CN113495045B - Dense oil reservoir starting pressure gradient electric simulation system and calculation method - Google Patents
Dense oil reservoir starting pressure gradient electric simulation system and calculation method Download PDFInfo
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Abstract
A dense oil reservoir starting pressure gradient electric simulation system and a calculation method are disclosed. The system may include a power supply, a switch, an ammeter, a solid state simulator, a voltmeter, a data acquisition instrument, a processor, wherein: the solid simulator comprises a simulation vertical well and a point hole, wherein the simulation vertical well is arranged in the center of the solid simulator in 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 a probe, and the other end of the voltmeter is connected with the connecting point hole; 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 calculates the starting pressure of the tight oil reservoir according to the acquired data. According to the invention, through an electric simulation experiment of the solid conductive medium and the semiconductor medium, the starting pressure gradient of the tight oil reservoir is measured, and technical support is provided for the seepage mechanism and yield prediction of the tight oil reservoir.
Description
Technical Field
The invention relates to an oil gas seepage technology, in particular to a dense oil reservoir starting pressure gradient electric simulation system and a computing method.
Background
The pore throat of the reservoir layer of the compact oil reservoir is fine, the pore structure is complex, the interaction between the fluid and the pore interface is obvious, and the liquid molecules are tightly adsorbed on the solid surface to form a fluid boundary layer which has a certain thickness and does not flow. The boundary layer thickness varies with the pressure gradient, forming the low-speed fidaxy percolation characteristics of a tight reservoir. When the displacement pressure gradient is less than a certain critical value, the dense oil reservoir pores are completely filled by a non-flowing fluid boundary layer, fluid cannot flow, and only pore fluid can participate in flow above the pressure gradient, and the critical pressure gradient is the starting pressure gradient. Therefore, the method for accurately measuring the starting pressure gradient has important significance for researching the low-speed non-Darcy seepage mechanism of the tight oil reservoir.
The current common measurement method for starting the pressure gradient is an actual core flow experiment method, including a flow-pressure difference method, an unsteady state method, a capillary balance method, an unsteady state displacement-capillary method and the like. The flow-differential pressure method is to measure a seepage curve by a steady-state method, and then fit the curve to obtain a starting pressure gradient. The unsteady state method is an experimental method for measuring pressure in unsteady state seepage, and on a logarithmic graph, the starting pressure gradient of the core is obtained by fitting measured pressure data and a theoretical dimensionless pressure curve. The capillary balance method adopts a communicating vessel principle, when the pressure gradient is measured and started, a capillary is connected to the inlet end and the outlet end of the core, the fluid at the inlet end flows to the outlet end through the core due to the action of gravity, and after the liquid levels at the two ends are fully balanced, a height difference is finally maintained, wherein the height difference is the minimum starting pressure value of the sample. The unsteady state displacement-capillary method is that the outlet end of the core holder is filled with liquid, then the liquid is injected in micro-flow, and the pressure at the moment is the minimum starting pressure when the liquid level at the outlet end of the core starts to move.
In the aspect of measuring the starting pressure gradient in the aspect of core flow experiments, the prior art comprises the steps of measuring the liquid flow at different pressures by utilizing a micro-flowmeter and a pressure sensor so as to calculate the starting pressure, and the essence of the method is that a differential pressure-flow method is used; and combining differential pressure-flow core test with theoretical calculation to simulate starting pressure.
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 more accurate change rules of yield, pressure and the like, but the method has the following defects: firstly, the small core displacement pressure difference is low, the flow rate of a liquid charge pump is small, the experimental accuracy is greatly dependent on the accuracy of an experimental instrument, the pressure difference and the flow rate need to be monitored accurately to the levels of 0.001MPa and 0.0001ml/min, and expensive experimental equipment support is needed; second, the experiment requires multiple sets of data to be measured at lower displacement pressures, displacement flows, resulting in a lengthy experimental period.
In the aspect of measuring the starting pressure gradient by an electric simulation experiment, the prior art comprises the steps of simulating the starting pressure by a diode and simulating cracks by a copper sheet, wherein the potential change amplitude is larger and the relative error is larger in the experimental process.
Therefore, it is necessary to develop a dense oil reservoir start-up pressure gradient electric simulation system and a calculation method.
The information disclosed in the background section of the invention 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 dense oil reservoir starting pressure gradient electric simulation system and a calculation method, which can be used for measuring the starting pressure gradient of a dense oil reservoir through an electric simulation experiment of a solid conductive medium and a semiconductor medium and providing technical support for dense oil reservoir seepage mechanism and yield prediction.
According to one aspect of the invention, a dense oil reservoir starting pressure gradient electric simulation system 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, wherein the simulation vertical well is arranged in the center of the solid simulator in 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 a probe, and the voltmeter is connected with the point hole; 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 calculates the starting pressure of the tight oil reservoir according to the acquired data.
Preferably, the circuit further comprises a ballast arranged in the series circuit for regulating the voltage in the circuit.
Preferably, the solid simulator further comprises an outer conductive medium, an inner conductive medium, and a semiconductor interlayer: the semiconductor interlayer is arranged between the outer conductive medium and the inner conductive medium and is used for isolating the outer conductive medium from the inner conductive medium; the surface of the outer conductive medium and the surface of the inner conductive medium are both provided with the dot holes.
Preferably, the semiconductor interlayer comprises a sheet-shaped insulating medium and a semiconductor chip: the semiconductor chip is embedded in the sheet-shaped insulating medium at intervals.
Preferably, in the series circuit, one of two ends of the solid simulator is connected with the simulation vertical well, and the other end is connected with the outer conductive medium.
According to another aspect of the invention, a method for calculating the starting pressure of a tight reservoir is provided. The method may include: calculating radial flow seepage resistance of the oil reservoir to be tested; starting a pressure gradient electric simulation system through a dense oil reservoir, drawing a volt-ampere curve, and further determining a conduction characteristic resistance; setting a flow similarity coefficient, and calculating the pressure and flow of the oil reservoir to be tested according to the radial flow seepage resistance and the on characteristic resistance; and drawing a pressure-flow curve, and further determining the starting pressure of the tight oil reservoir.
Preferably, the radial flow resistance of the reservoir to be tested is calculated by equation (1):
Wherein R ou is radial flow seepage resistance, mu is crude oil viscosity, k is permeability, h is oil reservoir thickness, and R is single well supply radius.
Preferably, plotting the voltammogram, and further determining the on-characteristic resistance comprises: reversely extending the back section straight line of the volt-ampere curve to be intersected with the x-axis, wherein the corresponding value of the intersection point is the breakdown voltage of the semiconductor, and the current corresponding to the breakdown voltage on the volt-ampere curve is the conducting current; and calculating the conduction characteristic resistance through the breakdown voltage and the conduction current.
Preferably, the pressure of the reservoir to be tested is calculated by equation (2):
Wherein P is the pressure of the oil reservoir to be tested, R ou is the radial flow seepage resistance, V d is the voltage, C q is the flow similarity coefficient, and R on is 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 oil reservoir to be tested, I d is the current, and C Q is the flow similarity coefficient.
Preferably, plotting the pressure-flow curve, and further determining the tight reservoir start-up pressure comprises: and reversely extending the back section straight line of the pressure-flow curve to be intersected 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. determining 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. carrying out an electric simulation experiment with starting pressure on a simulated stratum, so that the experimental period is greatly shortened;
3. The preparation method of the conductive medium material is simple, the preparation cost is low, and the complex and irregularly-shaped oil reservoir blocks can be prepared;
4. the phenomenon that electrolyte and electrode materials are subjected to electrolytic reaction in the existing electric simulation experiment is eliminated, and the accuracy of measuring the potential of the near-wellbore zone 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 present invention.
Drawings
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular descriptions of exemplary embodiments of the invention as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts throughout the exemplary embodiments of the invention.
FIG. 1 shows a schematic diagram of a tight reservoir start-up pressure gradient electrical simulation system according to one embodiment of the invention.
Fig. 2 shows a schematic side view of a semiconductor interlayer according to an embodiment of the present invention.
FIG. 3 shows a flow chart of the steps of a tight reservoir initiation pressure calculation method according to the present invention.
Fig. 4 shows a schematic diagram of a voltammogram according to an embodiment of the present invention.
FIG. 5 shows a schematic diagram of a pressure-flow curve according to one embodiment of the invention.
Reference numerals illustrate:
1. A power supply; 2. a switch; 3. a ballast; 4. a solid simulator; 5. an ammeter; 6. an outer conductive medium; 7. spot 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 illustrated 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 dense oil reservoir starting pressure gradient electric simulation system 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, wherein the simulation vertical well is arranged in the center of the solid simulator in 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 a probe, and the other end of the voltmeter is connected with the connecting point hole; 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 calculates the starting pressure of the tight 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 conductive medium and the inner conductive medium and isolates the outer conductive medium from the inner conductive medium; the surfaces of the outer conductive medium and the inner conductive medium are provided with dot holes.
In one example, the semiconductor interlayer includes a sheet-like insulating medium and a semiconductor chip: the semiconductor chips are embedded in a sheet-like insulating medium at intervals.
In one example, in a series loop, one of the two ends of the solid simulator is connected to a simulated vertical well and the other end is connected to an outside conductive medium.
Specifically, the dense 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, wherein the simulation vertical well is arranged in the center of the solid simulator in the radial direction, and the point hole is arranged on the surface of the solid simulator; the semiconductor device further comprises an outer conductive medium, an inner conductive medium and a semiconductor interlayer: the semiconductor interlayer is arranged between the outer conductive medium and the inner conductive medium and isolates the outer conductive medium from the inner conductive medium; the surfaces of the outer conductive medium and the inner conductive medium are respectively provided with dot holes, and the dot 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 regulating 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 a probe, and the other end of the voltmeter is connected with the connecting point hole; the probe can be fixedly placed in the point hole during measurement, the probe can also freely move on the outer surface of the outer conductive medium, 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 electric field equipotential line distribution diagram 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 calculates the starting pressure of the tight oil reservoir according to the acquired data;
In the series circuit, one of the two ends of the solid simulator is connected with the simulation vertical well, and the other end is connected with the outer surface of the outside 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 characteristics, and the semiconductor device after breakdown has an on characteristic resistance R on, the size of which is related to the on-state resistance and the area of the active region, and dense oil reservoirs with different seepage resistances are simulated by changing the size of the on characteristic resistance.
The system carries out an electric simulation experiment through the solid conductive medium and the semiconductor medium, determines the starting pressure gradient of the tight oil reservoir, and provides technical support for the seepage mechanism and yield prediction of the tight oil reservoir.
Application example
In order to facilitate understanding of the solution and the effects of the embodiments of the present invention, a specific application example is given below. It will be understood by those of ordinary skill in the art that the examples are for ease of understanding only and that any particular details thereof are not intended to limit the present invention in any way.
FIG. 1 shows a schematic diagram of a tight reservoir start-up pressure gradient electrical simulation system according to one embodiment of the invention.
The dense oil reservoir starting pressure gradient electric simulation system 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 regulates the voltage in the circuit.
The solid simulator 4 comprises a simulated vertical well 11 and a point hole 7, wherein the simulated vertical well 11 is arranged in 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; 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 conductive medium 6 and the inner conductive medium 9 and isolates the outer conductive medium 6 from the inner 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 6 and the inner side conductive medium 9 are respectively provided with a dot hole 7, the diameter of each dot hole 7 is 1mm, the depth of each dot hole is 0.5cm, and the dot 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 is provided with the probe 12, and the hole 7 is connected; the diameter of the copper probe 12 is 1mm, the lower end is covered 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, the potential of each point is measured and recorded by changing the position of the probe 12, and the electric field equipotential line distribution map can be measured;
The data acquisition instrument 15 is connected with the ammeter 5 and the voltmeter 8 and is used for acquiring data; the processor 16 is connected with the data acquisition instrument 15 and calculates the starting pressure of the tight oil reservoir according to the acquired data;
In the series circuit, one 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 outside conductive medium 6.
Fig. 2 shows a schematic side view of a semiconductor interlayer according to an embodiment of the present invention.
The semiconductor interlayer 10 in the solid 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 and are embedded in the polyethylene film with the thickness of a micron order, and serve as an interlayer 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. Gallium nitride semiconductor devices have breakdown voltage characteristics, the breakdown voltage V s is generally between 50 and 60V, the semiconductor devices after breakdown have on-characteristic resistors R on, the on-characteristic resistors are related to the on-state resistors and the areas of active areas, and dense oil reservoirs with different seepage resistances are simulated by changing the on-characteristic resistors.
In conclusion, the invention carries out an electric simulation experiment through the solid conductive medium and the semiconductor medium to determine the starting pressure gradient of the tight oil reservoir, and provides technical support for the seepage mechanism and yield prediction of the tight oil reservoir.
It will be appreciated by persons skilled in the art that the above description of embodiments of the invention has been given for the purpose of illustrating the benefits of embodiments of the invention only 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 initiation pressure calculation method according to the present invention.
In this embodiment, the tight reservoir start-up pressure calculation method according to the present invention may include: step 101, calculating radial flow seepage resistance of an oil reservoir to be tested; step 102, starting a pressure gradient electric simulation system through a dense oil reservoir, drawing a volt-ampere curve, and further determining a conduction characteristic resistance; step 103, setting a flow similarity coefficient, and calculating the pressure and flow of the oil reservoir to be tested according to the radial seepage resistance and the on characteristic resistance; and 104, drawing a pressure-flow curve, and further determining the starting pressure of the tight reservoir.
In one example, the radial flow resistance of the reservoir to be tested is calculated by equation (1):
Wherein R ou is radial flow seepage resistance, mu is crude oil viscosity, k is permeability, h is oil reservoir thickness, and R is single well supply radius.
In one example, plotting the voltammogram, and determining the on-characteristic resistance further comprises: reversely extending the back section line of the volt-ampere curve to be intersected with the x-axis, wherein the corresponding value of the intersection point is the breakdown voltage of the semiconductor, and the current corresponding to 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 pressure of the reservoir to be tested is calculated by equation (2):
Wherein P is the pressure of the oil reservoir to be tested, R ou is the radial flow seepage resistance, V d is the voltage, C q is the flow similarity coefficient, and R on is 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 oil reservoir to be tested, I d is the current, and C Q is the flow similarity coefficient.
In one example, plotting the pressure-flow curve, and determining the tight reservoir start-up pressure further includes: and reversely extending the back section straight line of the pressure-flow curve to be intersected with the x-axis, wherein the corresponding value of the intersection point is the starting pressure of the tight oil reservoir.
Specifically, the electric simulation experiment is a simulation experiment method formed according to the hydropower similarity principle. An electric 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.
Stabilized percolation of incompressible subsurface fluids through porous media complies with darcy's law and laplace's equation:
The flow of current in the conductive medium and the potential distribution satisfy ohm's law and the laplace 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 be similar under the similar boundary condition. According to ohm's law, the current in any flow cell in the electric field is:
According to darcy's law, the fluid flow in the pressure gradient direction cell block in the formation is:
The current, voltage and distribution in the electric field and the flow, pressure and distribution in the stable seepage field have the following corresponding proportional relations, the model data subscript is m, and the stratum data subscript is n:
The pressure similarity coefficient is:
Wherein C P is the pressure similarity coefficient, deltaU is the potential difference, deltaP is the pressure difference.
Flow similarity coefficient:
Where C Q is the flow similarity coefficient, I is the current, and Q is the well yield.
Coefficient of resistance similarity:
Where C R is the coefficient of resistance similarity, R m is the resistance of the electric field, and R n is the seepage resistance of the formation fluid.
According to formulas (6) and (7), the conditions between the similarity coefficients should be satisfied:
The stable seepage field satisfying the conditions has an analogy relation with the electric field, and the electric field can be used for simulating the stable seepage field to study seepage rules. Since the current can reach stability instantaneously in the experiment, the process of electric simulation is a single-phase stable flow process in the stratum. The current and voltage data in the electric field are measured, and the data can be converted into the output and pressure data in the seepage field by using a similar proportional relation. Equation (11) is a similarity criterion that the model must meet, where two parameters can be freely determined and the third parameter must be derived from the similarity criterion.
With the increasing complexity of developed oil fields, the electric simulation experiment is increasingly widely applied in the field of oil gas seepage, mainly due to the following advantages: the electric simulation experiment can be used for manufacturing various complex models at will, has short experimental period and low cost, and has more advantages compared with a rock core experiment.
Fig. 4 shows a schematic diagram of a voltammogram according to an embodiment of the present invention.
FIG. 5 shows a schematic diagram of a pressure-flow curve according to one embodiment of the invention.
The method for calculating the starting pressure of the tight oil reservoir according to the invention can comprise the following steps:
Calculating radial flow seepage resistance of the oil reservoir to be tested through the formula (1); starting a pressure gradient electric simulation system through a dense oil reservoir, switching on a switch, communicating a probe with any point on the outer surface of a point hole or an outer conductive medium, keeping the probe stationary, gradually increasing voltage V d through a ballast, observing the change condition of an ammeter I d, drawing a voltammogram, and reversely extending the back section straight line of the voltammogram to intersect with an x-axis as shown in fig. 4, wherein the corresponding value V T of the intersection point is the breakdown voltage of a semiconductor, and the current I s corresponding to the breakdown voltage on the voltammogram is the conducting current; and calculating the on characteristic resistance according to ohm law through the breakdown voltage and the on current.
Setting the flow similarity coefficient C Q, it can be obtained according to formulas (8) - (11):
And calculating the pressure of the oil deposit to be tested through a formula (2) according to the radial flow seepage resistance and the on characteristic resistance, and calculating the flow of the oil deposit to be tested through a formula (3). And then, a pressure-flow curve is drawn, as shown in fig. 5, the back section straight line of the pressure-flow curve is reversely prolonged to intersect with the x axis, and the corresponding value P T of the intersection point is the starting pressure of the tight reservoir.
According to the method, an electric simulation experiment is carried out through the solid conductive medium and the semiconductor medium, the starting pressure gradient of the tight oil reservoir is measured, and technical support is provided for the seepage mechanism and yield prediction of the tight oil reservoir.
It will be appreciated by persons skilled in the art that the above description of embodiments of the invention has been given for the purpose of illustrating the benefits of embodiments of the invention only and is not intended to limit embodiments of the invention to any examples given.
The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or 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 various embodiments described.
Claims (4)
1. A method for calculating a tight reservoir initiation pressure, comprising:
calculating radial flow seepage resistance of the oil reservoir to be tested;
Starting a pressure gradient electric simulation system through a dense oil reservoir, drawing a volt-ampere curve, and further determining a conduction characteristic resistance;
Setting a flow similarity coefficient, and calculating the pressure and flow of the oil reservoir to be tested according to the radial flow seepage resistance and the on characteristic resistance;
drawing a pressure-flow curve, and further determining the starting pressure of the tight oil reservoir;
The radial flow seepage resistance of the oil reservoir to be tested is calculated through the formula (1):
Wherein R ou is radial flow seepage resistance, mu is crude oil viscosity, k is permeability, h is oil reservoir thickness, and R is single well supply radius;
the dense oil reservoir starting pressure gradient electric simulation system comprises 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, wherein the simulation vertical well is arranged in the center of the solid simulator in 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 a probe, and the voltmeter is connected with the point hole;
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 calculates the starting pressure of the dense oil reservoir according to the acquired data;
wherein, the solid simulator also includes outside conductive medium, inboard conductive medium, semiconductor intermediate layer:
The semiconductor interlayer is arranged between the outer conductive medium and the inner conductive medium and is used for isolating the outer conductive medium from the inner conductive medium;
The surface of the outer conductive medium and the surface of the inner conductive medium are respectively provided with the point holes;
drawing a volt-ampere curve, and further determining the on characteristic resistance comprises the following steps:
reversely extending the back section straight line of the volt-ampere curve to be intersected with the x-axis, wherein the corresponding value of the intersection point is the breakdown voltage of the semiconductor, and the current corresponding to the breakdown voltage on the volt-ampere curve is the conducting current;
calculating the conduction characteristic resistance through the breakdown voltage and the conduction current;
Wherein, calculate the pressure of the reservoir to be tested through formula (2):
wherein P is the pressure of an oil reservoir to be tested, R ou is the radial flow seepage resistance, V d is the voltage, C q is the flow similarity coefficient, and R on is the on characteristic resistance;
The flow of the oil reservoir to be tested is calculated through a formula (3):
Q＝CQId (3)
Wherein Q is the flow of the oil reservoir to be tested, I d is the current, and C Q is the flow similarity coefficient.
2. The tight reservoir activation pressure calculation method according to claim 1, wherein the semiconductor interlayer comprises a sheet-like insulating medium and a semiconductor chip:
the semiconductor chip is embedded in the sheet-shaped insulating medium at intervals.
3. The tight reservoir activation pressure calculation method according to claim 1, wherein one of two ends of the solid simulator connected in a series circuit is connected to the simulated vertical well, and the other end is connected to the outside conductive medium.
4. The tight reservoir activation pressure calculation method of claim 1, wherein plotting a pressure-flow curve to determine tight reservoir activation pressure comprises:
and reversely extending the back section straight line of the pressure-flow curve to be intersected 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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| CN106401550B (en) * | 2016-10-17 | 2022-12-23 | 长江大学 | Electric simulation device and test method for compact oil volume fracture starting pressure seepage law |
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