Device for simulating core filling reservoir formation under action of buoyancy and simulation method thereof

Abstract

The invention relates to a device and a method for simulating core filling and reservoir formation under the action of buoyancy, the device for simulating core filling and reservoir formation under the action of buoyancy is a centrifugal cup, the centrifugal cup comprises a centrifugal cup base, a centrifugal cup cover and a fixed plug, the centrifugal cup cover is in threaded connection with an upper port of the centrifugal cup base, and the fixed plug is in threaded connection with the centrifugal cup cover. The lower end of the fixed plug extends into the centrifugal cup base, a hydrocarbon supply chamber with an open upper port is arranged in the middle of the bottom of the centrifugal cup base, the bottom of the centrifugal cup base protrudes inwards to form an annular supporting table, and the annular supporting table surrounds the upper portion of the hydrocarbon supply chamber; the fixed plug is sleeved with the upper end of the rubber sleeve, the annular supporting table is sleeved with the lower end of the rubber sleeve, a cavity between the rubber sleeve and the inner wall of the centrifugal cup base is a confining pressure cavity, the confining pressure cavity is provided with a confining pressure inlet, and the hydrocarbon supply chamber is provided with a hydrocarbon supply inlet and an exhaust outlet; an inner cavity of the rubber sleeve is a core chamber, and an upper port of the hydrocarbon supply chamber is opened in the core chamber. The centrifugal field is used for simulating the gravity field, and the effect of buoyancy in oil-gas migration and filling can be fully simulated.

Description

Technical Field

[0001] This invention relates to the field of deep oil and gas exploration technology, specifically to an apparatus and method for simulating core filling and reservoir formation under buoyancy. Background Technology

[0002] Oil and gas charging is a crucial step in hydrocarbon reservoir research. Currently, the publicly available method for conducting charging experiments involves filling a core saturated with water into a core holder, then injecting oil and gas from one end of the holder, with water and oil / gas exiting from the other end. This method presents two problems: 1) It confuses the migration and charging processes. Migration is a process of simultaneous injection and outflow, while charging is a process where oil is injected but not outflowed. Therefore, current charging experiments actually correspond to the migration process rather than the charging process; 2) When using actual cores for charging experiments, the core length is limited, typically 5-10 cm. Due to this limitation, the role of buoyancy during the charging process cannot be effectively demonstrated. Summary of the Invention

[0003] One objective of this invention is to provide a device for simulating core injection and hydrocarbon accumulation under buoyancy. This device is used to solve the problem that existing oil and gas injection experiments cannot simulate the injection process or that the role of buoyancy in the injection process cannot be effectively reflected. Another objective of this invention is to provide a simulation method for this device for simulating core injection and hydrocarbon accumulation under buoyancy.

[0004] The technical solution adopted by this invention to solve its technical problem is as follows: This device for core filling and hydrocarbon accumulation under simulated buoyancy is a centrifugal cup. The centrifugal cup includes a centrifugal cup seat, a centrifugal cup cover, and a fixed plug. The centrifugal cup cover is threaded to the upper port of the centrifugal cup seat, and the fixed plug is threaded to the central threaded hole of the centrifugal cup cover. The lower end of the fixed plug extends into the centrifugal cup seat. A hydrocarbon supply chamber with an open upper port is set in the center of the bottom of the centrifugal cup seat. The bottom of the centrifugal cup seat protrudes inward to form an annular support platform, which surrounds the upper part of the hydrocarbon supply chamber. The upper end of the rubber sleeve is fitted outside the fixed plug, and the lower end is fitted outside the annular support platform. The cavity between the rubber sleeve and the inner wall of the centrifugal cup seat is a confining pressure cavity. The confining pressure cavity is provided with a confining pressure inlet and a confining pressure valve. The hydrocarbon supply chamber is provided with a hydrocarbon supply inlet and an exhaust outlet. A hydrocarbon supply valve is set at the hydrocarbon supply inlet, and an exhaust valve is set at the exhaust outlet. The inner cavity of the rubber sleeve is the core chamber, and the upper port of the hydrocarbon supply chamber is open in the core chamber.

[0005] In the above scheme, an O-ring is installed between the centrifuge cup holder and the centrifuge cup lid.

[0006] In the above scheme, the confining pressure inlet is vertically set at the bottom of the centrifuge cup seat, and the confining pressure valve is horizontally built into the centrifuge cup seat.

[0007] In the above scheme, both the hydrocarbon supply inlet and the exhaust outlet are vertically located at the bottom of the centrifuge cup holder, the hydrocarbon supply valve is horizontally built into the centrifuge cup holder, and the exhaust valve is located at the bottom of the centrifuge cup holder.

[0008] In the above scheme, the hydrocarbon supply inlet is located at one end of the outer wall at the bottom of the centrifuge cup seat and is provided with a threaded coupling groove. During the simulation, the hydrocarbon supply inlet pipe is connected to the hydrocarbon supply inlet through the threaded coupling groove, and a pressure gauge is installed on the hydrocarbon supply inlet pipe to observe the fluid pressure in the hydrocarbon supply chamber.

[0009] The above simulation method for the apparatus of core filling and hydrocarbon accumulation under simulated buoyancy: Step 1: Close the confining pressure valve, fill the confining pressure chamber with water, tighten the centrifuge cup lid onto the centrifuge cup seat, and at the same time open the confining pressure valve to drain the excess water from the confining pressure chamber. Step 2: Select rock cores with similar physical properties in pairs and cut each pair of rock cores into the same length; Step 3: Saturate each pair of core samples with water; Step 4: Fill the core samples saturated with water into the core chambers of different centrifuge cups and secure them with fixing plugs; Step 5: Fill the confining pressure chamber of the centrifuge cup with fluid through the confining pressure inlet. When the pressure reaches the preset value, close the confining pressure valve to keep the confining pressure at the preset value. Step 6: Invert the centrifuge cup, open the exhaust valve and the hydrocarbon supply valve, connect the hydrocarbon supply inlet pipe to the hydrocarbon supply inlet through the threaded coupling groove, and fill the hydrocarbon supply inlet with oil and gas. At the same time, the air in the hydrocarbon supply chamber is discharged through the exhaust valve. Step 7: After the air in the hydrocarbon supply chamber is purged, close the purging valve and the hydrocarbon supply valve, or continue to fill the chamber with oil and gas until the fluid pressure in the hydrocarbon supply chamber reaches the preset value, and then close the hydrocarbon supply valve to maintain the fluid pressure in the hydrocarbon supply chamber at the preset value. Step 8: Place the centrifuge cups in pairs symmetrically in the centrifuge, ensuring that the hydrocarbon chamber in the centrifuge cups is flushed out. Set the centrifugation rate to the preset value and conduct a filling experiment simulating buoyancy and pressure. Beneficial effects

[0010] 1. This invention utilizes a centrifugal field to simulate a gravitational field. The centrifugal acceleration can reach tens of thousands of times the gravitational acceleration, thus fully simulating the role of buoyancy in oil and gas migration and injection in actual rock cores.

[0011] 2. The charging process of this invention differs from conventional charging experiments. It is a process in which oil and gas displace pore water and accumulate without being lost, which can better simulate the formation process of natural oil and gas reservoirs. It provides devices, methods and means for studying the laws and characteristics of oil and gas charging and formation.

[0012] 3. The hydrocarbon supply chamber of the present invention can be preset with a certain pressure to simulate the oil and gas transport and accumulation process under the combined action of buoyancy and pressure. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the device for simulating core filling and hydrocarbon accumulation under buoyancy according to the present invention.

[0014] Figure 2 The results are from the nuclear magnetic resonance imaging scan of rock sample A2.

[0015] Figure 3 The results are from the nuclear magnetic resonance imaging scan of rock sample B2.

[0016] In the diagram: 1. Confining pressure inlet, 2. Confining pressure valve, 3. Centrifuge cup seat, 4. O-ring, 5. Centrifuge cup cover, 6. Fixed plug, 7. Rubber sleeve, 8. Confining pressure chamber, 9. Core, 10. Hydrocarbon supply chamber, 11. Hydrocarbon supply valve, 12. Hydrocarbon supply inlet, 13. Exhaust valve, 14. Exhaust outlet. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings: Combination Figures 1-3 As shown, this device for simulating core filling and hydrocarbon accumulation under buoyancy is a centrifugal cup. The centrifugal cup includes a centrifugal cup seat 3, a centrifugal cup cover 5, and a fixed plug 6. The centrifugal cup cover 5 is threaded to the upper port of the centrifugal cup seat 3, and an O-ring 4 is provided between the centrifugal cup seat 3 and the centrifugal cup cover 5. The fixed plug 6 is threaded to the central threaded hole of the centrifugal cup cover 5, and the lower end of the fixed plug 6 extends into the centrifugal cup seat 3. The bottom of the centrifugal cup seat 3 has a hydrocarbon supply chamber 10 with an open upper port in the center. The bottom of the centrifugal cup seat 3 protrudes inward to form an annular support platform, which surrounds the upper part of the hydrocarbon supply chamber 10. The upper end of the rubber sleeve 7 is fitted outside the fixed plug 6, and the lower end is fitted outside the annular support platform. The cavity between the rubber sleeve 7 and the inner wall of the centrifugal cup seat 3 is a confining pressure chamber 8. The confining pressure chamber 8 is provided with a confining pressure inlet 1, and a confining pressure valve 2 is provided at the confining pressure inlet 1. The confining pressure inlet 1 is vertically set at the bottom of the centrifugal cup seat 3, and the confining pressure valve 2 is horizontally built into the centrifugal cup seat 3. The hydrocarbon supply chamber 10 is provided with a hydrocarbon supply inlet 12 and an exhaust outlet 14. The hydrocarbon supply inlet 12 is provided with a hydrocarbon supply valve 11, and the exhaust outlet 14 is provided with an exhaust valve 13. The inner 7 cavities of the rubber tube are core chambers, and the upper port of the hydrocarbon supply chamber 10 is open to the core chamber.

[0018] Both the hydrocarbon inlet 12 and the exhaust outlet 14 are vertically positioned at the bottom of the centrifuge cup holder 3. The hydrocarbon supply valve 11 is horizontally integrated into the centrifuge cup holder 3, and the exhaust valve 13 is located at the bottom of the centrifuge cup holder 3. The hydrocarbon supply inlet 12 has a threaded coupling groove at one end of its opening on the outer wall of the bottom of the centrifuge cup holder 3. During simulation, the hydrocarbon supply inlet pipe is connected to the hydrocarbon supply inlet 12 through the threaded coupling groove. A pressure gauge is installed on the hydrocarbon supply inlet pipe to observe the fluid pressure in the hydrocarbon supply chamber. When the centrifuge cup is placed in the centrifuge, the hydrocarbon supply inlet pipe needs to be unscrewed from the centrifuge cup.

[0019] The above simulation method for the apparatus of core filling and hydrocarbon accumulation under simulated buoyancy: Step 1: Close the confining pressure valve 2, fill the confining pressure chamber 8 with water, tighten the centrifuge cup lid 5 onto the centrifuge cup seat 3, and at the same time open the confining pressure valve 2 to drain the excess water in the confining pressure chamber 8. Step 2: Select rock cores with similar physical properties in pairs and cut each pair of rock cores into the same length; Step 3: Saturate each pair of core samples with water; Step 4: Fill the core samples saturated with water into the core chambers of different centrifuge cups and fix them with fixing plugs 6; Step 5: Fill the confining pressure chamber 8 of the centrifuge cup with fluid through the confining pressure inlet 1. When the pressure reaches the preset value, close the confining pressure valve 2 to keep the confining pressure at the preset value.

[0020] Step 6: Invert the centrifuge cup, open the exhaust valve 13 and the hydrocarbon supply valve 11, connect the hydrocarbon supply inlet pipe to the hydrocarbon supply inlet 12 through the threaded coupling groove, and fill the hydrocarbon supply inlet 12 with oil and gas. At the same time, the air in the hydrocarbon supply chamber 10 is discharged through the exhaust valve 13. Step 7: After the air in the hydrocarbon supply chamber 10 is purged, close the purging valve 13 and the hydrocarbon supply valve 11, or continue to fill the chamber with oil and gas until the fluid pressure in the hydrocarbon supply chamber reaches the preset value, and then close the hydrocarbon supply valve 11 to maintain the fluid pressure in the hydrocarbon supply chamber 10 at the preset value. Step 8: Place the centrifuge cups in pairs symmetrically in the centrifuge, ensuring that the hydrocarbon chamber in the centrifuge cups is flushed out. Set the centrifugation rate to the preset value and conduct a filling experiment simulating buoyancy and pressure.

[0021] The principle of this invention: The buoyancy force experienced during the oil and gas migration and charging process is ∆ρgh, where Δρ is the density difference between oil and water or oil and gas, g is the gravitational acceleration, and h is the height of the oil or gas column. In actual core charging tests, in order to increase the buoyancy force on the oil or gas column, in addition to increasing the height of the oil or gas column, the gravitational acceleration can also be increased. A centrifugal field is used to simulate the gravitational field, and the centrifugal acceleration can reach tens of thousands of times the gravitational acceleration, which can fully simulate the role of buoyancy in oil and gas migration and charging. In order to simulate the oil and gas charging and migration under the action of buoyancy in the centrifugal field, a centrifugal cup is designed as shown in the attached figure. Its structure mainly includes a centrifugal cup seat 3, a centrifugal cup cover 5, a confining pressure cavity 8, a rubber sleeve 7, a hydrocarbon supply chamber 10, and a fixing plug 6. The confining pressure chamber 8 is formed by the centrifuge cup seat 3, the centrifuge cup lid 5, and the rubber sleeve 7. When fluid is injected into the confining pressure chamber 8, the rubber sleeve 7 and the centrifuge cup seat 3, and the rubber sleeve 7 and the centrifuge cup lid 5, are self-sealed by the deformation and compression of the rubber sleeve 7. The centrifuge cup seat 3 and the centrifuge cup lid 5 are connected by threads and sealed with O-rings. To facilitate the injection and discharge of fluid into and out of the confining pressure chamber 8, confining pressure inlets 1 and confining pressure valves 2 are designed at the bottom and sides of the centrifuge cup seat. The confining pressure valve 2 is built into the centrifuge cup and is used to cut off or open the confining pressure inlet 1. The core is placed in the rubber sleeve 7. When fluid is injected into the confining pressure chamber 8, it compresses the rubber sleeve 7, causing the rubber sleeve 7 to hold the core 9 tightly, preventing the fluid from flowing over the side of the core under centrifugal force. To prevent the core from moving during centrifugation, the fixing plug 6 presses the core 9 against the centrifuge cup base support. At the same time, the bottom end of the fixing plug is tightly surrounded by the rubber sleeve, preventing fluid leakage along its side. The fixing plug and the centrifuge cup lid are connected and fixed by threads. Considering that in a centrifugal field, fluids with lower density flow towards the center and fluids with higher density flow towards the periphery, the hydrocarbon supply chamber is designed at the bottom of the centrifuge cup and only close to the core. Its function is to provide a hydrocarbon source for the filling and migration experiment, and at the same time store the water displaced during hydrocarbon filling. In order to facilitate the entry of oil and gas into the hydrocarbon supply chamber, hydrocarbon supply inlets and hydrocarbon supply valves are designed on the side and bottom of the centrifuge cup. The hydrocarbon supply valve is used to cut off and open the hydrocarbon supply inlet. After injecting oil and gas at a certain pressure into the hydrocarbon supply chamber, the hydrocarbon supply valve is closed, which can also simulate the oil and gas migration filling under the combined action of buoyancy and pressure. Example

[0022] This embodiment simulates the core filling and reservoir formation of kerosene under buoyancy.

[0023] In this embodiment, the centrifuge cup has an outer diameter of 61mm, a height of 129mm, and is made of stainless steel. The inner diameter of the rubber sleeve is 25.6mm, and the wall thickness is 3mm. The centrifuge cup seat has a wall thickness of 5mm, and the fixing plug is 25.4mm. The center diameter of the core sample is 25.4mm.

[0024] This example uses a Xiangyi GL21M centrifuge with a maximum speed of 21,000 r / min and a maximum centrifugal acceleration of 47,400 g.

[0025] The simulated buoyancy-based core filling and hydrocarbon accumulation steps include: Close the confining pressure valve, install the rubber tubes on the protrusions of different centrifuge cup holders, and fill the annular space between the rubber tubes and the centrifuge cup holders with water; install the centrifuge cup lids, and at the same time open the confining pressure valves to drain the excess fluid in the confining pressure chamber.

[0026] Select two pairs of core samples with similar physical properties, and cut each pair of core samples into the same length.

[0027] Saturate the core with water; The water-saturated core samples were placed into rubber tubes in different centrifuge cups and secured with fixing plugs.

[0028] Fluid is injected into the confining pressure chamber of the centrifuge cup through the confining pressure inlet. When the pressure reaches 2MPa, the confining pressure valve is closed to keep the confining pressure at the preset value.

[0029] Invert the centrifuge cup, open the exhaust valve and hydrocarbon supply valve, and fill the hydrocarbon supply inlet with kerosene. At the same time, the air in the hydrocarbon supply chamber is discharged through the exhaust valve.

[0030] After the air in the hydrocarbon supply chamber is purged, close the purging valve and then close the hydrocarbon supply valve.

[0031] Centrifuge cups containing cores A1 and A2, and cores B1 and B2, were placed symmetrically in pairs in a centrifuge, ensuring that the hydrocarbon chamber in the centrifuge cups was exposed to the outside. The centrifugation speed was set to 12000 r / min, the centrifugation radius was 0.15 m, and the corresponding centrifugation acceleration was 167.8 times the acceleration due to gravity. Centrifugation was carried out for 30 minutes to simulate the transport and filling process under the action of buoyancy.

[0032] After centrifugation, core samples A2 and B2 were subjected to nuclear magnetic resonance imaging (NMR) scans. The results showed that oil failed to infuse sample A2. Figure 2 ( ), while after the oil enters sample B2, it undergoes dominant transport along the limited channels.

Claims

1. A device for simulating core filling and hydrocarbon accumulation under buoyancy, characterized in that: This device for core filling and hydrocarbon accumulation under simulated buoyancy is a centrifugal cup. The centrifugal cup includes a centrifugal cup seat, a centrifugal cup cover, and a fixed plug. The centrifugal cup cover is threaded to the upper port of the centrifugal cup seat, and the fixed plug is threaded to the central threaded hole of the centrifugal cup cover. The lower end of the fixed plug extends into the centrifugal cup seat. The bottom of the centrifugal cup seat has a hydrocarbon supply chamber with an open upper port in the center. The bottom of the centrifugal cup seat protrudes inward to form an annular support platform, which surrounds the upper part of the hydrocarbon supply chamber. The upper end of the rubber sleeve is fitted over the fixed plug, and the lower end is fitted over the annular support platform. The cavity between the rubber sleeve and the inner wall of the centrifugal cup seat is a confining pressure chamber. The confining pressure chamber is equipped with a confining pressure inlet and a confining pressure valve. The hydrocarbon supply chamber is equipped with a hydrocarbon supply inlet and an exhaust outlet. The hydrocarbon supply inlet is equipped with a hydrocarbon supply valve, and the exhaust outlet is equipped with an exhaust valve. The inner cavity of the rubber sleeve is the core chamber, and the upper port of the hydrocarbon supply chamber is open to the core chamber.

2. The apparatus for core filling and hydrocarbon accumulation under simulated buoyancy as described in claim 1, characterized in that: An O-ring is provided between the centrifuge cup holder and the centrifuge cup lid.

3. The apparatus for core filling and hydrocarbon accumulation under simulated buoyancy as described in claim 2, characterized in that: The confining pressure inlet is vertically located at the bottom of the centrifuge cup holder, and the confining pressure valve is horizontally built into the centrifuge cup holder.

4. The apparatus for core filling and hydrocarbon accumulation under simulated buoyancy as described in claim 3, characterized in that: The hydrocarbon supply inlet and exhaust outlet are both vertically positioned at the bottom of the centrifuge cup holder, the hydrocarbon supply valve is horizontally embedded in the centrifuge cup holder, and the exhaust valve is located at the bottom of the centrifuge cup holder.

5. The apparatus for core filling and hydrocarbon accumulation under simulated buoyancy as described in claim 4, characterized in that: The hydrocarbon supply inlet is located at one end of the outer wall at the bottom of the centrifuge cup and is equipped with a threaded coupling groove. During the simulation, the hydrocarbon supply inlet pipe is connected to the hydrocarbon supply inlet through the threaded coupling groove. A pressure gauge is installed on the hydrocarbon supply inlet pipe to observe the fluid pressure in the hydrocarbon supply chamber.

6. A simulation method for the apparatus for simulating core filling and hydrocarbon accumulation under buoyancy as described in claim 5, characterized in that... Includes the following steps: Step 1: Close the confining pressure valve, fill the confining pressure chamber with water, tighten the centrifuge cup lid onto the centrifuge cup seat, and at the same time open the confining pressure valve to drain the excess water from the confining pressure chamber. Step 2: Select rock cores with similar physical properties in pairs and cut each pair of rock cores into the same length; Step 3: Saturate each pair of core samples with water; Step 4: Fill the core samples saturated with water into the core chambers of different centrifuge cups and secure them with fixing plugs; Step 5: Fill the confining pressure chamber of the centrifuge cup with fluid through the confining pressure inlet. When the pressure reaches the preset value, close the confining pressure valve to keep the confining pressure at the preset value. Step 6: Invert the centrifuge cup, open the exhaust valve and the hydrocarbon supply valve, connect the hydrocarbon supply inlet pipe to the hydrocarbon supply inlet through the threaded coupling groove, and fill the hydrocarbon supply inlet with oil and gas. At the same time, the air in the hydrocarbon supply chamber is discharged through the exhaust valve. Step 7: After the air in the hydrocarbon supply chamber is purged, close the purging valve and the hydrocarbon supply valve, or continue to fill the chamber with oil and gas until the fluid pressure in the hydrocarbon supply chamber reaches the preset value, and then close the hydrocarbon supply valve to maintain the fluid pressure in the hydrocarbon supply chamber at the preset value. Step 8: Place the centrifuge cups in pairs symmetrically in the centrifuge, ensuring that the hydrocarbon chamber in the centrifuge cups is flushed out. Set the centrifugation rate to the preset value and conduct a filling experiment simulating buoyancy and pressure.

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