A method for synchronously controlling coal seam gas and hard roof rock burst

Abstract

The present invention relates to a method for synchronous control of coal seam gas and rock burst pressure of hard roof. The method comprises: constructing a key layer horizontal well and a coal seam roof horizontal well based on the basic well, wherein the key layer horizontal well extends from the basic well to a drainage vertical well in the key layer of the area to be controlled; the coal seam roof horizontal well extends from the basic well to the drainage vertical well in the coal seam roof, and is connected with the drainage vertical well; performing staged fracturing construction in the key layer horizontal well, and performing fracturing construction in the coal seam roof horizontal well after the staged fracturing construction in the key layer horizontal well; wherein the coal seam roof horizontal well and the key layer horizontal well have a large vertical distance. Therefore, the synchronous control method of the present invention solves the problem of interference between drilling and fracturing of the key layer and the coal seam, can realize efficient drilling and completion of double-step horizontal wells, and non-interference staged and clustered fracturing of the key layer and the coal seam, thereby realizing synchronous control of coal seam gas and rock burst pressure dynamic disasters of hard roof.

Description

Technical Field

[0001] The present invention relates to a coal seam control method, belonging to the technical field of coal mining, and particularly to a method for synchronously controlling coal seam gas and hard roof rock burst pressure. Background Art

[0002] The safe and economical mining of coal resources plays a vital role in stabilizing the energy structure. As coal mining continues to expand in scope and depth, the geological conditions and mining environment become increasingly complex, making dynamic hazards such as coal seam gas and rock bursts in hard roofs more likely to occur. These hazards have already impacted the safe and economical mining of coal resources. Currently, there are some technical methods for managing these dynamic hazards. Long-bore segmented hydraulic fracturing technology is used in underground coal mines to address challenges such as coal seam gas extraction and rock bursts in hard roof strata. However, due to space and safety constraints in underground coal mines, these methods are limited in scope and slow in speed, failing to meet the demands of coal mining. Furthermore, underground coal mines currently only address single-factor hazards, lacking a comprehensive approach to addressing multiple hazards simultaneously. Consequently, existing technologies are unable to meet the scale and breadth of control required for safe and efficient mine operation. Therefore, a method for the large-scale, synchronized management of coal mine gas and rock bursts in hard roofs is urgently needed. Summary of the Invention

[0003] The following is a brief summary of one or more aspects to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all conceivable aspects and is neither intended to identify key or critical elements of all aspects nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that will be provided later.

[0004] The main purpose of the present invention is to solve the technical problems existing in the prior art and provide a method for synchronously controlling coal seam gas and hard roof impact pressure to solve the above-mentioned problems existing in the prior art.

[0005] To solve the above problems, the solution of the present invention is:

[0006] A method for synchronously controlling coal seam gas and hard roof rock burst pressure comprises the following steps:

[0007] S10, determine the coordinates and elevation data of the key layers and coal seams in the target mining area, and design a double-step horizontal well trajectory in the direct roof and upper hard roof key layers of the pre-mining working face of the coal mining area based on the coordinates and elevation data of the coal seams and key layers;

[0008] S20, conduct drainage and production vertical well construction;

[0009] S30, based on the double-step horizontal well trajectory of S10, carries out basic well construction and key layer horizontal well construction, and performs staged fracturing in the key layer horizontal well, followed by milling and removal of the uncemented production casing completion string section in the key layer horizontal well;

[0010] S40: Open the casing of the foundation well to drill and complete the coal seam roof horizontal well. The coal seam roof horizontal well is connected to the vertical well for drainage and production, and staged fracturing is carried out in the coal seam roof horizontal well.

[0011] S50, installation of drainage equipment and extraction construction are carried out in the vertical drainage well.

[0012] Preferably, in S10, the vertical distance d between the key layer and the coal seam is 40m-100m, and based on the coordinates and elevation data of the coal seam and the key layer, a double-step horizontal well trajectory is designed in the coal seam roof and the upper hard roof key layer. The double-step horizontal well adopts a long-radius horizontal well, with a build rate of <8° / 30m and a curvature radius R>286.5m;

[0013] The inclination point of the horizontal well in the coal seam roof must meet the following relationship:

[0014] h2=h1+d

[0015] h2 is the vertical depth of the inclination point of the horizontal well in the coal seam roof, h1 is the vertical depth of the inclination point of the basic well, and d is the vertical distance between the key layer and the coal seam.

[0016] Preferably, in said S30, the foundation well adopts a two-wellbore structure, the first well of the foundation well is drilled to 20 m below the bedrock and the cementing slurry is returned to the surface to obtain the cement ring of the first well of the foundation well;

[0017] The landing point of the second opening of the foundation well is set at the vertical middle position in the key layer, and the cementing cement returns to the ground to obtain the cement ring of the second opening of the foundation well;

[0018] During the construction of the key layer horizontal well, the foundation well is used as the basis. After the horizontal section is drilled, the production casing completion string of the key layer horizontal well is lowered. An isolation type grading collar is set in the production casing completion string of the key layer horizontal well. The distance from the bottom position of the secondary technical casing of the foundation well is 150m~200m. The horizontal section of the key layer horizontal well and the upper 150m~200m are cemented to form a cement ring for the horizontal section and the upper part. The outer annulus of the production casing completion string from the isolation type grading collar to the wellhead is not cemented, forming an uncemented production casing completion string section of the key layer horizontal well.

[0019] Preferably, before the staged fracturing construction in the horizontal well of the key layer, the isolation type staged collar accessory drilling and removal construction are carried out, and the key layer is transformed by using a pumping bridge plug and perforation combined with a bare casing staged multi-cluster temporary plugging and ball throwing fracturing method. The fracturing construction adopts a large displacement of 14m³~18m³, a large fluid volume of 800m³-1200m³ / stage, a high viscosity water-based fracturing fluid system, and a multi-stage clustered ball throwing temporary plugging process;

[0020] The multi-stage clustered ball-throwing temporary plugging process has a stage spacing of 30m to 40m, 2 to 3 clusters are perforated in each stage, the cluster spacing is controlled at 20m to 25m, each cluster is perforated 1m, the hole density is 10 to 16 holes / m, 60° spiral hole arrangement is used, large-aperture bullets are used, and the perforation diameter is ≥14mm; after the first cluster is fracturing, 10 to 16 low-temperature temporary plugging PGA degradable fracturing balls are put in to temporarily plug the first cluster, and the second cluster is fracturing; after the second cluster is fracturing, 10 to 16 low-temperature temporary plugging PGA degradable fracturing balls are put in again to temporarily plug the second cluster, and the third cluster is fracturing.

[0021] Preferably, the acoustic amplitude and acoustic variable density cementing quality logging methods are used to accurately detect the uncemented well section, where the acoustic amplitude of the first interface interpreted by the logging is greater than 30%, and the formation wave of the second interface is weak and difficult to identify, which is the uncemented well section. The 2m~3m above the uncemented position detected by the logging is selected as the milling position of the key layer horizontal well production casing completion pipe section.

[0022] Preferably, in said S40, a window is opened from 2m below to 20m above the foundation well inclination point, and casing segment milling of the foundation well secondary opening technology is performed, and the segment milling length is 22m;

[0023] The drilling of horizontal wells in the coal seam roof includes side drilling construction, inclined section and horizontal section construction. The side drilling construction is carried out by lowering the well inclination and azimuth at the window position. After completing the side drilling and continuing to drill 40m~100m, the rotary guide and straight screw drill tool combination tool is lowered to carry out the inclined section and horizontal section construction. After drilling is completed, the production casing is lowered and cementing is carried out to obtain the three-well cementing ring of the coal seam roof horizontal well.

[0024] Preferably, the coal seam roof horizontal well construction adopts the method of logging while drilling, comprehensive logging and multi-point coal exploration wellbore trajectory control. When the logging while drilling gamma value is between 50API and 100API, the lateral resistivity value is less than 50Ω.m, and the comprehensive logging shows that the drilling time is slow, the gas logging total hydrocarbon value is between 0.5% and 2%, and the rock cuttings show mudstone, indicating that the trajectory is in the roof mudstone, then composite drilling is carried out according to the current trajectory; when the logging while drilling gamma value is between 10API and 50API, the lateral resistivity value is less than 50Ω.m, and the comprehensive logging shows that the drilling time is slow, the gas logging total hydrocarbon value is between 0.5% and 2%, and the rock cuttings show mudstone, indicating that the trajectory is in the roof mudstone. At I, the lateral resistivity value is 50Ω.m~800Ω.m, and the comprehensive logging shows that the drilling time is relatively fast, the total hydrocarbon value of the gas logging is 2%~60%, and the rock cuttings show coal cuttings, indicating that the trajectory is in the coal seam. In this case, directional wellbore increase and oblique drilling are required to enter and exit the coal seam. Secondly, the coal seam is explored every 150m~200m of drilling. Directional wellbore decrease and oblique drilling are carried out to explore the coal seam. When coal is encountered, the exploration is considered completed. After that, the well inclination is increased to make the trajectory exit the coal seam, so that the horizontal well trajectory of the coal seam roof is controlled within the range of 0m~2m of the roof.

[0025] Preferably, the coal seam roof horizontal well staged fracturing construction adopts a pumping bridge plug and perforation combined with a bare casing multi-stage cluster ball temporary plugging method to perform coal seam roof staged hydraulic fracturing; complete the communication between the roof and the coal seam, and establish a coal seam gas seepage channel;

[0026] The staged fracturing operation adopts a large displacement of 8m³-14m³, a large fluid volume of 800m³ / stage-1200m³ / stage, a fracturing fluid system of clean water and quartz sand, and a multi-stage clustered ball-dropping temporary plugging process;

[0027] The multi-stage clustered ball-throwing temporary plugging process has a stage spacing of 30m to 40m, 2 to 3 clusters are perforated in each stage, the cluster spacing is controlled at 15m to 20m, each cluster is perforated at 1m, the hole density is 10 holes / m to 16 holes / m, the perforations are perforated vertically downward, and deep-penetrating bullets are used with an effective penetration depth of ≥1200mm; after the first cluster is fracturing, 10 to 16 low-temperature temporary plugging PGA degradable fracturing balls are thrown in to temporarily plug the first cluster, and the second cluster is fracturing; after the second cluster is fracturing, 10 to 16 low-temperature temporary plugging PGA degradable fracturing balls are thrown in again to temporarily plug the second cluster, and the third cluster is fracturing.

[0028] Preferably, in S20, a vertical drainage well is constructed. The vertical drainage well is set at a distance L from the wellhead of the foundation well, where L is 1000m to 1500m. A 2m to 4m hole is drilled in the coal seam and roof, and the hole diameter is not less than 0.5m. After the initial hole expansion is completed, the hole is detected by wellbore logging to confirm whether the hole meets the requirements. If the detected hole diameter does not reach 0.5m, the hole expansion tool needs to be lowered again to expand the hole until the well logging detection shows that the hole diameter is not less than 0.5m, which is considered to be qualified.

[0029] Preferably, the foundation well is composed of a cement sheath of a first opening of a double-step horizontal well foundation well and a cement sheath of a second opening of a double-step horizontal well foundation well. The depth of the cement sheath of the first opening of the double-step horizontal well foundation well is less than that of the second opening of the double-step horizontal well foundation well, and the cement sheath is sleeved on the cement sheath of the second opening of the double-step horizontal well foundation well.

[0030] Preferably, the key layer horizontal well includes a horizontal section of the key layer horizontal well and a cementing sheath on its upper portion, and the horizontal section of the key layer horizontal well and the cementing sheath on its upper portion are sleeved within the cementing sheath of the second opening of the double-step horizontal well foundation well, with the overlapping portion having a length of 150m to 200m;

[0031] Preferably, the vertical distance between the coal seam roof horizontal well and the key layer horizontal well is d, and the coal seam roof horizontal well includes a three-well cementing sheath of the coal seam roof horizontal well;

[0032] The drainage and production vertical well includes a cave and a cement ring of the first drainage and production vertical well and a cement ring of the second drainage and production vertical well. The cement ring of the first drainage and production vertical well is less deep than the cement ring of the second drainage and production vertical well and is sleeved on the cement ring of the second drainage and production vertical well.

[0033] Therefore, compared with the prior art, the advantages of the present invention are:

[0034] 1. The synchronous control method of the present invention can realize large-scale and high-intensity transformation of key layers and coal seams, and achieve synchronous control of coal mine gas and hard roof rock burst dynamic disasters, which has high engineering application significance.

[0035] 2. After the drilling and fracturing of the key layer horizontal well are completed, the key layer horizontal well is closed. When the coal seam roof horizontal well is drilled, the upper part is in a closed state, and there will be no interference with the drilling of the roof horizontal well. Therefore, the interference problem of multi-layer horizontal well drilling and completion construction is solved. It has the characteristics of high engineering practical operability, high construction efficiency, low construction cost, etc., and has good engineering application value.

[0036] 3. The dual-step horizontal well fracturing reconstruction method of the present invention solves the problem of dual-horizontal well fracturing being affected by the completion structure. Both horizontal wells can complete high-flow, high-liquid volume bare casing segmented and clustered fracturing. It features large-scale fracturing, high operation efficiency, and low operation risk, achieving high-intensity weakening of rock burst pressure in key strata and efficient, large-scale permeability enhancement of coal seams.

[0037] 4. The synchronous management method of the present invention solves the problem of interference between key strata and coal seams during drilling and fracturing, enabling efficient drilling and completion of dual-step horizontal wells and staged and clustered fracturing without interference between key strata and coal seams. It has certain technical reference value for coalbed methane development and key stratum disaster management. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the wellbore structure of the vertical drainage well of the present invention;

[0039] Figure 2 This is a schematic diagram of the wellbore structure of a key layer horizontal well of the present invention;

[0040] Figure 3 This is a schematic diagram of the staged fracturing construction of a horizontal well in a key layer of the present invention;

[0041] Figure 4 This is a schematic diagram of the wellbore structure of a coal seam roof horizontal well of the present invention;

[0042] Figure 5 This is a schematic diagram of the staged fracturing of a horizontal well in a coal seam roof according to the present invention;

[0043] Figure 6 It is a schematic diagram of the double-step horizontal well and screw pump extraction structure of the present invention.

[0044] Figure 7 It is a schematic diagram of the double-step horizontal well trajectory structure of the present invention.

[0045] The meaning of each number in the figure is:

[0046] 1-key layer, 2-coal seam, 3-drainage vertical well, 4-cave, 5-double-step horizontal well foundation well first opening cementing cement ring, 6-double-step horizontal well foundation well second opening cementing cement ring, 7-key layer horizontal well production casing completion string, 8-isolated graded collar, 9-first-level floating collar, 10-second-level floating collar, 11-key layer horizontal well horizontal section and its upper cementing cement ring, 12-isolated graded collar to wellhead production casing completion string outer annulus, 13-blind plug drillable bridge plug, 14-ball cage soluble bridge plug, 15-key layer clustered fracturing crack, 16-key layer water Milling position of horizontal well production casing completion string section, 17-annulus inside production casing of coal seam roof horizontal well, 18-cement ring of third spud of coal seam roof horizontal well, 19-clustered fracturing fractures of coal seam roof horizontal well, 20-screw pump, 21-air anchor, 22-tail pipe, 23-cement ring of first spud of drainage and production vertical well, 24-cement ring of second spud of drainage and production vertical well, 25-inclination point of foundation well, 26-inclination point of coal seam roof horizontal well, 27-landing point of foundation well, 28-landing point of coal seam roof horizontal well, 29-target point of key layer horizontal well, 30-connectivity target point of coal seam roof horizontal well.

[0047] The specific contents of the present invention are further explained in detail below with reference to the embodiments. DETAILED DESCRIPTION Example

[0048] This embodiment first provides an intelligent video surveillance system based on a network camera.

[0049] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0050] Directional terms mentioned in this document, such as "horizontal" and "depth", are consistent with the specific directions on the paper of the drawings in the specification or the corresponding directions in the space shown in the drawings. Example

[0051] Step 1: Determine the spatial location and distance between the key layers and coal seams in the target mining area.

[0052] Collect exploration and mine data of the target coal mining area, obtain the elevation, coordinates and other data of the coal seam and key layer, determine the spatial position and distance between the key layer and the coal seam, and the vertical distance d between the key layer and the coal seam is 40~100m.

[0053] Step 2: Double-step horizontal wellbore trajectory design ( Figure 7 ).

[0054] Based on the coordinates and elevation data of the coal seams and key strata, a double-step horizontal well trajectory was designed in the immediate roof and upper hard roof key strata of the pre-mining working face in the coal mine area. The double-step horizontal well utilizes a long-radius horizontal well with a build-up rate of less than 8° / 30m and a curvature radius R greater than 286.5m. This long-radius horizontal well requires less stringent drilling methods, drill pipe, inclination measurement tools, and drilling rig equipment, resulting in lower construction risks and higher drilling efficiency. The water-to-vertical ratio of the double-step horizontal well is controlled within 2, facilitating efficient double-step horizontal well completion and reducing the difficulty of double-step horizontal well drilling. The foundation well landing point 27 is located vertically in the middle of the key stratum to facilitate horizontal drilling of the key stratum.

[0055] The double-step horizontal well trajectory design is divided into the basic well, key layer horizontal well, and coal seam roof horizontal well trajectory design. Specifically, based on the trajectory control point data such as the basic well inclination point 25 vertical depth h1, the basic well landing point 27 coordinates and elevation, and the key layer horizontal well target point 29 coordinates and elevation, the basic well and key layer horizontal well trajectory design is completed with the help of COMPASS software. The coordinates and elevations of the basic well landing point and the key layer horizontal well target are obtained based on coal mine area exploration and mine data. The basic well inclination point vertical depth h1 = the basic well wellhead ground elevation - the wellhead vertical position key layer elevation - the curvature radius R. The basic wellhead ground elevation is obtained by GPS instrument measurement, and the wellhead vertical position key layer elevation is obtained based on coal mine area exploration and mine data. Based on trajectory control data such as the vertical depth h2 of the coal seam roof horizontal well inclination point 26, the coordinates and elevation of the coal seam roof horizontal well landing point 28, and the coordinates and elevation of the coal seam roof horizontal well connection target point 30, the coal seam roof horizontal well trajectory design was completed with the help of COMPASS software. The coordinates and elevations of the coal seam roof horizontal well landing point and connection target point were obtained based on coal mining area exploration and mine data. The coal seam roof horizontal well inclination point must satisfy the following relationship: the vertical depth h2 of the coal seam roof horizontal well inclination point = the vertical depth h1 of the foundation well inclination point + the vertical distance d between the key layer and the coal seam. Long-radius horizontal wells can be implemented in the coal seam roof close to the key layer, and the drilling construction is highly operable.

[0056] Step 3: Drilling and completion of vertical wells (see Figure 1 ).

[0057] A vertical drainage well 3 was constructed, using a two-wellbore structure. A hole was drilled in the coal seam and roof, with a length of 2-4 meters and a diameter of at least 0.5 meters. Preliminary work was completed to connect the horizontal well in the coal seam roof with the vertical drainage well. Given that the water-to-vertical ratio of the double-step horizontal well is within 2, the vertical drainage well was located at a distance of 1000-1500 meters from the foundation wellhead. Fiberglass casing was run in the hole-drilling section, while steel casing was run in the remaining two-well sections. Cave 4 was constructed using a staged reaming method. The fiberglass casing was first milled with a segment milling tool, and then a reaming tool was run to reame the hole. After the initial reaming, the cave was surveyed using caliper logging to confirm whether it met the requirements. If the measured diameter did not reach 0.5 meters, the reaming tool was run again to reame the hole until logging indicated a diameter of 0.5 meters, which was considered acceptable.

[0058] Step 4: Double-step horizontal well foundation well drilling and completion construction (see Figure 2 ).

[0059] The foundation well adopts a two-wellbore structure. The first opening is drilled to 20m below the bedrock and the surface casing is opened. The cementing slurry is returned to the ground. The second opening drilling first constructs a pilot well to expose the key layer and coal seam, obtain their accurate coordinates and elevation data, and update the coordinates and elevation data of the trajectory control points such as the landing point of the foundation well, the target point of the horizontal well in the key layer, the landing point of the horizontal well in the coal seam roof, and the target point of the horizontal well connecting the coal seam roof. The trajectory of the double-step horizontal well is updated according to the above trajectory design method, and then the pilot well section is backfilled with cement. Secondly, the second opening drilling needs to be combined with wireless drilling data. According to geological logging analysis, the well inclination and azimuth data were dynamically optimized to accurately land in the vertical middle of the key layer; the second-opening technical casing was laid, and the variable density cement slurry cementing process was adopted, in which the leading slurry was 1.60g / cm3 low-density cement slurry and the tailing slurry was 1.80g / cm3 high-density cement slurry, which improved the cementing quality of the second-opening of the foundation well and provided a good cementing section for the subsequent second-opening technical casing window of the foundation well, improved the efficiency of the window opening construction, and reduced the risk of window opening construction; at the same time, the use of variable density cement slurry can further alleviate the risk of cement slurry leakage through the formation, and facilitate the return of cement slurry to the ground.

[0060] Step 5: Drilling and completion of key horizontal sections (see Figure 2 ).

[0061] Based on the double-step horizontal well foundation, an MWD directional instrument + screw + drill bit combination tool is run in to drill the horizontal section of the key layer horizontal well. During the construction, less directional drilling and more composite drilling methods are adopted to reduce the full-angle change rate of the horizontal section, which is convenient for running the production casing completion string. After completing the horizontal section drilling, the key layer horizontal well production casing completion string 7 is run in to carry out cementing and completion. The isolation type stage collar 8 in the production casing completion string is located in the secondary technical casing of the foundation well and is about 150-200m away from the bottom of the secondary technical casing of the foundation well to ensure that the isolation type stage collar accessory packer unit is effectively set. The horizontal section of the key layer horizontal well and its upper 150-200m are cemented to form a cement sheath 11 in the horizontal section and its upper part. The outer annulus 12 of the production casing completion string from the isolation type stage collar to the wellhead is not cemented to ensure the cementing quality of the horizontal section and provide good wellbore conditions for subsequent key layer horizontal well fracturing.

[0062] The combination of the production casing completion string 7 for the key layer horizontal well is: float shoe + casing + first-level float collar + short casing + second-level float collar + casing string + isolation type stage collar + casing string; during cementing operation, the cement slurry volume is designed according to the volume of the annulus from the isolation type stage collar to the float shoe, and 20-25% cement slurry is added to ensure that the cement slurry in the outer annulus returns to a certain height above the isolation type stage collar, ensuring that the outer annulus of the production casing completion string below the isolation type stage collar is completely filled with cement slurry, thereby ensuring the cementing quality of the horizontal section of the key layer horizontal well.

[0063] The cementing operation is mainly completed according to the following method: first, cement slurry is injected, and then displacement fluid is injected. Before injecting the displacement fluid, a flexible plug is inserted. The amount of displacement fluid injected in the first stage is slightly less than the internal volume from the isolation stage collar 8 to the secondary floating collar 10. After the first stage of displacement fluid injection is completed, an opening plug is inserted, and the second stage of displacement fluid injection is carried out according to the internal volume from the wellhead to the isolation stage collar, ensuring that the opening plug hits the flexible plug before the flexible plug; the injection channel of the isolation stage collar is opened to expand and seal the packer; the pressure is continued to be held, the circulation hole of the isolation stage collar is opened, and the circulating medium of the mud pump is adjusted to circulate cement slurry in the annulus above the isolation stage collar; the closing plug is inserted and pushed to the isolation stage collar, the circulation hole is closed, and the solidification is carried out.

[0064] Step 6: Drilling and removal of the isolation type grading hoop accessories.

[0065] Specifically, after cementing is completed and waiting time is set for 48 to 72 hours, the production casing completion string is pressure tested at 20 MPa. If the pressure drop is ≤0.5 MPa within 30 minutes, it is considered qualified. The accessories of the isolation stage collar are drilled out, and a cone or grinding shoe tool is inserted to drill out the isolation stage collar accessories such as the opening plug, plug seat, flexible plug, and packer at one time, thereby providing a large-diameter inner annulus and providing an effective large injection channel for subsequent key layer fracturing.

[0066] Step 7: Staged fracturing of horizontal wells in key layers (see Figure 3 ).

[0067] Specifically, a pumped bridge plug and perforation system, combined with a bare casing segmented multi-cluster temporary plugging and ball-dropping fracturing method, is used to transform the critical formation. Fracturing operations utilize a high-volume 14-18 m³, a high-flux 800-1200 m³ / segment, a highly viscous water-based fracturing fluid system, and a multi-segment clustered ball-dropping temporary plugging process to enhance fracture widening and achieve high-intensity management of rock burst hazards in the critical formation. A blind drillable bridge plug 13, a cage-type soluble bridge plug 14, and the perforating gun tool string are pumped to the setting position using hydraulic high-pressure fluid. This then triggers an electrical signal to simultaneously set the bridge plug and release the perforating gun tool. The setting position is required to avoid casing collars, maintaining a minimum distance of 2 meters from the casing collar and at least 15 meters from the upper perforated section, avoiding sections with poor cementing quality. After fracturing, a blowout is performed. After pressure release in the critical formation, a blind drillable bridge plug 13 is pumped above the final fracturing segment to seal the critical formation.

[0068] The multi-stage clustered ball-throwing temporary plugging process has a stage spacing of 30-40m, 2-3 clusters of perforations in each stage, a cluster spacing controlled at 20-25m, a perforation of 1m in each cluster, a hole density of 10-16 holes / m, a 60° spiral perforation pattern, and a perforation aperture ≥14mm. After the first cluster is fracturing, 10-16 low-temperature temporary plugging PGA degradable fracturing balls are thrown in to temporarily plug the first cluster, and a second cluster is fracturing. After the second cluster is fracturing, 10-16 low-temperature temporary plugging PGA degradable fracturing balls are thrown in again to temporarily plug the second cluster, and a third cluster is fracturing to achieve uniform and efficient transformation of the key layer.

[0069] Step 8: Milling and removal of the uncemented production casing completion string section in the key horizontal well ( Figure 3 ).

[0070] Specifically, during actual construction, a cement sheath of a certain height existed above the isolation collar. To accurately identify the uncemented section, acoustic amplitude and variable-density cementing quality logging was used for precise detection. Uncemented sections were identified using cement bond quality rating standards. Log interpretation indicated an acoustic amplitude of >30% at the first interface and weak, difficult-to-identify formation waves at the second interface, indicating an uncemented section. A point 2 to 3 meters above the uncemented location detected by logging was selected as the key horizontal well production casing completion string segment milling location 16. A controllable hydraulic cutting segment milling tool was lowered at this segment milling location to segment the uncemented production casing completion string. The uncemented production casing completion string above the segment milling location was then completely removed.

[0071] The segmented milling uncemented production casing completion string should avoid casing joints and should not damage the second-opening technical casing of the foundation well; the removed uncemented production casing completion string can be reused, which has high economic benefits; secondly, after the uncemented production casing completion string is removed, a larger annular space is provided for the drilling of the coal seam roof horizontal well, which is convenient for the subsequent foundation well window opening and coal seam roof horizontal well third-opening drilling construction.

[0072] Step 9: Opening windows in the casing of the double-step horizontal well foundation well.

[0073] Specifically, a casing window is created in the secondary well casing using the segment milling and reaming method. The casing window location must meet the operability of horizontal well sidetracking and the drilling of the inclination section and horizontal section in the coal seam roof. The window is created from 2m below the inclination point to 20m above the inclination point of the foundation well. First, the secondary well casing is segment milled using the 22m segment milling method. After segment milling, a reaming tool is lowered to expand the segment milling section. The cement ring drill in this segment is then ground clean, completing the casing window. This provides a good open hole section for subsequent sidetracking, effectively avoiding the magnetic interference of the steel casing on the directional tool and facilitating sidetracking.

[0074] The casing window position is selected in the second opening of the foundation well with good cementing quality and stable formation without leakage. The window should avoid the casing collar and the centralizer; the drilling fluid needs to have high viscosity and high cutting performance to ensure that the drilling fluid can normally carry iron chips and cement chips.

[0075] Step 10: Drilling and completion of horizontal wells in the coal seam roof (see Figure 4 ).

[0076] Specifically, horizontal well drilling in coal seam roofs is divided into sidetracking and construction of a deflection section and horizontal section. Sidetracking is performed at the window opening location by lowering the wellbore inclination and azimuth. After completing the sidetracking and drilling 40-100 meters further, a rotary steerable and straight screw drill tool combination is lowered to construct the deflection section and horizontal section. The horizontal section construction adopts the method of logging while drilling + comprehensive logging + multi-point coal exploration wellbore trajectory control to ensure that the trajectory is controlled in the roof rock layer adjacent to the coal seam; after drilling is completed, the production casing is lowered, and the cementing adopts the variable density cement slurry cementing process. The leading slurry is 1.50g / cm3 low-density cement slurry, and the tailing slurry is 1.70g / cm3 medium-high density cement slurry, which can further alleviate the risk of cement slurry leakage through the formation and facilitate the return of cementing cement slurry to the ground; the amount of cementing cement slurry needs to consider the volume of the well section from the window position to the top of the horizontal well in the key layer with blind plugs and drillable bridge plugs at 13 locations, so as to achieve high-strength sealing of the string below the forging and washing position 16 of the production casing completion string of the horizontal well in the key layer, so as to achieve complete sealing of the weakened zone in the key layer, which is convenient for subsequent fracturing construction of the horizontal well in the coal seam roof.

[0077] The construction of the deflection section and the horizontal section adopts a rotary guide + straight screw drill tool combination for drilling, which can meet the drilling requirements of high deflection rate, quickly complete the construction of the deflection section + horizontal section, and realize the drilling of the deflection section + horizontal section in one trip, thereby improving drilling efficiency.

[0078] Ensuring that the horizontal section is controlled within the roof stratum adjacent to the coal seam primarily utilizes a wellbore trajectory control method based on logging while drilling (LWD), comprehensive mud logging, and multi-point coal exploration. When the LWD gamma value is between 50 and 100 API, the lateral resistivity is less than 50 Ω.m, the comprehensive mud logging indicates slow drilling, the gas logging total hydrocarbon value is between 0.5% and 2%, and the rock cuttings indicate mudstone, indicating that the trajectory is within the roof mudstone, composite drilling is performed according to the current trajectory. When the LWD gamma value is between 10 and 50 API, the lateral resistivity is between 50 and 800 Ω.m, the comprehensive mud logging indicates fast drilling, the gas logging total hydrocarbon value is between 2 and 60%, and the rock cuttings indicate coal cuttings, indicating that the trajectory is within the coal seam, directional drilling with deflection is required to enter and exit the coal seam. Subsequently, the coal seam is explored every 150 to 200 meters of drilling, and directional drilling is performed with deflection. Coal exploration is considered complete when coal is encountered, and the wellbore is then increased in deflection to exit the coal seam. Comprehensively utilize logging while drilling, comprehensive mud logging, and multi-point coal exploration methods to ensure that the horizontal section trajectory is controlled within the range of 0~2m from the roof.

[0079] Step 11: Staged fracturing of horizontal wells in the coal seam roof (see Figure 5 ).

[0080] Specifically, staged hydraulic fracturing of the coal seam roof is carried out using a combination of pumped bridge plugs and perforations with bare casing and multi-stage clustered ball-dropping for temporary plugging. This establishes communication between the roof and the coal seam and creates channels for coal seam gas seepage. Staged fracturing utilizes a high displacement of 8-14 m³, a high fluid volume of 800-1200 m³ / stage, a fracturing fluid system of clean water and quartz sand, and a multi-stage clustered ball-dropping temporary plugging process. This achieves uniform coal seam transformation, expands the fracturing range, and significantly improves coal seam permeability.

[0081] The multi-stage clustered ball-throwing temporary plugging process has a stage spacing of 30-40m, 2-3 clusters of perforations in each stage, a cluster spacing controlled at 15-20m, a perforation of 1m per cluster, a hole density of 10-16 holes / m, vertical downward perforations, and a deep-penetrating bullet with an effective penetration depth of ≥1200mm. After the first cluster is fracturing, 10-16 low-temperature temporary plugging PGA degradable fracturing balls are put in to temporarily plug the first cluster, and a second cluster is fracturing. After the second cluster is fracturing, 10-16 low-temperature temporary plugging PGA degradable fracturing balls are again put in to temporarily plug the second cluster, and a third cluster is fracturing to achieve uniform and efficient coal seam transformation.

[0082] The described coal seam roof segmented hydraulic fracturing construction achieves no interference with the upper key layer fracturing. After the upper key layer fracturing is completed, blind plugging and drillable bridge plug 13 sealing and cement sealing are performed. The coal seam roof horizontal well is completely in a closed space during fracturing, so that the key layer and the coal seam roof horizontal well fracturing construction do not affect each other.

[0083] Step 12: Construction of horizontal well drilling bridge plug in coal seam roof.

[0084] Specifically, after the fracturing is completed, the ball cage soluble bridge plug 14 is - The dissolution is completed under the action of the fracturing fluid, and the blind drillable bridge plug 13 of the horizontal well on the coal seam roof needs to be drilled out to achieve the connection of each segment of the horizontal well and complete the connection of the three-level seepage channel of the coal seam-fracturing crack-wellbore.

[0085] Step 13: Installation of drainage equipment and drainage construction (see Figure 6 ).

[0086] Screw pumps 20, gas anchors 21, and remote control systems are installed in vertical drainage and production wells, and production wellheads are installed in horizontal wells. Remote drainage management is implemented according to a refined drainage work system. Vertical wells produce water and gas, while horizontal wells produce only gas without water. This allows for dual-wellhead gas production in both vertical and horizontal wells, significantly increasing gas production in the well group.

[0087] The refined drainage and production work system is mainly divided into drainage and pressure reduction stage, critical gas production stage, gas volume increase stage, stable gas production stage and gas volume attenuation stage, which controls the bottom hole flow pressure and casing pressure to avoid sand and powder spitting out of the formation and blocking the seepage channel.

[0088] In this embodiment, the foundation well is composed of a double-step horizontal well foundation well first opening cementing cement ring 5 and a double-step horizontal well foundation well second opening cementing cement ring 6. The depth of the double-step horizontal well foundation well first opening cementing cement ring 5 is less than the double-step horizontal well foundation well second opening cementing cement ring 6, and is sleeved on the double-step horizontal well foundation well second opening cementing cement ring 6.

[0089] The key layer horizontal well includes a horizontal section of the key layer horizontal well and a cementing cement ring 11 on its upper portion. The horizontal section of the key layer horizontal well and the cementing cement ring 11 on its upper portion are sleeved in the second cementing cement ring 6 of the double-step horizontal well foundation well, and the overlapping portion has a length of 150m to 200m.

[0090] The vertical distance between the coal seam roof horizontal well and the key layer horizontal well is d, and the coal seam roof horizontal well includes a three-well cementing cement ring 18 of the coal seam roof horizontal well;

[0091] The drainage vertical well includes a cave 4 and a first drainage vertical well cementing cement ring 23 and a second drainage vertical well cementing cement ring 24. The first drainage vertical well cementing cement ring depth 23 is less than the second drainage vertical well cementing cement ring 24, and is sleeved on the second drainage vertical well cementing cement ring 24.

[0092] In this embodiment, although the above methods are illustrated and described as a series of actions for simplicity of explanation, it should be understood and appreciated that these methods are not limited by the order of the actions, because according to one or more embodiments, some actions may occur in a different order and / or concurrently with other actions from the illustrations and descriptions herein or not illustrated and described herein but understandable to those skilled in the art.

[0093] Note that references in the specification to "one embodiment," "an embodiment," "example embodiment," "some embodiments," etc., indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment may include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it would be within the knowledge of those skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments, whether or not explicitly described.

[0094] The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for synchronously controlling coal seam gas and hard roof rock burst, characterized in that: include: Construct a foundation well and a vertical drainage well; Based on the foundation well, a key layer horizontal well and a coal seam roof horizontal well are constructed. The key layer horizontal well extends from the foundation well to the drainage vertical well in the key layer of the area to be treated; the coal seam roof horizontal well extends from the foundation well to the drainage vertical well in the coal seam roof, and is connected to the drainage vertical well; Performing staged fracturing in the horizontal well of the key layer, and performing fracturing in the horizontal well of the coal seam roof after the staged fracturing in the horizontal well of the key layer; The blind plug for fracturing in the key layer horizontal well can be drilled with a bridge plug (19) and / or cement to seal it before drilling and fracturing the coal seam roof horizontal well.

2. The method for synchronously controlling coal seam gas and hard roof rock burst according to claim 1, characterized in that: include: The foundation well adopts a two-opening wellbore structure, comprising: a first-opening cementing ring (11) of a double-step horizontal well foundation well, and a second-opening cementing ring (12) of a double-step horizontal well foundation well. The first-opening cementing ring (11) of the double-step horizontal well foundation well is less deep than the second-opening cementing ring (12) of the double-step horizontal well foundation well, and is sleeved on the second-opening cementing ring (12) of the double-step horizontal well foundation well.

3. The method for synchronously controlling coalbed gas and hard roof rock burst according to claim 1, characterized in that: The key layer horizontal well comprises a horizontal section of the key layer horizontal well and a cementing cement ring (17) on its upper portion, and the horizontal section of the key layer horizontal well and the cementing cement ring (17) on its upper portion are sleeved in a second opening cementing cement ring (12) of a double-step horizontal well foundation well.

4. The method for synchronously controlling coal seam gas and hard roof rock burst according to claim 1, characterized in that: The drainage vertical well comprises a cave (10), a first-opening cementing ring (29) of the drainage vertical well, and a second-opening cementing ring (30) of the drainage vertical well. The first-opening cementing ring (29) of the drainage vertical well has a depth less than that of the second-opening cementing ring (30) of the drainage vertical well, and is sleeved on the second-opening cementing ring (30) of the drainage vertical well.

5. The method for synchronously controlling coal seam gas and hard roof rock burst according to claim 1, characterized in that: Before the staged fracturing operation in the horizontal well of the key layer, the isolation type staged collar accessories are drilled out, and the key layer is transformed by pumping bridge plugs and perforating in combination with bare casing staged multi-cluster temporary plugging and ball throwing fracturing. The fracturing operation adopts a large displacement of 14-18 m³, a large fluid volume of 800-1200 m³ / stage, a high viscosity water-based fracturing fluid system, and a multi-stage clustered ball throwing temporary plugging process; The multi-stage clustered ball-throwing temporary plugging process has a stage spacing of 30-40 m, 2-3 clusters of perforations in each stage, a cluster spacing controlled at 20-25 m, a perforation density of 1 m per cluster, a perforation density of 10-16 holes / m, a 60° spiral perforation pattern, a large-aperture bullet, and a perforation aperture ≥14 mm; after fracturing the first cluster, 10-16 low-temperature temporary plugging PGA degradable fracturing balls are dropped to temporarily plug the first cluster, and a second cluster is fracturing; after fracturing the second cluster, 10-16 low-temperature temporary plugging PGA degradable fracturing balls are again dropped to temporarily plug the second cluster, and a third cluster is fracturing.

6. The method for synchronously controlling coal seam gas and hard roof rock burst according to claim 1, characterized in that: The coal seam roof horizontal well staged fracturing construction adopts pumping bridge plug and perforation combined with light casing multi-stage cluster ball throwing temporary plugging method to perform staged hydraulic fracturing of the coal seam roof; complete the communication between the roof and the coal seam, and establish the coal seam gas seepage channel; The staged fracturing operation adopts a large displacement of 8-14 m³, a large fluid volume of 800-1200 m³ / stage, a fracturing fluid system of clean water and quartz sand, and a multi-stage clustered ball-dropping temporary plugging process; The multi-stage clustered ball-throwing temporary plugging process has a stage spacing of 30-40 m, 2-3 clusters of perforations in each stage, a cluster spacing controlled at 15-20 m, a perforation of 1 m per cluster, a perforation density of 10-16 holes / m, vertical downward perforation, and a deep-penetrating bullet with an effective penetration depth of ≥1200 mm. After the first cluster is fracturing, 10-16 low-temperature temporary plugging PGA degradable fracturing balls are dropped to temporarily plug the first cluster, and a second cluster is fracturing. After the second cluster is fracturing, 10-16 low-temperature temporary plugging PGA degradable fracturing balls are dropped again to temporarily plug the second cluster, and a third cluster is fracturing.

7. The method for synchronously controlling coalbed gas and hard roof rock burst according to claim 1, characterized in that: The foundation well adopts a two-opening wellbore structure. The first opening of the foundation well is drilled to 20 m below the bedrock and the cementing cement slurry is returned to the ground to obtain the cement ring (11) of the first opening of the double-step horizontal well foundation well. The landing point of the second opening of the foundation well is set at the vertical middle position in the key layer. The cementing cement is returned to the ground to obtain the cement ring (12) of the second opening of the double-step horizontal well foundation well.

8. The method for synchronously controlling coalbed gas and hard roof rock burst according to claim 7, characterized in that: The acoustic amplitude and acoustic variable density cementing quality logging method is used to accurately detect the uncemented section of the production casing of the horizontal well in the key layer. The acoustic amplitude of the first interface interpreted by the logging is greater than 30%, and the formation wave of the second interface is weak and difficult to identify, which is the uncemented section. The position 2 to 3 m above the uncemented position detected by the logging is selected as the milling position of the production casing completion string section of the horizontal well in the key layer (22); A window is opened from 2 m below the inclination point to 20 m above the inclination point of the foundation well, and the casing section milling of the foundation well second opening technology is carried out, with a section milling length of 22 m. The drilling of the coal seam roof horizontal well includes side drilling construction, inclination section and horizontal section construction. At the window opening position, the side drilling construction is carried out by lowering the well inclination and azimuth. After completing the side drilling and continuing to drill 40~100 m, the rotary guide and straight screw drill tool combination tool is lowered to carry out the inclination section and horizontal section construction. After drilling is completed, the production casing is lowered and cementing is carried out to obtain the cement ring of the coal seam roof horizontal well third opening (24).

9. The method for synchronously controlling coal seam gas and hard roof rock burst according to claim 7, characterized in that: In the construction of the key layer horizontal well, after the horizontal section is drilled with the foundation well as the foundation, a production casing completion string (13) of the key layer horizontal well is lowered, and an isolation type grading collar (14) is set in the production casing completion string (13) of the key layer horizontal well, and the distance from the bottom position of the second technical casing of the foundation well is 150~200m. The horizontal section of the key layer horizontal well and the upper 150~200m are cemented to form a cement ring (17) of the horizontal section and the upper part thereof. The outer annulus (18) of the production casing completion string from the isolation type grading collar (14) to the wellhead is not cemented, forming an uncemented production casing completion string section (22) of the key layer horizontal well.

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