Undercoal reservoir exploration-oriented in-well seismic data acquisition method
By optimizing the Walkaway VSP observation system and data inspection methods, the problem of difficult identification of sand bodies in sub-coal-bearing reservoirs was solved, high-precision well seismic data acquisition was achieved, and the accuracy of reservoir prediction was improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-03
- Publication Date
- 2026-03-10
AI Technical Summary
Sand bodies in sub-coal reservoirs are difficult to identify. In Walkaway VSP technology, the shot point and the geophone are not on the same horizontal plane, which leads to data errors and affects the accuracy of reservoir prediction.
The Walkaway VSP observation system was used, and the location of the seismic source was marked by GPS navigation and manual methods to ensure that the geophone remained stationary downhole. A reasonable layout of excitation and receiving points was designed, and the combination of manual and intelligent inspection methods improved the data quality.
Effectively obtaining seismic wave information from sub-coal reservoirs improves reservoir prediction accuracy and provides a reliable data foundation for oil and gas reservoir exploration.
Smart Images
Figure CN121634205A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of oil and gas field exploration and development engineering, and particularly relates to a borehole seismic data acquisition method for coal reservoir exploration. BACKGROUND
[0002] The ground seismic sand body identification and prediction technology is a technology for identifying and predicting reservoir sand bodies by using the reflection characteristics and amplitude values of seismic waves. Generally, the planar and spatial morphology of the sand body is analyzed by using the sand body reflection of the seismic profile or the seismic inversion result, and the morphology characteristics can be determined by the positions of the top and bottom surfaces and pinchout points of the sand body. However, the ground seismic sand body identification and prediction technology requires professional geological knowledge and geophysical technology, and also has certain uncertainty. Therefore, in actual application, comprehensive consideration and analysis need to be combined with the actual situation.
[0003] VSP (Vertical Seismic Profiling) is a seismic exploration method for obtaining seismic information in the vertical direction of the stratum to understand the underground geological structure and reservoir characteristics. The Walkaway VSP technology is an advanced wellbore geophysical technology of ground excitation and borehole reception, which is to arrange a series of shooting points along the well measurement line, to obtain the stratum velocity structure in the range through which the measurement line passes by receiving the seismic signal in the well, processing and interpreting the signal indoors.
[0004] The coal reservoir sand body is difficult to identify and the distribution characteristics are difficult to predict. When the Walkaway VSP technology is used, the shooting points are generally arranged on the ground and the geophones are arranged in the well, so the shooting points and the geophones are not on the same horizontal plane, it is difficult to analyze the reflection point distribution on the profile, and there is a certain error between the data collected by the Walkaway VSP measurement line and the actual geological characteristics of the target exploration area. SUMMARY
[0005] To solve the above problems of the prior art, the present application provides a borehole seismic data acquisition method for coal reservoir exploration, which aims to overcome the influence of each layer shielding on the weak signal of the reservoir, ensure the reliability of borehole seismic data acquisition, and improve the prediction accuracy of the coal reservoir by accurately obtaining the borehole seismic information reflecting the coal reservoir.
[0006] To achieve the above purpose, the present application provides a borehole seismic data acquisition method for coal reservoir exploration, comprising the following steps:
[0007] Step S1: arranging a Walkaway VSP observation system, the Walkaway VSP observation system comprising a shooting point measurement line and a receiving point system, each shooting point measurement line being provided with a group of seismic sources, and the receiving point system comprising a plurality of geophones;
[0008] Step S2: controlling the source to be fired alternately, and marking the firing point of the source by GPS navigation and manual method, collecting the downhole seismic data, and the hydrophone is not changed in position in the well during the collection.
[0009] Further, the step S1 comprises:
[0010] Step S101: according to the development direction of the reservoir, a main measurement line of the firing point is arranged perpendicular to the direction of the reservoir sand body, and a contact measurement line of the firing point is arranged parallel to the direction of the sand body.
[0011] Step S102: according to the depth of the sand body of the target reservoir, a receiving point system is designed, and the receiving point system comprises a plurality of hydrophones.
[0012] Further, in the step S101, the length of the main measurement line of the firing point is twice the depth of the reservoir.
[0013] Further, in the step S101, the length of the contact measurement line of the firing point is twice the depth of the reservoir.
[0014] Further, in the step S102, the receiving point system is deep into the coal seam.
[0015] Further, the interval between the adjacent hydrophones arranged in the preset space is 1 / 2 of the interval between the adjacent hydrophones outside the preset space.
[0016] Further, the preset space is from 100m below the lower edge of the coal seam to 100m above the upper edge of the coal seam.
[0017] Further, the downhole seismic data collection method for coal reservoir exploration comprises the following steps:
[0018] Data checking: the downhole seismic data collected in the step S2 is subjected to quality control by combining manual checking and intelligent checking.
[0019] Further, the manual checking refers to judging the observation system, data format and recording class report correctness by manual method, and for unqualified indexes, on-site rework is required.
[0020] Further, the intelligent checking refers to real-time statistics of signal-to-noise ratio and first arrival cross comparison data, when the signal-to-noise ratio is higher than a specified threshold value, or when the first arrival cross phenomenon appears, an alarm mechanism is started, the error reason is judged and corrected.
[0021] Compared with the prior art, the present application has the following beneficial effects:
[0022] This invention addresses the difficulty in predicting the lateral distribution characteristics of reservoir sand bodies by proposing a downhole seismic data acquisition method for sub-coalfield reservoir exploration. This method effectively obtains seismic wave information of sub-coalfield reservoirs in the Junggar Basin, improving the detailed description capability of reservoirs around wells and laying a solid technical foundation for dynamic monitoring of oil and gas reservoirs. Extensive downhole seismic data has been acquired for sub-coalfield reservoirs in multiple exploration areas both domestically and internationally. The application of this invention provides a robust data foundation for subsequent oil and gas exploration and development. Attached Figure Description
[0023] Figure 1 This is a flowchart of one embodiment of the present invention;
[0024] Figure 2 This is a schematic diagram showing the relationship between the receiving point system and the coal seam location according to an embodiment of the present invention;
[0025] Figure 3 This is a schematic diagram of the excitation point survey line according to an embodiment of the present invention, wherein the horizontal axis represents the east-west direction of the geodetic coordinate system and the vertical axis represents the north-south direction of the geodetic coordinate system. It is a design illustration and no specific dimensions are defined.
[0026] Figure 4 This is Walkaway common detector gather data acquired according to an embodiment of the present invention, where the horizontal axis represents the number of acquired channels (dimensionless) and the vertical axis represents time (ms).
[0027] Figure 5 This is a schematic diagram of Walkaway intelligent inspection data collected in the Junggar Basin according to an embodiment of the present invention. The horizontal axis represents the round-trip time in milliseconds (ms), and the vertical axis represents the depth in meters (m). Detailed Implementation
[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some 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.
[0029] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.
[0030] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0031] Furthermore, the use of "and / or" or "and / or" throughout the text implies three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies both A and B. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.
[0032] Based on the characteristics of the sub-coal reservoir seismic signals in the central Junggar Basin, such as shielding by coal seams, numerous and thin reservoirs, and uneven lithological distribution, a high-precision Walkaway observation system was selected for observation. This invention provides a method for downhole seismic data acquisition for sub-coal reservoir exploration. To better understand the purpose, structure, and function of this invention, a detailed description is provided below with reference to the accompanying drawings.
[0033] Example 1
[0034] like Figures 1-3 As shown in the figure, this embodiment provides a method for well seismic data acquisition for sub-coal reservoir exploration, including the following steps:
[0035] Step S1: Deploy the Walkaway VSP observation system. The Walkaway VSP observation system includes excitation point survey lines and receiving point systems. Each excitation point survey line is equipped with a set of seismic sources, and the receiving point system includes several detectors.
[0036] Step S2: Control the alternating excitation of the seismic sources. Each Walkaway line is equipped with a set of seismic sources, which ensures that all seismic sources are excited alternately without moving the geophone. By alternately exciting multiple sets of seismic sources, the acquired data can be more stable, especially the anisotropy results calculated based on the data can be more accurate. The excitation points of the seismic sources are marked by GPS navigation and manual methods. After the first GPS navigation, multiple sets of seismic sources are manually excited to facilitate accurate reaching of the excitation position during repeated excitation. This method effectively improves the problem of data acquisition errors caused by the traditional method of relying solely on GPS navigation.
[0037] The geophone is raised only once throughout the entire process, and the horizontal orientation of the geophone in the well remains unchanged during data acquisition. This also allows for better regularity of cable stretching, which is beneficial to improving data quality.
[0038] Furthermore, in step S1, the excitation point measurement line is divided into the main excitation point measurement line and the excitation point connecting measurement line. Step S1 includes:
[0039] Step S101: Based on the development direction of the reservoir, lay out the main excitation point survey line perpendicular to the strike direction of the reservoir sand body, and lay out the connecting survey line of the excitation point parallel to the strike direction of the sand body.
[0040] Step S102: Design a receiving point system based on the sand body depth of the target reservoir. The receiving point system includes several detectors.
[0041] Example 2
[0042] The difference from Example 1 is that in step S101 of this example, the length of the main measuring line of the excitation point is twice the reservoir depth.
[0043] In step S101, the length of the excitation point connection survey line is twice the reservoir depth.
[0044] In step S102, the receiving point system extends below the coal seam to receive signals. This method can effectively avoid coal seam shielding and reduce the impact of strong multiple waves on weak reservoir signals.
[0045] The spacing between adjacent detectors deployed within the preset space is half the spacing between adjacent detectors outside the preset space. In other words, the receiving point system is densified in the target reservoir area to improve the identification capability of the target reservoir.
[0046] In some preferred embodiments of this example, the preset space is 100m below the lower edge of the coal seam to 100m above the upper edge of the coal seam.
[0047] like Figure 4 , Figure 5 As shown, this embodiment effectively obtained seismic wave information of sub-coal reservoirs in the central Junggar Basin, improving the ability to finely describe reservoirs around wells and laying a solid technical foundation for dynamic monitoring of oil and gas reservoirs.
[0048] Example 3
[0049] The difference between this embodiment and Embodiment 1 and Embodiment 2 is that the well seismic data acquisition method for sub-coal reservoir exploration in this embodiment further includes the following steps:
[0050] Data inspection employs a combination of manual and intelligent inspection methods to perform quality control on the well seismic data acquired in step S2.
[0051] Manual inspection refers to judging the accuracy of the observation system, data format, and record reports by manual means. For unqualified indicators, on-site rework and improvement are required.
[0052] Intelligent inspection refers to the real-time statistics of signal-to-noise ratio and initial arrival comparison data. When the signal-to-noise ratio exceeds a specified threshold or when initial arrival crossover occurs, an alarm mechanism is activated to determine the cause of the error and correct it, and then further improve the operation.
[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.
Claims
1. A method for seismic data acquisition in a well for coal-seam exploration, characterized in that, The method comprises the following steps: Step S1: arranging a Walkaway VSP observation system, the Walkaway VSP observation system comprising a shot point line and a receiver point system, each shot point line being provided with a group of sources, and the receiver point system comprising a plurality of geophones; Step S2: controlling the sources to be excited alternately, and collecting the downhole seismic data by marking the shot point positions of the sources by GPS navigation and manual methods, wherein the geophone positions in the downhole are not changed during the collection.
2. The method for coal-seam-oriented reservoir exploration in seismic data acquisition in a well according to claim 1, characterized in that, The step S1 comprises: Step S101: arranging a shot point main line perpendicular to the development direction of the reservoir, and arranging a shot point connecting line parallel to the sand body trend direction according to the development direction of the reservoir; Step S102: designing a receiver point system according to the sand body depth of the target reservoir, the receiver point system comprising a plurality of geophones.
3. The method for coal-seam-oriented reservoir exploration in a well seismic data acquisition of claim 2, wherein, In the step S101, the length of the shot point main line is twice the depth of the reservoir.
4. The method for coal-seam-oriented reservoir exploration in a well seismic data acquisition of claim 2, wherein, In the step S101, the length of the shot point connecting line is twice the depth of the reservoir.
5. The method for coal-seam-oriented reservoir exploration in a well seismic data acquisition of claim 2, wherein, In the step S102, the receiver point system is deep into the coal seam.
6. The method for coal-seam-oriented subsurface reservoir exploration downhole seismic data acquisition of claim 2, wherein, The interval between the adjacent geophones arranged in the preset space is 1 / 2 of the interval between the adjacent geophones outside the preset space.
7. The method for coal-seam-oriented reservoir exploration in a well seismic data acquisition of claim 6, wherein, The preset space is 100m below the lower boundary of the coal seam to 100m above the upper boundary of the coal seam.
8. The method for coal-seam-oriented subsurface reservoir exploration downhole seismic data acquisition of claim 1, wherein, The method further comprises the following steps: Data checking: the downhole seismic data collected in the step S2 are subjected to quality control by combining manual checking and intelligent checking.
9. The method for coal-seam-oriented reservoir exploration in a well seismic data acquisition of claim 8, wherein, The manual checking refers to judging the observation system, data format and recording correctness by manual methods, and the unqualified indexes are required to be reworked and improved on site.
10. The method for coal-seam-oriented subsurface reservoir exploration downhole seismic data acquisition of claim 8, wherein, The intelligent checking refers to real-time statistics of the signal-to-noise ratio and the first arrival comparison data, and when the signal-to-noise ratio is higher than a specified threshold or the first arrival cross phenomenon appears, an alarm mechanism is started, the error causes are judged and corrected.