Coal bed gas horizontal well horizontal section coal body structure identification method

Abstract

The invention provides a method for identifying a horizontal section coal body structure of a coal bed gas horizontal well. The method comprises the following steps: predicting a plane distribution rule of a coal body structure of a deployed well area; establishing a corresponding relation between different coal body structures of the well area and well logging parameters, a tectonic curvature value and an indoor rock core observation result, and determining a longitudinal development position; constructing a three-dimensional distribution model of the well area coal body structure by using software; preferably selecting a primary structure coal development area for well position deployment; guiding and controlling drilling in a high-quality and primary structure coal development layer; performing coal body structure evaluation on sidetrack drilling points, collapse points, well leakage points and fault points after well completion; performing coal body structure evaluation by using the logging rock debris; and fine coal body structure identification is carried out in combination with borehole track space distribution characteristics. According to the method, a coal body structure in a deployment area is subjected to plane and longitudinal prediction before well drilling, spatial distribution is performed according to an actual well track after drilling is completed, and accurate coal body structure recognition is performed by comprehensively utilizing well drilling, logging rock debris and logging while drilling information.

Description

Technical Field

[0001] The invention belongs to the technical field of coalbed methane development, and in particular relates to a method for identifying coal body structure in a horizontal section of a coalbed methane horizontal well. Background Art

[0002] Since 2013, coalbed methane exploration and development has gradually carried out research and development tests on development methods, formed the L-type horizontal well type and supporting key development technologies, and achieved good results through field tests.

[0003] L-type horizontal wells have gradually become the main development well type, but the development still shows that the production effects of different well areas and the same well group are quite different. Studies have shown that the structure of the coal body in the horizontal section is one of the main factors affecting the production difference. It affects the production level and stable production capacity of a single well by affecting the fracturing transformation effect and drainage stability. In areas with complex local structural conditions, the coal body structure is diverse. The fracturing effect in the areas where broken coal and mylonitic coal are developed is not ideal, and coal powder is easily generated to block the seepage channel, resulting in low production. The existing coal body structure identification methods are all aimed at the longitudinal coal rock identification of vertical wells. The coal body structure of the horizontal section of horizontal wells is affected by multiple factors such as structure, drilling, and wellbore location. At present, there is a lack of prediction methods for the coal body structure of the horizontal section of horizontal wells.

[0004] In summary, it is necessary to invent a method for identifying the coal body structure in the horizontal section of a coalbed methane horizontal well to guide the drilling process in the native coal seam, and to guide the perforation layer selection and fracturing transformation design, the subsequent drainage control method and equipment selection based on the identification results, so as to further increase the single well production. Summary of the invention

[0005] The purpose of the present invention is to make up for the shortcomings of the prior art and provide a method for identifying the coal body structure in the horizontal section of a coalbed methane horizontal well, preferably to implement perforation transformation on the original structure coal seam, to achieve efficient transformation of high-quality coal seams, and thus to increase the single well production of the coalbed methane horizontal well.

[0006] A method for identifying the coal body structure in a horizontal section of a coalbed methane horizontal well comprises the following steps:

[0007] Step 1: Use the amplitude attribute, curvature attribute, and coherence attribute data of three-dimensional seismic attributes to predict the plane distribution law of the coal body structure in the well area;

[0008] Step 2: Establish the corresponding relationship between different coal body structures in the well area and logging parameters, structural curvature values, and indoor core observation results, clarify the vertical development position, and establish a vertical development model of the coal body structure;

[0009] Step 3: Based on the established coal body structure longitudinal development model and the predicted planar distribution law of the coal body structure, a three-dimensional distribution model of the coal body structure in the well area is constructed;

[0010] Step 4: Based on the three-dimensional distribution model of the coal body structure in the well area, the well site is preferably deployed in the area with primary structural coal development;

[0011] Step 5: Based on the three-dimensional distribution model of the coal structure in the well area, guide and control the drilling in the high-quality, primary structural coal layer;

[0012] Step 6: After the well is completed, the coal structure is evaluated for the side drilling points, collapse points, leakage points, and fault points;

[0013] Step 7: Use logging cuttings data to evaluate coal structure;

[0014] Step 8: Based on the spatial distribution characteristics of the actual drilling wellbore trajectory, the coal structure is finely identified by combining the gamma, gas logging and resistivity logging data while drilling.

[0015] Furthermore, in step 6, the side drilling point is affected by repeated drilling and drilling fluid immersion, and the mechanical properties of the coal rock become soft, which is evaluated as a coal body structure fracture point; the collapse point, well leakage point, and fault point are generally caused by the development of natural cracks or faults, and are evaluated as complex coal body structure areas, which are unfavorable transformation points.

[0016] Furthermore, in step 7, the primary-crushed coal cuttings are shiny, in small pieces, relatively uniform, and have a high hardness, and cannot be crushed by hand; the crushed-mylonitic coal has a dull luster, is powdery, contains small pieces, has a low hardness, and can be crushed into powder by hand.

[0017] Furthermore, in step 8, low gamma, high gas logging and high resistivity indicate high-quality primary structural coal; and low resistivity indicates tectonic coal.

[0018] The embodiments of the present invention bring the following beneficial effects:

[0019] The coal structure of the horizontal section is accurately identified by using data such as 3D seismic attributes, vertical well logging, structural curvature, indoor core observation results, drilling, logging cuttings, and logging while drilling. First, the coal structure is predicted before drilling to guide the drilling of horizontal wells in the original high-quality coal seams, so as to achieve "quality improvement, speed improvement, and efficiency improvement" in drilling; second, the coal structure is accurately identified after drilling, and the differentiated perforation transformation layer section is optimized and the scheme is designed to achieve efficient transformation of high-quality coal seams, thereby increasing the gas production of coalbed methane wells. It is one of the important means to increase the production of coalbed methane horizontal wells, suitable for large-scale production of horizontal wells and secondary production increase transformation in the later stage, with a wide range of promotion and great application value.

[0020] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart of a method for identifying coal body structure in a horizontal section of a coalbed methane horizontal well provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] like Figure 1 As shown, an embodiment of the present invention provides a method for identifying the coal body structure in the horizontal section of a coalbed methane horizontal well, which predicts the planar and vertical coal body structures in the deployment area using three-dimensional seismic attribute data and logging data to guide drilling in the primary structural coal development layer; after drilling is completed, the coal body structure is accurately identified based on the spatial layout of the wellbore trajectory, and comprehensive use of drilling, logging cuttings, while drilling and other data is made.

[0025] The specific steps include:

[0026] Step 1: Use the amplitude attribute, curvature attribute, and coherence attribute data of three-dimensional seismic attributes to predict the plane distribution law of the coal body structure in the well area;

[0027] Step 2: Establish the corresponding relationship between different coal body structures in the well area and logging parameters, structural curvature values, and indoor core observation results, clarify the vertical development position, and establish a vertical development model of the coal body structure;

[0028] Step 3: Based on the established coal body structure longitudinal development model and the predicted planar distribution law of the coal body structure, a three-dimensional distribution model of the coal body structure in the well area is constructed;

[0029] Step 4: Based on the three-dimensional distribution model of the coal body structure in the well area, the well site is preferably deployed in the area with primary structural coal development;

[0030] Step 5: Based on the three-dimensional distribution model of the coal structure in the well area, guide and control the drilling in the high-quality, primary structural coal layer;

[0031] Step 6: After completion, evaluate the coal structure of side drilling points, collapse points, well leakage points, and fault points. Due to repeated drilling and drilling fluid immersion, the mechanical properties of coal rock become soft at side drilling points, which are evaluated as coal structure fracture points; collapse points, well leakage points, and fault points are generally caused by the development of natural fissures or faults, and are evaluated as complex coal structure areas, which are unfavorable transformation points.

[0032] Step 7: Use logging rock cuttings data to evaluate the coal structure. Primary / crushed coal cuttings are shiny, in small pieces, relatively uniform, hard, and cannot be crushed by hand; broken / mylonitic coal is dull, powdery, mixed with small pieces, low hardness, and can be crushed into powder by hand.

[0033] Step 8: Based on the spatial distribution characteristics of the actual drilling wellbore trajectory, the coal structure is finely identified by combining the gamma, gas logging and resistivity logging data while drilling. Low gamma, high gas logging and high resistivity are high-quality primary structural coal; low resistivity is structural coal.

[0034] Specific Example 1: The coal seam in the ZS30 well area is buried at a depth of 680-730m, with a thickness of 5-6m and a gas content of 20-25m 3 / t, the overall performance of vertical wells in the early development was low production and low efficiency. Analysis shows that the main reason is that the well area is located in the wing of the syncline, the coal reservoir is highly heterogeneous, the vertical well development process has poor geological adaptability, and the original high-quality coal seam has not been efficiently transformed. In order to increase the gas production rate in the well area and mobilize high-quality resources, it is necessary to implement horizontal well development adjustments.

[0035] 1) The amplitude attribute, curvature attribute and coherence attribute data of 3D seismic attributes are used to predict the planar distribution law of the coal body structure in the well area. It is evaluated that the coal body structure in the well area is relatively complex, mainly primary-fragmented coal, and locally broken-granular-mylonitic coal.

[0036] 2) Based on the indoor observation results of the core of the evaluation well within the well area, the corresponding relationship between different coal body structures and logging parameters and structural curvature values ​​is established. The original structural coal well diameter is 22-24cm, the deep lateral is greater than 2000Ω·m, and the structural curvature is between -0.001-0.001. In the well area, the structural coal is mainly developed in the middle and lower parts of the coal seam vertically, and the lower part of the interlayer is generally developed as broken particles-mylonitic coal.

[0037] 3) Use Shiwen software to construct a three-dimensional distribution model of the coal structure in the well area;

[0038] 4) Optimize the primary structural coal development area to deploy 4 horizontal wells;

[0039] 5) Based on the vertical development position of the coal structure, guide and control drilling in the middle and upper high-quality, primary structural coal development layers;

[0040] 6) After drilling, the evaluation showed that no side drilling, collapse, leakage or fault occurred in the four wells during the drilling process.

[0041] 7) Use logging rock cuttings data to evaluate the coal structure. The rock cuttings description shows that the rock cuttings in the middle and upper parts are shiny, in small pieces, relatively uniform, hard, and cannot be crushed by hand, and are evaluated as primary / fragmented coal; the rock cuttings near the gangue and at the bottom of the gangue are dull, powdery, mixed with small pieces, low hardness, and can be crushed into powder by hand, and are evaluated as granular / mylonitic coal.

[0042] 8) Based on the spatial distribution characteristics of the actual drilling wellbore trajectory, the coal structure is finely identified. The -1 well was drilled in the middle and upper parts as a whole, with primary structure coal as the main component, the gamma value is generally less than 60API, and the gas logging value is greater than 50%; the -2 well was drilled in the lower part of the coal seam at the well section of 880-930m, with a gamma value of 60-80API, and a gas logging value of less than 30%, which was evaluated as a fragmented-grained structure coal; the -3 well was drilled in the lower part of the coal seam at the well section of 800-900m, with a gamma value of 80-110API, and a gas logging value of less than 40%, which was evaluated as a fragmented-grained structure coal; the -4 well was drilled in the lower part of the coal seam at the well sections of 780-820m and 1720-1760, with a gamma value of 70-100API, and a gas logging value of less than 40%, which was evaluated as a fragmented-grained structure coal.

[0043] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0044] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for identifying the coal body structure in the horizontal section of a coalbed methane horizontal well, characterized in that: The following steps are involved: Step 1: Use the amplitude attribute, curvature attribute, and coherence attribute data of three-dimensional seismic attributes to predict the plane distribution law of the coal body structure in the well area; Step 2: Establish the corresponding relationship between different coal body structures in the well area and logging parameters, structural curvature values, and indoor core observation results, clarify the vertical development position, and establish a vertical development model of the coal body structure; Step 3: Based on the established coal body structure longitudinal development model and the predicted planar distribution law of the coal body structure, a three-dimensional distribution model of the coal body structure in the well area is constructed; Step 4: Based on the three-dimensional distribution model of the coal body structure in the well area, the well site is preferably deployed in the area with primary structural coal development; Step 5: Based on the three-dimensional distribution model of the coal structure in the well area, guide and control the drilling in the high-quality, primary structural coal layer; Step 6: After the well is completed, the coal structure is evaluated for the side drilling points, collapse points, leakage points, and fault points; Step 7: Use logging cuttings data to evaluate coal structure; Step 8: Based on the spatial distribution characteristics of the actual drilling wellbore trajectory, the coal structure is finely identified by combining the gamma, gas logging and resistivity logging data while drilling.

2. According to the method for identifying the coal body structure of the horizontal section of a coalbed methane horizontal well in claim 1, in said step 6, after the well is completed, the coal body structure evaluation is performed on the side drilling point, collapse point, leakage point, and fault point, characterized in that: The sidetracking point is affected by repeated drilling and drilling fluid immersion, and the mechanical properties of the coal rock become soft, which is evaluated as a coal body structure fracture point; The collapse points, leakage points and fault points are generally caused by the development of natural fissures or faults, and are evaluated as areas with complex coal body structures and are unfavorable transformation points.

3. The method for identifying the coal structure of a horizontal section of a coalbed methane horizontal well according to claim 1, wherein in step 7, the coal structure is evaluated using logging cuttings data, characterized in that: The primary-crushed coal cuttings are shiny, in small pieces, relatively uniform, hard, and cannot be crushed by hand; the crushed-mylonitic coal has a dull luster, is powdery, mixed with small pieces, has a low hardness, and can be crushed into powder by hand.

4. According to the method for identifying the coal structure of the horizontal section of a coalbed methane horizontal well in claim 1, in step 8, based on the spatial distribution characteristics of the actual drilling wellbore trajectory, combined with the gamma, gas logging and resistivity logging data while drilling, the coal structure is finely identified, characterized in that: Low gamma, high gas logging, and high resistivity indicate high-quality primary structural coal; Low resistivity is tectonic coal.

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