CN113495045A - Electric simulation system and calculation method for starting pressure gradient of tight oil reservoir - Google Patents
Electric simulation system and calculation method for starting pressure gradient of tight oil reservoir Download PDFInfo
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Abstract
Discloses a compact oil reservoir starting pressure gradient electric simulation system and a calculation method. The system can include a power supply, a switch, an ammeter, a solid simulator, a voltmeter, a data acquisition instrument, and a processor, wherein: the solid simulator comprises a simulation vertical well and a point hole, the simulation vertical well is arranged at the center of the solid simulator along the radial direction, and the point hole is arranged on the surface of the solid simulator; the power supply, the switch, the ammeter and the solid simulator are connected in series to form a loop; the voltmeter is connected with the solid simulator in parallel, one end of the voltmeter is connected with the simulation vertical well, the other end of the voltmeter is provided with the probe, and the probe is connected with the point hole; the data acquisition instrument is connected with the ammeter and the voltmeter and is used for acquiring data; and the processor is connected with the data acquisition instrument and used for calculating the starting pressure of the compact oil reservoir according to the acquired data. The method provided by the invention performs an electrical simulation experiment through the solid conductive medium and the semiconductor medium to determine the starting pressure gradient of the compact oil reservoir, and provides technical support for the seepage mechanism and yield prediction of the compact oil reservoir.
Description
Technical Field
The invention relates to an oil-gas seepage technology, in particular to a compact reservoir starting pressure gradient electric simulation system and a calculation method.
Background
In a tight oil reservoir, the pore throat is fine, the pore structure is complex, the interaction between fluid and a pore interface is obvious, and liquid molecules are tightly adsorbed on the surface of a solid to form a fluid boundary layer with certain thickness and no flow. The thickness of the boundary layer changes along with the change of the pressure gradient, and the low-speed non-Darcy seepage characteristic of the compact oil reservoir is formed. When the displacement pressure gradient is less than a certain critical value, the compact reservoir pores are completely filled by the stagnant fluid boundary layer, the fluid cannot flow, and the pore fluid can participate in the flow only when the pore fluid is higher than the pressure gradient, and the critical pressure gradient is the starting pressure gradient. Therefore, the method has important significance for researching the low-speed non-Darcy seepage mechanism of the tight oil reservoir by accurately measuring the starting pressure gradient.
The conventional measurement method for starting the pressure gradient is an actual core flow experiment method, and comprises a flow-pressure difference method, an unsteady state method, a capillary balance method, an unsteady state displacement-capillary method and the like. The flow-pressure difference method is to measure the seepage curve by using a steady state method and then fit the curve to obtain the starting pressure gradient. The unsteady state method is an experimental method for measuring pressure in unsteady state seepage, and the starting pressure gradient of the rock core is worked out by fitting actual measurement pressure data and a theoretical dimensionless pressure curve on a logarithmic coordinate graph. The capillary tube balancing method adopts a communicating vessel principle, when the starting pressure gradient is measured, the capillary tube is connected at the inlet end and the outlet end of the rock core, fluid at the inlet end flows to the outlet end through the rock core under the action of gravity, liquid levels at two ends are fully balanced, and finally a height difference is kept, wherein the height difference is the minimum starting pressure value of the sample. The unsteady state displacement-capillary method is characterized in that the outlet end of the core holder is filled with liquid, then the liquid is injected in a micro flow manner, and when the liquid level of the outlet end of the core starts to move, the pressure at the moment is the minimum starting pressure.
In the aspect of measuring the starting pressure gradient in the aspect of core flow experiments, the prior art comprises the steps of measuring liquid flow under different pressures by using a micro-flow meter and a pressure sensor so as to calculate the starting pressure, wherein the essence of the method is to use a differential pressure-flow method; and (4) simulating the starting pressure by combining the differential pressure-flow core test with theoretical calculation.
The core flow experiment can be carried out by adopting an actual oil reservoir core, is relatively close to the actual geological condition, and can directly measure the change rules of relatively accurate yield, pressure and the like, but the method has the following defects: firstly, the small core displacement pressure difference is low, the flow of a liquid filling pump is small, the accuracy dependence of experiment accuracy on the precision of an experimental instrument is large, the pressure difference and the flow need to be monitored accurately to the levels of 0.001MPa and 0.0001ml/min, and expensive experimental equipment is needed for supporting; second, the experiment requires measuring multiple sets of data at lower displacement pressures and displacement flows, resulting in a long experimental period.
In the aspect of measuring the starting pressure gradient in an electrical simulation experiment, the prior art adopts a diode to simulate the starting pressure and adopts a copper sheet to simulate a crack, so that the potential variation amplitude is large and the relative error is large in the experiment process.
Therefore, it is necessary to develop a tight reservoir start pressure gradient electrical simulation system and a calculation method.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
The invention provides a compact reservoir starting pressure gradient electrical simulation system and a calculation method, which can carry out an electrical simulation experiment through a solid conductive medium and a semiconductor medium, determine the starting pressure gradient of a compact reservoir and provide technical support for predicting the seepage mechanism and the yield of the compact reservoir.
According to one aspect of the invention, a starting pressure gradient electrical simulation system for a tight oil reservoir is provided, which is characterized by comprising a power supply, a switch, an ammeter, a solid simulator, a voltmeter, a data acquisition instrument and a processor, wherein: the solid simulator comprises a simulation vertical well and a point hole, the simulation vertical well is radially arranged in the center of the solid simulator, and the point hole is arranged on the surface of the solid simulator; the power supply, the switch, the ammeter and the solid simulator are connected in series to form a loop; the voltmeter is connected with the solid simulator in parallel, one end of the voltmeter is connected with the simulation vertical well, and the other end of the voltmeter is provided with a probe which is connected with the point hole; the data acquisition instrument is connected with the ammeter and the voltmeter and is used for acquiring data; and the processor is connected with the data acquisition instrument and used for calculating the starting pressure of the tight oil reservoir according to the acquired data.
Preferably, the ballast is arranged in the series circuit and used for regulating the voltage in the circuit.
Preferably, the solid-state simulator further comprises an outer conductive medium, an inner conductive medium, a semiconductor interlayer: the semiconductor interlayer is arranged between the outer side conductive medium and the inner side conductive medium and isolates the outer side conductive medium from the inner side conductive medium; the surfaces of the outer side conductive medium and the inner side conductive medium are provided with the point holes.
Preferably, the semiconductor interlayer comprises a sheet-shaped insulating medium and a semiconductor chip: the semiconductor chips are embedded in the sheet-shaped insulating medium at intervals.
Preferably, in the series circuit, one end of the two ends of the solid simulator is connected with the simulation vertical well, and the other end of the solid simulator is connected with the outer conductive medium.
According to another aspect of the invention, a tight reservoir start pressure calculation method is provided. The method may include: calculating the radial flow seepage resistance of the oil reservoir to be tested; starting a pressure gradient electrical simulation system through the tight oil reservoir, drawing a volt-ampere curve, and further determining the on-state characteristic resistance; setting a flow similarity coefficient, and calculating the pressure and the flow of the oil reservoir to be tested according to the radial flow seepage resistance and the conduction characteristic resistance; and drawing a pressure-flow curve, and further determining the starting pressure of the tight oil reservoir.
Preferably, the radial flow seepage resistance of the reservoir to be tested is calculated by the formula (1):
wherein R isouFor radial flow seepage resistance, μ is crude oil viscosity, k is permeability, h is reservoir thickness, and r is single well supply radius.
Preferably, plotting the voltammetry curve and determining the on-characteristic resistance comprises: the rear section of the volt-ampere curve is extended to be intersected with an x axis in a straight and reverse mode, the corresponding value of the intersection point is the breakdown voltage of a semiconductor, and the current of the breakdown voltage on the volt-ampere curve is the conduction current; and calculating the on-characteristic resistance according to the breakdown voltage and the on-current.
Preferably, the pressure of the reservoir to be tested is calculated by equation (2):
where P is the pressure of the reservoir to be tested, RouFor radial flow seepage resistance, VdIs a voltage, CqAs flow similarity factor, RonIs the on characteristic resistance.
Preferably, the flow rate of the reservoir to be tested is calculated by equation (3):
Q＝CQId (3)
wherein Q is the flow of the reservoir to be tested, IdIs a current, CQIs the flow similarity coefficient.
Preferably, the step of drawing a pressure-flow curve, and then determining the tight reservoir initiation pressure comprises: and reversely extending the rear section of the pressure-flow curve to intersect with the x axis, wherein the corresponding value of the intersection point is the starting pressure of the tight oil reservoir.
The beneficial effects are that:
1. measuring the starting pressure gradient of the tight oil reservoir, and providing technical support for the seepage mechanism and yield prediction of the tight oil reservoir;
2. an electric simulation experiment with starting pressure is carried out on the simulated stratum, and the experiment period is greatly shortened;
3. the conductive medium material has simple preparation method and low manufacturing cost, and can be used for manufacturing complex and irregular oil reservoir blocks;
4. the phenomenon that the electrolyte and an electrode material have electrolytic reaction in the existing electric simulation experiment is eliminated, and the accuracy of measuring the near-wellbore potential is improved.
The method and apparatus of the present invention have other features and advantages which will be apparent from or are set forth in detail in the accompanying drawings and the following detailed description, which are incorporated herein, and which together serve to explain certain principles of the invention.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts.
FIG. 1 shows a schematic of a tight reservoir startup pressure gradient electrical simulation system according to one embodiment of the invention.
Figure 2 shows a schematic side view of a semiconductor interlayer, according to one embodiment of the present invention.
FIG. 3 shows a flow chart of the steps of a tight reservoir start pressure calculation method according to the present invention.
Fig. 4 shows a schematic diagram of a voltammogram according to an embodiment of the invention.
FIG. 5 shows a schematic diagram of a pressure-flow curve according to an embodiment of the invention.
Description of reference numerals:
1. a power source; 2. a switch; 3. a ballast; 4. a solid state simulator; 5. an ammeter; 6. an outer conductive medium; 7. punching holes; 8. a voltmeter; 9. an inner conductive medium; 10. a semiconductor interlayer; 11. simulating a vertical well; 12. a probe; 13. a sheet-like insulating medium; 14. a semiconductor chip; 15. a data acquisition instrument; 16. a processor.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
According to an embodiment of the invention, a starting pressure gradient electric simulation system for a tight oil reservoir is provided, which is characterized by comprising a power supply, a switch, an ammeter, a solid simulator, a voltmeter, a data acquisition instrument and a processor, wherein: the solid simulator comprises a simulation vertical well and a point hole, the simulation vertical well is arranged at the center of the solid simulator along the radial direction, and the point hole is arranged on the surface of the solid simulator; the power supply, the switch, the ammeter and the solid simulator are connected in series to form a loop; the voltmeter is connected with the solid simulator in parallel, one end of the voltmeter is connected with the simulation vertical well, the other end of the voltmeter is provided with the probe, and the probe is connected with the point hole; the data acquisition instrument is connected with the ammeter and the voltmeter and is used for acquiring data; and the processor is connected with the data acquisition instrument and used for calculating the starting pressure of the compact oil reservoir according to the acquired data.
In one example, a ballast is also included, disposed in the series circuit, for regulating the voltage in the circuit.
In one example, the solid state simulator further comprises an outer conductive medium, an inner conductive medium, a semiconductor interlayer: the semiconductor interlayer is arranged between the outer side conductive medium and the inner side conductive medium and isolates the outer side conductive medium from the inner side conductive medium; the surfaces of the outer side conductive medium and the inner side conductive medium are provided with point holes.
In one example, the semiconductor interlayer includes a sheet-like insulating medium and a semiconductor chip: the semiconductor chips are embedded in the sheet-like insulating medium at intervals.
In one example, in the series circuit, one of the two ends of the solid-state simulator is connected with the simulation vertical well, and the other end of the solid-state simulator is connected with the outer conductive medium.
Specifically, the tight oil reservoir starting pressure gradient electric simulation system comprises a power supply, a switch, a ballast, an ammeter, a solid simulator, a voltmeter, a data acquisition instrument and a processor, wherein:
the solid simulator comprises a simulation vertical well and a point hole, the simulation vertical well is arranged at the center of the solid simulator along the radial direction, and the point hole is arranged on the surface of the solid simulator; the device also comprises an outer side conductive medium, an inner side conductive medium and a semiconductor interlayer: the semiconductor interlayer is arranged between the outer side conductive medium and the inner side conductive medium and isolates the outer side conductive medium from the inner side conductive medium; the surfaces of the outer side conductive medium and the inner side conductive medium are both provided with point holes, and the point holes are uniformly distributed according to the size of the solid simulator;
the power supply, the switch, the ballast, the ammeter and the solid simulator are connected in series to form a loop, and the ballast is used for adjusting the voltage in the loop;
the voltmeter is connected with the solid simulator in parallel, one end of the voltmeter is connected with the simulation vertical well, the other end of the voltmeter is provided with the probe, and the probe is connected with the point hole; during measurement, the probe can be fixedly placed in the point hole and can also freely move on the outer surface of the outer side conductive medium, namely the potential of the point can be measured, and the potential of each point can be measured and recorded by changing the position of the probe, so that the distribution diagram of the equipotential lines of the electric field can be measured;
the data acquisition instrument is connected with the ammeter and the voltmeter and is used for acquiring data; the processor is connected with the data acquisition instrument, and the starting pressure of the compact oil reservoir is calculated according to the acquired data;
in the series loop, one end of the two ends of the solid simulator is connected with the simulation vertical well, and the other end of the solid simulator is connected with the outer surface of the outer conductive medium.
The semiconductor interlayer in the solid simulator is used as an interlayer between two layers of conductive media and comprises a sheet-shaped insulating medium and a semiconductor chip, the semiconductor chip is embedded into the sheet-shaped insulating medium at intervals, the two layers of conductive media and the semiconductor chip form a conductive path, and the sheet-shaped insulating medium has the function of isolating the conduction of the two layers of conductive media. The semiconductor chip has breakdown voltage characteristic, and the semiconductor device after breakdown has on-state characteristic resistance RonThe size of the resistance is related to the on-state resistance and the area of an active area, and the compact oil reservoir with different seepage resistances is simulated by changing the size of the on-state characteristic resistance.
The system performs an electrical simulation experiment through a solid conductive medium and a semiconductor medium to determine the starting pressure gradient of the compact oil reservoir, and provides technical support for the seepage mechanism and the yield prediction of the compact oil reservoir.
Application example
To facilitate understanding of the solution of the embodiments of the present invention and the effects thereof, a specific application example is given below. It will be understood by those skilled in the art that this example is merely for the purpose of facilitating an understanding of the present invention and that any specific details thereof are not intended to limit the invention in any way.
FIG. 1 shows a schematic of a tight reservoir startup pressure gradient electrical simulation system according to one embodiment of the invention.
The starting pressure gradient electric simulation system for the tight oil reservoir comprises a power supply 1, a switch 2, a ballast 3, an ammeter 5, a solid simulator 4, a voltmeter 8, a data acquisition instrument 15 and a processor 16, wherein:
the power supply 1 is a voltage-adjustable direct-current power supply, and the ballast 3 adjusts the voltage in the loop.
The solid simulator 4 comprises a simulation vertical well 11 and a point hole 7, the simulation vertical well 11 is arranged at the center of the solid simulator 4 along the radial direction, and the point hole 7 is arranged on the surface of the solid simulator 4; the semiconductor device further comprises an outer conductive medium 6, an inner conductive medium 9 and a semiconductor interlayer 10: the semiconductor interlayer 10 is arranged between the outer side conductive medium 6 and the inner side conductive medium 9 and isolates the outer side conductive medium 6 from the inner side conductive medium 9; the outer side conductive medium 6 and the inner side conductive medium 9 are both made of metal tin, the surfaces of the outer side conductive medium and the inner side conductive medium are both provided with point holes 7, the diameter of each point hole 7 is 1mm, the depth of each point hole is 0.5cm, and the point holes 7 are uniformly distributed according to the size of the solid simulator 4;
the power supply 1, the switch 2, the ballast 3, the ammeter 5 and the solid simulator 4 are connected in series to form a loop;
the voltmeter 8 is connected with the solid simulator 4 in parallel, one end of the voltmeter 8 is connected with the simulation vertical well 11, the other end of the voltmeter 8 is provided with the probe 12, and the connecting point hole 7 is formed; the diameter of the copper probe 12 is 1mm, the lower end of the copper probe is coated with a layer of insulating skin, only the probe 12 with the diameter of 1mm is exposed, the probe 12 is fixedly placed in the point hole 7 during measurement, the potential of the point can be measured, and the potential of each point is measured and recorded by changing the position of the probe 12, so that the distribution diagram of the equipotential lines of the electric field can be measured;
the data acquisition instrument 15 is connected with the ammeter 5 and the voltmeter 8 and used for acquiring data; the processor 16 is connected with the data acquisition instrument 15, and the starting pressure of the tight oil reservoir is calculated according to the acquired data;
in the series circuit, one end of the two ends of the solid simulator 4 is connected with the simulation vertical well 11, and the other end is connected with the outer conductive medium 6.
Figure 2 shows a schematic side view of a semiconductor interlayer, according to one embodiment of the present invention.
The semiconductor sandwich 10 in the solid-state simulator 4 includes a sheet-like insulating medium 13 and a semiconductor chip 14: the semiconductor chips 14 are embedded in the sheet-shaped insulating medium 13 at intervals, the sheet-shaped insulating medium 13 is a non-conductive polyethylene film, the semiconductor chips 14 are gallium nitride semiconductor devices, are rectangular sheets, have micron-sized thickness, are embedded in the polyethylene film, and are used as interlayers between two layers of conductive media as shown in fig. 2. The two layers of conductive media and the gallium nitride semiconductor form a conductive path, and the polyethylene film has the function of isolating the conduction of the two layers of conductive media. The gallium nitride semiconductor device has a breakdown voltage characteristic of breakdown voltage VsGenerally between 50 and 60V, and the semiconductor device after breakdown has an on-characteristic resistance RonThe size of the resistance is related to the on-state resistance and the area of an active area, and the compact oil reservoir with different seepage resistances is simulated by changing the size of the on-state characteristic resistance.
In conclusion, the starting pressure gradient of the compact oil reservoir is measured by performing an electrical simulation experiment on the solid conductive medium and the semiconductor medium, and technical support is provided for the seepage mechanism and the yield prediction of the compact oil reservoir.
It will be appreciated by persons skilled in the art that the above description of embodiments of the invention is intended only to illustrate the benefits of embodiments of the invention and is not intended to limit embodiments of the invention to any examples given.
FIG. 3 shows a flow chart of the steps of a tight reservoir start pressure calculation method according to the present invention.
In this embodiment, the tight reservoir start pressure calculation method according to the present invention may include: step 101, calculating the radial flow seepage resistance of an oil reservoir to be tested; step 102, starting a pressure gradient electrical simulation system through a tight oil reservoir, drawing a volt-ampere curve, and further determining the conduction characteristic resistance; 103, setting a flow similarity coefficient, and calculating the pressure and the flow of the oil reservoir to be tested according to the radial flow seepage resistance and the conduction characteristic resistance; and 104, drawing a pressure-flow curve, and further determining the starting pressure of the tight oil reservoir.
In one example, the radial flow seepage resistance of the reservoir to be tested is calculated by equation (1):
wherein R isouFor radial flow seepage resistance, μ is crude oil viscosity, k is permeability, h is reservoir thickness, and r is single well supply radius.
In one example, plotting the current-voltage curve, and thereby determining the on-characteristic resistance, comprises: the rear section of the volt-ampere curve is extended to be intersected with the x axis in a reverse direction, the corresponding value of the intersection point is the breakdown voltage of the semiconductor, and the current of the breakdown voltage on the volt-ampere curve is the conduction current; and calculating the on-characteristic resistance through the breakdown voltage and the on-current.
In one example, the reservoir pressure to be tested is calculated by equation (2):
where P is the pressure of the reservoir to be tested, RouFor radial flow seepage resistance, VdIs a voltage, CqAs flow similarity factor, RonIs the on characteristic resistance.
In one example, the flow rate of the reservoir to be tested is calculated by equation (3):
Q＝CQId (3)
wherein Q is the flow of the reservoir to be tested, IdIs a current, CQIs the flow similarity coefficient.
In one example, plotting a pressure-flow curve and determining the tight reservoir initiation pressure comprises: and (3) reversely extending the rear section of the pressure-flow curve to intersect with the x axis, wherein the corresponding value of the intersection point is the starting pressure of the tight oil reservoir.
Specifically, the electrical simulation experiment is a simulation experiment method formed according to the principle of water and electricity similarity. The electrical simulation experiment is to reproduce the object to be studied by using some physical phenomena of electricity, i.e., the physical phenomena expressed by the same mathematical differential equation are simulated with each other.
The steady seepage of incompressible subterranean fluids through porous media conforms to darcy's law and laplace's equation:
the flow of current in the conductive medium and the potential distribution satisfy ohm's law and laplace's equation:
according to the theory of water and electricity similarity, the shapes and the distribution of the seepage field and the electric field are similar, and the seepage field and the electric field can obtain similar solutions under similar boundary conditions. According to ohm's law, the current in any flowing unit in the electric field is:
according to darcy's law, the fluid flow in a block of cells in the formation along the direction of the pressure gradient is:
the current, voltage and distribution thereof in the electric field and the flow, pressure and distribution thereof in the stable seepage field have the following corresponding proportional relationship, the subscript of model data is m, the subscript of stratum data is n:
the pressure similarity coefficient is:
wherein, CPFor pressure similarity coefficients, Δ U is the potential difference and Δ P is the pressure difference.
Flow similarity coefficient:
wherein, CQIs the flow similarity coefficient, I is the current, and Q is the well production.
Resistance similarity coefficient:
wherein, CRAs a coefficient of resistance similarity, RmIs electricityResistance of the field, RnIs the formation fluid seepage resistance.
According to the formulas (6) and (7), the similarity coefficients satisfy the following conditions:
an analog relation exists between the stable seepage field and the electric field which meets the conditions, and the electric field can be used for simulating the stable seepage field and researching the seepage rule. Because the current can reach the stability in the experiment in the twinkling of an eye, therefore the process of electricity simulation is single-phase steady flow process in the stratum. The current and voltage data in the electric field are measured, and the yield and pressure data in the seepage field can be converted by utilizing the similar proportional relation. Equation (11) is a similarity criterion that the model must satisfy, where two parameters can be freely determined and the third parameter must be derived from the similarity criterion.
With the increasing complexity of oil fields which are put into development, electrical simulation experiments are increasingly widely applied in the field of oil and gas seepage, mainly due to the following advantages: the electric simulation experiment can be processed and manufactured various complex models at will, has short experiment period and low cost, and has more advantages compared with the core experiment.
Fig. 4 shows a schematic diagram of a voltammogram according to an embodiment of the invention.
FIG. 5 shows a schematic diagram of a pressure-flow curve according to an embodiment of the invention.
The tight reservoir start pressure calculation method according to the present invention may include:
calculating the radial flow seepage resistance of the reservoir to be tested through a formula (1); starting the pressure gradient electric simulation system through the tight oil reservoir, switching on the switch, communicating the probe with any point on the outer surface of the point hole or the outer conductive medium and keeping the point fixed, and gradually increasing the voltage V through the ballastdObserve the ammeter IdChanging the situation, drawing a voltammogram, and extending the back section of the voltammogram to a corresponding value V which is intersected with the x axis and is intersected with the x axis in a straight reverse manner as shown in FIG. 4TIs breakdown voltage of semiconductor in volt-ampereCorresponding current I on the curvesIs the conduction current; and calculating the on-characteristic resistance according to ohm law through breakdown voltage and on-current.
Setting a flow similarity coefficient CQFrom equations (8) to (11), it is possible to obtain:
and (3) calculating the pressure of the reservoir to be tested through a formula (2) and calculating the flow of the reservoir to be tested through a formula (3) according to the radial flow seepage resistance and the conduction characteristic resistance. Then drawing a pressure-flow curve, and as shown in FIG. 5, extending the straight line at the rear section of the pressure-flow curve reversely to the corresponding value P intersecting with the x-axis at the intersection pointTPressure is initiated for tight reservoirs.
The method performs an electrical simulation experiment through the solid conductive medium and the semiconductor medium to determine the starting pressure gradient of the compact oil reservoir, and provides technical support for the seepage mechanism and the yield prediction of the compact oil reservoir.
It will be appreciated by persons skilled in the art that the above description of embodiments of the invention is intended only to illustrate the benefits of embodiments of the invention and is not intended to limit embodiments of the invention to any examples given.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (10)
1. The utility model provides a tight oil reservoir starts pressure gradient electric analog system which characterized in that, this system includes power, switch, ampere meter, solid simulator, voltmeter, data acquisition appearance, treater, wherein:
the solid simulator comprises a simulation vertical well and a point hole, the simulation vertical well is radially arranged in the center of the solid simulator, and the point hole is arranged on the surface of the solid simulator;
the power supply, the switch, the ammeter and the solid simulator are connected in series to form a loop;
the voltmeter is connected with the solid simulator in parallel, one end of the voltmeter is connected with the simulation vertical well, and the other end of the voltmeter is provided with a probe which is connected with the point hole;
the data acquisition instrument is connected with the ammeter and the voltmeter and is used for acquiring data;
and the processor is connected with the data acquisition instrument and used for calculating the starting pressure of the tight oil reservoir according to the acquired data.
2. The tight reservoir initiation pressure gradient electrical simulation system of claim 1, wherein the solids simulator further comprises an outer conductive medium, an inner conductive medium, a semiconducting interlayer:
the semiconductor interlayer is arranged between the outer side conductive medium and the inner side conductive medium and isolates the outer side conductive medium from the inner side conductive medium;
the surfaces of the outer side conductive medium and the inner side conductive medium are provided with the point holes.
3. The tight reservoir initiation pressure gradient electrical simulation system of claim 2, wherein the semiconductor interlayer comprises a sheet-like insulating medium and a semiconductor chip:
the semiconductor chips are embedded in the sheet-shaped insulating medium at intervals.
4. The tight reservoir startup pressure gradient electrical simulation system of claim 2, wherein in a series circuit, one of the two ends connecting the solid simulator is connected to the simulation vertical well, and the other end is connected to the outside conductive medium.
5. A tight reservoir start pressure calculation method, comprising:
calculating the radial flow seepage resistance of the oil reservoir to be tested;
starting a pressure gradient electrical simulation system through the tight oil reservoir, drawing a volt-ampere curve, and further determining the on-state characteristic resistance;
setting a flow similarity coefficient, and calculating the pressure and the flow of the oil reservoir to be tested according to the radial flow seepage resistance and the conduction characteristic resistance;
and drawing a pressure-flow curve, and further determining the starting pressure of the tight oil reservoir.
6. The tight reservoir start pressure calculation method of claim 5, wherein the radial flow seepage resistance of the reservoir to be tested is calculated by equation (1):
wherein R isouFor radial flow seepage resistance, μ is crude oil viscosity, k is permeability, h is reservoir thickness, and r is single well supply radius.
7. The tight reservoir start-up pressure calculation method of claim 5, wherein plotting the voltammograms to determine the on-resistance comprises:
the rear section of the volt-ampere curve is extended to be intersected with an x axis in a straight and reverse mode, the corresponding value of the intersection point is the breakdown voltage of a semiconductor, and the current of the breakdown voltage on the volt-ampere curve is the conduction current;
and calculating the on-characteristic resistance according to the breakdown voltage and the on-current.
8. The tight reservoir start pressure calculation method of claim 5, wherein the pressure of the reservoir to be tested is calculated by equation (2):
wherein P is to be measuredTesting the pressure, R, of the reservoirouFor radial flow seepage resistance, VdIs a voltage, CqAs flow similarity factor, RonIs the on characteristic resistance.
9. The tight reservoir start pressure calculation method of claim 5, wherein the flow rate of the reservoir to be tested is calculated by equation (3):
Q＝CQId (3)
wherein Q is the flow of the reservoir to be tested, IdIs a current, CQIs the flow similarity coefficient.
10. The tight reservoir start pressure calculation method of claim 5, wherein plotting a pressure-flow curve to determine the tight reservoir start pressure comprises:
and reversely extending the rear section of the pressure-flow curve to intersect with the x axis, wherein the corresponding value of the intersection point is the starting pressure of the tight oil reservoir.
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