Method for establishing formation fluid property evaluation chart based on nuclear magnetic resonance

Abstract

The invention relates to the technical field of interpretation chart establishing methods, in particular to a formation fluid property evaluation chart establishing method based on nuclear magnetic resonance, which comprises the following steps of: analyzing three states of direct rock sample, soaking in water and soaking in manganese through nuclear magnetism, calculating correlation by utilizing analysis data, and establishing a formation fluid property evaluation method and chart. An oil layer area, an oil-water mixed layer area and a water layer area are effectively distinguished, the reservoir can be finely evaluated, and the oil-gas comprehensive interpretation coincidence rate is increased.

Description

Technical Field

[0001] The invention relates to the technical field of interpretation plate establishment methods, and is a method for establishing a plate for evaluating formation fluid properties based on nuclear magnetic resonance. Background Art

[0002] Nuclear magnetic resonance technology is widely used in oil field logging. By measuring the T2 spectrum in the pores of rock samples and the interaction between the fluid and the solid surface of the rock pores, the reservoir porosity, permeability, oil-water saturation, movable fluid saturation, movable water saturation and other evaluation parameters can be quickly obtained. It plays an important role in reservoir division, pore structure research, and identification of fluid properties.

[0003] As the difficulty of exploration and development while drilling increases, the conventional use of nuclear magnetic resonance to identify formation fluids has great limitations. In the actual analysis process, nuclear magnetic resonance generally only obtains two steps: pore signal and oil phase signal. In large pores, there is usually a large difference between the pore signal and the oil phase signal. Summary of the invention

[0004] The present invention provides a method for establishing a plate for evaluating formation fluid properties based on nuclear magnetic resonance, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problem that the existing nuclear magnetic resonance technology has great limitations in identifying formation fluids; the plate established by the method can perform a detailed evaluation of the reservoir.

[0005] The technical solution of the present invention is achieved by the following measures: A method for establishing a plate for evaluating formation fluid properties based on nuclear magnetic resonance, comprising the following steps:

[0006] Step 1:

[0007] a) Rock sample analysis

[0008] Direct NMR analysis: The rock samples are directly subjected to NMR analysis to collect the fluid content inside the rock samples.

[0009] Rock sample soaking analysis: Soak the rock sample in clean water for 6 hours until the water fills the internal space of the rock sample, then perform nuclear magnetic resonance analysis to collect the porosity inside the rock sample.

[0010] Manganese soaking analysis: soak the water-saturated rock sample again in manganese chloride solution for 6 hours, and after the manganese chloride solution replaces the water in the rock sample, perform nuclear magnetic resonance analysis to collect the oil saturation inside the rock sample;

[0011] b) Identification of bound fluid and movable fluid

[0012] Performing nuclear magnetic resonance analysis on the rock sample to obtain a nuclear magnetic resonance T2 spectrum, identifying a T2 cutoff value according to the morphology of the nuclear magnetic resonance T2 spectrum, the T2 cutoff value being the relaxation time limit for distinguishing a movable fluid from a bound fluid, and identifying the bound fluid from the movable fluid according to the T2 cutoff value, in which the fluid on the left side of the T2 cutoff value in the T2 spectrum is the bound fluid, and the fluid on the right side of the T2 cutoff value is the movable fluid;

[0013] Step 2: Calculate the fluid escape index using the rock sample fluid content obtained by direct nuclear magnetic resonance analysis and the movable fluid pore size of the rock sample, and calculate the remaining oil index using the oil content in the rock sample and the fluid content obtained by direct nuclear magnetic resonance analysis;

[0014] Step 3: Use the movable fluid part to establish a three-end member plate for evaluating nuclear magnetic resonance fluid properties, wherein the three-end member plate is constructed by the remaining oil index, the fluid escape index and the oil saturation; and identify the fluid properties of the rock sample based on the established three-end member plate.

[0015] The following are further optimizations and / or improvements to the above technical solutions:

[0016] When analyzing the above rock samples by soaking in water, it is best to soak the rock samples in clean water for 6 hours.

[0017] In the above-mentioned manganese analysis, it is best to soak the water-saturated rock sample in manganese chloride solution for another 6 hours.

[0018] The calculation formula of the above fluid dissipation index is as follows:

[0019] R fd =G / P

[0020] Where R fd represents: fluid escape index; G represents: movable fluid pore size; P represents: fluid content obtained by direct NMR analysis.

[0021] The calculation formula of the above residual oil index is as follows:

[0022] Remaining oil = P / M

[0023] Where R represents the residual oil index; P represents the fluid content obtained by direct NMR analysis; M represents the oil content in the rock sample.

[0024] Identification of T2 cutoff value for the above T2 spectrum:

[0025] a) For single peak T2 spectra, the T2 cutoff value is: based on relaxation time = 10ms, when the peak top is before 10ms, the half arc point of the peak fall is used as the standard; when the peak top is within 10ms, the center of the top is used as the standard; when the peak top is after 10ms, the half arc point of the peak onset is used as the standard;

[0026] b) For a bimodal T2 spectrum, the T2 cutoff value is based on the first peak landing point and the second peak starting point;

[0027] c) For a three-peak T2 spectrum, the T2 cutoff value is based on the landing point of the first peak and the starting point of the second peak.

[0028] The present invention uses nuclear magnetic resonance to analyze the three states of rock samples: direct, soaked in water, and soaked in manganese. Using the analysis data, the correlation is calculated, and a formation fluid property evaluation method and chart are established to effectively distinguish between oil layer areas, oil-water mixed layer areas, and water layer areas. The reservoir can be finely evaluated and the compliance rate of comprehensive oil and gas interpretation can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Attached Figure 1 This is the nuclear magnetic resonance analysis diagram of a non-igneous rock sample.

[0030] Attached Figure 2 This is the NMR analysis diagram of crude oil with different densities.

[0031] Attached Figure 3 This is the NMR analysis diagram of crude oil with different densities.

[0032] Attached Figure 4 The invention provides a method for identifying T2 values ​​of T2 spectra with different peak shapes for non-igneous rock samples.

[0033] Attached Figure 5 The invention provides a method for identifying T2 values ​​of T2 spectra with different peak shapes for non-igneous rock samples.

[0034] Attached Figure 6 This is a chart for evaluating the residual oil index and fluid escape index of movable fluid in non-igneous rock samples.

[0035] Attached Figure 7 This is a chart for evaluating the residual oil index and fluid escape index of movable fluid in non-igneous rock samples.

[0036] Attached Figure 8 A three-terminal diagram of movable fluid in non-igneous rock samples. DETAILED DESCRIPTION

[0037] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0038] The present invention will be further described below in conjunction with embodiments:

[0039] The research process of the method for establishing a chart for evaluating formation fluid properties based on nuclear magnetic resonance in the present invention is as follows:

[0040] Rock sample analysis:

[0041] a) Select a rock sample of igneous rock and seal it with plastic wrap, and perform nuclear magnetic resonance analysis within 24 hours (preferably within 24 hours);

[0042] b) directly subjecting the rock sample to nuclear magnetic analysis to collect the fluid content inside the rock sample (mainly analyzing the fluid content stored in the rock sample), see Figure 1 Dry sample signal;

[0043] c) Soak the rock sample in clean water for 6 hours (6 hours is the best time) to allow the clean water to fill the internal voids of the rock sample. Perform NMR analysis to collect the porosity inside the rock sample. Figure 1 Gap signal;

[0044] d) Soak the water-saturated rock sample again in manganese chloride solution for 6 hours (6 hours is the best time), so that the manganese chloride solution can replace the water in the rock sample, and perform nuclear magnetic resonance analysis to collect the oil saturation inside the rock sample. Figure 1 oil signal;

[0045] NMR of crude oil with different densities:

[0046] a) Select standard light oil (0.79g / cm 3 ), medium oil (0.85g / cm 3 ), heavy oil (0.89g / cm 3 ) Three oil samples, the NMR analysis of the three oil samples is shown in Figure 2 and Figure 3 ;

[0047] b) Injecting oil samples of different concentrations into a standard core column (core sample without fluid inside);

[0048] c) Conducting NMR analysis of a standard core column with an oil saturation of 50%;

[0049] d) Draw conclusions:

[0050] ① Within 24 hours, the dry sweep signal and the oil signal are well matched, which can accurately reflect the fluid properties and eliminate the influence of exogenous water in the pore signal;

[0051] ② The relaxation time of different oil qualities is different. The relaxation time of light oil is relatively long, and the main peak is located at the back; the relaxation time of heavy oil is relatively short, and the main peak is located at the front. This can be used as a basis for indirectly reflecting the oil quality.

[0052] T2 spectrum morphology recognition of different non-igneous rock samples, see Figure 4 and Figure 5 :

[0053] a) For single peak T2 spectra, the T2 cutoff value is: based on relaxation time = 10ms, when the peak top is before 10ms, the half arc point of the peak fall is used as the standard; when the peak top is within 10ms, the center of the top is used as the standard; when the peak top is after 10ms, the half arc point of the peak onset is used as the standard;

[0054] b) For a bimodal T2 spectrum, the T2 cutoff value is based on the first peak landing point and the second peak starting point;

[0055] c) For a three-peak T2 spectrum, the T2 cutoff value is based on the first peak landing point and the second peak starting point;

[0056] Parameter definition:

[0057] a) T2 cutoff value: It distinguishes the relaxation time boundary between movable fluid and bound fluid. The left side of T2 cutoff value is bound fluid and the right side is movable fluid.

[0058] b) Direct analysis of rock samples: the residual fluid content of the core obtained by direct measurement of rock samples (reflecting the fluid present in the rock sample at that time);

[0059] c) Rock sample water saturation analysis: The rock sample is soaked in water to completely fill the pores, and the pore signal is measured to calculate the porosity;

[0060] d) Manganese chloride replacement analysis: Rock samples are immersed in manganese chloride to measure the oil content, which is used to calculate data such as oil saturation.

[0061] Create a chart based on the data obtained from the above "Rock Sample Analysis":

[0062] a) The degree of fluid loss in the sample. The higher the ratio, the more fluid is lost, and vice versa. The calculation formula is:

[0063] R fd =G / P

[0064] Where R fd represents: fluid escape index; G represents: movable fluid pore size; P represents: directly analyzed fluid content;

[0065] b) The properties of the remaining fluid in the sample. The lower the ratio, the higher the remaining oil content. The higher the ratio, the lower the remaining oil content and the greater the probability of water in the reservoir fluid. The calculation formula is:

[0066] R Remaining oil = P / M

[0067] Where R represents the residual oil index; P represents the fluid content directly analyzed; M represents the oil content in the sample;

[0068] c) Using the fluid escape index as the horizontal coordinate and the remaining oil index as the vertical coordinate, construct the evaluation chart of the NMR movable fluid remaining oil index and fluid escape index, see Figure 6 ;

[0069] d) Basis Figure 6 The plate shown in the figure establishes the evaluation standard of NMR movable fluid index (see Table 1), which can effectively distinguish the oil layer area and the oil-water mixed layer area, and has a significant effect on the identification of formation fluid properties. Under the existing conditions, the fluid properties can be accurately identified, but the water layer area cannot be identified;

[0070] e) Figure 6 Based on the chart of , starting from the perspective of not dividing the T2 cutoff value, minimizing interference, the three analysis methods (direct analysis of rock samples, analysis of rock samples with clear water saturation, and replacement analysis of manganese chloride) originally measured in the sample (the same rock sample as the above-mentioned "rock sample analysis") were used to calculate the fluid escape index and the remaining oil index, and the evaluation chart of the original residual oil index and fluid escape index of nuclear magnetic resonance was established, see Figure 7 ;

[0071] f) Basis Figure 7 The plate shown establishes the evaluation standard of NMR raw index fluid properties (see Table 2); it can effectively distinguish between oil layer areas and oil-water mixed layer areas, and has a significant effect on the identification of formation fluids. It can effectively distinguish between oil layer areas and oil-water mixed layer areas, and has a significant effect on the identification of formation fluid properties. Under the existing conditions, the fluid properties can be accurately identified, but the water layer area cannot be identified.

[0072] g) Based on the above two charts ( Figure 6 and Figure 7 ) are unable to finely divide the reservoir fluid properties. All data are summarized to establish the correlation between oil saturation data and oil test conclusions. The oil saturation parameter is introduced into the above parameters. The abundance of oil and gas in the formation is combined with the fluid escape degree and residual oil. The three-terminal diagram for evaluating the fluid properties of nuclear magnetic resonance is established. Figure 8 ;

[0073] h) Basis Figure 8 The plate shown in the figure establishes the three-end member evaluation standard of nuclear magnetic resonance fluid properties (see Table 3), which effectively distinguishes the oil layer area, the oil-water mixed layer area and the water layer area, and has a good effect on the evaluation of reservoir fluid properties. The nuclear magnetic resonance analysis is used to accurately identify the fluid properties of rock samples and improve the compliance rate of oil and gas interpretation.

[0074] The method for establishing a formation fluid property evaluation chart based on nuclear magnetic resonance described in the present invention is also applicable to the identification of carbonate formation fluid properties.

[0075] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

[0076] Table 1

[0077] parameter Residual oil index Fluid Emission Index Oil reservoir area ≤3 ≤4 Oil-water mixed layer area ＞3 ＞4

[0078] Table 2

[0079] parameter Residual oil index Fluid Emission Index Oil reservoir area ≤5 ≤2 Oil-water mixed layer area ＞2 ＞2

[0080] Table 3

[0081] Evaluation Criteria Oil saturation Residual oil index Fluid Emission Index Oil reservoir area 0.28-1.00 0-1.00 0-0.72 Oil-water mixed layer area 0-0.28 0-0.50 0.72-1.00 Water layer area 0-0.28 0.50-1.00 0.72-1.00

Claims

1. A method for establishing a chart for evaluating formation fluid properties based on nuclear magnetic resonance, characterized in that The following steps are involved: Step 1: a) Rock sample analysis Direct NMR analysis: The rock samples are directly subjected to NMR analysis to collect the fluid content inside the rock samples. Rock sample soaking analysis: Soak the rock sample in clean water until the water fills the internal gaps of the rock sample, then perform nuclear magnetic resonance analysis to collect the porosity inside the rock sample. Manganese soaking analysis: soak the water-saturated rock sample again with manganese chloride solution, let the manganese chloride solution replace the water in the rock sample, and then perform nuclear magnetic resonance analysis to collect the oil saturation inside the rock sample; b) Identification of bound fluid and movable fluid Directly perform nuclear magnetic resonance analysis on the rock sample to obtain a nuclear magnetic resonance T2 spectrum, and identify a T2 cutoff value according to the morphology of the nuclear magnetic resonance T2 spectrum. The T2 cutoff value is a relaxation time limit for distinguishing a movable fluid from a bound fluid. The bound fluid and the movable fluid are identified according to the T2 cutoff value. In the T2 spectrum, the fluid located on the left side of the T2 cutoff value is the bound fluid, and the fluid located on the right side of the T2 cutoff value is the movable fluid; Step 2: Calculate the fluid escape index using the rock sample fluid content obtained by direct nuclear magnetic resonance analysis and the movable fluid pore size of the rock sample, and calculate the remaining oil index using the oil content in the rock sample and the fluid content obtained by direct nuclear magnetic resonance analysis; Step 3: Use the movable fluid part to establish a three-end member plate for evaluating nuclear magnetic resonance fluid properties, wherein the three-end member plate is constructed by the remaining oil index, the fluid escape index and the oil saturation; and identify the fluid properties of the rock sample based on the established three-end member plate.

2. The method for establishing a chart for evaluating formation fluid properties based on nuclear magnetic resonance according to claim 1, characterized in that When analyzing rock samples by soaking them in water, it is best to soak the rock samples in clean water for 6 hours.

3. The method for establishing a chart for evaluating formation fluid properties based on nuclear magnetic resonance according to claim 1 or 2, characterized in that When conducting manganese analysis, it is best to soak the water-saturated rock sample in manganese chloride solution for another 6 hours.

4. The method for establishing a chart for evaluating formation fluid properties based on nuclear magnetic resonance according to claim 1 or 2, characterized in that The calculation formula of fluid dissipation index is as follows: R fd =G / P Where R fd represents: fluid escape index; G represents: movable fluid pore size; P represents: fluid content obtained by direct NMR analysis.

5. The method for establishing a chart for evaluating formation fluid properties based on nuclear magnetic resonance according to claim 3, characterized in that The calculation formula of fluid dissipation index is as follows: R fd =G / P Where R fd represents: fluid escape index; G represents: movable fluid pore size; P represents: fluid content obtained by direct NMR analysis.

6. The method for establishing a chart for evaluating formation fluid properties based on nuclear magnetic resonance according to claim 1, 2 or 5, characterized in that The calculation formula of the residual oil index is as follows: Remaining oil = P / M Where R represents the residual oil index; P represents the fluid content obtained by direct NMR analysis; M represents the oil content in the rock sample.

7. The method for establishing a chart for evaluating formation fluid properties based on nuclear magnetic resonance according to claim 3, characterized in that The calculation formula of the residual oil index is as follows: Remaining oil = P / M Where R represents the residual oil index; P represents the fluid content obtained by direct NMR analysis; M represents the oil content in the rock sample.

8. The method for establishing a chart for evaluating formation fluid properties based on nuclear magnetic resonance according to claim 4, characterized in that The calculation formula of the residual oil index is as follows: Remaining oil = P / M Where R represents the residual oil index; P represents the fluid content obtained by direct NMR analysis; M represents the oil content in the rock sample.

9. The method for establishing a chart for evaluating formation fluid properties based on nuclear magnetic resonance according to claim 1, 2, 5, 7 or 8, characterized in that Identification of T2 cutoff value of T2 spectrum: a) For single peak T2 spectra, the T2 cutoff value is: based on relaxation time = 10ms, when the peak top is before 10ms, the half arc point of the peak fall is used as the standard; when the peak top is within 10ms, the center of the top is used as the standard; when the peak top is after 10ms, the half arc point of the peak onset is used as the standard; b) For a bimodal T2 spectrum, the T2 cutoff value is based on the first peak landing point and the second peak starting point; c) For a three-peak T2 spectrum, the T2 cutoff value is based on the landing point of the first peak and the starting point of the second peak.

10. The method for establishing a chart for evaluating formation fluid properties based on nuclear magnetic resonance according to claim 3, 4 or 6, characterized in that Identification of T2 cutoff value of T2 spectrum: a) For single peak T2 spectra, the T2 cutoff value is: based on relaxation time = 10ms, when the peak top is before 10ms, the half arc point of the peak fall is used as the standard; when the peak top is within 10ms, the center of the top is used as the standard; when the peak top is after 10ms, the half arc point of the peak onset is used as the standard; b) For a bimodal T2 spectrum, the T2 cutoff value is based on the first peak landing point and the second peak starting point; c) For a three-peak T2 spectrum, the T2 cutoff value is based on the landing point of the first peak and the starting point of the second peak.

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