A method and system for predicting original gas-oil ratio of a shale oil formation

Abstract

This invention relates to a method and system for predicting the original gas-oil ratio of shale oil formations. The method includes: selecting and processing source rock thermal simulation samples; conducting thermal simulation experiments on the source rock thermal simulation samples, measuring the volume V of gaseous hydrocarbons and the mass G of liquid hydrocarbons in the reaction products; determining the vitrinite reflectance Ro1 of the source rock using the residue after the reaction; calculating the original gas-oil ratio Rs1 of the thermally simulated formation using the gaseous hydrocarbon volume V and the liquid hydrocarbon mass G; fitting the correlation between the original gas-oil ratio Rs1 of the thermally simulated formation and the vitrinite reflectance Ro1 of the source rock; fitting the correlation between the measured original gas-oil ratio Rs of the formation and the original gas-oil ratio Rs1 of the thermally simulated formation; and fitting the original gas-oil ratio Rs calculated by the prediction model based on the correlation between the original gas-oil ratio Rs1 of the thermally simulated formation and the vitrinite reflectance Ro1 of the source rock, and the correlation between the measured original gas-oil ratio Rs of the formation and the original gas-oil ratio Rs1 of the thermally simulated formation. y This method and system are applicable to the prediction of the original gas-oil ratio in shale oil formations in other basins, reducing cumbersome calculation processes.

Description

Technical Field

[0001] This invention belongs to the field of petroleum exploration and development technology, and specifically relates to a method and system for predicting the original gas-oil ratio of shale oil formations. Background Technology

[0002] With the continuous maturation and improvement of crude oil extraction technology in my country, unconventional resources such as shale oil are gradually achieving large-scale and efficient development. Research on reservoir fluid properties is crucial for the exploration and development of unconventional reservoirs. Among these, the original formation gas-oil ratio is an important parameter, reflecting the magnitude of formation elastic energy and influencing the adjustment and implementation of subsequent development technology policies. It is also an important aspect of research on factors controlling crude oil production capacity. Currently, high-pressure physical property analysis of unconventional crude oil requires sampling at the bottom of the well using sealed equipment during target layer testing. This is costly and time-constrained, making it impractical to obtain a large number of data points through actual measurements. Therefore, prediction is needed to clarify the distribution pattern of the original gas-oil ratio on a planar surface.

[0003] There are various methods for predicting the gas-oil ratio in conventional reservoirs, such as empirical formulas, artificial neural networks, and support vector machines. These prediction models mainly rely on a large amount of basic experimental data and are formed through repeated learning and adjustment. They often suffer from limited applicability or low fitting accuracy, and cannot explain the process of predicting the gas-oil ratio from a mechanistic perspective.

[0004] Shale oil is an intrasource reservoir, situated within organic-rich shale formations. Compared to conventional oil reservoirs, its original gas-oil ratio is almost unaffected by migration, primarily influenced by the maturity of the original formation. During geological evolution, as the maturity of source rocks gradually increases, some high-molecular-weight, long-chain compounds break down into smaller, shorter-chain compounds, thus gradually increasing the gas-oil ratio. Previous methods using maturity to predict the original gas-oil ratio often treat maturity as an intermediate parameter, resulting in low accuracy. Therefore, there is an urgent need to propose a method for predicting and evaluating the original gas-oil ratio of formations based on maturity parameters, achieving accurate evaluation of the gas-oil ratio in shale reservoirs. Summary of the Invention

[0005] To address the aforementioned issues, this invention utilizes a thermal simulation experimental device to apply the results of the thermal simulation experiment to the prediction of the original gas-oil ratio, clarifying the relationship between the maturity of the source rock and the original gas-oil ratio of the formation, establishing a prediction model for the original formation gas-oil ratio, and thus providing a theoretical basis for the optimal selection of favorable areas for shale oil production and construction.

[0006] The technical solution adopted in this invention is as follows:

[0007] A method for predicting the original gas-oil ratio in shale oil formations, the method comprising the following steps:

[0008] Select and process hydrocarbon source rock thermal simulation samples;

[0009] Thermal simulation experiments were conducted on source rock thermal simulation samples to measure the volume V of gaseous hydrocarbons and the mass G of liquid hydrocarbons in the reaction products; the vitrinite reflectance Ro1 of the source rock was determined using the residue after the reaction.

[0010] The original gas-oil ratio Rs1 of the thermally simulated formation was calculated using the gaseous hydrocarbon volume V and the liquid hydrocarbon mass G.

[0011] The correlation between the original gas-oil ratio Rs1 and the vitrinite reflectance Ro1 of the source rock was fitted in thermal simulation.

[0012] The correlation between the measured original gas-oil ratio Rs and the thermally simulated original gas-oil ratio Rs1 of the formation was fitted.

[0013] Based on the correlation between the thermally simulated original gas-oil ratio Rs1 and the vitrinite reflectance Ro1 of source rocks, and the correlation between the measured original gas-oil ratio Rs and the thermally simulated original gas-oil ratio Rs1, the original gas-oil ratio Rs calculated by the fitted prediction model is used. y .

[0014] Furthermore, the selection and processing of source rock thermal simulation samples included: selecting source rock samples with high organic matter abundance and low maturity in the basin, requiring a total organic carbon content (TOC) greater than 0.5% and a vitrinite reflectance (Ro1) of less than 0.6%.

[0015] Furthermore, the original gas-oil ratio Rs1 of the thermally simulated formation is: Rs1=V / G*1000.

[0016] Furthermore, the correlation between the original gas-oil ratio Rs1 and the vitrinite reflectance Ro1 of the source rock in the thermal simulation is: Rs1 = ARo1 2 +BRo1+C, where A=2724.5, B=-3200.1, C=1075.3.

[0017] Furthermore, the correlation between the measured original gas-oil ratio Rs and the thermally simulated original gas-oil ratio Rs1 is fitted as follows: Rs=DRs1+E, where D=0.2485 and E=25.584.

[0018] Furthermore, the original gas-oil ratio Rsy calculated by the fitted prediction model is: Rs y =D(ARo1) 2 +BRo1+C)+E=GRo1 2 +HRo1+I; where G=677.04, H=-795.22, I=292.80.

[0019] Furthermore, the selection and processing of source rock thermal simulation samples includes: collecting at least 5 sets of test samples, each set of samples is divided into 10 portions, each portion weighing 150-200g, and the samples are crushed to 60 mesh.

[0020] Furthermore, the thermal simulation test on the source rock thermal simulation sample includes: conducting thermal simulation experiments on the 10 samples at corresponding isothermal points; placing one of the source rock sample powders into a reaction vessel, sealing the device and evacuating it; using a temperature control device to program the temperature of the reaction vessel to the specified temperature, and reacting at a constant temperature for 40 hours.

[0021] Furthermore, thermal simulation experiments were conducted on the 10 samples at temperature points of 340℃, 360℃, 380℃, 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, and 550℃, respectively.

[0022] Furthermore, the present invention also provides a prediction system for the original gas-oil ratio of shale oil formations, the system comprising:

[0023] The thermal simulation sample processing module is used to select and process thermal simulation samples of hydrocarbon source rocks;

[0024] The thermal simulation test module is used to conduct thermal simulation tests on source rock thermal simulation samples, measure the volume V of gaseous hydrocarbons and the mass G of liquid hydrocarbons in the reaction products, and determine the vitrinite reflectance Ro1 of the source rock using the residue after the reaction.

[0025] The calculation module is used to calculate the original gas-oil ratio Rs1 of the thermally simulated formation using the gaseous hydrocarbon volume V and the liquid hydrocarbon mass G.

[0026] The first fitting module is used to fit the correlation between the original gas-oil ratio Rs1 of the thermally simulated formation and the vitrinite reflectance Ro1 of the source rock.

[0027] The second fitting module is used to fit the correlation between the measured original gas-oil ratio Rs and the thermally simulated original gas-oil ratio Rs1 of the formation.

[0028] The third fitting module is used to fit the original gas-oil ratio Rs calculated by the prediction model based on the correlation between the thermally simulated original gas-oil ratio Rs1 and the vitrinite reflectance Ro1 of the source rock, and the correlation between the measured original gas-oil ratio Rs and the thermally simulated original gas-oil ratio Rs1. y .

[0029] Compared to existing technologies, this method and system primarily focus on the mechanism, exploring it through indoor experiments. The results of thermal simulation experiments are applied to predict the original gas-oil ratio of formations, establishing a relationship between source rock maturity and the original gas-oil ratio, and subsequently building a predictive model for the original gas-oil ratio. This method and system have a more reliable theoretical basis and are also applicable to predicting the original gas-oil ratio of shale oil formations in other basins. It reduces cumbersome calculation processes, is faster and more convenient, and lowers costs. The original gas-oil ratio can be calculated simply by collecting maturity data from the target layer, providing a theoretical basis for optimal sweet spot selection.

[0030] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention will be realized and obtained from the description and the drawings. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A flowchart of a method for predicting the original gas-oil ratio in shale oil formations;

[0033] Figure 2 This is a graph showing the relationship between the source rock maturity parameter Ro1 (vitrinite reflectance of the source rock) and the original gas-oil ratio Rs1 of the thermally simulated formation in the thermal simulation experiment.

[0034] Figure 3 A graph showing the relationship between the original gas-oil ratio Rs1 and the original gas-oil ratio Rs in the formation during thermal simulation.

[0035] Figure 4 This diagram serves as a verification of the accuracy of the original gas-oil ratio prediction model for shale oil formations in this invention.

[0036] Figure 5 This is a schematic diagram of a system for predicting the original gas-oil ratio in shale oil formations. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Taking a shale oil reservoir in a basin as an example, the gas-oil ratio evaluation is performed using a method for predicting the original gas-oil ratio of shale oil formations proposed in this invention. Figure 1 Specifically, it includes the following steps:

[0039] Hydrocarbon source rock thermal simulation samples were selected and processed. Specifically, wells G4 (hydrocarbon source rock maturity parameter Ro1 = 0.50%, total organic carbon content TOC = 5.04%), Z21 (hydrocarbon source rock maturity parameter Ro1 = 0.50%, total organic carbon content TOC = 6.89%), Z22 (hydrocarbon source rock maturity parameter Ro1 = 0.49%, total organic carbon content TOC = 15.0%), and Z7 (hydrocarbon source rock maturity parameter Ro1 = 0.60%, total organic carbon content TOC = 12.0%) were selected as target wells for thermal simulation experiments. Rock samples from the target layers of the target wells were collected, divided into 10 portions, and crushed to 60 mesh.

[0040] Thermal simulation experiments were conducted on source rock samples: Ten prepared samples were subjected to thermal simulation experiments at temperature points of 340℃, 360℃, 380℃, 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, and 550℃. One source rock sample powder was placed in a reaction vessel, sealed, and evacuated. The temperature of the reaction vessel was programmed to rise to the specified temperature using a temperature control device, and the reaction was carried out at this temperature for 40 hours. After the reaction was completed, the oil, gas, and water were separated by a condenser when the temperature inside the vessel dropped to room temperature. The gas volume V (mL) was measured using a metering tube, and the liquid products (oil and water) were collected by an electronic cold trap. After the oil and water were separated, the oil was weighed G (mg). The residue after the reaction was collected for later use. The above experimental steps were repeated for the remaining samples.

[0041] At some temperature points, the collected gas and oil products may contain trace amounts or be unable to be separated from the oil and water. Therefore, the products obtained at these temperature points are not included in the final calculation process. The original gas-oil ratio Rs1 of the thermally simulated formation is calculated using the gas volume V and crude oil weight G measured in the above steps, as shown in formula (1). The reaction residues at each temperature point are used to determine the vitrinite reflectance Ro1 of the source rock.

[0042] Rs1 = V / G * 1000 (1);

[0043] In the formula, Rs1 is the original gas-oil ratio of the thermally simulated formation, in m³. 3 / t; V is the volume of gaseous products collected in the thermal simulation experiment, in mL; G is the weight of crude oil collected in the thermal simulation experiment, in mg.

[0044] like Figure 2 As shown, the correlation between the original gas-oil ratio Rs1 and the vitrinite reflectance Ro1 of the source rock in thermal simulation is calculated using formula (2):

[0045] Rs1=ARo1 2 +BRo1+C (2);

[0046] In equation (2), Ro1 is the vitrinite reflectance of the source rock, which is also the maturity parameter of the source rock, in %; A, B, and C are all fitting parameters; A = 2724.5, B = -3200.1, C = 1075.3.

[0047] A relationship was established between the simulated original gas-oil ratio Rs1 and the measured original gas-oil ratio Rs. Several wells with measured original gas-oil ratio (Rs) data were selected. Well a was chosen to establish the relationship model between the simulated and measured gas-oil ratios, while the remaining well b was used for error analysis. The simulated original gas-oil ratio Rs1 of well a was calculated using the original gas-oil ratio prediction model obtained from the thermal simulation experiment. Then, the correlation between the simulated original gas-oil ratio Rs1 and the measured original gas-oil ratio Rs was fitted. Figure 3 As shown, the calculation formula is shown in formula (3).

[0048] Rs=DRs1+E (3);

[0049] In formula (3), Rs is the measured original gas-oil ratio of the formation, in m³. 3 / t;In formula (3), D and E are both fitting parameters, D=0.2485, E=25.584.

[0050] The original formation gas-oil ratio (Rs) of other wells was calculated using a formation original gas-oil ratio prediction model obtained through thermal simulation experiments. y Formula (4) is obtained by integrating formulas (2) and (3). The error is compared with the actual original gas-oil ratio in the formation. Figure 4 As shown, after comparison, it was found that the number of wells with a gas-oil ratio calculated using the model constructed in this invention and the original gas-oil ratio of the formation accounted for more than 85%, and the two were well correlated well, which verified the accuracy of the original gas-oil ratio prediction model for shale oil in this invention.

[0051] Rs y =D(ARo1) 2+BRo1+C)+E=GRo1 2 +HRo1+I (4);

[0052] In formula (4), Rs y The original gas-oil ratio of the formation calculated by the prediction model, in m³. 3 / t; Ro1 is the vitrinite reflectance of the source rock in the predicted well, in %; G, H, and I are all fitting parameters, G = 677.04, H = -795.22, and I = 292.80.

[0053] In addition, this invention also provides a system for predicting the original gas-oil ratio of shale oil formations, such as... Figure 5 As shown, the system includes:

[0054] The thermal simulation sample processing module is used to select and process thermal simulation samples of hydrocarbon source rocks;

[0055] The thermal simulation test module is used to conduct thermal simulation tests on source rock thermal simulation samples, measure the volume V of gaseous hydrocarbons and the mass G of liquid hydrocarbons in the reaction products, and determine the vitrinite reflectance Ro1 of the source rock using the residue after the reaction.

[0056] The calculation module is used to calculate the original gas-oil ratio Rs1 of the thermally simulated formation using the gaseous hydrocarbon volume V and the liquid hydrocarbon mass G.

[0057] The first fitting module is used to fit the correlation between the original gas-oil ratio Rs1 of the thermally simulated formation and the vitrinite reflectance Ro1 of the source rock.

[0058] The second fitting module is used to fit the correlation between the measured original gas-oil ratio Rs and the thermally simulated original gas-oil ratio Rs1 of the formation.

[0059] The third fitting module is used to fit the original gas-oil ratio Rs calculated by the prediction model based on the correlation between the thermally simulated original gas-oil ratio Rs1 and the vitrinite reflectance Ro1 of the source rock, and the correlation between the measured original gas-oil ratio Rs and the thermally simulated original gas-oil ratio Rs1. y .

[0060] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for predicting the original gas-oil ratio in shale oil formations, the method comprising the following steps: Select and process hydrocarbon source rock thermal simulation samples; Thermal simulation experiments were conducted on source rock thermal simulation samples to measure the volume V of gaseous hydrocarbons and the mass G of liquid hydrocarbons in the reaction products; the vitrinite reflectance Ro1 of the source rock was determined using the residue after the reaction. The original gas-oil ratio Rs1 of the thermally simulated formation was calculated using the gaseous hydrocarbon volume V and the liquid hydrocarbon mass G. The correlation between the original gas-oil ratio Rs1 and the vitrinite reflectance Ro1 of the source rock was fitted in thermal simulation. The correlation between the measured original gas-oil ratio Rs and the thermally simulated original gas-oil ratio Rs1 of the formation was fitted. Based on the correlation between the thermally simulated original gas-oil ratio Rs1 and the vitrinite reflectance Ro1 of source rocks, and the correlation between the measured original gas-oil ratio Rs and the thermally simulated original gas-oil ratio Rs1, the original gas-oil ratio Rs calculated by the fitted prediction model is used. y .

2. The method according to claim 1, wherein, The selection and processing of source rock thermal simulation samples included: selecting source rock samples with high organic matter abundance and low maturity in the basin, requiring a total organic carbon content (TOC) greater than 0.5% and a vitrinite reflectance (Ro1) less than 0.6%.

3. The method according to claim 1, wherein, The original gas-oil ratio Rs1 of the thermally simulated formation is: Rs1=V / G*1000.

4. The method of claim 1, wherein, The correlation between the original gas-oil ratio Rs1 and the vitrinite reflectance Ro1 of the source rock in the fitted thermal simulation is as follows: Rs1=ARo1 2 +BRo1+C, where A=2724.5, B=-3200.1, C=1075.

3.

5. The method of claim 1, wherein, The correlation between the measured original gas-oil ratio Rs and the thermally simulated original gas-oil ratio Rs1 is as follows: Rs = DRs1 + E, where D = 0.2485 and E = 25.

584.

6. The method according to claim 1, wherein, fitting a predicted model to calculate the original gas-oil ratio Rs of the formation y is: Rs y = D(ARo1 2 + BRo1 + C) + E = GRo1 2 + HRo1 + I; where G = 677.04, H = -795.22, and I = 292.

80.

7. The method according to any one of claims 1-6, wherein, The selection and processing of source rock thermal simulation samples includes: collecting at least 5 sets of test samples, each set of samples is divided into 10 portions, each portion is 150-200g, and the samples are crushed to 60 mesh.

8. The method of claim 7, wherein, Thermal simulation tests on source rock thermal simulation samples included: Thermal simulation experiments were conducted on the 10 samples at corresponding isothermal points; one of the source rock sample powders was placed in a reaction vessel, sealed, and evacuated; the temperature of the reaction vessel was programmed to rise to the specified temperature using a temperature control device, and the reaction was carried out at a constant temperature for 40 hours.

9. The method of claim 8, wherein, The 10 samples were subjected to thermal simulation experiments at temperature points of 340℃, 360℃, 380℃, 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, and 550℃, respectively.

10. A system for predicting the original gas-oil ratio in shale oil formations, the system comprising: The thermal simulation sample processing module is used to select and process thermal simulation samples of hydrocarbon source rocks; The thermal simulation test module is used to conduct thermal simulation tests on source rock thermal simulation samples, measure the volume V of gaseous hydrocarbons and the mass G of liquid hydrocarbons in the reaction products, and determine the vitrinite reflectance Ro1 of the source rock using the residue after the reaction. The calculation module is used to calculate the original gas-oil ratio Rs1 of the thermally simulated formation using the gaseous hydrocarbon volume V and the liquid hydrocarbon mass G. The first fitting module is used to fit the correlation between the original gas-oil ratio Rs1 of the thermally simulated formation and the vitrinite reflectance Ro1 of the source rock. The second fitting module is used to fit the correlation between the measured original gas-oil ratio Rs and the thermally simulated original gas-oil ratio Rs1 of the formation. The third fitting module is used to fit the original gas-oil ratio Rs calculated by the prediction model based on the correlation between the thermally simulated original gas-oil ratio Rs1 and the vitrinite reflectance Ro1 of the source rock, and the correlation between the measured original gas-oil ratio Rs and the thermally simulated original gas-oil ratio Rs1. y .

Images