Parameter optimization method for synergistic energy replenishment of CO2 and water-based fluids after depletion of shale reservoirs

Abstract

The present invention relates to an optimization method for the collaborative energy supplement parameters of CO2 and water-based fluids after the depletion development of shale reservoirs, which includes: obtaining the key parameters of shale reservoir formations; preparing shale oil and core samples; conducting mercury intrusion tests on each core sample to obtain pore size distribution data of shale core samples from two different horizons; performing two-dimensional nuclear magnetic resonance tests on dry shale samples from different horizons; restoring the initial reservoir conditions and conducting two-dimensional nuclear magnetic resonance tests on the state of shale oil in different horizons under the initial reservoir conditions; conducting two-dimensional nuclear magnetic resonance tests on different horizons after shale depletion development; simulating the process of collaborative energy supplement of CO2 and water-based fluids and conducting two-dimensional nuclear magnetic resonance tests on different horizons after energy supplement development; evaluating the development effect of collaborative energy supplement of CO2 and water-based fluids in different horizons of shale reservoirs; and optimizing the collaborative energy supplement parameters of CO2 and water-based fluids by using the weighted sum method. The present invention can evaluate the overall development effect of the reservoir under different energy supplement parameters.

Description

Technical field:

[0001] The present invention relates to the technical field of shale oil development, and in particular to a method for optimizing parameters of synergistic energy replenishment of CO2 and water-based fluid after depletion development of a shale oil reservoir. Background technology:

[0002] my country has abundant shale oil reserves. Its exploration and development can increase the diversity of national energy supply and improve the level of energy security, which is of great significance. The development of shale oil generally adopts the staged horizontal well volume fracturing technology, but the low porosity and low permeability characteristics of my country's continental shale reservoirs make the natural elastic energy of the reservoirs consume quickly during fracturing production, the production declines quickly, and it is difficult to obtain economically effective long-term production capacity. Therefore, improving the recovery rate of shale oil reservoirs is the current technical difficulty. Studies have shown that the water-based fracturing-imbibition agent system commonly used in oil and gas field development has a good degree of utilization of nano-pores and small-pore shale oil between clay layers, while CO2 mainly utilizes medium-pore and large-pore shale oil; if the synergistic effect of different types of injection media can be brought into play and the shale oil in the full-scale pores can be effectively utilized, it is expected to greatly increase its recovery rate. At present, the energy replenishment technology of shale oil reservoirs is still in the exploratory stage. It is of great significance to study the optimization method of the synergistic energy replenishment parameters of CO2 and water-based fluids after the exhaustion development of shale oil reservoirs to help the efficient development of shale oil.

[0003] At present, the research on the energy replenishment effect of shale oil reservoirs is mainly based on indoor experiments based on mass method, CT scanning, and online nuclear magnetic resonance testing technology. Prior art CN 118211505 A is a method for determining carbon dioxide huff and puff injection parameters, which uses indoor simulation experiments of carbon dioxide huff and puff and theoretical calculation formulas to determine the injection volume, maximum injection pressure, injection rate, well shut-in time, and flowback rate. The indoor experiment conducted is only for a single core, and can only give the overall recovery rate of the core. The experimental and numerical calculation formula assumptions are inconsistent with the actual complex reservoir conditions, and the calculation error is large. Prior art CN 114965540A is a shale oil reservoir core carbon dioxide huff and puff experimental method and device, which performs nuclear magnetic resonance T2 spectrum detection on the core before and after the experiment, compares the saturated oil and the huffed oil components, and performs nano CT scanning on the core after the simulated huff and puff process, so as to analyze the distribution morphology of the remaining oil after the huff and puff. This method fails to provide a quantitative evaluation method and parameter optimization method for the effect of carbon dioxide huff and puff. CN 115788373 A is a method for evaluating the replacement law of CO2 and shale oil reservoirs. In the experiment, the core is saturated with formation water and then displaced with simulated crude oil until no water is produced at the outlet to simulate the initial state of the core in the formation. This is a simulation method for conventional oil reservoirs, and the method is not suitable for shale oil reservoirs with the characteristics of "source generation and source storage"; when evaluating the oil displacement efficiency of different pore throats of the core through nuclear magnetic resonance T2 spectrum, the pore throat size is divided according to the relaxation time distribution range in the spectrum, and the specific value of the pore throat radius is not given; the influence of the replacement effect is studied by changing the injection pressure, constant flow rate, injection amount and action time by experiment, and no specific parameter optimization method is given. In the actual production process, the oil reservoir is first depleted and exploited, and CO2 and water-based fluids are mostly injected in coordination later, and the above methods only involve the injection of CO2. Summary of the invention:

[0004] The purpose of the present invention is to provide a method for optimizing parameters of synergistic energy replenishment of CO2 and water-based fluid after depletion development of shale oil reservoirs. This method for optimizing parameters of synergistic energy replenishment of CO2 and water-based fluid after depletion development of shale oil reservoirs is used to solve the problems of single evaluation method for energy replenishment effect of shale oil reservoirs and lack of parameter optimization method.

[0005] The technical solution adopted by the present invention to solve the technical problem is: the method for optimizing the parameters of the synergistic energy replenishment of CO2 and water-based fluid after the depletion development of shale oil reservoirs comprises the following steps:

[0006] Step 1: Obtain key reservoir parameters of shale oil reservoirs, including reservoir pressure, temperature, and overburden pressure at different layers;

[0007] Step 2, preparing shale oil and core samples: Shale oil has the same viscosity as formation crude oil at reservoir temperature. Cylindrical core samples are drilled from full-size cores of two different layers, 1# and 2#, in the shale oil reservoir, and are marked as 1# and 2# core samples, respectively. 11# and 12# rock samples are cut from the 1# core sample, and 21# and 22# rock samples are cut from the 2# core sample.

[0008] Step 3: Dry each rock sample at 110°C to a constant weight, then perform mercury injection testing on rock samples 12# and 22# to obtain pore size distribution data of shale rock samples 1# and 2# at two different layers;

[0009] Step 4: Two-dimensional NMR test of dry samples of shale at different layers, recording the NMR signal of dry samples of 11# and 21# rock samples respectively. 10 and NMR 20 ;

[0010] Step 5: restore the initial reservoir conditions and conduct two-dimensional nuclear magnetic resonance tests on the shale oil state in different layers under the initial reservoir conditions. The nuclear magnetic resonance signals of the 11# rock sample and the 21# initial saturated oil are recorded as NMR 11 and NMR 21 ;

[0011] Step 6: Simulate the depletion development process of shale reservoirs and conduct two-dimensional nuclear magnetic resonance tests after depletion development of shale in different layers. Record the NMR signals of shale oil in rock samples 11# and 21# respectively. 12 and NMR 22 ;

[0012] Step 7: Simulate the synergistic energy replenishment process of CO2 and water-based fluids, conduct two-dimensional nuclear magnetic resonance tests on shale in different layers after energy replenishment development, and obtain the shale oil nuclear magnetic resonance signal quantities through diffusion-relaxation nuclear magnetic resonance data processing. 13 and NMR 23 ;

[0013] Step 8: Evaluation of the effect of synergistic energy supplementation development of CO2 and water-based fluids in different layers of shale oil reservoirs;

[0014] Step nine, comprehensively consider the shale oil recovery rate of the entire reservoir, different layers, and different pore scales, and use the weighted sum method to optimize the synergistic energy replenishment parameters of CO2 and water-based fluids.

[0015] Step 1 in the above scheme is specifically: through comprehensive analysis of geological data, geophysical data, logging data, and well test data, key parameters of shale oil reservoirs are obtained, including reservoir pressure, temperature, and overlying rock pressure at different levels.

[0016] Step 2 in the above scheme is specifically as follows: shale oil is prepared using ground dehydrated and degassed crude oil and kerosene to make the shale oil have the same viscosity as the formation crude oil at reservoir temperature; cylindrical core samples with a diameter of 2.5 cm and a length of 6 cm are drilled from full-size coring cores of two different layers 1# and 2# of the shale oil reservoir, and are marked as 1# and 2# rock samples respectively; the 1# core sample is cut into cores with a length of approximately 5 cm and 1 cm respectively, and are marked as 11# and 12# rock samples; the 2# core sample is cut into cores with a length of approximately 5 cm and 1 cm respectively, and are marked as 21# and 22# rock samples; 12# and 22# rock samples are used for high-pressure mercury injection testing, and 11# and 21# rock samples are used for CO2 and water-based fluid synergistic energy replenishment parameter optimization experiments after shale oil reservoir depletion development.

[0017] Step 4 in the above scheme is as follows: 11# and 21# rock samples are placed in the middle position of two online nuclear magnetic resonance dedicated core holders respectively, the two holders are connected in parallel to the online nuclear magnetic resonance core test system, fluorine oil is used to increase the confining pressure to 2MPa and the temperature of the fluorine oil is increased to the reservoir temperature of the 1# and 2# layers of the shale reservoir respectively; the inlet and outlet ends of the holder are closed, and after 11# and 21# rock samples are vacuumed for 48 hours, the dry sample state nuclear magnetic resonance T1-T2 spectrum test of 11# and 21# rock samples is performed, and the dry sample nuclear magnetic resonance signal quantities of 11# and 21# rock samples are recorded as NMR 10 and NMR 20 .

[0018] Step 5 in the above scheme is as follows: The overburden pressure P of the 1# layer 10 , initial reservoir pore pressure P p10 ; Overburden pressure P of 2# layer 20 , initial reservoir pore pressure P p20 ; The initial effective stresses of 1# and 2# layers are P e10 and P e20 . ; In the core of the 1# layer, the fluorine oil confining pressure is gradually increased to the overburden pressure P 10 During the process, the outlet of the holder is closed and shale oil is injected into the holder until the initial pore pressure of the reservoir reaches P p10 , always make the difference between the confining pressure and the pore pressure equal to the initial effective stress value P e10 , until the flow rate at the inlet end of the holder is zero for 4 hours. At this time, the conditions of the 11# rock sample are the reservoir temperature and initial pressure of the 1# layer; the saturated oil state nuclear magnetic resonance T1-T2 spectrum test of the 11# rock sample under the initial reservoir conditions is carried out, and the initial saturated oil nuclear magnetic resonance signal is recorded as NMR 11 ; In the 2# layer core, the fluorine oil confining pressure is gradually increased to the overburden pressure P 20 During the process, the outlet of the holder is closed and shale oil is injected into the holder until the initial pore pressure of the reservoir reaches P p20, always make the difference between the confining pressure and the pore pressure equal to the initial effective stress value P e20 , until the flow rate at the inlet end of the holder is zero for 4 hours. At this time, the conditions of the 21# rock sample are the reservoir temperature and initial pressure of the 2# layer; the saturated oil state nuclear magnetic resonance T1-T2 spectrum test of the 21# rock sample under the initial reservoir conditions is carried out, and the initial saturated oil nuclear magnetic resonance signal is recorded as NMR 21 .

[0019] Step 6 in the above scheme is as follows: keep the outlets of the two clamps closed, close the inlet of the clamp at the same time, and set the pressure of the back pressure valve at the emptying end to the bottom flow pressure of the production well P f11 , P f11 <P p10 And P f11 <P p20 , slowly open the two clamp drain valves, the rock sample pore pressure decreases, the effective stress increases, and the shale oil flows out until the drain flow is zero for 4 consecutive hours, realizing the simulation of shale reservoir depletion development process; perform nuclear magnetic resonance T1-T2 spectrum tests on 11# and 21# rock samples after depletion development, and record the shale oil nuclear magnetic resonance signal quantities, respectively. 12 and NMR 22 .

[0020] Step 7 in the above scheme is as follows: close the valves at the two holder exhaust ends, open the injection end, and inject pressure P i11 , P i11 >P f11 , inject CO2 into the two holders until the injection flow rate is zero for 4 consecutive hours; the injection pressure P i21 , P i21 >P i11 , inject water-based fluid into the two holders until the injection flow rate is zero for 4 consecutive hours, and then close the injection end; after the well is shut down for a period of time t1, set the back pressure valve pressure at the emptying end to the bottom flow pressure of the production well P f21 , P f21 <P i11 , slowly open the two clamps emptying ends, shale oil, CO2 and water-based fluids flow out until the flow at the emptying end is zero for 4 consecutive hours, realizing the simulation of shale oil reservoir energy replenishment and post-energy replenishment development process; perform nuclear magnetic resonance T1-T2 spectrum test on 11# and 21# rock samples after energy replenishment development, and obtain shale oil nuclear magnetic resonance signal quantities of NMR by diffusion-relaxation nuclear magnetic resonance data processing. 13 and NMR 23 .

[0021] Step eight in the above scheme is specifically:

[0022] ① Using the saturated oil NMR signal under the initial reservoir conditions in step 5 minus the dry sample NMR signal in step 4, the distribution curve of the shale oil NMR signal on different relaxation time coordinate axes is obtained, and compared with the pore size distribution data of the shale rock sample in step 3, the conversion relationship between the NMR relaxation time and the mercury injection pore radius is obtained; according to the peak distribution interval of the shale oil NMR signal, the multi-scale pores of the rock sample are divided into micro-nano pores, small pores, medium pores and large pores, and the radius values ​​and relaxation time values ​​corresponding to the different scale pores of the 11# rock sample and the 21# rock sample are determined according to the above conversion relationship;

[0023] ② According to step 4, the NMR signal quantities of dry samples of different pore sizes of rock samples 11# and 21# are determined as follows: N10 , NMR S10 , NMR M10 , NMR L10 and NMR N20 , NMR S20 , NMR M20 , NMR L20 According to step 5, the oil NMR signals of different pore sizes of rock samples 11# and 21# under initial reservoir conditions are determined as follows: N11 , NMR S11 , NMR M11 , NMR L11 and NMR N21 , NMR S21 , NMR M21 , NMR L21 ;

[0024] ③ Calculation of recovery factor of shale reservoir depletion development: According to step 6, the oil NMR signals of different scales of pores in 11# and 21# samples after depletion development are respectively N12 , NMR S12 , NMR M12 , NMR L12 and NMR N22 , NMR S22 , NMR M22 , NMR L22 ; Determine the total recovery factor η of the 1# layer rock sample depletion development according to formula 1 11 , according to formula 2-formula 5, the micro-nanopore recovery factor η is determined respectively N11 , small hole recovery factor η S11 , medium pore recovery factor η M11 and macropore recovery factor η L11 Similarly, determine the total recovery factor η of the 2# layer rock sample depletion development 21 , micro-nanopore recovery factor η N21 , small hole recovery factor η S21 , medium pore recovery factor η M21and macropore recovery factor η L21 The overall recovery factor η1 of shale reservoir depletion development is determined according to Formula 6;

[0025]

[0026] ④ Calculation of recovery factor of synergistic energy supplementation development of CO2 and water-based fluid: According to step 7, the NMR signals of oil in pores of different scales in 11# and 21# rock samples after synergistic energy supplementation development of CO2 and water-based fluid are determined as follows: N13 , NMR S13 , NMR M13 , NMR L13 and NMR N23 , NMR S23 , NMR M23 , NMR L23 ; Determine the total recovery factor η of the 1# layer rock sample CO2 and water-based fluid synergistic energy development 12 , according to formula 8-formula 11, the micro-nanopore recovery factor η is determined respectively N12 , small hole recovery factor η S12 , medium pore recovery factor η M12 and macropore recovery factor η L12 Similarly, the total recovery factor η of the 2# layer rock sample CO2 and water-based fluid synergistic energy development is determined 22 , micro-nanopore recovery factor η N22 , small hole recovery factor η S22 , medium pore recovery factor η M22 and macropore recovery factor η L22 ; Determine the overall recovery factor η2 of the synergistic energy supplement development of CO2 and water-based fluid in the entire shale oil reservoir according to formula 12;

[0027]

[0028]

[0029] Step 9 in the above scheme is specifically: the overall recovery rate of the reservoir synergistic energy replenishment η2, the total recovery rate of the 1# layer η 12 , micro-nanopore recovery factor η N12 , small hole recovery factor η S12 , medium pore recovery factor η M12 and macropore recovery factor η L12 、Total recovery factor of 2# layer η 22 , micro-nanopore recovery factor η N22 , small hole recovery factor η S22 , medium pore recovery factor η M22 and macropore recovery factor η L22 The corresponding weight coefficients are W2, W 12 , W N12 , WS12 , W M12 , W L12 , W 22 , W N22 , W S22 , W M22 , W L22 ; The optimization objective function f(x) is shown in Formula 13, and the sum of the weight coefficients of each parameter is 1, as shown in Formula 14; Taking f(x) as the objective function, and taking the energy replenishment timing, energy replenishment pressure, energy replenishment injection speed, energy replenishment injection volume, CO2 and water-based fluid injection ratio, injection sequence, well soaking time, and flowback speed as variables, the CO2 and water-based fluid synergistic energy replenishment parameters are optimized; the specific method is:

[0030]

[0031] ① Optimization of energy replenishment timing: Select parallel shale core samples and reduce the bottom flow pressure of the production well to P in step 6. f11 , P f12 , P f13 ...P f1n Corresponding time points T1, T2, T3...T n Start to use CO2 and water-based fluid to replenish energy, T1, T2, T3...T n That is the corresponding energy replenishment opportunity; for different energy replenishment opportunities, the objective function f(x) is calculated respectively, and the energy replenishment opportunity T corresponding to the maximum f(x) x This is the optimized energy replenishment opportunity;

[0032] ② Energy replenishment pressure optimization: At the optimal energy replenishment time T x Inject CO2 and water-based fluid to different energy injection pressures P i11 , P i12 , P i13 ...P i1n and P i21 , P i22 , P i23 ...P i2n For different recharging pressures, the objective function f(x) is calculated respectively, and the CO2 and water-based fluid recharging pressure P corresponding to the maximum f(x) is i1x and P i2x That is the optimized CO2 and water-based fluid recharge pressure;

[0033] ③ Optimization of energy injection speed: At the optimal energy injection time T x Different CO2 and water-based fluid injection rates q i11 ,q i12 ,q i13 ……q i1n and q i21 ,q i22,q i23 ……q i2n Add energy until the pressure reaches P i1x and P i2x For different energy injection rates, the objective function f(x) is calculated, and the CO2 and water-based fluid energy injection rates q corresponding to the maximum f(x) are calculated. i1x and q i2x That is, the optimized CO2 and water-based fluid energy injection rate;

[0034] ④ Optimization of the injection ratio of CO2 and water-based fluid: At the optimal energy replenishment time T x The injection speed q was 3:1, 2:1, 1:1, 1:2, and 1:3 with different CO2 and water-based fluid injection ratios. i1x and q i2x Add energy until the pressure finally reaches P i2x ; For different injection ratios, the objective function f(x) is calculated respectively, and the injection ratio corresponding to the maximum f(x) is the optimized CO2 and water-based fluid energy replenishment injection ratio;

[0035] ⑤ Optimization of CO2 and water-based fluid injection sequence: At the optimal energy replenishment time T x The injection rate and injection ratio of CO2 and water-based fluid are optimized to replenish the pressure until the pressure reaches P. i2x ; For different injection sequences, the objective function f(x) is calculated respectively, and the injection sequence corresponding to the maximum f(x) is the optimized CO2 and water-based fluid energy replenishment injection sequence;

[0036] ⑥ Optimization of energy replenishment and well soaking time: At the optimal energy replenishment time T x The optimized CO2 and water-based fluid injection rate q i1x and q i2x Add energy until the final pressure reaches P i2x , respectively at different soaking times t1, t2, t3...t n Then, the post-energy replenishment development is started; for different well-shutdown times, the objective function f(x) is calculated respectively, and the well-shutdown time corresponding to the maximum f(x) is the optimized CO2 and water-based fluid energy replenishment well-shutdown time;

[0037] ⑦ Optimization of return flow rate after energy replenishment: At the optimal energy replenishment time T x With the optimal CO2 and water-based fluid injection ratio and energy injection rate q i1x and q i2x Add energy until the pressure finally reaches P i2x , during the soaking time t x Then, different return speeds q f1 ,q f2 ,q f3 ……qfn Carry out post-energy replenishment development; for different return flow rates, calculate the objective function f(x) respectively, and the return flow rate corresponding to the maximum f(x) is the optimized CO2 and water-based fluid return flow rate after energy replenishment.

[0038] Beneficial effects:

[0039] 1. In the test process of the present invention, there is no need to repeatedly take out rock samples, so that the rock samples are always in the high temperature and high pressure state of the reservoir, and the whole process of depletion mining-energy replenishment-mining of different layers under the conditions of shale oil reservoirs is truly reflected, avoiding interference from human factors and achieving high measurement results.

[0040] 2. The present invention can not only evaluate the overall development effect of the reservoir with different energy replenishment parameters under reservoir conditions, but also study the multi-scale pore development effect of shale in different layers and its contribution to the total recovery rate from a microscopic perspective, optimize the energy replenishment parameters, and analyze the process and mechanism of synergistic energy replenishment of CO2 and water-based fluids.

[0041] 3. The present invention can conduct parallel experiments on multiple cores of different layers in parallel to simulate the energy replenishment effect of the entire reservoir, while optimizing the energy replenishment parameters of the entire reservoir and different layers, further improving the comprehensiveness and accuracy of the method. If it is necessary to focus on the development of shale oil in a certain layer or a certain scale of pores, this can be achieved by changing the weight coefficients in formulas 13 and 14.

[0042] 4. The CO2 and water-based fluid synergistic energy replenishment parameter optimization method determined by the present invention can provide important experimental data and method support for the design of shale oil field development plans and the optimization of reasonable CO2 energy replenishment construction parameters. Description of the drawings:

[0043] Figure 1 It is a flow chart of the present invention;

[0044] Figure 2 Schematic diagram of the online nuclear magnetic resonance testing system for shale oil reservoirs provided for this application;

[0045] Figure 3 This is the test result of dry sample NMR T1-T2 spectrum of rock sample #11 in step 4;

[0046] Figure 4 This is the result of the saturated oil nuclear magnetic T1-T2 spectrum test of the 11# rock sample in step 5;

[0047] Figure 5 This is the result of the nuclear magnetic T1-T2 spectrum test of the 11# rock sample after the depletion development in step 6;

[0048] Figure 6 This is the nuclear magnetic resonance T1-T2 spectrum test result of rock sample 11# after the synergistic energy replenishment development of CO2 and water-based fluid in step seven.

[0049] In the figure: 1 constant speed constant pressure pump, 2 first valve, 3 first intermediate container, 4 second valve, 5 second intermediate container, 6 third valve, 7 third intermediate container, 8 fourth valve, 9 fifth valve, 10 first fluid preheater, 11 second fluid preheater, 12 sixth valve, 13 seventh valve, 14 first back pressure valve, 15 second back pressure valve, 16 first fluid collecting container, 17 second fluid collecting container, 18 fluorine oil, 19 non-magnetic clamp plug, 20 nuclear magnetic resonance special core clamp, 21 shale rock sample, 22 nuclear magnetic control and data acquisition system, 23 pipeline, 24 eighth valve, 25 ninth valve, 26 third fluid preheater, 27 fourth fluid preheater, 28 first constant pressure pump, 29 second constant pressure pump, 30 tenth valve, 31 eleventh valve, 32 first vacuum pump, 33 second vacuum pump. Specific implementation method:

[0050] The present invention will be further described below:

[0051] See also Figure 1 The method for optimizing parameters of synergistic energy replenishment of CO2 and water-based fluid after depletion development of shale oil reservoirs includes the following steps:

[0052] Step 1: Obtain key parameters of shale oil reservoir: Through comprehensive analysis of geological, geophysical, logging, well testing and other data, the reservoir pressure, temperature and overburden pressure of the 1# layer of the shale oil reservoir are obtained to be 31.2MPa, 115℃ and 47MPa respectively, and the reservoir pressure, temperature and overburden pressure of the 2# layer are 30.5MPa, 105℃ and 45MPa respectively.

[0053] Step 2, prepare shale oil and core samples: simulate shale oil by using ground dehydrated and degassed crude oil and kerosene in a volume ratio of 1:1, that is, simulated shale oil with the same viscosity (0.64mPa·s) as formation crude oil at a reservoir temperature of 110°C is obtained. Cylindrical core samples with a diameter of 2.5cm and a length of 6cm are drilled from full-size core cores of two different layers of the shale oil reservoir 1# and 2#, and are marked as 1# and 2# rock samples respectively. The 1# core sample is cut into cores with a length of 5cm and 1cm, respectively, and are marked as 11# and 12# rock samples. The 2# core sample is cut into cores with a length of 5cm and 1cm, respectively, and are marked as 21# and 22# rock samples. The 12# and 22# rock samples are used for high-pressure mercury injection testing, and the 11# and 21# rock samples are used for the optimization experiment of the synergistic energy replenishment parameters of CO2 and water-based fluids after the depletion development of shale oil reservoirs.

[0054] Step 3: Dry the 11#, 12#, 21# and 22# rock samples at 110°C to constant weight. Then, mercury injection testing was performed on the 12# and 22# rock samples to obtain the pore size distribution data of the 1# and 2# shale rock samples at two different layers.

[0055] Step 4: Use the non-magnetic clamp plug 19 to place the 11# and 21# rock samples 21 in the middle position of two online nuclear magnetic resonance dedicated core clamps 20, and use the pipeline 23 to connect the two clamps in parallel to the online nuclear magnetic resonance core test system 22. Open the eighth valve 24 and the ninth valve 25, the first constant pressure pump 28 and the second constant pressure pump 29, use the fluorine oil 18 to increase the confining pressure to 2MPa, and use the third fluid preheaters 26 and 27 to increase the temperature of the fluorine oil 18 to the reservoir temperature of 115°C and 105°C of the 1# and 2# layers of the shale oil reservoir, respectively. Close the valves 10, 11, the sixth valve 12, and the seventh valve 13 at the inlet and outlet of the clamp, open the tenth valve 30 and the eleventh valve 31, use the first vacuum pump 32 and the second vacuum pump 33 to evacuate the 11# and 21# rock samples for 48 hours, and use the nuclear magnetic resonance control and data acquisition system 22 to perform nuclear magnetic resonance T1-T2 spectrum tests on the dry sample state of the 11# and 21# rock samples. The two-dimensional nuclear magnetic resonance test results of the dry sample of the 11# rock sample are as follows: Figure 3 As shown, record the NMR signal of 11# and 21# rock samples 10 and NMR 20 They are 0.4654[PU] and 1.1313[PU] respectively.

[0056] Step 5: Restore the initial reservoir conditions: Overburden pressure P of layer 1# 10 is 47MPa, and the initial pore pressure of the reservoir P p10 The overburden pressure of the 2# layer is 31.2MPa. 20 is 45MPa, and the initial pore pressure of the reservoir P p20 The initial effective stress P of the 1# and 2# layers is 30.5MPa. e10 and P e20 15.8MPa and 14.5MPa respectively. Open the first fluid preheater 10 and set the temperature to 115°C. In the process of gradually increasing the confining pressure of fluorine oil 18 to the overlying stratum pressure of 15.8MPa in the 1# layer core, close the tenth valve 30 at the outlet of the clamp, open the first valve 2 and the fourth valve 8 at the inlet, and use the constant speed and constant pressure pump 1 to inject shale oil in the first intermediate container 3 into the clamp to the initial reservoir pore pressure of 31.2MPa (always make the difference between the confining pressure and the pore pressure equal to the initial effective stress value of 15.8MPa), until the flow rate at the inlet of the clamp is zero for 4 hours, close the fourth valve 8, and the conditions of the 11# rock sample are 1# layer reservoir temperature of 115°C and initial pressure of 31.2MPa. Perform the saturated oil state nuclear magnetic resonance T1-T2 spectrum test of the 11# rock sample under the initial reservoir conditions, and record the initial saturated oil nuclear magnetic resonance signal NMR 11is 8.4096 [PU]. Open the second fluid preheater 11 and set the temperature to 105°C. In the process of gradually increasing the confining pressure of fluorine oil 18 to the overburden pressure of 14.5 MPa in the 2# layer core, close the eleventh valve 31 at the outlet of the clamp, open the fifth valve 9 at the inlet, and use the constant speed and constant pressure pump 1 to inject shale oil in the first intermediate container 3 into the clamp to the initial reservoir pore pressure of 30.5 MPa (always make the difference between the confining pressure and the pore pressure equal to the initial effective stress value of 14.5 MPa), until the flow rate at the inlet of the clamp is zero for 4 hours, close the first valve 2 and the fifth valve 9, at this time, the conditions of the 21# rock sample are 105°C and the initial pressure of 30.5 MPa in the 2# layer reservoir. The saturated oil state nuclear magnetic resonance T1-T2 spectrum test of the 21# rock sample under the initial reservoir conditions is carried out. The two-dimensional nuclear magnetic resonance test results of the saturated oil state of the 11# rock sample are as follows Figure 4 As shown, the initial saturated oil NMR signal is recorded 21 The value is 6.9168 [PU]. Steps 3-5 obtain the differences in the size distribution of micro-nano pores, small pores, medium pores and large pores in shale at different layers.

[0057] Step 6, shale oil reservoir depletion development process: the fourth valve 8, the fifth valve 9, the tenth valve 30 and the eleventh valve 31 at the inlet and outlet ends of the two clamps remain closed, and the pressure of the first back pressure valve 14 and the second back pressure valve 15 at the emptying end (the bottom flow pressure of the production well P f11 ) is 24MPa, slowly open the sixth valve 12 and the seventh valve 13 at the two clamps' emptying ends, the rock sample pore pressure decreases, the effective stress increases, and the shale oil flows out. Use the first fluid collection container 16 and the second fluid collection container 17 to collect the produced fluid until the flow at the emptying end is zero for 4 consecutive hours, close the sixth valve 12 and the seventh valve 13, and simulate the depletion development process of the shale reservoir. Perform nuclear magnetic resonance T1-T2 spectrum tests on 11# and 21# rock samples after depletion development. The two-dimensional nuclear magnetic resonance test results of 11# rock sample after depletion development are as follows Figure 5 As shown, the shale oil nuclear magnetic signal NMR is recorded 12 and NMR 22 They are 7.7022[PU] and 6.5308[PU] respectively. The overall recovery factor of shale oil reservoir depletion development and the multi-scale pore recovery factor of different layers can be obtained.

[0058] Step 7, CO2 and water-based fluid synergistic energy replenishment process: close the sixth valve 12 and the seventh valve 13 at the two clamps' emptying ends, open the fourth valve 8 and the fifth valve 9 at the injection end, open the third valve 6, and use the constant speed and constant pressure pump 1 to inject at a pressure P i11 Inject CO2 from the third intermediate container 7 into the two holders at 30 MPa until the injection flow rate is zero for 4 consecutive hours, and close the third valve 6. Open the second valve 4 to inject the pressure P i21The water-based fluid in the second intermediate container 5 is injected into the two holders at 40 MPa until the injection flow rate is zero for 4 consecutive hours, the fourth valve 8 and the fifth valve 9 at the injection end are closed, and the second valve 4 is closed. After the well is shut down for a period of time t1 of 10 days, the pressure of the first back pressure valve 14 and the back pressure valve 15 at the emptying end (the bottom flow pressure of the production well P f21 ) is 24MPa, slowly open the sixth valve 12 and the seventh valve 13 at the two clamps' drain ends, and shale oil, CO2 and water-based fluids flow out until the drain end flow rate is zero for 4 consecutive hours, realizing the simulation of shale oil reservoir energy replenishment and post-energy replenishment development process. The nuclear magnetic resonance T1-T2 spectrum test of 11# rock sample and 21# rock sample after energy replenishment development is carried out. The two-dimensional nuclear magnetic resonance test results of 11# rock sample after energy replenishment development are as follows Figure 6 As shown, the shale oil NMR signal quantity NMR is obtained through diffusion-relaxation NMR data processing. 13 and NMR 23 The total recovery rate of different layers of shale oil reservoirs after energy replenishment and the multi-scale pore recovery rate of different layers are obtained to optimize the parameters of synergistic energy replenishment of CO2 and water-based fluids.

[0059] Step 8: Evaluation of the effect of synergistic energy supplementation development of CO2 and water-based fluids in different layers of shale reservoirs:

[0060] ① The saturated oil NMR signal under the initial reservoir conditions in step 5 was subtracted from the dry sample NMR signal in step 4 to obtain the distribution curve of the shale oil NMR signal on different relaxation time axes. Compared with the pore size distribution data of the shale sample in step 3, the maximum T2 relaxation time of 158.49 ms was corresponded to the maximum pore size of 45.21 μm, and the minimum T2 relaxation time of 0.251 ms was corresponded to the minimum pore size of 3.02 nm, and the conversion relationship between NMR relaxation time and mercury injection pore radius was obtained. According to the peak distribution range of shale oil nuclear magnetic resonance signal, the multi-scale pores of rock samples are divided into micro-nano pores, small pores, medium pores and large pores. According to the above conversion relationship, the T2 relaxation time range of micro-nano pores of rock samples 11# and 21# is 0.251-1.259 ms, and the pore diameter distribution range is 3.02-33.43 nm. The T2 relaxation time range of small pores is 0.398-1.585 ms, and the pore diameter distribution range is 6.01-47.13 nm. The T2 relaxation time range of medium pores is 1.585-12.589 ms, and the pore diameter distribution range is 47.13 nm-1.04 μm. The T2 relaxation time range of large pores is 12.589-158.49 ms, and the pore diameter distribution range is 1.04-45.21 nm.

[0061] ② Further determine the NMR signal of the dry sample of pores of different scales in the 11# rock sample according to step 4 N10 , NMRS10 , NMR M10 , NMR L10 They are 0.3146, 0.0558, 0.0951, 0 [PU], 21# rock sample and NMR N20 , NMR S20 , NMR M20 , NMR L20 The oil NMR signals of different pore sizes of rock sample 11 under initial reservoir conditions were further determined according to step 5. N11 , NMR S11 , NMR M11 , NMR L11 They are 4.8744, 0.8363, 2.4467, 0.2522 [PU], respectively, and NMR of rock sample 21# N21 , NMR S21 , NMR M21 , NMR L21 They are 4.8168, 0.7382, 1.1791 and 0.1827 [PU] respectively.

[0062] ③ Calculation of recovery factor of shale reservoir depletion development: According to step 6, determine the NMR signal of oil in pores of different scales in 11# rock sample after depletion development N12 , NMR S12 , NMR M12 , NMR L12 The NMR signals of oil in pores of different scales in rock sample 21 are 4.5332, 0.7652, 2.2021, and 0.2018 [PU], respectively. N22 , NMR S22 , NMR M22 , NMR L22 They are 4.5877, 0.6886, 1.0932, and 0.1613 [PU] respectively. The total recovery factor η of the 1# layer rock sample depletion development is determined according to formula 1 11 The micro-nanopore recovery factor η is 8.9% and is determined according to Formula 2-Formula 5. N11 , small hole recovery factor η S11 , medium pore recovery factor η M11 and macropore recovery factor η L11 They are 7.5%, 9.1%, 10.4% and 20.0% respectively. Similarly, the total recovery factor η of the depletion development of the 2# layer rock sample is determined 21 , micro-nanopore recovery factor η N21 , small hole recovery factor η S21 , medium pore recovery factor η M21 and macropore recovery factor η L21They are 6.7%, 5.7%, 7.7%, 8.8% and 13.3% respectively. According to Formula 6, the overall recovery factor η1 of the depletion development of the entire shale oil reservoir (including different layers) is determined to be 8.0%.

[0063]

[0064] ④ Calculation of recovery factor of synergistic energy supplementation development of CO2 and water-based fluid: According to step 7, determine the NMR signal of oil in pores of different scales in 11# rock sample after synergistic energy supplementation development of CO2 and water-based fluid N13 , NMR S13 , NMR M13 , NMR L13 They are 3.5475, 0.6217, 1.5458, 0.0912 [PU], respectively, 21# rock sample NMR N23 , NMR S23 , NMR M23 , NMR L23 The total recovery factor η of the 1# layer rock sample CO2 and water-based fluid synergistic energy recovery development is determined according to formula 7. 12 The micro-nanopore recovery factor η is 32.8% and is determined according to formula 8-11. N12 , small hole recovery factor η S12 , medium pore recovery factor η M12 and macropore recovery factor η L12 They are 29.1%, 27.5%, 38.3% and 63.8% respectively. Similarly, the total recovery factor η of the 2# layer rock sample for the synergistic energy supplement development of CO2 and water-based fluid is determined 22 , micro-nanopore recovery factor η N22 , small hole recovery factor η S22 , medium pore recovery factor η M22 and macropore recovery factor η L22 They are 28.9%, 30.0%, 20.1%, 26.9% and 48.3% respectively. According to formula 12, the overall recovery factor η2 of the synergistic energy supplement development of CO2 and water-based fluid in the entire shale oil reservoir is determined to be 31.1%. The calculation process is shown in Table 1.

[0065]

[0066] Table 1 Results of NMR testing and recovery calculation of shale oil reservoirs

[0067]

[0068] Step 9: Comprehensively consider the shale oil recovery rate of the reservoir as a whole, different layers, and different scales of pores, and use the weighted sum method to optimize the parameters of the synergistic energy replenishment of CO2 and water-based fluids. The overall recovery rate of the reservoir synergistic energy replenishment η2, the total recovery rate of the 1# layer η 12 , micro-nanopore recovery factor η N12 , small hole recovery factor η S12 , medium pore recovery factor η M12 and macropore recovery factor η L12 、Total recovery factor of 2# layer η 22 , micro-nanopore recovery factor η N22 , small hole recovery factor η S22 , medium pore recovery factor η M22 and macropore recovery factor η L22 Corresponding weight coefficients W2, W 12 , W N12 , W S12 , W M12 , W L12 , W 22 , W N22 , W S22 , W M22 , W L22 They are 0.4, 0.1, 0.05, 0.05, 0.05, 0.05, 0.1, 0.05, 0.05, 0.05, 0.05, and 0.05 respectively. The sum of the weight coefficients of each parameter is 1, as shown in formula 14. The optimization objective function f(x) calculated according to formula 13 is equal to 32.8%. Taking f(x) as the objective function, and taking the energy replenishment timing, energy replenishment pressure, energy replenishment injection speed, energy replenishment injection volume, CO2 and water-based fluid injection ratio, injection sequence, well soaking time, and flowback speed as variables, the CO2 and water-based fluid coordinated energy replenishment parameters are optimized. The specific method is:

[0069]

[0070] ① Optimization of energy replenishment timing. Parallel sample shale cores were selected. In step 6, the bottom flow pressure of the production well dropped to 24MPa, 20MPa, 16MPa, and 12MPa at the corresponding time points of 6d, 12d, 20d, and 30d, respectively. Then, the synergistic energy replenishment of CO2 and water-based fluid was started. 6d, 12d, 20d, and 30d are the corresponding energy replenishment timings. For different energy replenishment timings, the objective function f(x) was calculated to be 32.8%, 36.2%, 37.9%, and 37.6%, respectively. The energy replenishment timing of 20d corresponding to the maximum f(x) of 37.9% is the optimal energy replenishment timing.

[0071] ② Optimization of charging pressure. At the optimal charging time of 20 days, CO2 and water-based fluids were injected to different charging pressures of 30MPa, 32MPa, 34MPa, 36MPa, 38MPa and 40MPa, 42MPa, 44MPa, 46MPa, 48MPa. For different charging pressures, the objective function f(x) was calculated to be 32.8%, 34.7%, 35.4%, 35.6%, and 35.3%, respectively. The maximum f(x) of 35.6% corresponds to the CO2 and water-based fluid charging pressures of 36MPa and 46MPa, which are the optimal charging pressures for CO2 and water-based fluids.

[0072] ③ Optimization of energy injection rate. At the optimal energy injection time of 20 days, different CO2 and water-based fluid energy injection rates of 0.0001ml / min, 0.0002ml / min, 0.0003ml / min and 0.0001ml / min, 0.0002ml / min, 0.0003ml / min were used to replenish energy until the pressure reached 36MPa and 46MPa. For different energy injection rates, the objective function f(x) was calculated to be 35.1%, 35.6%, and 35.4%, respectively. The maximum f(x) of 35.6% corresponds to the CO2 and water-based fluid energy injection rates of 0.0002ml / min and 0.0002ml / min, which are the optimal CO2 and water-based fluid energy injection rates.

[0073] ④ Optimization of the injection ratio of CO2 and water-based fluid. At the optimal energy replenishment time 20d, different CO2 and water-based fluid injection ratios of 3:1, 2:1, 1:1, 1:2, and 1:3 were used to replenish energy at an injection rate of 0.0002ml / min until the pressure finally reached 46MPa. For different injection ratios, the objective function f(x) was calculated to be 39.8%, 40.2%, 36.5%, 33.2%, and 29.2%, respectively. The maximum f(x) of 40.2% corresponds to an injection ratio of 2:1, which is the optimal injection ratio of CO2 and water-based fluid energy replenishment.

[0074] ⑤ Optimization of injection sequence of CO2 and water-based fluid. At the optimal energy replenishment time of 20 days, CO2 first / water-based fluid second and water-based fluid first / CO2 second were injected at an injection rate of 0.0002ml / min and an injection ratio of 2:1 to replenish the pressure until the pressure reached 46MPa. For different injection sequences, CO2 first / water-based fluid second and water-based fluid first / CO2 second were calculated to have objective functions f(x) of 40.2% and 37.8% respectively. The injection sequence corresponding to the maximum f(x) of 40.2% was CO2 first / water-based fluid second, which was the optimal injection sequence for energy replenishment.

[0075] ⑥ Optimization of energy replenishment and well soaking time. At the optimal energy replenishment time of 20 days, the injection rate was 0.0002ml / min to replenish energy until the final pressure reached 46MPa, and the post-energy replenishment development was started after different well soaking times of 1d, 5d, 10d, 15d, 20d, 25d, and 30d. For different well soaking times, the objective function f(x) was calculated to be 30.2%, 36.5%, 40.2%, 40.8%, 41.2%, 41.0%, and 40.7%, respectively. The maximum f(x) of 41.2% corresponds to a well soaking time of 20d, which is the optimal well soaking time for CO2 and water-based fluid energy replenishment.

[0076] ⑦ Optimization of the return flow rate after energy replenishment. At the optimal energy replenishment time of 20 days, the injection rate was 0.0002ml / min to replenish the energy until the final pressure reached 46MPa. After 20 days of well shut-in, the post-energy replenishment development was carried out at different return flow rates of 0.00001ml / min, 0.00002ml / min, 0.00003ml / min, and 0.00004ml / min. For different return flow rates, the objective function f(x) was calculated to be 40.2%, 41.2%, 41.8%, and 41.5%, respectively. The maximum f(x) of 41.8% corresponds to a return flow rate of 0.00003ml / min, which is the optimal return flow rate after CO2 and water-based fluid replenishment.

[0077] Steps 4 to 7 of the present invention are performed using an online nuclear magnetic resonance testing system for shale oil reservoirs. The online nuclear magnetic resonance testing system for shale oil reservoirs includes a constant speed and constant pressure pump 1, a first intermediate container 3, a second intermediate container 5, a third intermediate container 7, a nuclear magnetic resonance dedicated core clamp 20, and a nuclear magnetic control and data acquisition system 22. The constant speed and constant pressure pump 1 is connected to the first intermediate container 3, the second intermediate container 5, and the third intermediate container 7 in parallel. The first intermediate container 3, the second intermediate container 5, and the third intermediate container 7 are connected to the first fluid preheater 10 and the second fluid preheater 11 in parallel. Each fluid preheater is respectively connected to a nuclear magnetic resonance dedicated core clamp 20. The outlet end of a nuclear magnetic resonance dedicated core clamp is connected to an eighth valve 24, a third fluid preheater 26, a first constant pressure pump, and a second fluid preheater. 28, the outlet end is also connected to the tenth valve 30 and the first vacuum pump 32; the outlet end of another nuclear magnetic resonance dedicated core clamp is connected to the ninth valve 25, the fourth fluid preheater 27, and the second constant pressure pump 29, and the outlet end is also connected to the eleventh valve 31 and the second vacuum pump 33; a shale sample 21 is placed in each nuclear magnetic resonance dedicated core clamp, and the shale sample 21 is blocked by the non-magnetic clamp plugs 19 at both ends, and the annular space between the nuclear magnetic resonance dedicated core clamp 20 and the shale sample 21 is filled with fluorine oil 18, and the inlet end of each nuclear magnetic resonance dedicated core clamp is also provided with a valve, a back pressure valve and a fluid collection container; the first intermediate container 3 contains shale oil, the second intermediate container 5 contains water-based fluid, and the third intermediate container 7 contains carbon dioxide.

[0078] Step 3: Perform high-pressure mercury injection testing on parallel rock samples in accordance with the standard GB / T 21650.1-2008 Determination of pore size distribution and porosity of solid materials by mercury injection and gas adsorption method Part 1: Mercury injection method to obtain the pore size distribution data of the rock samples; Step 4-Step 7: Perform nuclear magnetic resonance T1-T2 spectrum testing on the rock samples in accordance with the standard SY / T 6490-2014 Laboratory Measurement Specification for Nuclear Magnetic Resonance Parameters of Rock Samples to obtain nuclear magnetic resonance T1-T2 spectrum data of shale under different states.

[0079] If there are multiple layers in the shale oil reservoir, the number of core holders can be increased to simulate the synergistic energy replenishment process of CO2 and water-based fluid after the core exhaustion development of the corresponding layer. The weight coefficient in this embodiment is obtained by the expert estimation method. If the actual production process focuses on the development of shale oil in a certain layer or a certain scale of pores, it can be achieved by changing the weight coefficients in formulas 13 and 14. In addition, the optimization order of CO2 and water-based fluid synergistic energy replenishment parameters can be adjusted according to on-site needs.

[0080] During the implementation of this method, the whole process of depletion exploitation-energy recharge-exploitation at different strata under shale reservoir conditions is truly reflected. There is no need to remove cores during the experiment, and human interference is eliminated. The measurement results are highly accurate. The overall macro-reservoir and multi-scale pore energy recharge development effects at different micro-strata are comprehensively considered, and the optimization of the synergistic energy recharge parameters of CO2 and water-based fluids after depletion development of shale reservoirs is achieved using a multi-objective optimization method.

[0081] The present invention provides a method for optimizing CO2 and water-based fluid energy replenishment parameters after depletion development of a shale oil reservoir. First, a simulation of depletion development of a shale oil reservoir under reservoir temperature and pressure conditions is carried out, and then a shale core CO2 and water-based fluid collaborative energy replenishment experiment is carried out. The online nuclear magnetic resonance joint measurement technology is used to observe and identify in real time the depletion development, the oil recovery efficiency of pores of different scales in shale cores at different layers before and after energy replenishment, the amount of remaining oil and their distribution. The influence of energy replenishment timing, energy replenishment pressure, energy replenishment injection rate, CO2 and water-based fluid injection ratio, injection sequence, well soaking time and backflow rate on the energy replenishment effect is analyzed, and an energy replenishment parameter optimization process and method are proposed based on multi-objective optimization.

Claims

1. A method for optimizing parameters of synergistic energy replenishment of CO2 and water-based fluid after depletion development of shale oil reservoirs, characterized in that The steps include: Step 1: Obtain key reservoir parameters of shale oil reservoirs, including reservoir pressure, temperature, and overburden pressure at different layers; Step 2, preparing shale oil and core samples: Shale oil has the same viscosity as formation crude oil at reservoir temperature. Cylindrical core samples are drilled from full-size cores of two different layers, 1# and 2#, in the shale oil reservoir, and are marked as 1# and 2# core samples, respectively. 11# and 12# rock samples are cut from the 1# core sample, and 21# and 22# rock samples are cut from the 2# core sample. Step 3: Dry each rock sample at 110°C to a constant weight, then perform mercury injection testing on rock samples 12# and 22# to obtain pore size distribution data of shale rock samples 1# and 2# at two different layers; Step 4: Two-dimensional NMR test of dry samples of shale at different layers, recording the NMR signal of dry samples of 11# and 21# rock samples respectively. 10 and NMR 20 ; Step 5: restore the initial reservoir conditions and conduct two-dimensional nuclear magnetic resonance tests on the shale oil state in different layers under the initial reservoir conditions. The nuclear magnetic resonance signals of the 11# rock sample and the 21# initial saturated oil are recorded as NMR 11 and NMR 21 ; Step 6: Simulate the depletion development process of shale reservoirs and conduct two-dimensional nuclear magnetic resonance tests after depletion development of shale in different layers. Record the NMR signals of shale oil in rock samples 11# and 21# respectively. 12 and NMR 22 ; Step 7: Simulate the synergistic energy replenishment process of CO2 and water-based fluids, conduct two-dimensional nuclear magnetic resonance tests on shale in different layers after energy replenishment development, and obtain the shale oil nuclear magnetic resonance signal quantities through diffusion-relaxation nuclear magnetic resonance data processing. 13 and NMR 23 ; Step 8, the evaluation of the effect of synergistic energy supplementation development of CO2 and water-based fluids at different layers of shale oil reservoirs, including: using the saturated oil nuclear magnetic resonance signal under the initial reservoir conditions in step 5, the dry sample nuclear magnetic resonance signal in step 4, and the pore size distribution data of the shale rock sample in step 3, the multi-scale pores of the rock sample are divided into micro-nano pores, small pores, medium pores and large pores; according to steps 4 and 5, the dry sample nuclear magnetic resonance signal of pores of different scales of 11# rock sample and 21# rock sample and the oil nuclear magnetic resonance signal of pores of different scales under the initial reservoir conditions are determined respectively; according to step 6, the Determine the nuclear magnetic resonance signal amount of oil in pores of different scales of 11# and 21# rock samples after depletion development; determine the total recovery rate, micro-nanopore recovery rate, small pore recovery rate, medium pore recovery rate and large pore recovery rate of rock samples at different levels of 11# and 21# rock samples after depletion development; determine the nuclear magnetic resonance signal amount of oil in pores of different scales of 11# and 21# rock samples after synergistic energy supplementation development of CO2 and water-based fluid according to step seven, and determine the micro-nanopore recovery rate, small pore recovery rate, medium pore recovery rate and large pore recovery rate of different levels of 11# and 21# rock samples; Step 9: Comprehensively consider the shale oil recovery rate of the reservoir as a whole, different layers, and different scales of pores, and use the weighted sum method to optimize the parameters of the synergistic energy replenishment of CO2 and water-based fluids, including the overall recovery rate of the reservoir synergistic energy replenishment η2, the total recovery rate of the 1# layer η 12 , micro-nanopore recovery factor η N12 , small hole recovery factor η S12 , medium pore recovery factor η M12 and macropore recovery factor η L12 、Total recovery factor of 2# layer η 22 , micro-nanopore recovery factor η N22 , small hole recovery factor η S22 , medium pore recovery factor η M22 and macropore recovery factor η L22 The corresponding weight coefficients are W2, W 12 , W N12 , W S12 , W M12 , W L12 , W 22 , W N22 , W S22 , W M22 , W L22 ; The optimization objective function f(x) is shown in Formula 13, and the sum of the weight coefficients of each parameter is 1, as shown in Formula 14; Taking f(x) as the objective function, and taking the energy replenishment timing, energy replenishment pressure, energy replenishment injection rate, CO2 and water-based fluid injection ratio, injection sequence, well soaking time, and flowback rate as variables, the CO2 and water-based fluid synergistic energy replenishment parameters are optimized; For different energy replenishment opportunities, the objective function f(x) is calculated respectively, and the energy replenishment opportunity T corresponding to the maximum f(x) is x That is the optimized energy replenishment timing; for different energy replenishment pressures, the objective function f(x) is calculated respectively, and the CO2 and water-based fluid energy replenishment pressure P corresponding to the maximum f(x) is i1x and P i2x That is, the optimized CO2 and water-based fluid energy replenishment pressure; for different energy replenishment injection rates, the objective function f(x) is calculated respectively, and the CO2 and water-based fluid energy replenishment injection rate q corresponding to the maximum f(x) is i1x and q i2x That is the optimized CO2 and water-based fluid energy replenishment injection rate; for different injection ratios, the objective function f(x) is calculated respectively, and the injection ratio corresponding to the maximum f(x) is the optimized CO2 and water-based fluid energy replenishment injection ratio; for different injection sequences, the objective function f(x) is calculated respectively, and the injection sequence corresponding to the maximum f(x) is the optimized CO2 and water-based fluid energy replenishment injection sequence; for different shut-in times, the objective function f(x) is calculated respectively, and the shut-in time corresponding to the maximum f(x) is the optimized CO2 and water-based fluid energy replenishment shut-in time; for different return flow rates, the objective function f(x) is calculated respectively, and the return flow rate corresponding to the maximum f(x) is the optimized CO2 and water-based fluid return flow rate after energy replenishment.

2. The method for optimizing parameters of synergistic energy replenishment of CO2 and water-based fluid after depletion development of shale oil reservoirs according to claim 1 is characterized by: The step 1 is specifically as follows: by comprehensively analyzing geological data, geophysical data, logging data, and well test data, key parameters of shale oil reservoirs are obtained, including reservoir pressure, temperature, and overburden pressure at different levels.

3. The method for optimizing parameters of synergistic energy replenishment of CO2 and water-based fluid after depletion development of shale oil reservoirs according to claim 2 is characterized by: The step 2 is specifically as follows: shale oil is prepared by using ground dehydrated and degassed crude oil and kerosene so that the shale oil has the same viscosity as the formation crude oil at the reservoir temperature; cylindrical core samples with a diameter of 2.5 cm and a length of 6 cm are drilled from full-size coring cores of two different layers 1# and 2# of the shale oil reservoir, and are marked as 1# and 2# rock samples respectively; the 1# core sample is cut into cores with lengths of 5 cm and 1 cm respectively, and are marked as 11# and 12# rock samples; the 2# core sample is cut into cores with lengths of 5 cm and 1 cm respectively, and are marked as 21# and 22# rock samples; the 12# and 22# rock samples are used for high-pressure mercury injection testing, and the 11# and 21# rock samples are used for the optimization experiment of the synergistic energy replenishment parameters of CO2 and water-based fluids after the depletion development of shale oil reservoirs.

4. The method for optimizing parameters of synergistic energy replenishment of CO2 and water-based fluid after depletion development of shale oil reservoirs according to claim 3 is characterized by: The step 4 is specifically as follows: placing the 11# and 21# rock samples in the middle position of two online nuclear magnetic resonance dedicated core holders, respectively, the two holders are connected in parallel to the online nuclear magnetic resonance core test system, using fluorine oil to increase the confining pressure to 2MPa and increase the fluorine oil temperature to the reservoir temperature of the 1# and 2# layers of the shale reservoir respectively; closing the inlet and outlet ends of the holder, vacuuming the 11# and 21# rock samples for 48 hours, and then performing the nuclear magnetic resonance T1-T2 spectrum test of the dry sample state of the 11# and 21# rock samples, and recording the nuclear magnetic resonance signal quantities of the dry samples of the 11# and 21# rock samples, respectively. 10 and NMR 20 .

5. The method for optimizing parameters of synergistic energy replenishment of CO2 and water-based fluid after depletion development of shale oil reservoirs according to claim 4 is characterized by: The step 5 is specifically as follows: the overburden pressure P of the 1# layer 10 , initial reservoir pore pressure P p10 ; Overburden pressure P of 2# layer 20 , initial reservoir pore pressure P p20 ; The initial effective stresses of 1# and 2# layers are P e10 and P e20 ; In the core of the 1# layer, the fluorine oil confining pressure is gradually increased to the overburden pressure P 10 During the process, the outlet of the holder is closed and shale oil is injected into the holder until the initial pore pressure of the reservoir reaches P p10 , always make the difference between the confining pressure and the pore pressure equal to the initial effective stress value P e10 , until the flow rate at the inlet end of the holder is zero for 4 hours. At this time, the conditions of the 11# rock sample are the reservoir temperature and initial pressure of the 1# layer; the saturated oil state nuclear magnetic resonance T1-T2 spectrum test of the 11# rock sample under the initial reservoir conditions is carried out, and the initial saturated oil nuclear magnetic resonance signal is recorded as NMR 11 ; In the 2# layer core, the fluorine oil confining pressure is gradually increased to the overburden pressure P 20 During the process, the outlet of the holder is closed and shale oil is injected into the holder until the initial pore pressure of the reservoir reaches P p20 , always make the difference between the confining pressure and the pore pressure equal to the initial effective stress value P e20 , until the flow rate at the inlet end of the holder is zero for 4 hours. At this time, the conditions of the 21# rock sample are the reservoir temperature and initial pressure of the 2# layer; the saturated oil state nuclear magnetic resonance T1-T2 spectrum test of the 21# rock sample under the initial reservoir conditions is carried out, and the initial saturated oil nuclear magnetic resonance signal is recorded as NMR 21 .

6. The method for optimizing parameters of synergistic energy replenishment of CO2 and water-based fluid after depletion development of shale oil reservoirs according to claim 5 is characterized by: The specific step six is: keep the outlet ends of the two clamps closed, close the inlet end of the clamp at the same time, set the pressure of the back pressure valve at the emptying end to the bottom flow pressure P of the production well f11 , P f11 <P p10 And P f11 <P p20 , slowly open the two clamp drain valves, the rock sample pore pressure decreases, the effective stress increases, and the shale oil flows out until the drain flow is zero for 4 consecutive hours, realizing the simulation of shale reservoir depletion development process; perform nuclear magnetic resonance T1-T2 spectrum tests on 11# and 21# rock samples after depletion development, and record the shale oil nuclear magnetic resonance signal quantities, respectively. 12 and NMR 22 .

7. The method for optimizing parameters of synergistic energy replenishment of CO2 and water-based fluid after depletion development of shale oil reservoirs according to claim 6 is characterized by: The step 7 is as follows: close the two valves at the discharge end of the clamp and open the injection end to inject pressure P i11 , P i11 >P f11 , inject CO2 into the two holders until the injection flow rate is zero for 4 consecutive hours; the injection pressure P i21 , P i21 >P i11 , inject water-based fluid into the two holders until the injection flow rate is zero for 4 consecutive hours, and then close the injection end; After the well is shut down for a period of time t1, the pressure of the back pressure valve at the drain end is set to the bottom flow pressure P of the production well. f21 , P f21 <P i11 , slowly open the two clamps emptying ends, shale oil, CO2 and water-based fluids flow out until the flow at the emptying end is zero for 4 consecutive hours, realizing the simulation of shale oil reservoir energy replenishment and post-energy replenishment development process; perform nuclear magnetic resonance T1-T2 spectrum test on 11# and 21# rock samples after energy replenishment development, and obtain shale oil nuclear magnetic resonance signal quantities of NMR by diffusion-relaxation nuclear magnetic resonance data processing. 13 and NMR 23 .

8. The method for optimizing parameters of synergistic energy replenishment of CO2 and water-based fluid after depletion development of shale oil reservoirs according to claim 7 is characterized by: The step eight is specifically as follows: ① Using the saturated oil NMR signal under the initial reservoir conditions in step 5 minus the dry sample NMR signal in step 4, the distribution curve of the shale oil NMR signal on different relaxation time coordinate axes is obtained, and compared with the pore size distribution data of the shale rock sample in step 3, the conversion relationship between the NMR relaxation time and the mercury injection pore radius is obtained; according to the peak distribution interval of the shale oil NMR signal, the multi-scale pores of the rock sample are divided into micro-nano pores, small pores, medium pores and large pores, and the radius values ​​and relaxation time values ​​corresponding to the different scale pores of the 11# rock sample and the 21# rock sample are determined according to the above conversion relationship; ② According to step 4, the NMR signal quantities of dry samples of different pore sizes of rock samples 11# and 21# are determined as follows: N10 , NMR S10 , NMR M10 , NMR L10 and NMR N20 , NMR S20 , NMR M20 , NMR L20 According to step 5, the oil NMR signals of different pore sizes of rock samples 11# and 21# under initial reservoir conditions are determined as follows: N11 , NMR S11 , NMR M11 , NMR L11 and NMR N21 , NMR S21 , NMR M21 , NMR L21 ; ③ Calculation of recovery factor of shale reservoir depletion development: According to step 6, the oil NMR signals of pores of different scales in 11# and 21# samples after depletion development are respectively N12 , NMR S12 , NMR M12 , NMR L12 and NMR N22 , NMR S22 , NMR M22 , NMR L22 ; Determine the total recovery factor η of the 1# layer rock sample depletion development according to formula 1 11 , according to formula 2-formula 5, the micro-nanopore recovery factor η is determined respectively N11 , small hole recovery factor η S11 , medium pore recovery factor η M11 and macropore recovery factor η L11 Similarly, determine the total recovery factor η of the 2# layer rock sample depletion development 21 , micro-nanopore recovery factor η N21 , small hole recovery factor η S21 , medium pore recovery factor η M21 and macropore recovery factor η L21 ; Determine the overall recovery factor η1 of shale oil reservoir depletion development according to formula 6; ④ Calculation of recovery factor of synergistic energy supplementation development of CO2 and water-based fluid: According to step 7, the NMR signals of oil in pores of different scales in 11# and 21# rock samples after synergistic energy supplementation development of CO2 and water-based fluid are determined as follows: N13 , NMR S13 , NMR M13 , NMR L13 and NMR N23 , NMR S23 , NMR M23 , NMR L23 ; Determine the total recovery factor η of the 1# layer rock sample CO2 and water-based fluid synergistic energy development 12 According to formula 8-formula 11, the micro-nanopore recovery factor η is determined respectively N12 , small hole recovery factor η S12 , medium pore recovery factor η M12 and macropore recovery factor η L12 Similarly, the total recovery factor η of the 2# layer rock sample CO2 and water-based fluid synergistic energy development is determined 22 , micro-nanopore recovery factor η N22 , small hole recovery factor η S22 , medium pore recovery factor η M22 and macropore recovery factor η L22 ; Determine the overall recovery factor η2 of the synergistic energy supplement development of CO2 and water-based fluid in the entire shale oil reservoir according to formula 12; 9. The method for optimizing parameters of synergistic energy replenishment of CO2 and water-based fluid after depletion development of shale oil reservoirs according to claim 8, characterized in that: The step nine is specifically as follows: ① Optimization of energy replenishment timing: Select parallel shale core samples and reduce the bottom flow pressure of the production well to P in step 6. f11 , P f12 , P f13 ...P f1n Corresponding time points T1, T2, T3...T n Start to use CO2 and water-based fluid to replenish energy, T1, T2, T3...T n That is the corresponding energy replenishment opportunity; for different energy replenishment opportunities, the objective function f(x) is calculated respectively, and the energy replenishment opportunity T corresponding to the maximum f(x) x This is the optimized energy replenishment opportunity; ② Energy replenishment pressure optimization: At the optimal energy replenishment time T x Inject CO2 and water-based fluid to different energy injection pressures P i11 , P i12 , P i13 ...P i1n and P i21 , P i22 , P i23 ...P i2n , for different recharging pressures, the objective function f(x) is calculated respectively, and the CO2 and water-based fluid recharging pressure P corresponding to the maximum f(x) is i1x and P i2x That is the optimized CO2 and water-based fluid recharge pressure; ③ Optimization of energy injection speed: At the optimal energy injection time T x Different CO2 and water-based fluid injection rates q i11 ,q i12 ,q i13 ……q i1n and q i21 ,q i22 ,q i23 ……q i2n Add energy until the pressure reaches P i1x and P i2x ; For different energy injection rates, the objective function f(x) is calculated respectively, and the CO2 and water-based fluid energy injection rate q corresponding to the maximum f(x) is calculated. i1x and q i2x That is, the optimized CO2 and water-based fluid energy injection rate; ④ Optimization of the injection ratio of CO2 and water-based fluid: At the optimal energy replenishment time T x The injection speed q was 3:1, 2:1, 1:1, 1:2, and 1:3 with different CO2 and water-based fluid injection ratios. i1x and q i2x Add energy until the pressure finally reaches P i2x ; For different injection ratios, the objective function f(x) is calculated respectively, and the injection ratio corresponding to the maximum f(x) is the optimized CO2 and water-based fluid energy replenishment injection ratio; ⑤ Optimization of CO2 and water-based fluid injection sequence: At the optimal energy replenishment time T x The injection rate and injection ratio of CO2 and water-based fluid are optimized to replenish the pressure until the pressure reaches P. i2x ; For different injection sequences, the objective function f(x) is calculated respectively, and the injection sequence corresponding to the maximum f(x) is the optimized CO2 and water-based fluid energy replenishment injection sequence; ⑥ Optimization of energy replenishment and well soaking time: At the optimal energy replenishment time T x The optimized CO2 and water-based fluid injection rate q i1x and q i2x Add energy until the final pressure reaches P i2x , respectively at different soaking times t1, t2, t3...t n Then, the post-energy replenishment development is started; for different well-shutdown times, the objective function f(x) is calculated respectively, and the well-shutdown time corresponding to the maximum f(x) is the optimized CO2 and water-based fluid energy replenishment well-shutdown time; ⑦ Optimization of return flow rate after energy replenishment: At the optimal energy replenishment time T x With the optimal CO2 and water-based fluid injection ratio and energy injection rate q i1x and q i2x Add energy until the pressure finally reaches P i2x , during the soaking time t x Then, different return speeds q f1 ,q f2 ,q f3 ……q fn Carry out post-energy replenishment development; for different return flow rates, calculate the objective function f(x) respectively, and the return flow rate corresponding to the maximum f(x) is the optimized CO2 and water-based fluid return flow rate after energy replenishment.

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