Methods, systems, and apparatuses for predicting gas content of tight sand

Abstract

The application provides a method, system and device for determining gas-bearing property of tight sandstone, which comprises the following steps: obtaining gas generation intensity information of a hydrocarbon source layer which supplies hydrocarbon for the tight sandstone; determining critical porosity information corresponding to different gas generation intensities; and determining the gas-bearing property of the tight sandstone according to the gas generation intensity information and the critical porosity information. Based on the technical scheme of the application, the relationship between gas generation intensity and critical porosity is established by analyzing the critical condition in the tight sandstone gas reservoir, and a method for determining the critical porosity of the tight sandstone gas reservoir based on the gas generation intensity is formed, so that the gas-bearing property of the tight sandstone gas reservoir can be accurately predicted from the geological aspect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas exploration, in particular to a method, system and device for predicting gas-bearing property of tight sandstone. BACKGROUND

[0002] With the development of China's oil industry and exploration technology, the exploration field is expanding, and the focus of oil and gas resource research is gradually shifting from conventional to unconventional. Tight sandstone gas has become an important replacement energy for current and future oil and gas resource exploration. Tight sandstone generally refers to sandstone with a permeability of less than 1 mD and a porosity of less than 10%. Generally, reservoir reconstruction is needed to obtain productivity. Its accumulation is mainly controlled by both hydrocarbon source and reservoir. At present, many large oil and gas basins in China have favorable geological conditions for forming tight sandstone gas reservoirs.

[0003] For oil and gas basins with reservoirs, some scholars currently judge whether they can form large gas fields according to gas generation intensity. They believe that large tight sandstone gas fields generally develop in the center and periphery of the gas source, and the gas generation intensity is greater than 20x18 8 m 3 / km 2 . When studying the tight sandstone gas fields in Ordos Basin and Sichuan Basin, it is found that tight sandstone gas has the characteristics of near-source and high-efficiency accumulation. This high-efficiency accumulation enables large-area tight sandstone to form large gas fields in areas with a hydrocarbon source rock gas generation intensity of 20x18 8 m 3 / km 2 . However, the specific exploration results show that these gas fields have relatively large differences in physical properties. For example, the average porosity in Ordos Basin is as high as 8.45%, and the minimum is only 4.7%. The porosity of the main tight gas fields in Sichuan Basin is between 4.2% and 10%. The porosity of Dabei gas field in Tarim Basin is only 2.62%, and the porosity of Kuqa gas field is slightly greater than 4%. The gas generation intensity of the main source rocks in these basins is different. For example, the gas generation intensity of Ordos is generally 20x18 8 m 3 / km 2 , while the gas generation intensity of the tight sandstone gas field in western Sichuan Basin is about 10x18 8 m 3 / km 2 . Therefore, using the gas generation intensity of the main source rock as the basis for judging whether it can accumulate is not accurate.

[0004] In addition, the critical filling porosity is usually used to determine whether the tight sandstone can form a reservoir, and the critical filling porosity refers to the minimum porosity value of the reservoir into which the natural gas can enter in the tight sandstone reservoir; however, different gas generation intensities can generate different gas expansion forces, and the reservoir porosity that can be filled into is related to the gas generation intensity; in the area with large gas generation intensity, the critical porosity that can be filled into the reservoir is small, and in the area with small gas generation intensity, the natural gas can only be filled into the reservoir with relatively large porosity, and therefore, it is not accurate to use a fixed value as the basis for determining whether the reservoir can be formed.

[0005] Obviously, the critical condition for the natural gas to be filled into the reservoir is dynamic, that is, a single absolute index cannot be used to determine whether the gas field can be formed, and therefore, a method for accurately evaluating the gas content of the exploration target from the geological aspect is urgently needed. SUMMARY

[0006] In view of the problems in the prior art, the present application provides a method, system and device for predicting the gas content of tight sandstone, a judgment model of the critical condition for the natural gas filling is established by comprehensively combining the representative gas generation intensity and porosity in the research of the source rock and the reservoir, and the gas content of the exploration target is evaluated from the geological aspect in the early exploration.

[0007] The method for predicting the gas content of tight sandstone provided by the present application comprises the following steps.

[0008] Obtaining the gas generation intensity information of the source rock layer that supplies hydrocarbon for the tight sandstone;

[0009] Determining the critical porosity information corresponding to different gas generation intensities;

[0010] According to the gas generation intensity information and the critical porosity information, the gas content of the tight sandstone is determined.

[0011] In one embodiment, the step of obtaining the gas generation intensity information of the source rock layer that supplies hydrocarbon for the tight sandstone comprises the following steps.

[0012] Compiling a source rock thickness plane distribution map;

[0013] According to the measured single-well source rock vitrinite reflectance data, a source rock Ro plane distribution map is compiled, and the Ro plane distribution map is a vitrinite reflectance plane distribution map;

[0014] Compiling a source rock gas generation rate plane distribution map;

[0015] After the source rock thickness plane distribution map, the source rock Ro plane distribution map and the source rock gas generation rate plane distribution map are gridded in the same scale, a source rock gas generation intensity plane distribution map is prepared through calculation, so as to obtain the gas generation intensity information of the source rock layer that supplies hydrocarbon for the tight sandstone.

[0016] Through the present embodiment, the hydrocarbon source rock thickness plane distribution map, the hydrocarbon source rock Ro plane distribution map and the hydrocarbon source rock gas production rate plane distribution map are gridded in the same scale, then multiplied according to the calculation formula of the gas generation intensity, and then multiplied by the density constant value and the coefficient of the formula, that is, the hydrocarbon source rock gas generation intensity plane distribution map is obtained through calculation. Compared with the conventional fixed parameter calculation method, the anisotropy of the formation lithology in the plane and in the vertical direction is considered, and the obtained gas generation intensity result is also more in line with the geological reality, thereby providing effective data support for subsequent development of geological discrimination of gas bearing property.

[0017] In one embodiment, the hydrocarbon source rock thickness plane distribution map is prepared, including:

[0018] The effective hydrocarbon source rock thickness in the tight sandstone is determined according to the single well lithology and the measured organic carbon content value, or according to the geological background and the formation correlation of the tight sandstone;

[0019] The hydrocarbon source rock thickness plane distribution map is prepared according to the effective hydrocarbon source rock thickness;

[0020] The region with the organic carbon content value greater than 0.5% is the effective hydrocarbon source rock.

[0021] Through the present embodiment, the effective hydrocarbon source rock thickness in the work area is determined by the single well lithology comprehensive column chart and the measured TOC value, wherein the TOC>0.5% is considered as the effective hydrocarbon source rock according to the industry standard. For the area with less measured samples, the effective hydrocarbon source rock thickness can also be determined by formation correlation, and the hydrocarbon source rock thickness plane distribution map is prepared in combination with the geological background of the work area.

[0022] In one embodiment, the hydrocarbon source rock gas production rate plane distribution map is prepared, including:

[0023] The low mature hydrocarbon source rock is selected as a sample;

[0024] The sample is subjected to a gas generation thermal simulation experiment and the gas production rate thereof is obtained;

[0025] The hydrocarbon source rock Ro plane distribution map is gridded and fitted with the gas production rate;

[0026] The hydrocarbon source rock gas production rate plane distribution map is prepared according to the fitting result of the hydrocarbon source rock Ro and the gas production rate;

[0027] Through the present embodiment, the low mature hydrocarbon source rock sample is selected to carry out a hydrocarbon generation thermal simulation experiment to obtain the gas production rate, the laboratory result is converted to the geological condition, the hydrocarbon source rock Ro plane distribution map is gridded, and the gas production rate is fitted according to the quadratic function to form the hydrocarbon source rock gas production rate plane distribution map.

[0028] In one embodiment, the critical porosity information corresponding to different gas generation intensities is determined, comprising:

[0029] analyzing the force of natural gas molecules in the process of tight sandstone gas reservoir accumulation to determine the relationship parameter between the gas generation intensity and the critical pore throat radius;

[0030] obtaining the linear relationship between the porosity and the critical pore throat radius according to the reservoir mercury injection data to determine the critical porosity information corresponding to different gas generation intensities;

[0031] Through the embodiment, the force of natural gas molecules in the process of tight sandstone gas reservoir accumulation is analyzed, that is, when the expansion force of dynamic gas and the resistance (the resultant force of capillary force and static liquid column pressure) of natural gas charging are equal, it is the critical state of natural gas charging, at this time, the pore throat radius generating capillary force is the critical pore throat radius, after obtaining the critical pore throat radius, the linear relationship between the porosity and the critical pore throat radius is obtained by fitting the lower envelope line of porosity according to the measured reservoir mercury injection data, the critical porosity value is calculated according to the relationship between the critical pore throat radius and the gas generation intensity, and the charging area and the non-charging area are divided, so that the critical porosity information corresponding to different gas generation intensities is obtained.

[0032] In one embodiment, the formula for determining the relationship parameter between the gas generation intensity and the critical pore throat radius is:

[0033]

[0034] The calculation formula of the gas expansion force F2 and the static liquid column pressure f2 is respectively:

[0035]

[0036] f2=ρ w gH;

[0037] Wherein, F2 is the gas expansion force, N; f2 is the static liquid column pressure, N; Z is the natural gas compression factor, dimensionless; ρ gl is the underground natural gas density, Kg / m 3 ; R is the gas constant, 8.31433 J / mol·K; T is the thermodynamic temperature, K; M is the molecular molar mass, kg / mol; q e is the gas generation intensity of source rock, m 3 / m 2 ; H s is the thickness of source rock, m; is the porosity of source rock, decimal; ρ w is the water density, kg / m 3 ; g is the acceleration of gravity, 9.8 m / s 2H is the height of the static liquid column, m;

[0038] According to the thickness of the source rock, the porosity of the source rock, the gas generation intensity of the source rock and a plurality of geological parameters of the source rock, the critical pore throat radius of the source rock under different conditions is obtained, so as to further obtain the relationship between the gas generation intensity and the critical porosity.

[0039] In one embodiment, determining the gas-bearing property of the tight sandstone comprises:

[0040] According to the gas generation intensity information and the critical porosity information, a critical porosity plane distribution map is compiled;

[0041] The parameter information of the current tight sandstone is compared with the critical porosity plane distribution map to determine the gas-bearing property thereof;

[0042] According to the relationship between the gas generation intensity and the critical porosity and the gas generation intensity plane distribution map, a critical porosity plane distribution map is compiled, and the stratum porosity plane distribution map is obtained by modeling using logging, seismic and other data, and the gas-bearing property of the tight sandstone is determined by comparing the critical porosity plane distribution map.

[0043] In one embodiment, the parameter information of the current tight sandstone is compared with the critical porosity plane distribution map to determine the gas-bearing property thereof, comprising:

[0044] The gas generation intensity and the porosity of a source layer currently supplying hydrocarbon for the tight sandstone are obtained;

[0045] According to the change of the critical pore throat radius under different gas generation intensities, the charging area and the un-charging area are divided in the critical porosity plane distribution map;

[0046] The logarithm formed by the gas generation intensity and the porosity is put into the critical porosity plane distribution map, and it is determined whether the logarithm falls into the charging area or the un-charging area;

[0047] If the logarithm falls into the charging area, it is determined that the natural gas can be charged into the reservoir of the current tight sandstone;

[0048] If the logarithm falls into the un-charging area, it is determined that the natural gas cannot be charged into the reservoir of the current tight sandstone;

[0049] By the embodiment, the predicted porosity plane or space distribution is corresponded to the critical porosity plane distribution or space distribution, and falling into the filling area indicates that the current tight sandstone reservoir can be filled, while falling into the unfilled area indicates that the current tight sandstone reservoir cannot be filled, that is, in short, the area with the porosity greater than the critical porosity can be filled to form a reservoir, while the area with the porosity less than the critical porosity cannot be filled to form a reservoir, and the gas-bearing property of the exploration target is determined from the geological point of view.

[0050] The application further provides a system for predicting the gas-bearing property of tight sandstone, comprising:

[0051] A gas generation intensity map compiling module is configured to compile a gas generation intensity plane distribution map.

[0052] A critical porosity determining module is configured to determine the critical porosity corresponding to different gas generation intensities.

[0053] A gas-bearing property evaluating module is configured to compile a critical porosity plane distribution map according to the gas generation intensity plane distribution map and the critical porosity corresponding to different gas generation intensities, so as to predict the gas-bearing property of the current tight sandstone according to the measured parameter information of the tight sandstone.

[0054] The application further provides a device for predicting the gas-bearing property of tight sandstone, comprising:

[0055] A memory is configured to store a computer program.

[0056] A processor is configured to execute the computer program to realize the steps of the method for predicting the gas-bearing property of tight sandstone according to any one of the above.

[0057] The above technical features can be combined in various suitable manners or replaced by equivalent technical features, as long as the purpose of the application can be achieved.

[0058] The method, system and device for predicting the gas-bearing property of tight sandstone provided by the application have at least the following beneficial effects compared with the prior art:

[0059] (1) Based on the analysis of the critical condition in the tight sandstone gas reservoir, the relationship between the gas generation intensity and the critical porosity is established, a method for determining the critical porosity of the tight sandstone gas reservoir based on the gas generation intensity is formed, and the gas-bearing property of the tight sandstone gas reservoir is accurately predicted from the geological point of view. BRIEF DESCRIPTION OF DRAWINGS

[0060] The application will be described in more detail below based on the embodiments and with reference to the drawings. Wherein:

[0061] Figure 1 A flow chart of the method for predicting the gas-bearing property of tight sandstone in an embodiment of the application is shown.

[0062] Figure 2 shows a pore throat radius versus porosity relationship and a porosity lower limit determination chart in one embodiment of the present application;

[0063] Figure 3 shows a gas generation intensity versus critical pore radius relationship chart in one embodiment of the present application;

[0064] Figure 4 shows a gas generation intensity versus critical porosity relationship and a filling result determination chart in one embodiment of the present application;

[0065] Figure 5 shows a schematic diagram of a device for predicting gas content of tight sandstone in one embodiment of the present application;

[0066] Figure 6 shows a flowchart of predicting gas content of tight sandstone in the present application;

[0067] In the drawings, the same components have the same reference numerals, and the drawings are not drawn to scale.

[0068] Reference Signs:

[0069] 101 - input device, 102 - processor, 103 - memory, 104 - controller, 105 - output device. DETAILED DESCRIPTION

[0070] Abbreviations

[0071] The following abbreviations can be used in the present application. The definitions of the most prominent abbreviations used in the present application are given below:

[0072] TOC: total organic carbon content, %;

[0073] Ro: vitrinite reflectance, %;

[0074] The present application will be further described with reference to the accompanying drawings.

[0075] Example 1

[0076] The present application provides a method for predicting gas content of tight sandstone, as shown in Figure 1 and Figure 6 , comprising:

[0077] Step S100, obtaining gas generation intensity information of a hydrocarbon source layer supplying hydrocarbon for the tight sandstone;

[0078] Step S110, a hydrocarbon source rock thickness plane distribution map is prepared, effective hydrocarbon source rock thickness in the work area is determined through a single well lithology comprehensive column chart and a measured TOC value (a TOC > 0.5% is considered as an effective hydrocarbon source rock), for an area with less measured samples, the effective hydrocarbon source rock thickness can also be determined by stratigraphic correlation, and the hydrocarbon source rock thickness plane distribution map is prepared in combination with the geological background of the work area; on the single well comprehensive chart, a thickness weighted average of the measured TOC value is obtained, an average value of the effective hydrocarbon source rock TOC is obtained, and the hydrocarbon source rock TOC plane distribution map is prepared in combination with the geological background of the work area;

[0079] Step S120, a hydrocarbon source rock Ro plane distribution map is prepared according to the measured single well hydrocarbon source rock vitrinite reflectance data;

[0080] Step S130, a hydrocarbon source rock gas production rate plane distribution map is prepared,

[0081] Step S131, low mature hydrocarbon source rock is selected as a sample;

[0082] Step S132, a gas generation thermal simulation experiment is performed on the sample and a gas production rate is obtained;

[0083] Step S133, the simulation experiment result is converted to a temperature corresponding Ro under geological conditions, and the Ro is fitted with the gas production rate;

[0084] that is, low mature hydrocarbon source rock samples are selected to carry out a hydrocarbon generation thermal simulation experiment to obtain a gas production rate, and the experimental result is converted to a geological condition, and a Ro-gas production rate relationship is fitted according to a quadratic function, after the Ro plane distribution map obtained in the above is gridded, the hydrocarbon source rock gas production rate plane distribution map can be obtained;

[0085] Step S140, after the hydrocarbon source rock thickness plane distribution map, the hydrocarbon source rock Ro plane distribution map and the hydrocarbon source rock gas production rate plane distribution map are gridded in the same scale, the hydrocarbon source rock gas generation intensity plane distribution map is prepared through calculation to obtain the gas generation intensity information of the hydrocarbon source layer for the dense sandstone, that is, after the hydrocarbon source rock thickness plane distribution map, the hydrocarbon source rock Ro plane distribution map and the hydrocarbon source rock gas production rate plane distribution map are gridded in the same scale, a multiplication is performed according to the calculation formula of the gas generation intensity, and then the density constant value and the coefficient of the formula are multiplied, and the hydrocarbon source rock gas generation intensity plane distribution map can be obtained.

[0086] It should be noted that compared with the conventional fixed parameter calculation method, the present scheme considers the anisotropy of the stratum lithology in the plane and in the vertical direction, and the obtained gas generation intensity result is more consistent with the geological reality, and provides effective data support for subsequent geological identification of gas bearing property.

[0087] Step S200, critical porosity information corresponding to different gas generation intensities is determined;

[0088] Step S210, analysis of the force on the gas molecules in the process of the tight sandstone gas reservoir accumulation, that is, when the expansion force of the dynamic gas and the resistance (the resultant force of the capillary force and the static column pressure) are equal, it is the critical state of the gas charging, at this time, the pore throat radius generating the capillary force is the critical pore throat radius, and the value of the critical pore throat radius can be obtained by the following formula:

[0089]

[0090] Wherein:

[0091] F2: gas expansion force, N, the calculation formula is:

[0092]

[0093] f2: static column pressure, N, the calculation formula is:

[0094] f2 = p w gH;

[0095] Therefore, the value of the critical pore throat radius is:

[0096]

[0097] Wherein, F2 is the gas expansion force, N; f2 is the static column pressure, N; Z is the natural gas compression factor, dimensionless; p gl is the underground natural gas density, kg / m 3 ; R is the gas constant, 8.31433 J / mol·K; T is the thermodynamic temperature, K; M is the molecular molar mass, kg / mol; q e is the gas generation intensity of source rock, m 3 / m 2 ; H s is the source rock thickness, m; The porosity of the source rock is a decimal; p w is the water density, kg / m 3 ; g is the gravitational acceleration, 9.8 m / s 2 ; H is the static column height, m.

[0098] Step S220, according to the reservoir pressure mercury data obtained from the core analysis of the drilled wells in the oilfield, the linear relationship between the porosity and the critical pore throat radius value is obtained by fitting with the lower envelope line of the porosity,

[0099] Step S230, the critical porosity value is calculated according to the critical pore throat radius obtained above and the relationship diagram between the gas generation intensity and the critical porosity is obtained, that is, the critical porosity information corresponding to different gas generation intensities is determined.

[0100] Step S300, determining the gas-bearing property of the tight sandstone according to the gas generation intensity information and the critical porosity information;

[0101] Step S310, compiling a critical porosity plane distribution map according to the gas generation intensity information and the critical porosity information;

[0102] Step S320, modeling by using logging, seismic and other data to obtain a formation porosity plane distribution map;

[0103] Step S330, dividing the charging area and the non-charging area in the critical porosity plane distribution map according to the change of the critical pore throat radius under different gas generation intensities;

[0104] Step S340, corresponding the predicted porosity plane or space distribution with the critical porosity plane distribution map or space distribution map;

[0105] Step S350, judging the gas-bearing property according to whether the predicted porosity plane or space distribution falls into the charging area or the non-charging area, that is, falling into the charging area indicates that it can be charged into the current tight sandstone reservoir, while falling into the non-charging area indicates that it cannot be charged into the current tight sandstone reservoir; in short, the area with porosity greater than the critical porosity can be charged into reservoir, while the area with porosity less than the critical porosity cannot be charged into reservoir, thus realizing the judgment of the gas-bearing property of the exploration target from the geological point of view.

[0106] Embodiment 2

[0107] Taking a certain area in the Ordos Basin as an example, the critical porosity values of the tight sandstone reservoir corresponding to different gas generation intensities in the area are determined, and the specific steps are as follows:

[0108] Step S100, obtaining the gas generation intensity information of the source rock layer supplying hydrocarbon for the tight sandstone;

[0109] Step S110, according to the literature research, determining that the natural gas in the area mainly comes from the Benxi and Taiyuan coal seams, compiling a source rock thickness plane distribution map, determining the effective source rock thickness in the work area through the single-well lithology comprehensive column chart and the measured TOC value (considering TOC≥0.5% as effective source rock), for the area with less measured samples, the effective source rock thickness can also be determined by stratigraphic correlation, and the source rock thickness plane distribution map is compiled in combination with the geological background of the work area; on the single-well comprehensive chart, the thickness weighted average of the measured TOC value is obtained, and the average value of the effective source rock TOC is obtained, and the source rock TOC plane distribution map is compiled in combination with the geological background of the work area;

[0110] Step S120, compiling a source rock Ro plane distribution map according to the measured single-well source rock vitrinite reflectance data;

[0111] Step S130, a hydrocarbon source rock gas production rate plane distribution map is drawn up,

[0112] Step S131, low mature hydrocarbon source rock is selected as a sample;

[0113] Step S132, a sample is subjected to a gas generation thermal simulation experiment and its gas production rate is obtained;

[0114] Step S133, a simulation experiment result is converted to a geological condition to obtain a temperature corresponding to Ro, and Ro is fitted with a gas production rate;

[0115] That is, low mature hydrocarbon source rock samples are selected to carry out a hydrocarbon generation thermal simulation experiment to obtain a gas production rate, and the experimental result is converted to a geological condition, and a relationship between Ro and the gas production rate is fitted according to a quadratic function. After the Ro plane distribution map obtained above is gridded, a hydrocarbon source rock gas production rate plane distribution map can be obtained;

[0116] Step S140, after a hydrocarbon source rock thickness plane distribution map, a hydrocarbon source rock Ro plane distribution map and a hydrocarbon source rock gas production rate plane distribution map are gridded in the same scale, a hydrocarbon source rock gas generation intensity plane distribution map is drawn up to obtain hydrocarbon source rock gas generation intensity information.

[0117] Step S200, a relationship between the gas generation intensity and the critical filling porosity in the region is determined;

[0118] Step S210, a force analysis of a natural gas molecule in a tight sandstone gas reservoir accumulation process is carried out to obtain a critical pore throat radius value;

[0119] Step S220, a relationship between a pore median radius and a porosity lower limit is established according to measured core mercury injection data, as shown in FIG. 2, that is, a relationship between the pore median radius and the porosity can be obtained as follows: Figure 2

[0120]

[0121] Step S230, a critical pore median (critical pore throat) radius under different gas generation intensities is calculated, and a filling area and a non-filling area are determined, as shown in FIG. 3; Figure 3

[0122] Step S300, a critical porosity corresponding to different gas generation intensities is calculated according to the above formula;

[0123] Specifically, as shown in FIG. 4, Figure 4 ​​As shown, each point in the region has a gas generation intensity value, and correspondingly, an average porosity value, when the number pair formed by the gas generation intensity and the porosity falls in the charging region, it is considered that the natural gas can be charged into the tight sandstone reservoir, otherwise, it is considered that the natural gas cannot enter the reservoir; the predicted porosity plane or spatial distribution is corresponded with the above-mentioned critical porosity plane or spatial distribution map, the area with the porosity greater than the critical porosity can be charged into the reservoir, and the area with the porosity less than the critical porosity cannot be charged into the reservoir, that is, the gas-bearing property of the exploration target is judged from the geological point of view;

[0124] It should be noted that the number of gas layers interpreted according to the gas logging data in the region is basically consistent with the number of layers with the porosity greater than the critical porosity value obtained by the model, and the coincidence rate is generally greater than 90%, therefore, it can be considered that the critical porosity values obtained by the model based on different gas generation intensities to judge the gas-bearing property of the exploration target basically meet the natural gas exploration and development situation, and can effectively guide the gas-bearing property evaluation work.

[0125] Embodiment 3

[0126] The present application provides a system for predicting the gas-bearing property of tight sandstone, comprising:

[0127] a gas generation intensity map compiling module, configured to compile a gas generation intensity plane distribution map of the tight sandstone according to the parameter information of the tight sandstone;

[0128] a critical porosity determining module, configured to determine the critical porosity corresponding to different gas generation intensities according to the natural gas equilibrium state;

[0129] a gas-bearing property evaluation module;

[0130] The gas-bearing property evaluation module compiles a critical porosity plane distribution map according to the gas generation intensity plane distribution map and the critical porosity corresponding to different gas generation intensities, so as to predict the gas-bearing property of the current tight sandstone according to the measured parameter information of the tight sandstone.

[0131] Embodiment 4

[0132] The present application provides a device for predicting the gas-bearing property of tight sandstone, comprising:

[0133] a memory, configured to store a computer program;

[0134] a processor, configured to execute the computer program to realize the steps of the method for predicting the gas-bearing property of tight sandstone.

[0135] Specifically, as Figure 5As shown, the device for predicting the gas content of tight sandstone comprises an input device 101, a processor 102, a memory 103, a controller and an output device 105 which communicate with each other through one or more communication buses; the memory 103 stores computer instructions; when the electronic device receives an instruction from the input device 101, the controller 103 reads the pre-stored computer instructions for processing, reading and execution, so that the processor 102 executes the steps of the method for predicting the gas content of tight sandstone and presents the determination result on the output device 105.

[0136] Further, it also includes visible input devices such as a mouse, a keyboard, etc., and software modules for importing data into the program.

[0137] It should be noted that the output device 105 includes an electronic display screen and also includes a designed result display program interface.

[0138] In the description of the present application, it should be understood that the terms "upper", "lower", "bottom", "top", "front", "back", "inner", "outer", "left", "right" and the like indicate the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0139] Although the present application is described herein with reference to particular embodiments, it should be understood that these examples are merely illustrative of the principles and applications of the present application. It should therefore be understood that numerous modifications can be made to the exemplary embodiments, and that other arrangements can be devised without departing from the spirit and scope of the present application as defined by the appended claims. It should be understood that different dependent claims and features herein can be combined in ways other than the original claims describe. It should also be understood that features described in connection with individual embodiments can be used in other embodiments.

Claims

1. A method of predicting gas potential of a tight sand, characterized in that, The method comprises the following steps: obtaining gas generation intensity information of a source rock layer supplying hydrocarbon for the tight sandstone; determining critical porosity information corresponding to different gas generation intensities; determining gas content of the tight sandstone according to the gas generation intensity information and the critical porosity information; determining gas content of the tight sandstone comprises: preparing a critical porosity plane distribution map according to the gas generation intensity information and the critical porosity information; comparing parameter information of the current tight sandstone with the critical porosity plane distribution map to determine its gas content; comparing parameter information of the current tight sandstone with the critical porosity plane distribution map to determine its gas content comprises: obtaining gas generation intensity and porosity of a source rock layer currently supplying hydrocarbon for the tight sandstone; dividing a charging area and an uncharging area in the critical porosity plane distribution map according to changes in critical pore throat radius under different gas generation intensities; placing a logarithm formed by the gas generation intensity and the porosity in the critical porosity plane distribution map and determining whether the logarithm falls in the charging area or the uncharging area; if the logarithm falls in the charging area, it is determined that natural gas can be charged into the reservoir of the current tight sandstone; if the logarithm falls in the uncharging area, it is determined that natural gas cannot be charged into the reservoir of the current tight sandstone.

2. The method of predicting gas potential of tight sand of claim 1, wherein, The method for obtaining gas generation intensity information of a source rock layer supplying hydrocarbon for the tight sandstone comprises: preparing a source rock thickness plane distribution map; preparing a source rock Ro plane distribution map according to measured single-well source rock vitrinite reflectance data, the Ro plane distribution map being a vitrinite reflectance plane distribution map; preparing a source rock gas production rate plane distribution map; after the source rock thickness plane distribution map, the source rock Ro plane distribution map and the source rock gas production rate plane distribution map are gridized in the same scale, a source rock gas generation intensity plane distribution map is prepared by calculation to obtain gas generation intensity information of a source rock layer supplying hydrocarbon for the tight sandstone.

3. The method of predicting gas potential of tight sand of claim 2, wherein, The method for preparing a source rock thickness plane distribution map comprises: determining effective source rock thickness in the tight sandstone according to single-well lithology and measured organic carbon content values, or according to the geological background and stratigraphic correlation of the tight sandstone; preparing a source rock thickness plane distribution map according to the effective source rock thickness; wherein the organic carbon content value is greater than The area where the organic carbon content value is greater than 0.3% is the effective source rock.

4. The method of predicting gas potential of tight sand of claim 2, wherein, The method for preparing a source rock gas production rate plane distribution map comprises: selecting low-mature source rock as a sample; performing a gas generation thermal simulation experiment on the sample and obtaining its gas production rate; gridizing the source rock Ro plane distribution map and fitting it with the gas production rate; preparing a source rock gas production rate plane distribution map according to the fitting result of the source rock Ro and the gas production rate.

5. The method of predicting gas potential of tight sand of any one of claims 1 to 4, wherein, The method for determining critical porosity information corresponding to different gas generation intensities comprises: determining a relationship parameter between the gas generation intensity and the critical pore throat radius through force analysis of natural gas molecules in the process of tight sandstone gas reservoir accumulation; obtaining a linear relationship between porosity and the critical pore throat radius according to reservoir mercury injection data to determine critical porosity information corresponding to different gas generation intensities.

6. The method of predicting gas potential of tight sand of claim 5, wherein, The formula for determining the relationship parameter between the gas generation intensity and the critical pore throat radius is: ； The calculation formulas of the gas expansion force and the hydrostatic pressure are respectively ； ； wherein, is the gas expansion force, N; is the hydrostatic pressure, N; Z is the natural gas compressibility factor, dimensionless; is the in-situ natural gas density, ; R is the gas constant, ; T is the thermodynamic temperature, K; M is the molecular molar mass, ; is the hydrocarbon source rock gas generation intensity, ; is the hydrocarbon source rock thickness, m; is the hydrocarbon source rock porosity, decimal; is the water density, ; g is the gravitational acceleration, ; H is the hydrostatic height, m.

7. A system for predicting gas potential in tight sandstones, characterized in that, The method comprises the following steps: a gas intensity map compiling module, configured to compile a gas intensity plane distribution map; a critical porosity determining module, configured to determine critical porosities corresponding to different gas intensities; a gas-bearing property evaluating module, configured to compile a critical porosity plane distribution map according to the gas intensity plane distribution map and the critical porosities corresponding to different gas intensities, and to predict the gas-bearing property of the current tight sandstone according to the measured parameter information of the tight sandstone; the method for predicting the gas-bearing property of the current tight sandstone, comprising: obtaining the gas intensity and the porosity of a source rock currently supplying hydrocarbon for the tight sandstone; dividing the critical porosity plane distribution map into a charging area and a non-charging area according to the change of the critical pore throat radius under different gas intensities; placing a logarithm formed by the gas intensity and the porosity into the critical porosity plane distribution map, and judging whether the logarithm falls into the charging area or the non-charging area; if the logarithm falls into the charging area, judging that natural gas can be charged into the reservoir of the current tight sandstone; if the logarithm falls into the non-charging area, judging that natural gas cannot be charged into the reservoir of the current tight sandstone.

8. Apparatus for predicting gas potential of tight sandstones, characterized in that, comprising: a memory, configured to store a computer program; a processor, configured to execute the computer program to realize the steps of the method for predicting the gas-bearing property of the tight sandstone according to any one of claims 1 to 6.

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