe line Fluid pressure After the displacement pressure of constant speed and constant pressure pump, constant speed and constant pressure pump is closed；

S23, the valve for opening outlet port of rock core holder start vacuum pump for rock core vacuumizing and are then shut off outlet end valve Door closes vacuum pump；

S24, starting constant speed and constant pressure pump, uniform pressure constant pressure displacement open core holding unit arrival end valve, keep rock core saturation real Water flooding is tested, core holding unit arrival end valve is then shut off, closes constant speed and constant pressure pump；

S25, using the T of rock core under magnetic resonance detection saturated-water phase₂Map；

Gas phase effective permeability measurement under S3, rock core constraint water state

S31, blow valve, gas cylinder are opened, with the experiment water flooding in gas emptying gas cylinder outlet end pipeline, is then shut off emptying Valve opens core holding unit arrival end valve and core holding unit goes out after the Fluid pressure in cylinder outlet end pipe line is stablized Mouth end valve door, constant pressure displacement, until metering device shows that result no longer changes；

S32, the T that rock core under water state is fettered using magnetic resonance detection₂Map calculates rock core irreducible water saturation；

S33, using gas flowmeter, record gas flow under current displacement pressure difference, calculate gas of the rock core in the case where fettering water state Phase effective permeability；

S34, core holding unit arrival end valve, outlet port of rock core holder valve, gas cylinder and gas flowmeter are closed；

S4, Gas And Water Relative Permeability measurement

S41, starting constant speed and constant pressure pump and the second backpressure pump, the pressure of displacement pressure and the second back-pressure valve that setting constant speed and constant pressure pumps Power, using water drive gas until the outlet end of core holding unit no longer generates bubble, records core holding unit with constant displacement pressure difference Arrival end and outlet port of rock core holder are in the pressure of different time nodes, the T of experiment stratum water flow and rock core₂Map, meter Calculate different time nodes rock core water saturation and corresponding water phase effective permeability；

S42, according to the situation of change of different time nodes rock core water saturation, calculate the tolerance in different time nodes rock core Change rate, to calculate the throughput and gas phase effective permeability of different moments；

Water phase effective permeability measurement under S5, rock core remnants gaseity

S51, the T for detecting rock core under remaining gaseity₂Map calculates rock core residual gas saturation；

S52, with constant pressure displacement test water flooding, measure under current displacement pressure difference experiment stratum water flow, calculate rock core and exist Water phase effective permeability under remaining gaseity；

S6, Gas And Water Relative Permeability Drawing of Curve

Using rock core water containing saturability value as abscissa, using relative permeability value as ordinate, rectangular coordinate system is established, using smooth Curve draws the corresponding gas phase permeability saturation curve of different rock core water containing saturabilities and water phase permeability saturation curve respectively.

5. a kind of method of unstable state water drive gas method test Gas And Water Relative Permeability curve according to claim 4, special Sign is, in S33, Continuous plus gas phase effective permeability of the rock core in the case where fettering water state three times, and it is less than relative error 3%.

6. a kind of method of unstable state water drive gas method test Gas And Water Relative Permeability curve according to claim 4, special Sign is, in S52, Continuous plus water phase effective permeability of the rock core under remaining gaseity three times, and it is less than relative error 3%.