System and method for evaluating gas injection water coning effect in a bottom water sandstone reservoir

Abstract

The application discloses a system for evaluating gas injection pressure water coning effect of bottom water sandstone reservoirs, which comprises a core device, a displacement device and a measuring device. The core device is internally arranged with an experimental core and is provided with multiple injection points along the axial direction of the experimental core. A pressure measuring point and a probe measuring point are arranged on the core section of each injection point. The displacement device is connected with the core device, used for injecting water to the experimental core saturated with formation water and displaced with crude oil to simulate a strong bottom water drive process, and injecting gas to any injection point at different speeds and / or different amounts to simulate a gas injection pressure water coning process. The measuring device is connected with the core device, used for measuring pressure changes of different pressure measuring points and ultrasonic signal changes of different probe measuring points in the strong bottom water drive simulation process and the gas injection pressure water coning simulation process respectively. The gas swept range is determined by comparing the same position and same type of measurement data. The application solves the problem of simulating the gas injection pressure water coning process of the bottom water sandstone reservoirs.

Description

Technical Field

[0001] This invention relates to the field of petroleum development experimental technology, and in particular to a system and method for evaluating the effect of gas injection pressure water cones in bottom water sandstone reservoirs. Background Technology

[0002] The Triassic bottom-water sandstone reservoirs in the Tarim Oilfield are characterized by abundant natural energy and large water bodies, accounting for a significant proportion of the region's total production. The oilfield primarily relies on natural energy development, but in the mid-to-late stages, bottom-water coning becomes pronounced, leading to rapid increases in water cut. Wells generally have high water cuts, resulting in low recovery rates and significant development potential. Due to the high formation temperature and formation water salinity, chemical flooding systems are difficult to apply, and chemical plugging systems have a short effective duration. Gas injection, however, has proven effective in controlling water and increasing oil production in the oilfield. Furthermore, the large bottom water volume and high-pressure conditions provide a strong ability to dissolve CO2, achieving carbon sequestration. This is of great significance for the application of CCUS technology in deep oil and gas reservoirs in Northwest China. The Tarim Triassic bottom-water sandstone reservoir has high formation pressure, and the density of CO2 in the reservoir is greater than that of crude oil. Under the influence of gravity differentiation, CO2 will accumulate at the oil-water interface, which can theoretically inhibit bottom water uplift and alleviate the formation of water cones. In order to further understand the effect of gas injection water cones and the gas-water flow law, it is necessary to carry out gas injection water cone effect evaluation experiments to provide important theoretical support for gas injection technology to enhance oil recovery in bottom-water reservoirs.

[0003] Currently, the evaluation methods for the gas injection effect in bottom-water reservoirs mainly focus on increasing oil (or gas) and reducing water cut. The techniques employed primarily involve numerical simulation based on geological models and core physical simulation experiments. Numerical simulation methods establish ideal or actual geological models of the actual block, and then conduct simulation studies on the oil displacement effect under different gas injection methods. This involves quantitative analysis of dynamic parameters such as oil increase and water cut reduction by comparing different simulation schemes, and qualitative analysis of the coneing effect from the dynamic simulation process of the three-dimensional geological model. However, it cannot quantify the coneing effect. Core physical simulation methods conduct core displacement experiments under different gas injection methods, comparing and analyzing the dynamic characteristics of the produced fluids (oil, water, gas) to analyze the oil increase and water control effect. However, it cannot simulate the formation of water cones or the coneing effect.

[0004] Existing technologies lack methods for evaluating the effect of gas injection cones in bottom-water reservoirs, resulting in unclear injection parameters and post-injection formation fluid flow patterns. This affects the gas injection effect in bottom-water reservoirs and increases the investment risk of gas injection in deep reservoirs. Summary of the Invention

[0005] The purpose of this invention is to provide an experimental device and method for evaluating the effect of CO2 injection and water-pressing cones in bottom-water sandstone reservoirs, to simulate the process of CO2 injection and water-pressing cones under strong bottom-water reservoir conditions, analyze the flow law of formation fluids after CO2 injection, and clarify the effect of CO2 injection and water-pressing cones.

[0006] To address the aforementioned technical problems, this invention provides a system for evaluating the effect of gas injection pressure cones in bottom-water sandstone reservoirs. The system includes: a core device containing an experimental core with multiple injection points along its axial direction; a pressure measuring point and a probe measuring point on the core cross-section at each injection point; a displacement device connected to the core device for injecting water into the experimental core (which has been saturated with formation water and displaced crude oil) to simulate a strong bottom-water drive process, and for injecting gas into any injection point at different rates and / or different amounts to simulate a gas injection pressure cone process; and a measuring device connected to the core device for measuring pressure changes at different pressure measuring points and ultrasonic signal changes at different probe measuring points during both the strong bottom-water drive simulation and the gas injection pressure cone simulation processes. The gas sweep range is determined by comparing measurement data from the same location and of the same type.

[0007] Preferably, the measuring device is further configured to determine the bottom water rise position and calculate the water production per unit time during the strong bottom water drive simulation process based on the pressure changes at different pressure measuring points and the ultrasonic signal changes at different probe measuring points during the strong bottom water drive simulation process, and to calculate the water production per unit time during the air injection water cone simulation process based on the pressure changes at different pressure measuring points and the ultrasonic signal changes at different probe measuring points during the air injection water cone simulation process, thereby obtaining the change in water production rate after air injection.

[0008] Preferably, the core device includes: the experimental core; a core holder, which is vertically placed on the experimental platform and forms an annular space between the inner wall of the core holder and the outer wall of the experimental core for accommodating and fixing the experimental core; multiple pressure sensors disposed on the outer wall of the experimental core, each pressure sensor being disposed at a corresponding pressure measuring point; multiple ultrasonic probes disposed on the outer wall of the experimental core, each ultrasonic probe being disposed at a corresponding probe measuring point; and an injection valve disposed at each injection point, each valve being used to achieve individual communication between the displacement device and the corresponding injection point.

[0009] Preferably, the experimental core is assembled from several columnar cores selected vertically from the target reservoir, wherein the core assembly is rotatable to simulate edge-bottom water-oil reservoirs with different dip angles.

[0010] Preferably, the system further includes a switching valve disposed between the displacement device and the production end of the experimental core. The switching valve is used to switch from the strong bottom water drive simulation process to the gas injection pressure cone simulation process when closed. When the switching valve and all gas injection valves are closed, the gas injection pressure cone simulation process ends and enters the continuous bottom water drive process.

[0011] Preferably, the measuring device is further used to measure the pressure changes at different pressure measuring points and the ultrasonic signal changes at different probe measuring points during continuous bottom water drive, and compare them with the pressure changes at different pressure measuring points and the ultrasonic signal changes at different probe measuring points during strong bottom water drive simulation, to determine the sweep range of residual gas and the change in water production rate under residual gas conditions, and further clarify the influence law of residual gas on bottom water cone in order to evaluate the effect of gas injection pressure cone.

[0012] Preferably, the displacement device includes an annular pressure pump connected to the sidewall of the core holder within the core device, the annular pressure pump being used to apply annular pressure to the experimental core to simulate the saturation of formation water processes.

[0013] Preferably, the displacement device further includes an injection pump connected to the production end of the experimental core and an injection pump connected to the injection end of the experimental core. During the simulation of the crude oil displacement process, the injection pump, when simultaneously turned on with the annular pressure pump, applies both annular pressure and production pressure to the experimental core until the pressure at each pressure measuring point reaches the target reservoir pressure. The injection pump injects experimental displacement crude oil, which is petroleum ether, into the experimental core when the pressure at each pressure measuring point reaches the target reservoir pressure.

[0014] Preferably, the displacement device further includes a water injection pump connected to the injection end of the experimental core, the water injection pump being used to inject water into the experimental core in a constant pressure mode to simulate the bottom water drive process.

[0015] On the other hand, embodiments of the present invention also provide a method for evaluating the effect of gas injection water coneing in bottom water sandstone reservoirs. The method is used to implement the system described above. The method includes: arranging experimental cores inside a core assembly, and setting multiple injection points along the axial direction of the experimental cores, wherein pressure measurement points and probe measurement points are set on the core cross-section at each injection point; using a displacement device to inject water into the experimental cores saturated with formation water and displaced crude oil to simulate a strong bottom water drive process, and using a measuring device to measure the pressure changes at different pressure measurement points and the ultrasonic signal changes at different probe measurement points during the strong bottom water drive simulation and the gas injection water coneing simulation; using a displacement device to inject gas into any injection point at different speeds and / or different amounts to simulate the gas injection water coneing process, and measuring the pressure changes at different pressure measurement points and the ultrasonic signal changes at different probe measurement points during the gas injection water coneing simulation; and determining the gas sweep range by comparing measurement data from the same location and of the same type.

[0016] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0017] This invention proposes a system and method for evaluating the effect of gas injection water coneing in bottom-water sandstone reservoirs. This system and method can analyze the changes in water cut and oil production after gas injection by measuring the produced oil / water volume before and after gas injection, combined with the pressure and gas distribution patterns within the core during the gas injection process. This clarifies the effect of gas injection water coneing, deepens the understanding of the water control mechanism in bottom-water reservoirs, and solves the problem of simulating and evaluating the effect of gas injection water coneing in bottom-water sandstone reservoirs.

[0018] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0020] Figure 1 This is a schematic diagram of the overall structure of a system for evaluating the effect of gas injection pressure water cones in bottom water sandstone reservoirs, according to an embodiment of this application.

[0021] Figure 2 This is a schematic diagram of the specific structure of a system for evaluating the effect of gas injection pressure water cones in bottom water sandstone reservoirs, according to an embodiment of this application.

[0022] Figure 3This is a schematic cross-sectional view of the core holder in a system used to evaluate the effect of gas injection pressure water cones in bottom water sandstone reservoirs.

[0023] Figure 4 This is a schematic diagram of the core pressure change curves before and after gas injection in a system used to evaluate the effect of gas injection pressure cones in bottom water sandstone reservoirs.

[0024] Figure 5 This is a schematic diagram of the core pressure change curves before and after gas injection in a system used to evaluate the effect of gas injection pressure cones in bottom water sandstone reservoirs.

[0025] Figure 6 This is a schematic diagram of the steps involved in evaluating the effectiveness of a gas injection pressure water cone method for bottom water sandstone reservoirs. Detailed Implementation

[0026] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that, as long as there is no conflict, the various embodiments and features in the various embodiments of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0027] Furthermore, the steps illustrated in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Also, although a logical order is shown in the flowcharts, in some cases the steps shown or described may be performed in a different order than that shown here.

[0028] To address the problems mentioned in the background art, this application proposes a system and method for evaluating the effect of gas injection pressure cones in bottom-water sandstone reservoirs. The system and method include: a displacement device, a multi-injection-point rotatable long core flow device, and a measuring device containing pressure points and ultrasonic probes. The displacement device injects water into the long core at constant pressure to simulate the bottom-water drive process in a bottom-water reservoir; gas is injected at different injection points in the long core at different rates, pressures, and injection volumes to simulate the vertical gas injection layer at the top of the water body in the bottom-water reservoir and the gas injection conditions; the pressure points and ultrasonic probes are used to determine the fluid pressure within the core after gas injection and the gas injection sweep range; the measuring device calculates the water production rate before and after gas injection, analyzes the pressure changes along the core during the bottom-water drive process before and after gas injection, clarifies the effect of the gas injection pressure cone, and deepens the understanding of the gas injection water control mechanism in bottom-water reservoirs.

[0029] Figure 1 This is a schematic diagram of the overall structure of a system for evaluating the effect of gas injection pressure water cones in bottom water sandstone reservoirs, according to an embodiment of this application. Figure 1As shown in the embodiment of the present invention, the system for evaluating the effect of gas injection pressure water cone in bottom water sandstone reservoirs (hereinafter referred to as the "water cone effect evaluation system") includes: core device A, displacement device B, and measuring device C.

[0030] like Figure 1 As shown, the core apparatus A contains experimental cores, with multiple injection points evenly distributed along the axial direction of the cores. At each injection point, a corresponding pressure measurement point and probe measurement point are located on the core cross-section. Displacement apparatus B is connected to core apparatus A. Displacement apparatus B is used to simulate a strong bottom water drive process by injecting water into the experimental cores saturated with formation water and displaced crude oil, and to simulate a gas-injection water cone process by injecting gas at different rates and / or quantities into any injection point.

[0031] Measuring device C is connected to core device A. Measuring device C is used to measure pressure changes at different pressure measuring points and ultrasonic signal changes at different probe measuring points during the strong bottom water drive simulation process, and also to measure pressure changes at different pressure measuring points and ultrasonic signal changes at different probe measuring points during the gas injection water cone simulation process. By comparing measurement data from the same location and of the same type, the gas sweep range is determined. Thus, this embodiment of the invention utilizes a water cone effect evaluation system to test the gas flow state before and after gas injection, thereby helping to evaluate the gas injection water cone effect.

[0032] Figure 2 This is a schematic diagram of the specific structure of a system for evaluating the effect of gas injection pressure water cones in bottom water sandstone reservoirs, according to an embodiment of this application. The following is in conjunction with... Figure 1 and Figure 2 The specific structure and function of the water cone effect evaluation system described in the embodiments of the present invention will be explained.

[0033] like Figure 2 As shown, core apparatus A includes: experimental core 9, core holder 4, multiple pressure sensors 6, multiple ultrasonic probes 5, and gas injection valves 7 (7-1 to 7-6). The core holder 4 is placed vertically on the experimental platform, and an annular space is formed between the inner wall of the core holder and the outer wall of the experimental core 9 (see reference). Figure 3 The core holder 4 is used to hold and fix the experimental core 9.

[0034] Furthermore, in this embodiment of the invention, the experimental core 9 is a long core system, specifically formed by splicing together several columnar cores selected vertically from the target reservoir. The core device A is rotatable and is used to simulate edge-bottom water-oil reservoirs with different dip angles.

[0035] Figure 3 This is a schematic cross-sectional view of the core holder in a system used to evaluate the effectiveness of pneumatic water injection cones in bottom-water sandstone reservoirs. Figure 3As shown, multiple pressure sensors 6 are installed on the outer wall of the experimental core 9. Furthermore, a pressure sensor 6 corresponding to the current section is installed on the core section at each injection point, and each pressure sensor 6 is installed at a corresponding pressure measurement point. Multiple ultrasonic probes 5 are installed on the outer wall of the experimental core 9. Furthermore, several ultrasonic probes 5 corresponding to the current section are installed on the core section at each injection point (for example, two ultrasonic probes 5 are symmetrically arranged), and each ultrasonic probe 5 is installed at a corresponding symmetrical probe measurement point.

[0036] Each pressure measurement point is constructed as an injection port to simulate different injection sites in a bottom water reservoir. An injection valve 7 is installed at the inlet section of each injection port. Each injection valve 7 is used to establish a separate connection between the displacement device B and the corresponding injection point.

[0037] In addition, core device A also includes a back pressure control valve 11. The back pressure valve 11 is used to control the internal pressure of the core 9.

[0038] Furthermore, the core device A disclosed in this invention is a long core flow system with multiple injection points, including a long core 9, a temperature- and pressure-resistant core holder 4, a back pressure control valve 11, a pressure sensor 6, and an ultrasonic probe 5. The long core 9 is placed in the holder 4, with pressure measuring points distributed on the side of the holder 4, and multiple pairs of ultrasonic probes 5 symmetrically distributed at both ends. The end (production end) of the core 9 is connected to the back pressure control valve 11. The pressure measuring points serve two purposes: firstly, they connect to the pressure sensor 6 for real-time pressure monitoring; secondly, they act as gas injection points to simulate different gas injection sites in bottom water reservoirs. The ultrasonic probes 5 reflect the gas distribution during the gas injection process. The back pressure control valve 11 controls the internal pressure of the core. In addition, the multi-injection-point long core flow system has a rotation function, enabling it to simulate bottom water reservoirs with different dip angles.

[0039] Continue to refer to Figure 2 Displacement device B is a device composed of multiple high-temperature and high-pressure injection pumps 1, 2, and 3. It is mainly used to pump formation fluid into core 9 at a constant pressure or flow rate to simulate the energy of water bodies in injection-production wells and bottom water reservoirs.

[0040] Specifically, the displacement device B includes a water injection pump (not shown) connected to the injection end of the experimental core 9. The water injection pump is used to inject formation water into the experimental core 9 in a constant pressure mode to simulate a strong bottom water drive process.

[0041] Furthermore, the water cone effect evaluation system described in this embodiment of the invention also includes a switching valve 8 disposed between the displacement device B and the production end of the experimental core 9. The switching valve 8, when closed, switches the system simulation experiment from a strong bottom water drive simulation process to an air-injected water cone simulation process. Specifically, when the switching valve 8 and all air injection valves 7 are closed, the air-injected water cone simulation process ends and enters a continuous strong bottom water drive process.

[0042] In addition, the displacement device B also includes an annular pressure pump 2 connected to the sidewall of the core holder 4. The annular pressure pump 2 is used to apply annular pressure to the experimental core 9 to simulate the saturation of formation water. The displacement device B also includes an air injection pump 1 connected to the production end of the experimental core 9 and an oil injection pump 3 connected to the injection end of the experimental core 9. During the simulation of the crude oil displacement process, the air injection pump 1, when simultaneously turned on with the annular pressure pump 2, applies both annular pressure and production pressure to the experimental core 9 until the pressure at each pressure measuring point reaches the target reservoir pressure. Then, the oil injection pump 3 injects experimental displacement crude oil into the experimental core 9 when the pressure at each pressure measuring point reaches the target reservoir pressure. The experimental displacement crude oil is petroleum ether.

[0043] Furthermore, during the simulation of the gas injection water cone, the gas injection pump 1 injects gas into any injection point of the core 9 at different speeds and / or different amounts, thereby simulating the gas injection water cone process.

[0044] Furthermore, such as Figure 2 As shown, the measuring device C includes a gas flow meter 12, a test tube 13, an electronic balance 14, and a data acquisition and measurement processor 10.

[0045] The measuring device C is used to determine the bottom water rise position and calculate the water production per unit time during the strong bottom water drive simulation process based on the pressure changes at different pressure measuring points and the ultrasonic signal changes at different probe measuring points. It also calculates the water production per unit time during the gas injection water cone simulation process based on the pressure changes at different pressure measuring points and the ultrasonic signal changes at different probe measuring points. On the one hand, by comparing the pressure and ultrasonic signals of the gas injection water cone stage with those of the strong bottom water stage, the sweep range of the gas can be determined. On the other hand, by comparing the water production per unit time during the gas injection water cone stage with that during the strong bottom water stage, the change law of water production rate before and after gas injection can be determined.

[0046] In addition, the measuring device C is also used to measure the pressure changes at different pressure measuring points and the ultrasonic signal changes at different probe measuring points during the continuous bottom water drive process. The pressure changes at different pressure measuring points and the ultrasonic signal changes at different probe measuring points during the continuous bottom water drive process are compared with the pressure changes at different pressure measuring points and the ultrasonic signal changes at different probe measuring points during the strong bottom water drive simulation process. This determines the sweep range of residual gas and the change in water production rate under residual gas conditions. Based on this, the influence law of residual gas on bottom water cone inlet is clarified to evaluate the effect of gas injection pressure cone.

[0047] In this way, the measuring device C records the pressure and gas distribution at different measuring points in real time, as well as the oil / gas / water volume in the produced fluid at different times. It then sequentially injects saturated formation water, formation crude oil, and constant-pressure bottom water into a long core to drive it to a high water cut. Next, it injects gas into different pressure measuring points to simulate the water-pressurization cone process in a bottom-water reservoir. By measuring the water production rate of the produced section before and after gas injection, and combining this with the pressure and gas distribution patterns within the core during gas injection, the effect of the gas injection water-pressurization cone process is analyzed, and the effectiveness of gas injection in controlling water is dissected.

[0048] The following are two application examples of the water cone effect evaluation system shown in the embodiments of the present invention:

[0049] Example 1

[0050] The experimental temperature was 110℃, the core permeability was between 500 and 800 md, and the total length of the experimental core was 30.43 cm. The core was placed vertically, and the bottom of the core was injected with water at a constant pressure of 52.1 MPa to simulate strong bottom water drive. The core outlet pressure (produced end pressure) was kept constant at 49.6 MPa. The effects of water-pressurized cones with injection volumes of 0.2 PV and 0.5 PV were compared under the condition that the CO2 injection rate was 0.1 mL / min.

[0051] Figure 4 This is a schematic diagram of the core pressure change curves before and after gas injection in a first example of a system used to evaluate the effect of gas injection and water coneing in bottom-water sandstone reservoirs. The coneing effect evaluation experiment was conducted according to the experimental procedures until the bottom water was driven to the point where no oil production was observed. At this point, the calculated water production rate was 0.2418 mL / min. The pressure distribution along different pressure measurement points in the core is shown in [reference needed]. Figure 4 The pressure change curve before gas injection is shown in the figure. CO2 was injected into 0.2 PV from valve 7-4 at a rate of 0.1 mL / min. After the bottom water drive pressure stabilized, the product water rate was calculated to be 0.2074 mL / min. The distribution of residual CO2 gas monitored by the ultrasonic probe within the range of valves 7-3 to 7-7, along the pressure distribution at different pressure measurement points in the core, is shown in the figure. Figure 4The pressure change curve of 0.2PV gas injection is shown in the figure. CO2 was injected at a rate of 0.1 mL / min from valve 7-4 to 0.5PV. After the bottom water drive pressure stabilized, the product water rate was calculated to be 0.1741 mL / min. The distribution of residual CO2 gas monitored by the ultrasonic probe within the range of valves 7-2 to 7-7, along the pressure distribution at different pressure measurement points in the core, is shown in the figure. Figure 4 The pressure change curve at 0.5 PV injection point shows that the larger the injection volume, the greater the distance CO2 diffuses into the water, and the pressure near the injection point increases significantly, indicating a better effect of the pressure cone.

[0052] Example 2

[0053] The experimental temperature was 110℃, the core permeability was between 500 and 800 md, the total length of the experimental core was 31.25 cm, the core was placed vertically, the bottom pressure of the core was 52.1 MPa, constant pressure water injection simulated strong bottom water drive, the core outlet pressure (production end pressure) was kept constant at 49.6 MPa, and the effect of water cone pressure was compared under CO2 injection rates of 0.1 mL / min and 0.5 mL / min.

[0054] Figure 5 This is a schematic diagram of the core pressure change curves before and after gas injection in a second example of a system used to evaluate the effect of gas injection and water coneing in bottom-water sandstone reservoirs. The coneing effect evaluation experiment was conducted according to the experimental procedures until the bottom water was driven to the point where no oil production was observed. At this point, the calculated water production rate was 0.2355 mL / min. The pressure distribution along different pressure measurement points in the core is shown in [reference needed]. Figure 5 The pressure change curve before gas injection is shown in the figure. CO2 was injected from valve 7-4 at a rate of 0.1 mL / min to 0.2 PV. After the bottom water drive pressure stabilized, the product water rate was calculated to be 0.1986 mL / min. The pressure distribution along different pressure measurement points in the core is shown in the figure. Figure 5 The pressure change curve at an injection rate of 0.1 mL / min is shown. The residual CO2 gas distribution, monitored by an ultrasonic probe, is within the range of valves 7-3 to 7-7. CO2 is injected from valve 7-4 at a rate of 0.5 mL / min to 0.2 PV. At the end of the injection, the water production at the output end is zero, indicating that high-speed gas injection and pressure increase can suppress bottom water rise. After the bottom water drive pressure stabilizes after the injection, the water production rate is calculated to be 0.1689 mL / min. The pressure distribution along different pressure measurement points in the core is shown in [reference needed]. Figure 5 The pressure change curve is shown when the gas injection rate is 0.5 mL / min. The residual CO2 gas distribution, monitored by an ultrasonic probe, is within the range of valves 7-2 to 7-7. This indicates that a higher injection rate and higher injection pressure result in a larger area of ​​CO2 reaching the water body, and a better effect of the pressure cone.

[0055] Based on the above-mentioned water cone effect evaluation system, this invention also provides a method for evaluating the effect of gas injection water cones in bottom-water sandstone reservoirs (also referred to as the "water cone effect evaluation method"). The water cone effect evaluation method is an implementation method of the above-mentioned water cone effect evaluation system. The water cone effect evaluation method is implemented according to the following steps:

[0056] Step S601: An experimental rock core is arranged inside the core device, and multiple injection points are set along the axial direction of the experimental rock core. A pressure measuring point and a probe measuring point are set on the rock core cross section at each injection point.

[0057] Step S602 uses a displacement device to inject water into the experimental core that has been saturated with formation water and displaced crude oil to simulate the strong bottom water drive process, and uses a measuring device to measure the pressure changes at different pressure measuring points and the ultrasonic signal changes at different probe measuring points during the strong bottom water drive simulation process and the gas injection water cone simulation process.

[0058] Step S603 uses a displacement device to inject gas into any injection point at different speeds and / or different amounts to simulate the gas injection water cone process. During the gas injection water cone simulation, the pressure changes at different pressure measurement points and the ultrasonic signal changes at different probe measurement points are measured. By comparing the measurement data of the same location and the same type, the gas wave range is determined.

[0059] Specifically, in step one (saturation of formation water process), select several representative small columnar cores of the target reservoir in the vertical direction, with a diameter of 2.5cm. According to the principle of harmonization and averaging, splice them together to form a long core 9 with a length greater than 30cm, and place it in the multi-injection point core holder 4. Rotate the core holder 4 to the vertical direction, and use the ring pressure pump 2 to increase the ring pressure of the holder 4 to about 3MPa to evacuate the core 9 and saturate it with formation water.

[0060] Step 2 (Saturation of Formation Oil Process): Prepare Formation Crude Oil for the Target Area. Saturate petroleum ether into core 9, and simultaneously increase the pressure of the clamp 4 and the back pressure valve 11 using the ring pressure pump 2 and the gas injection pump 1, maintaining a pressure difference of about 3 MPa between the two until the pressure at the pressure measuring point in core 9 reaches the target reservoir pressure; then use formation crude oil to displace the petroleum until the produced fluid is entirely formation crude oil.

[0061] Step 3 (Constant Pressure Bottom Water Drive to High Water Cut): Water is injected into the core at constant pressure using an injection pump to simulate a strong bottom water drive process. The entire core simulates an oil-water transition zone. During the bottom water drive process, the signals from ultrasonic measuring points and the pressure changes at pressure measuring points are recorded. The pressure fluctuations at the pressure measuring points are used to roughly determine the layer where the bottom water is lifted, thereby calculating the water production rate per unit time at the production end and determining the water production rate Vw.

[0062] Step 4 (Simulation Process of Water Pressure Cone): Close valve 8, and use air injection pump 1 to inject different amounts of gas at different speeds into the corresponding pressure measuring points through any one of the valves (7-1~7-6). Monitor the pressure changes at other pressure measuring points and the signal changes at the ultrasonic measuring points throughout the entire air injection process, and calculate the water production rate Vw at the output end per unit time. ， By comparing the pressure and ultrasonic signals during the bottom water drive stage, the gas wave range and the change in permeable velocity after gas injection were determined.

[0063] Step 5 (Continuous Strong Bottom Water Drive Process): Stop gas injection and close valve 7. Continue the bottom water drive process, monitor the pressure at the pressure measuring point and the ultrasonic measuring point signal throughout the entire gas injection process, compare them with the pressure and ultrasonic signal of the bottom water drive stage, determine the range of residual gas and the change in water production rate under residual gas conditions, clarify the influence law of residual gas on bottom water cone ingress, and evaluate the effect of gas injection pressure cone.

[0064] This invention discloses a system and method for evaluating the effect of gas injection pressure cones in bottom-water sandstone reservoirs. The system and method include a displacement device, a multi-injection-point rotatable long core flow device, and a measuring device containing pressure points and ultrasonic probes. The displacement device consists of several high-temperature, high-pressure injection pumps used to pump formation fluid into the core at a constant pressure or flow rate, simulating the energy of water in injection-production wells and bottom-water reservoirs. Connected to this is the multi-injection-point long core flow device, which includes a long core, a temperature- and pressure-resistant core holder, a back pressure control valve, a pressure sensor, and ultrasonic probes. The long core is placed in the holder, which has pressure measuring points on its sides. Multiple pairs of ultrasonic probes are symmetrically distributed at both ends, and the end is connected to the back pressure control valve. The pressure measuring points are used both to connect to the pressure sensor for real-time pressure monitoring and as injection points to simulate different injection sites in bottom-water reservoirs. The ultrasonic probes reflect the gas distribution during injection. The back pressure control valve controls the internal pressure of the core. The multi-injection-point long core flow system has a rotation function to simulate bottom-water reservoirs with different dip angles. The measuring device includes a gas flow meter, test tubes, an electronic balance, and a data acquisition processor for automatic data acquisition. It records in real-time the pressure and gas distribution at different measuring points, as well as the oil / gas / water volume in the produced fluid at different times. The device sequentially injects saturated formation water, formation crude oil, and constant-pressure bottom water into a long core to drive it to a high water cut. Then, gas is injected into different pressure measuring points to simulate the gas injection water cone process in a bottom-water reservoir. By measuring the oil / water volume in the produced fluid before and after gas injection, and combining this with the pressure and gas distribution patterns along the core, the device analyzes the increase in water cut and changes in oil production after gas injection, thus dissecting the effect of the gas injection water cone. Therefore, this invention solves the problem of evaluating the effect of the gas injection water cone by measuring the oil / water volume in the produced fluid before and after gas injection, and combining this with the pressure and gas distribution patterns within the core during the gas injection process.

[0065] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0066] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0067] The phrase "an embodiment" or "an embodiment" used in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0068] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A system for evaluating the effect of pneumatic water cone injection in bottom-water sandstone reservoirs, characterized in that, include: The core device contains experimental cores and has multiple injection points along the axial direction of the experimental cores. Each injection point has a pressure measuring point and a probe measuring point on its core cross-section. Each pressure measuring point is constructed as a gas injection port to simulate different gas injection sites in bottom water reservoirs. The experimental cores are assembled from several columnar cores selected vertically from the target reservoir to form a long core system. The displacement device, which is connected to the core device, is used to inject water into the injection end of the experimental core that has been saturated with formation water and displaced crude oil to simulate a strong bottom water drive process, and to inject gas into any injection point at different rates and / or different amounts to simulate a gas injection water cone process. The measuring device, connected to the core device, is used to measure pressure changes at different pressure measuring points and ultrasonic signal changes at different probe measuring points during both the strong bottom water drive simulation process and the gas injection water cone simulation process. By comparing measurement data from the same location and of the same type, the gas sweep range is determined, including: Based on the pressure changes at different pressure measurement points and the ultrasonic signal changes at different probe measurement points during the strong bottom water drive simulation process, the bottom water rise position is determined. The water production per unit time during the strong bottom water drive simulation process is calculated using the production volume at the output end of the core sample obtained from the metrological experiment. Then, based on the pressure changes at different pressure measurement points and the ultrasonic signal changes at different probe measurement points during the gas injection water-pressurization cone simulation process, the gas sweep range is determined. The water production per unit time during the gas injection water-pressurization cone simulation process is calculated again using the production volume at the output end of the core sample obtained from the metrological experiment. This obtains the variation law of water production rate before and after gas injection, and determines the sweep range of residual gas and the change of water production rate under residual gas conditions. This clarifies the influence law of residual gas on bottom water cone propulsion, thereby evaluating the effect of the gas injection water-pressurization cone. The injection end and the production end are located on the two end faces of the experimental core, respectively.

2. The system according to claim 1, characterized in that, The core device includes: The core samples used in the experiment; A core holder is placed vertically on the experimental platform, and an annular space is formed between the inner wall of the core holder and the outer wall of the experimental core for accommodating and fixing the experimental core. Multiple pressure sensors are installed on the outer wall of the experimental core, with each pressure sensor corresponding to a pressure measurement point. Multiple ultrasonic probes are installed on the outer wall of the experimental core, with each probe positioned at a corresponding measuring point; and An air injection valve is installed at each injection point, and each valve is used to achieve individual communication between the displacement device and the corresponding injection point.

3. The system according to claim 1 or 2, characterized in that, The core device is rotatable and is used to simulate edge-bottom water-oil reservoirs with different dip angles.

4. The system according to claim 2, characterized in that, The system also includes a switching valve disposed between the displacement device and the production end of the experimental core. The switching valve is used to switch from the strong bottom water drive simulation process to the gas injection water cone simulation process when closed. When the switching valve and all gas injection valves are closed, the gas injection water cone simulation process ends and enters the continuous bottom water drive process.

5. The system according to claim 1 or 2, characterized in that, The displacement device includes an annular pressure pump connected to the sidewall of the core holder within the core device. The annular pressure pump is used to apply annular pressure to the experimental core to simulate the saturation of formation water.

6. The system according to claim 5, characterized in that, The displacement device further includes an air injection pump connected to the production end of the experimental core and an oil injection pump connected to the injection end of the experimental core, wherein, during the simulation of the crude oil displacement process, The air injection pump is used to apply annular pressure and production pressure to the experimental core simultaneously when it is turned on at the same time as the annular pressure pump, until the pressure at each pressure measurement point reaches the target reservoir pressure. The oil injection pump is used to inject experimental displacement crude oil into the experimental core when the pressure at each pressure measurement point reaches the target reservoir pressure. The experimental displacement crude oil is petroleum ether.

7. The system according to claim 5, characterized in that, The displacement device also includes a water injection pump connected to the injection end of the experimental core, the water injection pump being used to inject water into the experimental core in a constant pressure mode to simulate the bottom water drive process.

8. A method for evaluating the effect of gas injection pressure water cones in bottom-water sandstone reservoirs, characterized in that, The method is used to implement the system as described in any one of claims 1 to 7, and the method includes: The experimental rock core is arranged inside the rock core device, and multiple injection points are set along the axial direction of the experimental rock core. A pressure measuring point and a probe measuring point are set on the rock core cross section at each injection point. The experimental core, which had been saturated with formation water and displaced crude oil, was injected with water using a displacement device to simulate a strong bottom water drive process. The pressure changes at different pressure points and the changes in ultrasonic signals at different probe points were measured using a measuring device during the strong bottom water drive simulation and the gas injection water cone simulation. The process of gas injection and water pressure cone is simulated by injecting gas into any injection point at different speeds and / or in different amounts using a displacement device. During the simulation, the pressure changes at different pressure measurement points and the ultrasonic signal changes at different probe measurement points are measured. By comparing the measurement data of the same location and the same type, the gas wave range is determined.

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