Geothermal resource-rich sedimentary basin ground temperature gradient prediction method

Abstract

The invention discloses a geothermal resource-rich sedimentary basin ground temperature gradient prediction method, which comprises the following steps: S1, determining the boundary of a research area, and collecting the coordinates and original temperature data of drill holes in the area; s2, carrying out geological unit division on the research area; s3, the well points with the temperature data and the divided geological units are projected to a planar graph of the research area; s4, calculating ground temperature gradients of different units; and S5, predicting the ground temperature gradient of the research area and compiling a ground temperature gradient map. The method is suitable for the technical field of ground temperature gradient prediction, and ground temperature gradient prediction of a certain range of the basin is carried out by establishing a geological unit division method based on ground temperature gradient influence factors and combining existing temperature measurement data; the problems that an existing ground temperature gradient prediction method is insufficient in basis and low in accuracy are solved. The method achieves the reasonable and accurate prediction of the ground temperature gradient in a certain range of the basin under the condition that the temperature measurement data of the basin is less, thereby providing an important basis for the selection, development and utilization of the geothermal resources of the sedimentary basin.

Description

Technical Field

[0001] The present invention belongs to the technical field of geothermal gradient prediction, and specifically relates to a method for predicting the geothermal gradient in sedimentary basins rich in geothermal resources. Background Art

[0002] The geothermal gradient refers to the rate of change of the geothermal temperature with depth below the constant temperature zone inside the Earth. Generally, the determination of the geothermal gradient is obtained through systematic temperature measurement data. The geothermal gradient can describe the thermal state of sedimentary basins, which not only contains information about the origin and evolution of the basins, but also has great guiding significance for the discovery and utilization of geothermal resources. For the selection and development and utilization of geothermal resources, accurate prediction of the geothermal gradient is of great significance.

[0003] During the investigation and research on geothermal resources in sedimentary basins, it is found that the well control degree varies greatly in different regions of the basin, and only a few wells in oil and gas wells or geothermal well boreholes have systematic temperature measurement data, and some temperature measurement data corresponding to some depth points are available at some well points. In the case of lack of temperature measurement data, there is a lack of effective methods for predicting the geothermal gradient of the basin in the past, which has an adverse impact on the evaluation and development and utilization of geothermal resources in the basin.

[0004] Therefore, establishing an effective method for calculating the geothermal gradient for geothermal resource-rich basins is of great significance for geothermal resource evaluation and selection. Through investigation and research, it is found that under the same thermal background, the magnitude of the geothermal gradient is mainly affected by factors such as structure and lithology. Under the conditions of the same region and the same lithology, the geothermal gradient is consistent. In the process of calculating the geothermal gradient, scattered temperature data can be unified to form relatively complete temperature data, and then the geothermal gradient can be calculated.

[0005] Existing methods for calculating the geothermal gradient usually calculate the geothermal gradient using systematic temperature measurement data of individual well points or temperature measurement data of a small number of depth points of some well points, and use these limited data combined with the experience of researchers to predict the geothermal gradient in a certain range of the basin. Its characteristic is that the calculation of the geothermal gradient on a single well point is relatively accurate, but limited by the data level and the deviation of human experience, the prediction of the geothermal field in a certain range of the sedimentary basin lacks basis and it is difficult to reflect the true geothermal field situation of the basin.

[0006] In view of the above problems, the present invention provides a method for predicting the geothermal gradient in geothermal resource-rich basins, which can provide essential technical methods for geothermal research in sedimentary basins. Summary of the Invention

[0007] The purpose of the present invention is to overcome the defects of the prior art and provide a method for predicting the geothermal gradient in sedimentary basins rich in geothermal resources.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] A method for predicting the geothermal gradient in a sedimentary basin rich in geothermal resources, comprising the following steps:

[0010] S1 Determine the boundary of the study area and collect the coordinates and original temperature data of boreholes within the area;

[0011] S2 Conduct geological unit division on the study area;

[0012] S3 Project the well points with temperature data and the divided geological units onto the plan of the study area;

[0013] S4 Calculate the geothermal gradients of different units;

[0014] S5 Predict the geothermal gradient of the study area and compile a geothermal gradient map.

[0015] Preferably, in step S1, determining the target formation series is further included.

[0016] Preferably, in step S1, the temperature data of oil and gas wells comes from formation testing and well logging temperature measurement, and the temperature data of geothermal wells comes from well logging data and on-site water temperature data.

[0017] Preferably, in step S2, combining the main influencing factors of geothermal gradient, sorting out the main geological information of the corresponding target formation series in the study area, conducting division of key geological elements such as tectonic units and lithology on the target formation series, and establishing a geological unit with multi-element superposition based on the influencing factors of geothermal gradient.

[0018] Preferably, in step S2, establishing a geological unit with multi-element superposition based on the influencing factors of geothermal gradient includes the following steps:

[0019] S21 Divide the sub-secondary tectonic units in the basin study area;

[0020] S22 Collect drilling data in the study area, and comprehensively use drilling core-taking and logging data to divide the lithology of sedimentary rocks in the target area;

[0021] S23 Use the above division results, superimpose various factors such as tectonic units and lithology, and divide multiple geological units in the target area according to the element combination of tectonics + lithology.

[0022] Preferably, in step S2, divide the sub-secondary tectonic units in the basin study area according to different geological tectonic characteristics of the basin.

[0023] Preferably, in step S2, the tectonic units in the sag area of a continental faulted basin include steep slope zones, gentle slope zones, sag zones, and central fault zone tectonic units.

[0024] Preferably, in step S2, the lithology division is classified based on the principle of the difference in rock thermal conductivity, which is the most critical parameter affecting the geothermal gradient.

[0025] Preferably, in step S2, according to the difference in thermal conductivity, sedimentary rocks are classified into conglomerate, sandy conglomerate, sandstone, muddy sandstone and mudstone.

[0026] Preferably, in step S3, the well points with temperature data collected in step 1 and the geological units established in step 2 are projected onto the same plan view.

[0027] Preferably, in step S4, according to the geothermal data at different depths of the existing well points in each unit on the plane, the geothermal gradient calculation is carried out for different units respectively.

[0028] Preferably, in step S4, the geothermal gradient calculation includes the following steps:

[0029] S41: Statistically analyze the well temperature data and the corresponding depths of each well in each unit;

[0030] S42: According to the geological unit division result based on the influencing factors of geothermal gradient in step S2, it is considered that the same unit has similar geothermal conditions and geothermal gradients. For different units, the temperature data corresponding to different positions and different depths in each unit are unified and calculated at the same position;

[0031] S43: According to the conclusion of step S42, using the collected geothermal data, calculate the geothermal gradients of the corresponding intervals of different units.

[0032] Preferably, in step S43, when calculating the geothermal gradients of the corresponding intervals of different units, the calculation formula is:

[0033] G = 100 * (T 1 - T 0 ) / (H 1 - H 0 );

[0034] Wherein, H 1 , H 0 are depths, and T 1 , T 0 are the temperatures corresponding to the corresponding depths.

[0035] Preferably, in step S5, based on the principle that the geothermal gradient values of the same unit are the same or similar, the Kriging interpolation method is used to draw the geothermal gradient value line map of the study area.

[0036] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are:

[0037] In the present invention, by establishing a geological unit division method based on the influencing factors of geothermal gradient and combining the existing temperature measurement data to carry out the geothermal gradient prediction within a certain range of the basin, the problems of insufficient basis and low accuracy of the existing geothermal gradient prediction methods are solved; it realizes the reasonable and accurate prediction of the geothermal gradient within a certain range of the basin under the condition of less temperature measurement data in the basin, thereby providing an important basis for the selection area and development and utilization of geothermal resources in sedimentary basins. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is the flow chart of the present invention;

[0039] Figure 2 is the geological unit division map in the embodiment of the present invention;

[0040] Figure 3 is the superposition map of well points + geological units in the embodiment of the present invention;

[0041] Figure 4 is the geothermal gradient prediction map in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0042] The following further describes the specific implementation manners of a geothermal gradient prediction method for a sedimentary basin rich in geothermal resources according to the present invention with reference to the attached Figures 1-4 drawings. The geothermal gradient prediction method for a sedimentary basin rich in geothermal resources according to the present invention is not limited to the descriptions of the following embodiments.

[0043] Embodiment 1:

[0044] A geothermal gradient prediction method for a sedimentary basin rich in geothermal resources, as Figure 1 shown, includes the following steps:

[0045] S1 Determine the boundary of the study area, and collect the coordinates and original temperature data of the boreholes within the area;

[0046] S2 Carry out the division of geological units in the study area;

[0047] S3 Project the well points with temperature data and the divided geological units onto the plan of the study area;

[0048] S4 Calculate the geothermal gradients of different units;

[0049] S5 Predict the geothermal gradient of the study area and compile the geothermal gradient map.

[0050] Embodiment 2:

[0051] A geothermal gradient prediction method for a sedimentary basin rich in geothermal resources, as Figure 1 shown, the other steps are similar to those in Embodiment 1. Further, in step S1, it also includes determining the target formation.

[0052] Further, in step S1, the temperature data of the oil and gas wells are from formation testing and well logging temperature measurement, and the temperature data of the geothermal wells are from well logging data and on-site water temperature data.

[0053] Example 3:

[0054] A method for predicting the geothermal gradient in a sedimentary basin rich in geothermal resources, as Figure 1 shown. Other steps are similar to those in Example 1. Further, in step S2, combining the main influencing factors of the geothermal gradient, sorting out the main geological information of the corresponding target formation in the study area, dividing the key geological elements such as tectonic units and lithologies of the target formation, and establishing a geological unit with multi-element superposition based on the influencing factors of the geothermal gradient.

[0055] Furthermore, in step S2, establishing a geological unit with multi-element superposition based on the influencing factors of the geothermal gradient includes the following steps:

[0056] S21 Divide the sub-secondary tectonic units in the basin study area;

[0057] S22 Collect drilling data in the study area, and comprehensively use drilling core and logging data to divide the lithology of sedimentary rocks in the target area;

[0058] S23 Use the above division results, superimpose various factors such as tectonic units and lithologies, and divide multiple geological units in the target area according to the element combination of tectonics + lithology.

[0059] Furthermore, in step S2, divide the sub-secondary tectonic units in the basin study area according to different geological tectonic characteristics of the basin.

[0060] Furthermore, in step S2, the tectonic units in the sag area of the continental faulted basin include steep slope zone, gentle slope zone, sag zone, and central fault zone tectonic units.

[0061] Furthermore, in step S2, the lithology is classified according to the principle of the most critical parameter for influencing the geothermal gradient, the difference in rock thermal conductivity.

[0062] Furthermore, in step S2, according to the difference in thermal conductivity, sedimentary rocks are divided into conglomerate, sandy conglomerate, sandstone, muddy sandstone, and mudstone.

[0063] Example 4:

[0064] A method for predicting the geothermal gradient in a sedimentary basin rich in geothermal resources, as Figure 1 shown. Other steps are similar to those in Example 1. Further, in step S3, project the well points with temperature data collected in step 1 and the geological units established in step 2 onto the same plane map.

[0065] Example 5:

[0066] A method for predicting the geothermal gradient of a sedimentary basin rich in geothermal resources, as Figure 1 shown. The other steps are similar to those in Embodiment 1. Further, in step S4, according to the geothermal data at different depths of the existing well points in each unit of the plane, the geothermal gradient calculation is carried out for different units respectively.

[0067] Furthermore, in step S4, the geothermal gradient calculation includes the following steps:

[0068] S41: Statistically analyze the well temperature data and the corresponding depths of each well in each unit;

[0069] S42: According to the result of the geological unit division based on the influencing factors of the geothermal gradient in step S2, it is considered that the same unit has similar geothermal conditions and geothermal gradients. For different units, the temperature data corresponding to different positions and different depths in each unit are unified and calculated at the same position;

[0070] S43: According to the conclusion of step S42, using the collected geothermal data, calculate the geothermal gradients of the corresponding intervals of different units.

[0071] Furthermore, in step S43, when calculating the geothermal gradients of the corresponding intervals of different units, the calculation formula is:

[0072] G = 100 * (T 1 - T 0 ) / (H 1 - H 0 );

[0073] wherein, H 1 , H 0 are depths, and T 1 , T 0 are the temperatures corresponding to the corresponding depths.

[0074] Embodiment 6:

[0075] A method for predicting the geothermal gradient of a sedimentary basin rich in geothermal resources, as Figure 1 shown. The other steps are similar to those in Embodiment 1. Further, in step S5, based on the principle that the geothermal gradient values of the same unit are the same or similar, the Kriging interpolation method is used to draw the geothermal gradient value line map of the study area.

[0076] Embodiment 7:

[0077] As Figure 1 shown, a method for predicting the geothermal gradient of a sedimentary basin rich in geothermal resources, the specific steps are as follows:

[0078] Step 1: Determine the boundary of the study area and the target formation series, and collect the original temperature data of the boreholes in the area;

[0079] Step 2: Combine the main influencing factors of geothermal gradient, sort out the main geological information of the study area, divide the key geological elements such as tectonic units and lithology in the study area, and establish a geological unit based on the multi-factor superposition of geothermal gradient influencing factors (such as Figure 2 shown);

[0080] Step 3: Project the well points with temperature data collected in step 1 and the geological units established in step 2 onto the same plane;

[0081] Step 4: Based on the geothermal data of different depths of existing well points in each unit on the plane, calculate the geothermal gradient for different units respectively;

[0082] Step 5: Predict the geothermal gradient of the study area and compile a geothermal gradient map.

[0083] Example 8 (verification example):

[0084] The geothermal gradient prediction method was applied in the western Chezhen Sag of the Jiyang Depression in the Bohai Bay Basin using geological data from oil and gas exploration wells in the region. The overall structural background of the western Chezhen Sag in the study area is a depression area of ​​the secondary structural unit of the basin, and its deep part should have a consistent geothermal structural background.

[0085] 1. The western part of Chezhen Depression was selected as the study area, and Shahejie Formation was selected as the target stratum. The sedimentary boundary at the bottom of Shahejie Formation 3 was determined as the boundary of the study area, of which the northern part was the major fault boundary, the western and southern parts were the stratigraphic overlap boundaries, and the eastern side was the boundary with the eastern part of the basin. There are 14 wells with oil test and temperature measurement data in the depression, all of which are oil and gas wells. The temperature data of each well are shown in Table 1.

[0086] 2. The relevant geological data of Chezhen Depression were collected, and it was confirmed that the depression is a dustpan-shaped fault basin with fault in the north and overlap in the south. The main geological factors affecting the geothermal gradient are regional structure and lithology. According to the structural characteristics of the western part of Chezhen Depression, the structural belt of the study area is divided into steep slope fault zone, gentle slope zone and depression zone. According to the collected drilling coring and logging data, the sedimentary rock lithology of the study area was divided into four types: conglomerate, sandy conglomerate, mudstone and muddy sandstone. According to the results of structural and lithological division, the study area is divided into four geological units: steep slope fault zone-conglomerate zone, steep slope zone-sandy conglomerate zone, depression zone-mudstone zone and gentle slope zone-mudstone sandstone zone (such as Figure 2 shown below).

[0087] 3. Extract the well coordinates collected in step 1 and project them into the geological units divided in step 2 (such as Figure 3 shown below).

[0088] 4. The well and temperature data of 4 different units were classified and statistically analyzed (as shown in Table 2). The temperature data corresponding to different depths at different positions in the same unit were uniformly grouped under the same position for calculation. Using the collected geothermal data, according to the calculation formula: G = 100*(T 1 -T 0 ) / (H 1 -H 0 ), where H 1 and H 0 are depths, and T 1 and T 0 are the temperatures corresponding to the respective depths, the geothermal gradients of the corresponding intervals of different units were calculated. The calculation results are shown (as shown in Table 2).

[0089] 5. According to the geothermal gradient results calculated for each unit in Step 4, taking the principle that the geothermal gradient values of the same unit are the same or similar, the Kriging interpolation method was used to draw the geothermal gradient isoline map of the study area (as Figure 4 shown).

[0090] Table 1

[0091] Hash sign Temperature measurement depth Measured temperature C78 2172 89 C59 2750 111 C20 2040 83 C22 3165 123 CG25 3796 146 CG201 3328 129 C664 3631 140 CG29 1591 69 C101 2732 108 C39 2413 97 C2 1533 67 C36 1447 64 CG19 2166 89 CG54 1890 79

[0092] Table 2

[0093]

[0094] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources, characterized in that: The following steps are involved: S1 determines the boundary of the study area and collects the coordinates and original temperature data of the boreholes in the area; S2 divides the study area into geological units; S3 projects the well points with temperature data and the divided geological units onto the plane map of the study area; S4 calculates geothermal gradients of different units; S5 Predict the geothermal gradient of the study area and compile a geothermal gradient map.

2. A method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources as claimed in claim 1, characterized in that: The step S1 also includes determining the target layer system.

3. The method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources according to claim 1, characterized in that: In step S1, the temperature data of oil and gas wells come from formation testing and well logging, and the temperature data of geothermal wells comes from well logging data and field water temperature data.

4. The method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources according to claim 1, characterized in that: In step S2, the main geological information corresponding to the target stratum in the study area is sorted out in combination with the main influencing factors of the geothermal gradient, and the key geological elements such as structural units and lithology are divided for the target stratum to establish a geological unit with multiple elements superimposed based on the influencing factors of the geothermal gradient.

5. A method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources as claimed in claim 4, characterized in that: In the step S2, a geological unit based on the superposition of multiple factors affecting geothermal gradient is established, comprising the following steps: S21 divides the basin study area into sub-secondary tectonic units; S22 collects drilling data in the study area and uses drilling coring and logging data to zonate the sedimentary rock lithology in the target area; S23 uses the above division results to superimpose multiple factors such as structural units and lithology, and divides the target area into multiple geological units based on the combination of structural + lithological elements.

6. A method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources as claimed in claim 5, characterized in that: In step S2, the basin study area is divided into sub-secondary structural units according to different geological structural characteristics of the basin.

7. A method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources as claimed in claim 5, characterized in that: In step S2, the structural units of the depression area of ​​the continental fault basin include steep slope zone, gentle slope zone, depression zone and central fault zone structural units.

8. A method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources as claimed in claim 5, characterized in that: In step S2, the lithology is classified based on the difference in rock thermal conductivity, which is the most critical parameter affecting the geothermal gradient.

9. A method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources as claimed in claim 8, characterized in that: In step S2, the sedimentary rocks are classified into conglomerate, sandy conglomerate, sandstone, argillaceous sandstone and mudstone according to the difference in thermal conductivity.

10. The method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources according to claim 1, characterized in that: In step S3, the well points with temperature data collected in step 1 and the geological units established in step 2 are projected onto the same plane map.

11. The method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources according to claim 1, characterized in that: In step S4, geothermal gradient calculations are performed for different units respectively according to the geothermal data of different depths of existing well points in each unit on the plane.

12. A method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources as claimed in claim 11, characterized in that: In step S4, the geothermal gradient calculation includes the following steps: S41 counts the well temperature data and corresponding depth of each well in each unit; S42, according to the geological unit division result based on the geothermal gradient influencing factor in step S2, it is considered that the same unit has similar geothermal conditions and geothermal gradients, and for different units, the temperature data corresponding to different positions and depths in each unit are unified and calculated at the same position; S43 calculates the geothermal gradients of the corresponding layers of different units using the collected geothermal data according to the conclusion of step S42.

13. A method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources as claimed in claim 12, characterized in that: In step S43, the geothermal gradient of the layer sections corresponding to different units is calculated, and the calculation formula is: G = 100*(T1-T0) / (H1-H0); Among them, H1 and H0 are depths, and T1 and T0 are temperatures corresponding to the corresponding depths.

14. The method for predicting geothermal gradient in a sedimentary basin rich in geothermal resources according to claim 1, characterized in that: In step S5, the geothermal gradient value line map of the study area is drawn using the Kriging interpolation method based on the principle that the geothermal gradient values ​​of the same unit are the same or similar.

Images