A device and method for testing wettability under reservoir conditions

Abstract

This invention discloses an apparatus and method for testing wettability under reservoir conditions, comprising a high-temperature, high-pressure self-priming-displacement system, a crude oil circulation metering system and a formation water circulation metering system connected to the high-temperature, high-pressure self-priming-displacement system; the high-temperature, high-pressure self-priming-displacement system includes a nuclear magnetic resonance (NMR) instrument and a high-temperature, high-pressure core holder placed inside the NMR instrument; an annular heating system is provided outside the high-temperature, high-pressure core holder; the crude oil circulation metering system and the formation water circulation metering system include graduated containers and connected circulation pumps. This invention effectively reduces the end-effect of the core by utilizing two independent circulation systems (crude oil and formation water) and a NMR instrument, overcoming the shortcomings of traditional testing methods such as low testing accuracy and inability to simulate reservoir conditions, thus achieving in-situ testing of wettability under reservoir conditions.

Description

Technical Field

[0001] This invention relates to the field of experimental apparatus technology, specifically to an apparatus and method for testing wettability under reservoir conditions. Background Technology

[0002] Wettability is one of the important characteristic parameters of oil and gas reservoir rocks. It affects the distribution of pore fluids, determines the microscopic displacement efficiency of rocks, restricts the formulation and implementation of recovery schemes, and plays an important role in the evaluation of parameters such as permeability and saturation. With the continuous expansion of the oil exploration field, more and more unconventional reservoir rocks have been found to exhibit oil-wet characteristics, which makes the corresponding rock physics laws of the reservoirs very different from those of water-wet reservoirs. Therefore, objectively evaluating reservoir wettability lays the foundation for the analysis of reservoir seepage mechanisms and the formulation of enhanced oil recovery technology policies. Based on the analysis of the interaction between fluids and rocks, scholars at home and abroad have proposed a variety of methods for evaluating rock wettability. For example, CN114235641A proposes a method for measuring rock wettability using nuclear magnetic resonance (NMR). This method combines NMR technology with a combination of centrifugation and self-absorption methods to evaluate the wettability of tight rocks. While this method improves the accuracy of traditional self-absorption methods for evaluating wettability, it does not achieve rock wettability evaluation under reservoir conditions. Furthermore, the experimental process involves multiple centrifugation and self-absorption processes, requiring repeated loading and unloading of the rock sample, which damages the pore-throat structure of the sample, leading to significant discrepancies between the evaluation results and actual results. Patent CN102393351B proposes a "Method and Apparatus for Measuring Rock Wettability under Reservoir Conditions," which is based on the self-absorption method and uses a high-pressure container and viewing window to meet the requirements of measuring rock wettability under high temperature and pressure conditions in reservoirs. However, this method ignores adsorbed oil remaining on the pipeline walls and rock sample surface during the experiment, causing deviations between the measurement results and actual oil and water production (especially for unconventional reservoirs with well-developed micro- and nano-pore throats), thus making it difficult for the evaluation results to objectively reflect the wettability characteristics of the rock sample.

[0003] In summary, the main problems with current wettability testing methods and devices are as follows: ① Most wettability testing devices do not consider temperature and pressure conditions, and cannot accurately reflect the actual reservoir conditions; ② Some wettability testing devices are cumbersome, requiring continuous loading and unloading of rock samples during the experiment, which leads to changes in the microscopic pore throat structure of the rock samples, making it difficult for the evaluation results to objectively reflect the wettability characteristics of the rock samples; ③ The testing accuracy of some wettability testing devices is insufficient for unconventional reservoirs with well-developed micro- and nano-pore throats, and they ignore residual fluids adhering to pipelines and core surfaces, resulting in significant differences between the measurement results and the actual oil and water production of the rock samples. Therefore, in order to objectively understand and evaluate the wettability characteristics under reservoir conditions, it is urgent to propose a wettability testing device with high testing accuracy that can model reservoir conditions, providing a basis for the objective understanding of reservoir rock sample wettability. Summary of the Invention

[0004] To address the above problems, this invention provides a wettability testing device and method under reservoir conditions, enabling objective evaluation of rock sample wettability under reservoir conditions (i.e., reservoir temperature and pressure). The device is highly accurate, has a wide range of applications, and can meet the needs of most seepage experiments.

[0005] The present invention adopts the following technical solution:

[0006] A wettability testing device and method under reservoir conditions, comprising a high-temperature and high-pressure self-priming-displacement system, a crude oil circulation metering system and a formation water circulation metering system connected to the high-temperature and high-pressure self-priming-displacement system;

[0007] The high temperature and high pressure self-absorption-displacement system includes a nuclear magnetic resonance spectrometer (2), a high temperature and high pressure clamp (1) placed in the nuclear magnetic resonance spectrometer, a ring heating system is provided outside the high temperature and high pressure clamp (1), controlled by a heating device (3), the high temperature and high pressure clamp (1) is connected to a confining pressure control pump (4), and a pressure gauge (5) is connected to the pipeline.

[0008] Preferably, the crude oil circulation system includes a crude oil circulation pump (6), a formation crude oil container (7) and a degassed crude oil container (8) connected to the inlet of the crude oil circulation pump, and the formation crude oil container (7) and the degassed crude oil container (8) are both placed in an air circulation heating system (10);

[0009] Preferably, the formation crude oil container (7) is connected to a pressure control pump (9), which can effectively provide fluid pressure to the formation crude oil container (7);

[0010] Preferably, the formation water circulation system includes a formation water circulation pump (11) and a formation water container (12), and the intermediate formation water container is placed in an air circulation heating system (14).

[0011] Preferably, the formation crude oil container (7), the degassed crude oil container (8), and the formation water container (12) are piston containers with graduations and viewing windows, which can accurately record the amount of water and oil produced in the experiment.

[0012] A wettability testing device and method under reservoir conditions, characterized by comprising the following steps:

[0013] S1. Drill core samples according to the national standard GB / T 29172-2012 Core Analysis Methods, wash and dry them with oil, and determine the basic physical properties of the core, including the core dry weight. m 1. Length L ,diameterd Penetration rate K and porosity ;

[0014] S2. After vacuuming the core, saturate it with a formation aqueous solution containing a certain mass concentration of manganese chloride at a pressure of 20 MPa for 48 hours to distinguish oil and water signals. Measure the weight of the core after saturation. m 2;

[0015] S3. Load the core in the saturated state in step S2 into the high temperature and high pressure holder (1), increase the confining pressure to the experimental set value through the confining pressure control pump (4), close valves A, B, C, D, H, I, L and N, establish a certain pressure difference using the crude oil circulation pump (6), inject crude oil into the degassed crude oil container (8) to establish bound water saturation, record the water production and oil production during the displacement process, and calculate the bound water saturation of the core.

[0016] (1)

[0017] V w —Cumulative water production, cm 3 ;

[0018] V p —Core pore volume, cm³ 3 ;

[0019] S w1 —Bound water saturation, %

[0020] S4. Close valves G and J, open valves H and I, inject 10 times the pore volume of formation crude oil to simulate reservoir temperature, pressure, and fluid conditions, and measure the nuclear magnetic resonance of the core sample. T 1- T 2 spectra;

[0021] S5. Close valves H, I, F, and K, and open valves B, D, L, M, and N. Use the formation water circulation pump (11) to establish a low circulation speed to achieve self-priming of the core and strip away the formation crude oil remaining on the core surface. During the experiment, the amount of self-priming water and oil discharged is recorded through the formation water container (12). V o1 Simultaneously, nuclear magnetic resonance measurements were taken of the rock core. T 1- T 2. Spectra, when nuclear magnetic resonance T 1- T The spectrum showed no significant change and the self-priming water and oil displacement were also observed. V o1After no significant increase, self-priming stopped;

[0022] S6. Close valves B and D, establish a certain pressure difference using the formation water circulation pump (11), and inject formation water into the core. During the experiment, the oil production is measured using the formation water intermediate container (12). V o2 And water production, and nuclear magnetic resonance measurements of the core after oil production ceased. T 1- T 2. Spectrum analysis to calculate oil saturation of core samples. S o2 ;

[0023] S7. Close valves L and N, and open valves F, H, I, A, and C. Establish a low circulation speed using the crude oil circulation pump (6) to achieve self-priming oil drainage from the core. During the experiment, the self-priming oil drainage volume is recorded through the formation crude oil container (7). V w1 Nuclear magnetic resonance (NMR) measurements of the core were taken after water production ceased. T 1- T 2. Spectrum analysis to calculate core water saturation S w1 ;

[0024] S8. Close valves A and C, establish a certain pressure difference through the crude oil circulation pump (7), and inject the formation crude oil into the core. Record the water production at the outlet during the experiment. V w2 Nuclear magnetic resonance (NMR) measurements of the core were taken after water production ceased. T 1- T 2. Spectrum analysis to calculate water saturation of the core. S w2 ;

[0025] S9. Based on the saturation obtained during self-priming water drainage, water-driven oil, self-priming oil drainage, and oil-driven water, the water wettability index, oil wettability index, and relative wettability index of the core are calculated using formulas (4) to (5). At the same time, referring to the provisions of the industry standard "SY / T5153-2007 Method for Determining the Wettability of Reservoir Rocks", the wettability of the reservoir rock sample is evaluated according to the magnitude of the relative wettability index.

[0026] The calculation formula is as follows:

[0027]

[0028]

[0029] (4);

[0030] (5);

[0031] (6);

[0032] T 2o,i —Nuclear magnetic resonance imaging of crude oil T 1- T 2. Spectral relaxation time, ms;

[0033] m ( T 2o ) i —Crude oil corresponds to nuclear magnetic resonance T 1- T 2. Amplitude values ​​of the spectrum curve;

[0034] T 2w,i —Nuclear magnetic resonance corresponding to water T 1- T 2. Spectral relaxation time, ms;

[0035] m ( T 2w ) i —Water-related nuclear magnetic resonance T 1- T 2. Amplitude values ​​of the spectrum curve;

[0036] T 2—Nuclear Magnetic Resonance T 1- T 2nd Spectrum i The transverse relaxation time, in milliseconds;

[0037] m ( T 2) Nuclear Magnetic Resonance Imaging T 1- T 2nd spectral curve i The amplitude value corresponding to the second horizontal relaxation time;

[0038] S oi —Oil saturation, %

[0039] S wi —Water saturation, %

[0040] W w —Wetting index, decimal;

[0041] W o —Water wetting index, decimal;

[0042] I—Relative wetting index, decimal.

[0043] The beneficial effects of this invention are:

[0044] 1. The present invention cleverly uses two circulation devices, crude oil and water, to reduce the number of times the rock sample is loaded and unloaded during the experiment (only one loading and unloading is required during the entire experiment), which greatly avoids the error caused by the change in the pore throat structure of the rock sample due to repeated loading and unloading;

[0045] 2. This invention combines nuclear magnetic resonance technology with a manganese chloride solution of a certain concentration to separate the nuclear magnetic resonance signals of oil and water, thereby accurately calculating and obtaining the water production and oil production in different processes and improving the measurement accuracy in the experimental process;

[0046] 3. This invention uses an external heating device and a high-pressure clamp to simulate the temperature and pressure conditions under reservoir conditions throughout the entire experimental process, making the wettability evaluation results more objective and reliable. Attached Figure Description

[0047] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention, and are not intended to limit the present invention.

[0048] Figure 1 This is a schematic diagram of the structure of the present invention;

[0049] The figure shows

[0050] 1—High-temperature and high-pressure clamp, 2—Nuclear magnetic resonance spectrometer, 3—Heating device, 4—Confining pressure control pump, 5—Pressure gauge, 6—Crude oil circulation pump, 7—Formation crude oil container, 8—Degassed crude oil container, 9—Pressure control pump one, 10—Air circulation heating device one, 11—Formation water circulation pump, 12—Formation water container, 13—Pressure control pump two, 14—Air circulation heating device two, A—Valve one, B—Valve two, C—Valve three, D—Valve four, E—Valve five, F—Valve six, G—Valve seven, H—Valve eight, I—Valve nine, J—Valve ten, K—Valve eleven, L—Valve twelve, M—Valve thirteen, N—Valve fourteen. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0052] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0053] like Figure 1 As shown, a wettability testing device and method under reservoir conditions includes a high-temperature and high-pressure self-priming-displacement system, a crude oil circulation metering system and a formation water circulation metering system connected to the high-temperature and high-pressure self-priming-displacement system, and a high-precision metering device.

[0054] The high-temperature and high-pressure self-absorption-displacement system includes a nuclear magnetic resonance spectrometer 8 and a high-temperature and high-pressure clamp 1 placed in the nuclear magnetic resonance spectrometer;

[0055] The high-temperature and high-pressure clamp 1 is made of alloy material and has a coil inside for connecting to the nuclear magnetic resonance spectrometer. The clamp can hold a real sandstone model of 25.4mm×25.4mm×100mm.

[0056] The high-temperature and high-pressure clamp 1 is equipped with an external ring heating system, and the temperature is adjusted by the heating device 3. The experimental temperature is room temperature - 150℃.

[0057] The high-temperature and high-pressure clamp 1 is connected to a confining pressure control pump 4, and the confining pressure is adjusted by a pressure gauge 5. The experimental confining pressure of this invention is 0-70MPa.

[0058] The formation crude oil container 7, the degassed crude oil container 8, and the formation water container 12 are piston containers with graduations and viewing windows, with an accuracy of 0.001 mL.

[0059] The formation water container 12 contains a formation water solution of a certain concentration of manganese chloride to achieve the signal that distinguishes between the oil phase and the water phase in nuclear magnetic resonance.

[0060] The formation crude oil container 7, the degassed crude oil container 8, and the formation water container 12 are all placed in air circulation heating device one and air circulation heating device two, and the experimental temperature is room temperature - 150℃.

[0061] The crude oil circulation pump 6 and the formation water circulation pump 7 are responsible for injecting or circulating formation crude oil, degassed crude oil and water into the core respectively. The maximum displacement pressure is 50 MPa, the displacement flow rate is 0.001 mL / min to 100 mL / min, and the maximum capacity is 150 mL.

[0062] The specific steps are as follows:

[0063] 1. Core samples were drilled according to the national standard GB / T 29172-2012, and then washed and dried with oil. The basic physical properties of the core samples were determined, including the dry weight of the core. m 1. Length L ,diameterd Penetration rate K and porosity ;

[0064] 2. After vacuuming the core, it was saturated with a formation aqueous solution containing a certain mass concentration of manganese chloride at a pressure of 20 MPa for 48 hours to distinguish oil and water signals. The weight of the core after saturation was measured. m 2;

[0065] 3. Load the core in the saturated state in step 2 into the high temperature and high pressure holder (1), increase the confining pressure to the experimental set value through the confining pressure control pump (4), close valves A, B, C, D, H, I, L and N, establish a certain pressure difference using the crude oil circulation pump (6), inject crude oil into the degassed crude oil container (8) to establish bound water saturation, record the water production and oil production during the displacement process, and calculate the bound water saturation of the core.

[0066] (1)

[0067] V w —Cumulative water production, cm 3 ;

[0068] V p —Core pore volume, cm³ 3 ;

[0069] S w —Bound water saturation, %

[0070] 4. Close valves G and J, open valves H and I, inject formation crude oil, simulate reservoir temperature, pressure, and fluid conditions, and measure the nuclear magnetic resonance of the core sample. T 1- T 2 spectra;

[0071] 5. Close valves H, I, F, and K, and open valves B, D, L, M, and N. Use the formation water circulation pump (11) to establish a low circulation speed to achieve self-priming of the core and strip away the formation crude oil remaining on the core surface. During the experiment, record the self-priming water discharge volume through the formation water container (12). V o1 Simultaneously, nuclear magnetic resonance measurements were taken of the rock core. T 1- T 2. Spectra, when nuclear magnetic resonance T 1- T The spectrum showed no significant change and the self-priming water and oil displacement were also observed. V o1 After no significant increase, self-absorption ceased; the oil saturation of the core was then calculated.S o1 ;

[0072] 6. Close valves B and D, establish a certain pressure difference using the formation water circulation pump (11), and inject formation water into the core. During the experiment, measure the oil production using the intermediate formation water container (12). V o2 And water production, and nuclear magnetic resonance measurements of the core after oil production ceased. T 1- T 2. Spectrum analysis to calculate oil saturation of core samples. S o2 ;

[0073] 7. Close valves L and N, and open valves F, H, I, A, and C. Establish a low circulation speed using the crude oil circulation pump (6) to achieve self-priming oil drainage from the core. During the experiment, record the self-priming oil drainage volume using the formation crude oil container (7). V w1 Nuclear magnetic resonance (NMR) measurements of the core were taken after water production ceased. T 1- T 2. Spectrum analysis to calculate core water saturation S w1 ;

[0074] 8. Close valves A and C, establish a certain pressure difference through the crude oil circulation pump (7), and inject the formation crude oil into the core. Record the water production at the outlet during the experiment. V w2 Nuclear magnetic resonance (NMR) measurements of the core were taken after water production ceased. T 1- T 2. Spectrum analysis to calculate water saturation of the core. S w2 ;

[0075] 9. Based on the saturation obtained during self-priming water drainage, water-driven oil, self-priming oil drainage, and oil-driven water, the water wettability index, oil wettability index, and relative wettability index of the core are calculated using formulas (4) to (5). Meanwhile, referring to the industry standard "SY / T5153-2007 Method for Determining the Wettability of Reservoir Rocks", the wettability of the reservoir rock sample is evaluated based on the magnitude of the relative wettability index.

[0076] The calculation formula is as follows:

[0077]

[0078]

[0079] (4);

[0080] (5);

[0081] (6);

[0082] T 2o,i —Nuclear magnetic resonance imaging of crude oil T 1- T 2. Spectral relaxation time, ms;

[0083] m ( T 2o ) i —Crude oil corresponds to nuclear magnetic resonance T 1- T 2. Amplitude values ​​of the spectrum curve;

[0084] T 2w,i —Water-related nuclear magnetic resonance T 1- T 2. Spectral relaxation time, ms;

[0085] m ( T 2w ) i —Water-related nuclear magnetic resonance T 1- T 2. Amplitude values ​​of the spectrum curve;

[0086] T 2—Nuclear Magnetic Resonance T 1- T 2nd Spectrum i The transverse relaxation time, in milliseconds;

[0087] m ( T 2) Nuclear Magnetic Resonance Imaging T 1- T 2nd spectral curve i The amplitude value corresponding to the second horizontal relaxation time;

[0088] S oi —Oil saturation, %

[0089] S wi —Water saturation, %

[0090] W w —Water wetting index, decimal;

[0091] W o —Water wetting index, decimal;

[0092] I —Relative wetting index, decimal.

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for testing wettability under reservoir conditions, characterized in that, S1, drill core according to the provisions of the national standard "GB / T 29172-2012 core analysis method", and wash oil drying, determination of the basic physical parameters of the core, including core dry weight m 1, length L , diameter d , permeability K and porosity φ ; S2. After vacuuming the core, saturate it with a formation aqueous solution containing a certain mass concentration of manganese chloride at a pressure of 20 MPa for 48 hours to distinguish oil and water signals. Measure the weight of the core after saturation. m 2; S3. Load the core in the saturated state in step S2 into the high temperature and high pressure holder (1), increase the confining pressure to the experimental set value through the confining pressure control pump (4), close valves A, B, C, D, H, I, L and N, establish a certain pressure difference using the crude oil circulation pump (6), inject crude oil into the degassed crude oil container (8) to establish the bound water saturation, record the water production and oil production during the displacement process, and calculate the bound water saturation of the core. ； V w —Cumulative water production, mL; V p —Core pore volume, mL; S w1 —Bound water saturation, % S4, close valves G and J, open valves H and I, inject 10 times the pore volume of formation crude oil to simulate reservoir temperature, pressure, and fluid conditions, and measure the nuclear magnetic resonance of the core. T 1- T 2 spectra; S5. Close valves H, I, F and K, and open valves B, D, L, M and N. Establish a low circulation speed using the formation water circulation pump (11) to achieve self-priming of the core and strip away the formation crude oil remaining on the core surface. During the experiment, the amount of self-priming water and oil discharged is recorded through the formation water container (12). V o1 Simultaneously, nuclear magnetic resonance measurements were taken of the rock core. T 1- T 2. Spectra, when nuclear magnetic resonance T 1- T The spectrum showed no significant change and the self-priming water and oil displacement were also observed. V o1 After no significant increase, self-absorption ceased; the oil saturation of the core was then calculated. S o1 ; S6. Close valves B and D, and inject formation water into the core using the formation water circulation pump (11). During the experiment, the oil production is measured using the formation water container (12). V o2 And water production, and nuclear magnetic resonance measurements of the core after oil production ceased. T 1- T 2. Spectrum analysis to calculate oil saturation of core samples. S o2 ; S7. Close valves L and N, and open valves F, H, I, A, and C. Establish a low circulation speed using the crude oil circulation pump (6) to achieve the purpose of self-priming oil drainage from the core. During the experiment, the self-priming oil drainage volume is recorded through the formation crude oil container (7). V w1 Nuclear magnetic resonance (NMR) measurements of the core were taken after water production ceased. T 1- T 2. Spectrum analysis to calculate core water saturation S w1 ; S8. Close valves A and C, establish a certain pressure difference through the crude oil circulation pump (6), and inject the formation crude oil into the core. Record the water production at the outlet during the experiment. V w2 Nuclear magnetic resonance (NMR) measurements of the core were taken after water production ceased. T 1- T 2. Spectrum analysis to calculate water saturation of the core. S w2 ; S9. Based on the saturation obtained during self-priming water drainage, water-driven oil, self-priming oil drainage and oil-driven water, calculate the water wettability, oil wettability and relative wettability index of the core using formulas (4) to (5); refer to the provisions of the industry standard "SY / T 5153-2007 Method for Determining the Wettability of Reservoir Rocks", evaluate the wettability of the reservoir rock sample according to the magnitude of the relative wettability index; ； ； ； ； （6）； T 2o,i ，m ( T 2o ) i ，T 2w,i ，m ( T 2w ) i —NMR of crude oil and water T 1- T 2. Spectral relaxation time and curve amplitude values; T 2, m ( T 2) Nuclear Magnetic Resonance Imaging T 1- T 2nd Spectrum i The second horizontal relaxation time and corresponding amplitude value; S oi , S wi —Oil and water saturation; W w , W o , I —Oil, water, relative wetting index.

2. The method according to claim 1, wherein the wettability testing device comprises a high-temperature and high-pressure self-priming-displacement system, and a crude oil circulation system and a formation water circulation system connected thereto; The high temperature and high pressure self-absorption-displacement system includes a nuclear magnetic resonance spectrometer (2) and a high temperature and high pressure holder (1) placed in the nuclear magnetic resonance spectrometer; The crude oil circulation system includes a crude oil circulation pump (6), a formation crude oil container (7) connected to the inlet of the crude oil circulation pump, and a degassed crude oil container (8); The formation water circulation system includes a formation water circulation pump (11) and a formation water container (12); The high-temperature and high-pressure clamp (1) is connected to the confining pressure control pump (4), and a pressure gauge (5) is connected to the pipeline; The high-temperature and high-pressure clamp (1) is equipped with an annular heating system, which is controlled by a heating device (3).

3. The method according to claim 2, characterized in that, The formation crude oil container (7) and the degassed crude oil container (8) are installed in the air circulation heating device (10).

4. The method according to claim 2, characterized in that, The formation crude oil container (7) is connected to a pressure control pump (9).

5. The method according to claim 2, characterized in that, The formation water container (12) is installed in the air circulation heating device (14).

6. The method according to claim 1, characterized in that, The formation water container (12) is connected to a pressure control pump (13).

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