Method for evaluating efficiency of chemical additive based on online nuclear magnetic resonance scanning technology

Abstract

The invention provides a chemical additive efficiency evaluation method based on an online nuclear magnetic resonance scanning technology, and belongs to the technical field of oil and gas field development and carbon sequestration. The evaluation method comprises the following steps that a chemical additive injection module is additionally arranged in displacement equipment, and an online nuclear magnetic resonance scanning device is integrated; respectively injecting saturated simulated formation water, a Mn < 2 + > solution and simulated oil into the rock core for displacement, recording parameters and calculating the oil displacement efficiency before improvement; after the chemical additive is injected, displacement is conducted again till the outlet end of the rock core does not produce oil, parameters are recorded, and the improved oil displacement efficiency is calculated; calculating the oil displacement efficiency improvement rate according to the oil displacement efficiency; the saturation distribution of the simulated oil is analyzed through an online nuclear magnetic resonance T2 spectrum; the influence of the chemical additive on the CO2 storage efficiency is evaluated by quantifying the improvement rate of the CO2 solubility and combining with the residual gas saturation. The method can achieve the double-effect collaborative evaluation of the recovery efficiency and the sealing rate.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development and carbon sequestration, and particularly relates to an evaluation method for the efficiency of chemical additives based on on-line nuclear magnetic resonance scanning technology. Background Art

[0002] The CO2 flooding technology is an important means to improve the recovery rate of low-permeability reservoirs. Its mechanisms include enhancing light hydrocarbon extraction, reducing crude oil viscosity / density / interfacial tension, and at the same time realizing CO2 geological sequestration. However, traditional CO2 flooding has problems such as serious gas channeling, small swept volume, and low sequestration rate. In the prior art, chemical additives (such as demixing agents and cosolvents) are used to improve the CO2 flooding effect, but there is a lack of a systematic evaluation method:

[0003] 1) Traditional experiments only evaluate the effect of additives through a single index such as recovery rate or sequestration rate, without combining the microscopic displacement mechanism;

[0004] 2) It is impossible to monitor the multi-phase dynamic interaction process of CO2 - crude oil - additive in real time;

[0005] 3) A quantitative evaluation system for the synergistic enhancement of oil displacement and sequestration by chemical additives has not been established.

[0006] Based on this, it is very important to provide a full-process evaluation method from micro to macro and from oil displacement to sequestration through on-line nuclear magnetic resonance technology combined with multi-parameter displacement experiments. Summary of the Invention

[0007] The purpose of the present invention is to provide an evaluation method for the efficiency of chemical additives based on on-line nuclear magnetic resonance scanning technology, so as to solve the technical problems in the prior art such as single evaluation method for chemical additives, inability to monitor the multi-phase action mechanism in real time, and lack of synergistic optimization analysis of displacement and sequestration.

[0008] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0009] The present invention provides an evaluation method for the efficiency of chemical additives based on on-line nuclear magnetic resonance scanning technology, including the following steps:

[0010] 1) Add a chemical additive injection module to the displacement device and integrate an on-line nuclear magnetic resonance scanning device;

[0011] 2) Inject saturated simulated formation water, Mn 2+ solution and simulated oil into the core for displacement respectively, record the gas injection volume, oil production volume and gas discharge volume, and perform T2 spectrum sampling to obtain the oil displacement efficiency S o,base before improvement;

[0012] 3) After injecting chemical additives, perform displacement again until no oil is produced at the outlet end of the core. Record the gas injection volume, oil production volume, and gas discharge volume, and conduct T2 spectrum sampling to obtain the enhanced oil displacement efficiency S. o,add After the displacement at the current pressure point is completed, increase the pressure to conduct displacement at the next pressure point.

[0013] 4) S o,base and S o,add are obtained according to the oil displacement efficiency calculation formula. The oil displacement efficiency calculation formula is:

[0014]

[0015] Among them, S represents the oil displacement efficiency, O represents the oil production volume, and G i represents the gas injection volume;

[0016] Calculate the oil displacement efficiency improvement rate according to the oil displacement efficiency. The oil displacement efficiency improvement rate calculation formula is:

[0017]

[0018] Among them, η EOR represents the oil displacement efficiency improvement rate, S o,add represents the oil displacement efficiency after efficiency improvement, and S o,base represents the oil displacement efficiency before efficiency improvement;

[0019] 5) Analyze the saturation distribution of the simulated oil through online nuclear magnetic resonance T2 spectrum.

[0020] 6) Evaluate the impact of chemical additives on the CO2 sequestration efficiency by quantifying the improvement rate of CO2 solubility and combining with the residual gas saturation.

[0021] The calculation formula for the improvement rate of CO2 solubility is:

[0022]

[0023] Among them, E represents the improvement rate of CO2 solubility, and G x represents the gas injection volume in step 3), and G o represents the gas discharge volume in step 3).

[0024] Further, in step 1), the magnetic field strength of the online nuclear magnetic resonance scanning device is 0.5 - 1.5 T, and the resolution ≤ 10 μm.

[0025] Further, the displacement is carried out under the conditions of pure CO2 flooding or water - alternating - gas flooding.

[0026] Further, in the steps 2) and 3), during the displacement process, the pressure is independently 8 - 15 MPa, and the temperature is independently 40 - 80 °C;

[0027] When using pure CO2 flooding, by adjusting the back-pressure valve at the outlet end of the core holder, the pressure is increased to 0.1 MPa lower than the injection pressure at the inlet end;

[0028] When using water - alternating - gas flooding, the gas - to - water ratio of the water - alternating - gas flooding is 1 - 3:1.

[0029] Further, the injection flow rate of the saturated simulated formation water is 0.01 mL / min, and the displacement is stopped when the liquid production volume of the saturated simulated formation water reaches 4 - 5 PV;

[0030] The Mn 2+ solution displacement is stopped when the liquid production volume reaches 4 - 5 PV;

[0031] The injection rate of the simulated oil is 0.01 mL / min, and the displacement is stopped when the liquid production volume of the simulated oil reaches 4 - 5 PV and the liquid at the outlet is 100% simulated oil.

[0032] Further, in the step 6), when quantifying the promotion rate of CO2 solubility, the change rate of the nuclear magnetic relaxation time ≤ 15%, and the residual gas saturation increases by 10 - 30%.

[0033] The beneficial effects of the present invention:

[0034] 1) The evaluation method of the present invention uses a dual - effect synergistic evaluation technology, which can quantitatively evaluate the increase in oil recovery (5 - 15%) and the increase in sequestration rate (8 - 20%) synchronously;

[0035] 2) The evaluation method of the present invention realizes the visualization of the microscopic mechanism, and dynamically analyzes the extraction selectivity of chemical additives for crude oil components (C5 - C30) through the T2 spectrum;

[0036] 3) The evaluation method of the present invention can construct a performance database containing 20 types of additives, so as to optimize a chemical system suitable for different reservoir conditions (temperature 40 - 120 °C, salinity 5000 - 30000 mg / L). Brief Description of the Drawings

[0037] Figure 1 is a schematic diagram of the experimental device for the embodiments of the present invention;

[0038] Figure 2 is a schematic diagram of the total production of different - scale pores in Embodiments 1 - 2;

[0039] Figure 3 is a curve graph of the synergistic optimization relationship between oil displacement - sequestration efficiency in Embodiment 1. Detailed implementation mode

[0040] The present invention provides a method for evaluating the efficiency of chemical additives based on online nuclear magnetic resonance scanning technology, including the following steps:

[0041] 1) Add a chemical additive injection module to the displacement device and integrate an online nuclear magnetic resonance scanning device;

[0042] 2) Inject saturated simulated formation water, Mn 2+ solution and simulated oil into the core for displacement respectively, record the gas injection volume, oil production volume and gas discharge volume, and conduct T2 spectrum sampling to obtain the oil displacement efficiency S o,base before improvement;

[0043] 3) After injecting the chemical additive, conduct displacement again until no oil is produced at the outlet end of the core, record the gas injection volume, oil production volume and gas discharge volume, and conduct T2 spectrum sampling to obtain the oil displacement efficiency S o,add after improvement. After the displacement at the current pressure point is completed, increase the pressure to conduct displacement at the next pressure point;

[0044] 4) S o,base and S o,add are obtained according to the oil displacement efficiency calculation formula. The oil displacement efficiency calculation formula is:

[0045]

[0046] Among them, S represents the oil displacement efficiency, O represents the oil production volume, and G i represents the gas injection volume;

[0047] Calculate the oil displacement efficiency improvement rate according to the oil displacement efficiency. The oil displacement efficiency improvement rate calculation formula is:

[0048]

[0049] Among them, η EOR represents the oil displacement efficiency improvement rate, S o,add represents the oil displacement efficiency after efficiency improvement, and S o,base represents the oil displacement efficiency before efficiency improvement;

[0050] 5) Analyze the saturation distribution of the simulated oil through online nuclear magnetic resonance T2 spectrum;

[0051] 6) Evaluate the influence of chemical additives on the CO2 sequestration efficiency by quantifying the improvement rate of CO2 solubility and combining the residual gas saturation,

[0052] The calculation formula for the improvement rate of CO2 solubility is:

[0053]

[0054] Among them, E represents the promotion rate of CO2 solubility, and G x represents the gas injection volume in step 3), and G o represents the gas discharge volume in step 3).

[0055] In the present invention, the evaluation of the influence of chemical additives on the CO2 sequestration efficiency is reflected in the promotion rate of carbon dioxide solubility and the residual gas saturation, and the residual gas saturation is obtained by T2 spectrum analysis.

[0056] In the present invention, in the said step 1), the magnetic field strength of the on-line nuclear magnetic resonance scanning device is 0.5 - 1.5 T, preferably 0.8 - 1.2 T, and more preferably 1 T; the resolution ≤ 10 μm, preferably ≤ 9.5 μm, and more preferably ≤ 9 μm.

[0057] In the present invention, the displacement is carried out under the conditions of pure CO2 flooding or water alternating gas flooding.

[0058] In the present invention, in the said step 2) and step 3), during the displacement process, the pressure is independently 8 - 15 MPa, preferably 9 - 14 MPa, and more preferably 10 - 13 MPa; the temperature is independently 40 - 80 °C, preferably 45 - 75 °C, and more preferably 50 - 70 °C;

[0059] When pure CO2 flooding is adopted, by adjusting the back-pressure valve at the outlet end of the core holder, the pressure is increased to 0.1 MPa lower than the injection pressure at the inlet end;

[0060] When water alternating gas flooding is adopted, the gas-water ratio of water alternating gas flooding is 1 - 3:1, preferably 1.5 - 2.5:1, and more preferably 2:1.

[0061] In the present invention, the T2 spectrum can calculate the contribution of pores of different scales to the total recovery degree, and the calculation formula is:

[0062]

[0063] Among them, C represents the contribution of pores of different scales to the total recovery degree, and A i is the integral area of the T2 spectrum under the original oil-bearing conditions and the T2 spectrum after CO2 flooding at a certain pressure in a certain interval, S0 is the area of the integral of the T2 spectrum under the saturated oil condition and the X-axis, and S i is the integral area of the T2 spectrum after CO2 flooding at a certain pressure and the X-axis.

[0064] In the present invention, the injection flow rate of the saturated simulated formation water is 0.01 mL / min, and the displacement is stopped when the liquid production volume of the saturated simulated formation water reaches 4 - 5 PV;

[0065] The Mn 2+Stop displacement when the liquid output of the solution reaches 4 - 5 PV;

[0066] Inject the simulated oil at a rate of 0.01 mL / min. Stop displacement when the liquid output of the simulated oil reaches 4 - 5 PV and the liquid at the outlet is 100% simulated oil.

[0067] In the present invention, Mn 2+ The solution functions to shield hydrogen signals.

[0068] In the present invention, in step 6), when quantifying the promotion rate of CO2 solubility, the change rate of nuclear magnetic relaxation time ≤ 15%, and the residual gas saturation increases by 10 - 30%.

[0069] In the present invention, the core also includes pre - treating the core. The pre - treatment method is to sequentially wash the core with oil and then dry it.

[0070] The specific method of washing the oil is as follows: Wash the core with a toluene - ethanol mixed solution with a volume ratio of 2 - 4:1 until there is no residual crude oil. Preferably, the ratio is 2.5 - 3.5:1, and more preferably 3:1.

[0071] The drying is carried out at 100 - 140 °C for 20 - 28 h. Preferably, it is dried at 110 - 130 °C for 22 - 26 h, and more preferably dried at 120 °C for 24 h.

[0072] The porosity of the core is measured by a helium porosity meter, and the porosity is 5 - 25%. The permeability is measured by the steady - state method, and the permeability is 0.1 - 50 mD.

[0073] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0074] Example 1

[0075] Add a chemical additive injection module to the displacement equipment and integrate an on - line nuclear magnetic resonance scanning device;

[0076] Wash the core with a toluene - ethanol mixed solution with a volume ratio of 3:1 until there is no residual crude oil, and then dry it at 120 °C for 24 h to obtain a pre - treated core;

[0077] Saturate the simulated formation water at a flow rate of 0.01 mL / min. Stop displacement when the liquid output of the saturated simulated formation water reaches 4 - 5 PV; Use Mn 2+ solution to displace the pre - treated core. Wait for Mn 2+Stop displacement when the liquid output of the solution reaches 4 - 5 PV; finally, inject the prepared simulated oil (compound crude oil according to the production gas-oil ratio as the simulated oil in the experiment in accordance with the national standard GB / T26981 - 2011) into the pretreated core at a speed of 0.01 mL / min. Stop displacement when the liquid output of the simulated oil reaches 4 - 5 PV and the liquid at the outlet is 100% simulated oil, and perform nuclear magnetic resonance scanning, record the gas injection volume, oil production volume, and gas discharge volume, and perform T2 spectrum sampling.

[0078] Obtain the oil displacement efficiency S before enhancement. o,base For displacement, use pure CO2 flooding.

[0079] After injecting chemical additives (the chemical reagents are biomass-based small molecule NH-1, biomass derivative - polymer compound L-1, lignin derivative L-2, lignin derivative L-OH, and low-carbon alcohol EG), perform displacement again until no oil is produced at the outlet end of the core. Record the gas injection volume, oil production volume, and gas discharge volume, and perform T2 spectrum sampling.

[0080] Obtain the enhanced oil displacement efficiency S. o,add After the displacement at the current pressure point ends, increase the pressure to perform displacement at the next pressure point.

[0081] S o,base and S o,add According to the calculation formula of oil displacement efficiency, the calculation formula of oil displacement efficiency is:

[0082]

[0083] Among them, S represents the oil displacement efficiency, O represents the oil production volume, and G i represents the gas injection volume.

[0084] Calculate the oil displacement efficiency improvement rate according to the oil displacement efficiency. The calculation formula of the oil displacement efficiency improvement rate is:

[0085]

[0086] Among them, η EOR represents the oil displacement efficiency improvement rate, S o,add represents the oil displacement efficiency after efficiency improvement, and S o,base represents the oil displacement efficiency before efficiency improvement.

[0087] Analyze the saturation distribution of the simulated oil through on-line nuclear magnetic resonance T2 spectrum.

[0088] Evaluate the influence of chemical additives on the CO2 sequestration efficiency by quantifying the improvement rate of CO2 solubility and combining with the residual gas saturation.

[0089] The calculation formula of the improvement rate of CO2 solubility is:

[0090]

[0091] Among them, E represents the promotion rate of CO2 solubility, and G x represents the gas injection volume in step 3), and G o represents the gas discharge volume in step 3).

[0092] From Figure 2 it can be seen that the T2 spectrum can be used to calculate the contribution of pores of different scales to the total recovery degree, and the calculation formula is:

[0093]

[0094] Among them, C represents the contribution of pores of different scales to the total recovery degree, and A i is the integral area of the T2 spectrum under the original oil-bearing conditions in a certain interval and the T2 spectrum after CO2 flooding at a certain pressure, S0 is the area of the integral of the T2 spectrum under the oil-saturated condition and the X-axis, and S i is the integral area of the T2 spectrum after CO2 flooding at a certain pressure and the X-axis,

[0095] Figure 2 Among them, S1 is the integral area of the T2 spectrum after CO2 flooding under the pressure of water flooding and the X-axis, and S2 is the integral area of the T2 spectrum after CO2 flooding under the pressure of gas flooding and the X-axis.

[0096] The curve graph of the synergistic optimization relationship between the oil displacement-sequestration efficiency of Example 1 is as Figure 3 shown. From Figure 3 it can be known the influence degree of each component in the chemical additive on improving the recovery rate and the sequestration rate, and then the chemical additives are compounded to improve the chemical composite system for efficient CO2 extraction and sequestration.

[0097] Example 2

[0098] Compared with the example, the difference is only that in Example 2, water-alternating-gas flooding is adopted, and the gas-water ratio is 1:1.

[0099] From the above examples, it can be known that the present invention provides an evaluation method for the efficiency of chemical additives based on on-line nuclear magnetic resonance scanning technology, including the following steps: adding a chemical additive injection module to the displacement equipment and integrating an on-line nuclear magnetic resonance scanning device; saturating the simulated formation water, Mn 2+The solution and the simulated oil are respectively injected into the core for displacement. Record the parameters and calculate the oil displacement efficiency before enhancement. After injecting the chemical additive, conduct displacement again until no oil is produced at the outlet end of the core. Record the gas injection volume, oil production volume, and gas discharge volume, and conduct T2 spectrum sampling to obtain the enhanced oil displacement efficiency. Calculate the enhancement rate of the oil displacement efficiency according to the oil displacement efficiency. Analyze the saturation distribution of the simulated oil through online nuclear magnetic resonance T2 spectrum. Evaluate the impact of the chemical additive on the CO2 sequestration efficiency by quantifying the enhancement rate of the CO2 solubility and combining it with the residual gas saturation. The evaluation method of the present invention uses the dual-effect synergistic evaluation technology, which can synchronously and quantitatively evaluate the enhancement of the recovery rate (5-15%) and the increase in the sequestration rate (8-20%).

[0100] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. An evaluation method for the efficiency of chemical additives based on online nuclear magnetic resonance scanning technology, characterized in that, It includes the following steps: 1) Add a chemical additive injection module to the displacement equipment and integrate an on-line nuclear magnetic resonance scanning device; 2) Inject saturated simulated formation water, Mn 2+ solution and simulated oil into the core for displacement respectively, record the gas injection volume, oil production volume and gas discharge volume, and conduct T2 spectrum sampling to obtain the oil displacement efficiency S o,base ; 3) After injecting chemical additives, displacement is carried out again until no oil is produced at the outlet end of the core. Record the gas injection volume, oil production volume, and gas discharge volume, and perform T2 spectrum sampling to obtain the enhanced oil displacement efficiency S o,add , after the displacement at the current pressure point ends, increase the pressure to carry out the displacement at the next pressure point; 4)S o,base and S o,add Obtained according to the oil displacement efficiency calculation formula, the oil displacement efficiency calculation formula is: Among them, S represents the oil displacement efficiency, O represents the oil production, and G i represents the gas injection volume; Calculate the enhanced oil displacement efficiency rate according to the oil displacement efficiency. The calculation formula for the enhanced oil displacement efficiency rate is: Among them, η EOR represents the enhanced oil displacement efficiency rate, S o,add represents the oil displacement efficiency after the efficiency improvement, S o,base represents the oil displacement efficiency before the efficiency improvement; 5) Analyze the saturation distribution of the simulated oil through on-line nuclear magnetic resonance T2 spectrum; 6) Evaluate the influence of the chemical additive on the CO2 sequestration efficiency by quantifying the enhanced rate of CO2 solubility and combining with the residual gas saturation. The calculation formula for the enhanced rate of CO2 solubility is: Among them, E represents the promotion rate of CO2 solubility, and G x represents the gas injection volume in step 3), and G o represents the gas discharge volume in step 3).

2. The evaluation method for the efficiency of chemical additives based on the online nuclear magnetic resonance scanning technology according to claim 1, characterized in that In the step 1), the magnetic field strength of the on-line nuclear magnetic resonance scanning device is 0.5 - 1.5T, and the resolution is ≤10μm.

3. The evaluation method of the efficiency of chemical additives based on the online nuclear magnetic resonance scanning technology according to claim 1 or 2, characterized in that, The displacement is carried out under the conditions of pure CO2 flooding or water alternating gas flooding.

4. The evaluation method of the efficiency of chemical additives based on the online nuclear magnetic resonance scanning technology according to claim 3, wherein, In the steps 2) and 3), during the displacement process, the pressure is independently 8 - 15MPa, and the temperature is independently 40 - 80°C; When pure CO2 flooding is adopted, adjust the back pressure valve at the outlet end of the core holder to increase the pressure to 0.1MPa lower than the injection pressure at the inlet end; When water alternating gas flooding is adopted, the gas-water ratio of water alternating gas flooding is 1 - 3:

1.

5. The evaluation method of the efficiency of chemical additives based on online nuclear magnetic resonance scanning technology according to claim 1 or 2 or 4, characterized in that The injection flow rate of the saturated simulated formation water is 0.01mL / min, and the displacement is stopped when the liquid production of the saturated simulated formation water reaches 4 - 5PV; The Mn 2+ Stop displacement when the liquid output of the solution reaches 4 - 5 PV; The injection rate of the simulated oil is 0.01mL / min, and the displacement is stopped when the liquid production of the simulated oil reaches 4 - 5PV and the liquid at the outlet is 100% simulated oil.

6. The evaluation method of the efficiency of chemical additives based on the online nuclear magnetic resonance scanning technology according to claim 5, characterized in that In the step 6), when quantifying the enhanced rate of CO2 solubility, the change rate of the nuclear magnetic relaxation time is ≤15%, and the residual gas saturation increases by 10 - 30%.

Images