A method for optimizing and accelerating drilling of a horizontal section of a horizontal well for shale gas

Abstract

The present application provides a horizontal well horizontal section drilling optimization and speed-up method of shale gas, relates to the field of oil and gas exploration and development, and comprises the following steps: determining a target box of a horizontal well and optimizing a wellbore trajectory of the horizontal well before drilling; and drilling the horizontal section according to the target box and the wellbore trajectory of the horizontal section and optimizing horizontal well horizontal section drilling parameters and process measures while drilling. The horizontal well horizontal section drilling optimization and speed-up method of shale gas can improve the rate of penetration of the horizontal section, reduce the number of trips and the drilling cycle.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration and development, and in particular to a method for optimizing and accelerating the drilling of horizontal sections in shale gas wells. Background Technology

[0002] As oil and gas exploration and development continues to advance towards deeper, more unconventional, offshore, and lower-lying areas, unconventional oil and gas has become an important replacement resource for conventional oil and gas. Shale gas, belonging to unconventional oil and gas resources, mainly refers to natural gas resources contained in shale formations, which differ significantly from conventional oil and gas resources in terms of sedimentary conditions, structural characteristics, and extraction methods. Drilling still faces challenges such as high horizontal run counts, low "one-run" ratios, and long drilling cycles, hindering the economic viability of shale gas development.

[0003] Statistical analysis of a large number of completed well histories revealed that the main geological and engineering factors restricting the "one-trip drilling" of horizontal sections in existing shale gas wells include: ① failure of downhole measurement and control tools (including rotary steerable drilling, MWD, LWD, and other downhole measurement and control tools); ② low mechanical drilling speed of PDC drill bits for rock breaking; ③ failure of downhole motors; ④ other complex downhole conditions such as lost circulation and stuck pipe. Among these, reasons ① and ② account for approximately 80% of the reasons for starting drilling in the third horizontal section, and are the main reasons restricting the "one-trip drilling" of horizontal sections in shale gas wells.

[0004] To address the frequent failures of downhole monitoring and control tools in horizontal sections, drilling engineers have developed a series of high-performance monitoring and control tools and systems, including rotary valve MWD, dual-battery systems, Baker Hughes Auto-Track Curve rotary steering, Schlumberger Power Drive Archer, and Power Drive Orbit rotary steering systems. These technologies have, to some extent, solved the problems of instrument signal loss and short tool life caused by plugging materials. Meanwhile, to address the low mechanical drilling speed of PDC drill bits in horizontal sections, measures such as drill bit model optimization, enhanced drilling parameters, and the development of drilling technology templates have been implemented based on extensive well history data. These measures have significantly improved the average mechanical drilling speed and the longest footage per run in horizontal sections.

[0005] The aforementioned technical measures mainly focus on upgrading equipment, optimizing drill bits, and strengthening parameters, neglecting the impact of severe downhole vibration induced by geological conditions and engineering measures during horizontal drilling on drilling efficiency. Downhole vibration during drilling mainly manifests in three forms: longitudinal, lateral, and torsional (stick-slip) vibration of the drill bit and drill string. Appropriate vibration can reduce wellbore friction resistance and improve drill bit rock-breaking efficiency and increase mechanical drilling speed. However, severe downhole vibration induced by formation heterogeneity, wellbore friction, drill bit wear, and uneven stress on the drill string can cause numerous hazards to drilling operations, including: ① Severe vibration reduces drill bit rock-breaking efficiency and decreases drill bit mechanical drilling speed; ② Severe vibration accelerates drill bit wear, even causing drill bit cutting teeth to break or fracture; ③ Severe vibration increases the probability of downhole monitoring and control tool failure and reduces tool lifespan; ④ Severe vibration accelerates drill string fatigue and can even induce complex downhole accidents such as drill string breakage. Given that downhole vibration is unavoidable during drilling, and that severe downhole vibration increases the probability of failure of monitoring and control tools (MCWWMs), oilfield service companies such as Schlumberger and Baker Hughes widely equip their MWDWMs (rotary steerable drilling tools, MWD, LWD, etc.) with triaxial accelerometers and speed sensors. These sensors measure, store, and upload data in real time during drilling, recording the intensity of different types of downhole vibration and the corresponding cumulative time for different vibration levels. Based on data from 232 downhole vibration measurement and tool usage studies, Baker Hughes found that severe downhole vibration accounts for 29% of MWD / LWD failures during drilling, and that the greater the amplitude of drill string vibration, the higher the probability of MWDWM failure within a short period. In addition to considering the probability of MWDWM failure at different vibration levels over cumulative time, Schlumberger also considered the impact of instantaneous severe impacts during drilling on the stability of MWDWMs, assuming the MWDWMs are subjected to severe vibration impacts exceeding 50 x 9.8 m / s² per second. 2 The number of times (CPS, counts per second) is used as an indicator of the failure risk of measurement and control tools while drilling. It is based on the fact that the downhole measurement and control instrument experiences severe vibration and impact intensity exceeding 50 x 9.8 m / s per second per drilling pass during the drilling process. 2 Based on the cumulative number of failures, the failure risk of the drilling monitoring and control tool is divided into four risk levels: low (0), medium (1), high (2), and extremely prone to failure (3).

[0006] However, the aforementioned vibration reduction measures are mainly aimed at homogeneous reservoirs such as the North American shale gas field and the Permian, Eagle Ford, and Bakken shale gas fields. For other shale gas fields, the effects of these measures are not ideal. This is especially true for heterogeneous reservoirs where the target layer consists of minerals such as quartz, plagioclase, carbonate rocks, clay, and pyrite, with a target box thickness ranging from 1 to 3 meters. These heterogeneous reservoirs exhibit significant vertical fluctuations in reservoir mineral composition and formation element content, leading to substantial variations in formation rock strength due to these mineral composition fluctuations. During horizontal well drilling, the wellbore trajectory adjustment is determined by the geological steering engineer based on geological requirements. From the perspective of later well completion and fracturing, geological steering engineers prefer reservoirs with better "brittleness," easier fracture extension, higher silica content, richer formation carbon content, and higher formation GR values. However, during actual horizontal well drilling, errors in geological modeling, geological structures such as faults, depressions, and uplifts, as well as the "zero deviation" of measurement-while-drilling tools, often lead to deviations in wellbore trajectory control. After the horizontal wellbore trajectory exits the target box, the geosteering engineer often issues instructions requiring the on-site directional engineer to readjust the wellbore trajectory back into the target box. During the wellbore trajectory adjustment process, the drill bit will traverse heterogeneous reservoirs. The rock strength of the cutting formation on both sides of the drill bit differs significantly, which can easily induce severe downhole torsion (stick-slip) and lateral vibration, leading to a decrease in the mechanical rate of penetration (MRP) of the drill bit, rapid drill bit wear, and failure of downhole monitoring and control (WWD) instruments. When the same model of PDC drill bit is drilling in heterogeneous formations in the horizontal section, the mechanical rate of penetration is even lower, the drilling footage is shorter, and the wear is more severe. At the same time, failure of downhole monitoring and control tools (rotary steerable drilling, MWD, LWD, etc.) often leads to tripping out of the well.

[0007] In view of this, based on years of experience in production design in this and related fields, the inventor has designed a method for optimizing and accelerating horizontal section drilling in shale gas wells through repeated experiments, in order to solve the problems existing in the prior art. Summary of the Invention

[0008] The purpose of this invention is to provide a method for optimizing and accelerating horizontal well drilling in shale gas, which can improve the mechanical drilling rate in the horizontal section, reduce the number of drilling trips, and shorten the drilling cycle.

[0009] To achieve the above objectives, this invention proposes a method for optimizing and accelerating the drilling of the horizontal section of a shale gas well, wherein the method includes:

[0010] Determine the target box of the horizontal well and optimize the wellbore trajectory of the horizontal section of the horizontal well before drilling;

[0011] Drill the horizontal section according to the wellbore trajectory of the target box and the horizontal section of the horizontal well, and optimize the drilling parameters and process measures of the horizontal section of the horizontal well while drilling.

[0012] Compared with the prior art, the present invention has the following features and advantages:

[0013] The present invention proposes a method for optimizing and accelerating horizontal drilling in shale gas horizontal wells. By pre-drilling optimization of the wellbore trajectory of the horizontal section, and then combining this with optimization of drilling parameters and process measures, the wellbore trajectory can effectively avoid the drill bit crossing heterogeneous reservoirs, thereby reducing the drilling footage and downhole vibration intensity when crossing heterogeneous reservoirs. Ultimately, this achieves the goal of increasing the mechanical drilling rate of the horizontal section, reducing the number of drilling trips and the drilling cycle. Attached Figure Description

[0014] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. Those skilled in the art, guided by the teachings of this invention, can select various possible shapes and proportions to implement the invention according to specific circumstances.

[0015] Figure 1 The flowchart shows the drilling optimization and acceleration method for horizontal sections of shale gas wells proposed in this invention.

[0016] Figure 2 This is a schematic diagram illustrating the wellbore trajectory adjustment when the drill bit is positioned above the upward-tilting box in this invention;

[0017] Figure 3 This is a schematic diagram illustrating the wellbore trajectory adjustment when the drill bit is positioned above the downward-tilting box in this invention.

[0018] Figure 4 This is a schematic diagram illustrating the wellbore trajectory adjustment when the drill bit is positioned below the upward-tilting box in this invention;

[0019] Figure 5 This is a schematic diagram illustrating the wellbore trajectory adjustment when the drill bit is positioned below the downward-tilting box in this invention.

[0020] Figure 6 This is a vertical distribution diagram of formation rock strength in a pilot well according to an embodiment of the present invention;

[0021] Figure 7 This is a vertical distribution diagram of formation element content in a pilot well according to an embodiment of the present invention;

[0022] Figure 8 This is a diagram showing the distribution of the horizontal section well inclination angle with well depth in one embodiment of the present invention;

[0023] Figure 9This is a diagram showing the percentage of major elements in the horizontal section of the strata in one embodiment of the present invention.

[0024] Figure 10 This is the distribution of compressive strength of rocks in a horizontal section of the strata in one embodiment of the present invention. Detailed Implementation

[0025] The details of the present invention can be more clearly understood by referring to the accompanying drawings and the description of specific embodiments. However, the specific embodiments of the present invention described herein are for illustrative purposes only and should not be construed as limiting the invention in any way. Under the teachings of this invention, those skilled in the art can conceive of any possible modifications based on the invention, and these should all be considered to fall within the scope of the invention.

[0026] This invention proposes a method for optimizing and accelerating the drilling of horizontal sections in shale gas wells, such as... Figure 1 As shown, the drilling optimization and speed-up methods for the horizontal section of this horizontal well include:

[0027] Determine the target box of the horizontal well and optimize the wellbore trajectory of the horizontal section of the horizontal well before drilling;

[0028] Drill the horizontal section according to the wellbore trajectory of the target box and the horizontal section of the horizontal well, and optimize the drilling parameters and process measures of the horizontal section of the horizontal well while drilling.

[0029] The present invention proposes a method for optimizing and accelerating horizontal drilling in shale gas horizontal wells. By pre-drilling optimization of the wellbore trajectory of the horizontal section, and then combining this with optimization of drilling parameters and process measures, the wellbore trajectory can effectively avoid the drill bit crossing heterogeneous reservoirs, thereby reducing the drilling footage and downhole vibration intensity when crossing heterogeneous reservoirs. Ultimately, this achieves the goal of increasing the mechanical drilling rate of the horizontal section, reducing the number of drilling trips and the drilling cycle.

[0030] In an optional embodiment of the present invention, the target box is determined based on the vertical distribution characteristics of rock mineral composition and rock strength of the drilling platform where the horizontal well is located, and the lateral distribution patterns and characteristics of the geological structure of the reservoir of the horizontal well.

[0031] In one optional example of this implementation, the core and logging data of the drilling platform's pilot well are used to obtain the vertical distribution characteristics of the rock mineral composition and rock strength of the drilling platform.

[0032] It should be noted that the pilot well is the first well drilled on the drilling platform using a vertical well design.

[0033] In one optional example of this implementation, the reservoir geological model is completed using the three-dimensional seismic data of the drilling platform and its reservoir, and the lateral distribution pattern and characteristics of the geological structure of the drilling platform's reservoir are determined.

[0034] In an optional embodiment of the present invention, the preferred rule for the wellbore trajectory of the horizontal section of the pre-drilling horizontal well is that the wellbore trajectory avoids traversing well sections with drastic fluctuations in formation mineral composition and formation rock strength. This ensures that the wellbore trajectory passes through high-silica homogeneous reservoirs as much as possible.

[0035] In an optional embodiment of the present invention, the drilling parameters and process measures for the horizontal section of the horizontal well are optimized during drilling, including:

[0036] During well drilling, determine whether the drill bit has entered the target box in the horizontal section;

[0037] After determining the target box in the horizontal section where the drill bit enters, obtain the current well depth, inclination angle α, and formation dip angle β of the target box;

[0038] The drill bit is drilled horizontally within the target box. The drill bit position is determined during drilling, and the wellbore trajectory is adjusted according to the drill bit position to ensure that the drill bit is within the target box.

[0039] In one optional example of this implementation, if it is determined during well drilling that the drill bit has not yet entered the target box, the wellbore trajectory is adjusted and drilling continues until the drill bit enters the target box.

[0040] In one optional example, during horizontal drilling, if it is determined that the drill bit is inside the target box, the time-depth seismic data is iterated and the geological model is updated in a timely manner based on the actual vertical depth of the drill bit. This allows for prediction of changes in the geological structure of the horizontal section, and the wellbore trajectory is adjusted in advance to ensure that the drill bit drills inside the target box.

[0041] In another alternative example, if the drill bit is determined to be outside the target box during horizontal drilling, drilling parameters are adjusted.

[0042] Furthermore, the process of adjusting drilling parameters includes:

[0043] Determine if the current mud pump pressure has reached the specified safety limit. If not, increase the mud pump discharge rate in increments of 0.5 L / s until the mud pump pressure reaches the specified safety limit. Then, determine if the current drilling pressure is ≤80 KN. If not, continuously decrease the drilling pressure to 80 KN or below in increments of 10 KN. Next, determine if the drilling rig is using a top drive. If a top drive is used, increase the top drive speed to 110-120 r / min. If a top drive is not used, adjust the rotary table speed to above 80 r / min.

[0044] Preferably, after adjusting the drilling parameters, the wellbore trajectory adjustment method is determined based on the relative position of the drill bit and the target housing, and the current well depth and inclination angle α of the drill bit. This adjustment method ensures that the drill bit re-drills into the target housing. Specifically, it is first determined whether to use a rotary steering system or a downhole motor, then whether to enter the target housing using an inclination-increasing or inclination-decreasing method, and finally, the inclination angle for continued stable drilling after entering the target housing is determined. Through the optimization of drilling parameters and process measures during trajectory adjustment, the goal of reducing downhole vibration intensity and decreasing the drilling length in heterogeneous reservoirs is achieved. The specific implementation steps are as follows:

[0045] After completing the drilling parameter adjustment, determine if the drill bit is above the target box. If so, determine if the current well inclination angle α ≥ 90° is valid. If valid, the drill bit is above the upward-inclined target box. Determine if a rotary steering system is used. If so, use the rotary steering system to descend the inclination angle at (90 + β - (2 ~ 4))° until the drill bit re-enters the target box. It is recommended to use a large angle difference to adjust the wellbore trajectory to reduce the drilling footage in heterogeneous formations. If a downhole motor is used, use the downhole motor to descend the inclination angle at 180° for 0.3 ~ 0.5m, followed by compound drilling. Determine if the drill bit has entered the target box. If not, repeat the process with the downhole motor until the drill bit enters the target box. Once the drill bit has entered the target box, control the well inclination angle α ≤ (90 + β ± 1)° for stable drilling. See [link to relevant documentation]. Figure 2 .

[0046] If the drill bit is above the target box and the current well inclination angle α < 90°, then the drill bit is above the downward-sloping target box. Determine whether to use a rotary steering system. If so, the rotary steering system should be used to descend the well inclination angle at (90-β-(2~4))° until the drill bit re-enters the target box. It is recommended to use a large angle difference to adjust the wellbore trajectory to reduce the drilling footage in heterogeneous formations. If a downhole motor is used, the downhole motor should be used to directional descend the well inclination angle at 180° for 0.3~0.5m, followed by compound drilling. Determine whether the drill bit has entered the target box. If not, the downhole motor should repeat the process until the drill bit enters the target box. Once it is confirmed that the drill bit has entered the target box, control the well inclination angle α ≤ (90-β±1)° for stable drilling. See Figure 3 .

[0047] If the drill bit is determined to be below the target box, check if the current well inclination angle α ≥ 90° holds true. If it does, the drill bit is below the upward-sloping target box. Check if a rotary steering system is used. If so, the rotary steering system increases the inclination angle at (90 + β + (2 ~ 4))° until the drill bit re-enters the target box. It is recommended to use a large angle difference to adjust the wellbore trajectory to reduce the drilling footage in heterogeneous formations. If a downhole motor is used, the downhole motor increases the inclination angle at 0° for 0.3 ~ 0.5 m, then performs compound drilling. Check if the drill bit has entered the target box. If not, the downhole motor repeats this process until the drill bit enters the target box. Once the drill bit has entered the target box, control the well inclination angle α ≤ (90 + β ± 1)° for stable inclination drilling. See Figure 4 .

[0048] When the drill bit is below the target box and the current well inclination angle α < 90°, the drill bit is below the downward-sloping target box. Determine whether to use a rotary steering system. If so, increase the inclination angle with (90-β+(2~4))° until the drill bit re-enters the target box. It is recommended to use a large angle difference to adjust the wellbore trajectory to reduce drilling footage in heterogeneous formations. If a downhole motor is used, increase the inclination angle with a tool face angle of 0° for 0.3~0.5m, then perform compound drilling. Determine if the drill bit has entered the target box. If not, repeat the process with the downhole motor until the drill bit enters the target box. Once the drill bit has entered the target box, control the inclination angle α ≤ (90-β±1)° for stable drilling. See [link to relevant documentation]. Figure 5 .

[0049] Please refer to Figures 1 to 10 The present invention will now describe in detail the method for optimizing and accelerating the drilling of horizontal sections in shale gas wells, with reference to an embodiment.

[0050] This embodiment uses a horizontal well on a drilling platform in the southern Sichuan region (Southwest Oil and Gas Field) as a simulated implementation case. The drilling platform employs a bidirectional arrangement of 6-12 horizontal wells (preferably 8). Reservoir geological modeling is completed using 3D seismic data. The first well on the drilling platform is drilled vertically (also known as a pilot well) to penetrate the reservoir section and complete coring operations. After coring, the vertical well section is backfilled, and then the horizontal well build-up section and horizontal section drilling operations are completed. Specifically:

[0051] Step 1: Pre-drilling selection of wellbore trajectory for the horizontal section of the horizontal well;

[0052] Step 1-1: Using the core and logging data from the Longmaxi Formation pilot well of the drilling platform, obtain the vertical distribution characteristics of the mineral composition and rock strength of the Longmaxi Formation rocks on the drilling platform.

[0053] Steps 1-2: Using the 3D seismic data of the Longmaxi Formation reservoir from the drilling platform, complete the geological modeling of the Longmaxi Formation reservoir and determine the location of Longyi 1 in the Longmaxi Formation from the drilling platform.2 -Longyi1 1 The vertical depth of small layers, the lateral distribution patterns and characteristics of geological structures such as faults, uplifts, and depressions;

[0054] Steps 1-3, combined with the guide well 1 2 -Longyi1 1 The stratigraphic composition and vertical distribution characteristics of rock mineral components and rock strength of the group, and Long-1 2 -Longyi1 1 The vertical depth of the sub-layers and the lateral distribution of geological structures (e.g., the distribution patterns of reservoir porosity, organic carbon, and gas content curves) are considered when selecting the optimal wellbore trajectory for the horizontal section of the Longyi 1 well. 2 -Longyi1 1 The target reservoir is a small layer with high silica content and homogeneous rock strength. Combined with the vertical depth of the target reservoir and the lateral distribution and characteristics of geological structures such as faults, uplifts, and depressions, the horizontal well trajectory is selected. In addition, the well trajectory avoids well sections that cross the formation mineral composition and formation rock strength with drastic fluctuations.

[0055] Step 2: Optimization of drilling parameters and process measures for the horizontal section of the horizontal well while drilling; taking the horizontal section of well Wei 202HHX-Y on this drilling platform as an implementation case, the target box A point of this well has a depth of 3250m, and the depth range of the horizontal section is 3250m-5250m. The distribution of well inclination angle, formation element content percentage, and formation rock strength with depth in the horizontal section is shown in the figure. Figures 7-9 Specifically,

[0056] Step 2-1: During the drilling process, determine whether the drill bit has entered the target box in the horizontal section. If it has not entered, adjust the trajectory and continue drilling until it enters the target box. The well depth of the target box A point is 3250m.

[0057] Step 2-2: After determining that the current wellbore trajectory has entered the target box in the horizontal section, obtain the current well depth, well inclination angle α, and formation dip angle β of the target box, where well inclination angle α = 78° and formation dip angle β = 7°;

[0058] In steps 2-3, the drill bit continues drilling in the horizontal section within the target box. The geological steering engineer iterates the time-depth seismic data and updates the geological model in a timely manner based on the actual vertical depth of the Longmaxi Formation sub-layers, predicts changes in the geological structure of the horizontal section, and adjusts the wellbore trajectory in advance to ensure that the drill bit drills within the target box. Specifically, as the drill bit continues drilling in the horizontal section, the well inclination angle slowly increases to 80°-83° at a depth of 3250m-3600m, and the wellbore trajectory remains within the target box. As drilling continues, the well inclination angle gradually decreases, dropping to 80.64° at a depth of 3666m.

[0059] Steps 2-4: During horizontal drilling, if the drill bit is determined to have exited the target enclosure, the geological steering engineer will adjust the wellbore trajectory using rotary steering or downhole motors to ensure the drill bit re-enters the target enclosure. This is in consideration of the target formation in the southern Sichuan shale gas region, Longyi 1. 2 -Longyi1 1 The heterogeneous vertical distribution of mineral components and rock strength in the sub-layers leads to severe torsion (stick-slip) and lateral vibration during the PDC drill bit's traversal of these heterogeneous reservoirs. This accelerates drill bit wear and increases the risk of failure for downhole monitoring and control tools (rotary steerable drilling, MWD, LWD, etc.), resulting in premature tripping, increased horizontal runs, and longer drilling cycles. Specifically,

[0060] When the well depth reached 3666m, the well inclination angle decreased to 80.64°. The percentage of silicon in the formation changed significantly with increasing well inclination. Geological steering determined the well trajectory to exit the target box and enter Longyi 1. 1 The drill bit is located below the downward-dipping target box in the lower part of the Wufeng Formation.

[0061] Once it is confirmed that the drill bit has exited the target box and is located below the downward-sloping target box, the geological steering engineer issues a well trajectory adjustment command, and rotates the steering to increase the inclination of the well at a target well inclination angle of 85° (90-β+2, β=7°).

[0062] Rotary steerable drilling was carried out to a depth of 3754m, with an inclination angle of 85.2°. Based on the changes in formation element content percentages, it was determined that the drill bit had returned to the target box. The geological steering issued a well trajectory adjustment command, and the rotary steerable continued drilling at a stable inclination angle of 82°-84° (90-β±1, β=7°). Post-drilling horizontal logging data showed... Figure 8 After the drill bit exits the target box, it returns to the formation drilled by the target box. The formation is highly heterogeneous with large variations in rock strength. During the trajectory adjustment process, the downhole twisting (stick-slip) and lateral vibration are severe. After the drill bit is pulled out, the cutting teeth of the drill bit wear is obvious.

[0063] Upon receiving the command, the rotary steering system rapidly reduced the inclination angle during drilling, lowering it to 81.65° at a depth of 3789m. Subsequently, stable drilling continued in the 3789m-4850m section, with the actual inclination angle controlled between 80° and 83°. The wellbore trajectory remained consistently within the Longyi 1 borehole. 1 Inside the target container;

[0064] According to Longmaxi Group Longyi 1 1Based on the actual vertical depth of the Wufeng Formation sub-layers, iterative deep seismic data was used to update the geological model. It was predicted that a micro-uplift structure existed at a depth of 4950m in the Wei 202HX-Y horizontal well. Subsequently, the geological steering engineer issued a wellbore trajectory adjustment command in advance, starting from 4850m and slowly increasing the inclination angle with rotary steering. At a depth of 4950m, the inclination angle increased to 84.11°. Then, a command was issued to slowly decrease the inclination angle to the final depth of 5250m, reducing the inclination angle to 80.11°. By timely updating the geological model, predicting the geological structure of the horizontal section, and adjusting the wellbore trajectory in advance, although the inclination angle varied significantly between 4950m and 5250m, the wellbore trajectory remained within the target box.

[0065] This invention proposes a drilling optimization and acceleration method for horizontal sections of shale gas wells, fully considering the heterogeneous characteristics of the Longmaxi shale gas reservoir in southern Sichuan. From the perspective of balancing well completion, fracturing, and drilling optimization, it optimizes and accelerates drilling by pre-drilling selection of high-silica or high-GR reservoirs in the horizontal section, combined with optimized drilling parameters during drilling through heterogeneous reservoirs to reduce downhole vibration intensity. It also assists in rapid crossing with large "angle difference" (difference between wellbore trajectory and reservoir dip angle) to reduce drilling footage in heterogeneous sections. This achieves the goal of encountering reservoirs with better physical properties in the horizontal section while reducing the length of the drill bit crossing heterogeneous sections and downhole vibration intensity, ultimately improving the mechanical drilling rate in the horizontal section, reducing the number of trips, and shortening the drilling cycle.

[0066] The detailed explanations of the above embodiments are intended only to explain the present invention so as to facilitate a better understanding of the present invention. However, these descriptions should not be construed as limiting the present invention for any reason. In particular, the various features described in different embodiments can be arbitrarily combined with each other to form other embodiments. Unless there is an explicit description to the contrary, these features should be understood to be applicable to any embodiment, and not limited to the described embodiments.

Claims

1. A method for optimizing and accelerating drilling in the horizontal section of a shale gas well, characterized in that, The methods for optimizing and accelerating drilling in the horizontal section of a horizontal well include: The target box of the horizontal well is determined and the wellbore trajectory of the horizontal section of the horizontal well is optimized before drilling. Specifically, using core and logging data from the pilot well of the drilling platform where the horizontal well is located, the vertical distribution characteristics of the rock mineral composition and rock strength of the drilling platform are obtained. The target box is determined based on the vertical distribution characteristics of the rock mineral composition and rock strength of the drilling platform, and the lateral distribution patterns and characteristics of the geological structure of the reservoir in the horizontal well. The preferred rule for the wellbore trajectory of the horizontal section of the pre-drilling horizontal well is that the wellbore trajectory avoids crossing well sections where the mineral composition and rock strength of the formation fluctuate drastically. Drill the horizontal section according to the wellbore trajectory of the target box and the horizontal section of the horizontal well, and optimize the drilling parameters and process measures of the horizontal section of the horizontal well while drilling; including: During well drilling, determine whether the drill bit has entered the target box in the horizontal section; After determining that the drill bit has entered the target box in the horizontal section, the current well depth, inclination angle α, and formation dip angle β of the target box are obtained; Continue drilling the drill bit in the horizontal section within the target box, determine the position of the drill bit while drilling, and adjust the wellbore trajectory based on the drill bit position to ensure that the drill bit returns to the target box.

2. The method for optimizing and accelerating drilling in the horizontal section of shale gas wells as described in claim 1, characterized in that, Using the three-dimensional seismic data of the reservoir of the drilling platform, a reservoir geological model was completed to determine the lateral distribution pattern and characteristics of the geological structure of the reservoir of the drilling platform.

3. The method for optimizing and accelerating horizontal section drilling in shale gas wells as described in claim 1, characterized in that, If it is determined during the drilling process that the drill bit has not yet entered the target box, the wellbore trajectory is adjusted and drilling continues until the drill bit enters the target box.

4. The method for optimizing and accelerating drilling in the horizontal section of shale gas wells as described in claim 1, characterized in that, During horizontal drilling, if it is determined that the drill bit is inside the target box, the time-depth seismic data is iterated and the geological model is updated in a timely manner based on the actual vertical depth of the drill bit. The geological structure changes in the horizontal section are predicted, and the wellbore trajectory is adjusted in advance to ensure that the drill bit drills inside the target box.

5. The method for optimizing and accelerating drilling in the horizontal section of shale gas wells as described in claim 1, characterized in that, If, during horizontal drilling, it is determined that the drill bit is outside the target box, drilling parameters are adjusted.

6. The method for optimizing and accelerating drilling in the horizontal section of shale gas wells as described in claim 5, characterized in that, The process of adjusting the drilling parameters includes: Determine if the current mud pump pressure has reached the specified safety limit. If not, increase the mud pump discharge rate in increments of 0.5 L / s until the mud pump pressure reaches the specified safety limit. Then, determine if the current drilling pressure is ≤80 KN. If not, continuously decrease the drilling pressure to 80 KN or below in increments of 10 KN. Next, determine if the drilling rig is using a top drive. If a top drive is used, increase the top drive speed to 110-120 r / min. If a top drive is not used, adjust the rotary table speed to above 80 r / min.

7. The method for optimizing and accelerating drilling in the horizontal section of shale gas wells as described in claim 1, characterized in that, After completing the drilling parameter adjustment, the wellbore trajectory adjustment method is determined based on the relative position of the drill bit and the target box and the current well depth and inclination angle α of the drill bit. The adjustment method is used to ensure that the drill bit re-drills back into the target box.

8. The method for optimizing and accelerating horizontal section drilling in shale gas wells as described in claim 7, characterized in that, If the drill bit is above the target housing and the well inclination angle α ≥ 90°, then the drill bit is above the upward-sloping target housing.

9. The method for optimizing and accelerating drilling in the horizontal section of a shale gas well as described in claim 8, characterized in that, If the adjustment method is determined to be the use of a rotary steering system, the rotary steering system will drill at a target well inclination angle of (90+β-(2~4))° until the drill bit re-enters the target box.

10. The method for optimizing and accelerating drilling in the horizontal section of a shale gas well as described in claim 8, characterized in that, If the adjustment method is determined to be using a downhole motor, the downhole motor is used to directionally reduce the inclination and drill for 0.3~0.5m at a tool face angle of 180°, followed by compound drilling. After the compound drilling has reached a predetermined distance, it is determined whether the drill bit has entered the target box. The directional reduction drilling, compound drilling, and determination steps are repeated until it is determined that the drill bit has entered the target box.

11. The method for optimizing and accelerating drilling in the horizontal section of a shale gas well as described in claim 8, characterized in that, If the drill bit is above the target housing and the well inclination angle α < 90°, then the drill bit is above the downward-sloping target housing.

12. The method for optimizing and accelerating horizontal section drilling in shale gas wells as described in claim 11, characterized in that, If the adjustment method is determined to be the use of a rotary steering system, then the rotary steering system will drill at a target well inclination angle of (90-β-(2~4))° until the drill bit re-enters the target box.

13. The method for optimizing and accelerating horizontal section drilling in shale gas wells as described in claim 11, characterized in that, If the adjustment method is determined to be using a downhole motor, the downhole motor is used to directionally reduce the inclination and drill for 0.3~0.5m at a tool face angle of 180°, followed by compound drilling. After the compound drilling has reached a predetermined distance, it is determined whether the drill bit has entered the target box. The directional reduction drilling, compound drilling, and determination steps are repeated until it is determined that the drill bit has entered the target box.

14. The method for optimizing and accelerating drilling in the horizontal section of shale gas wells as described in claim 7, characterized in that, If the drill bit is located below the target housing and the well inclination angle α ≥ 90°, then the drill bit is positioned below the upward-sloping target housing.

15. The method for optimizing and accelerating drilling in the horizontal section of a shale gas well as described in claim 14, characterized in that, If the adjustment method is determined to be the use of a rotary steering system, then the rotary steering system will increase the drilling inclination at a target well inclination angle of (90+β+(2~4))° until the drill bit re-enters the target box.

16. The method for optimizing and accelerating drilling in the horizontal section of a shale gas well as described in claim 14, characterized in that, If the adjustment method is determined to be using a downhole motor, then the downhole motor is used to perform directional drilling with a tool face angle of 0° for 0.3~0.5m, followed by compound drilling. After the compound drilling has reached a predetermined distance, it is determined whether the drill bit has entered the target box. The directional drilling, compound drilling and determination steps are repeated until it is determined that the drill bit has entered the target box.

17. The method for optimizing and accelerating drilling in the horizontal section of shale gas wells as described in claim 7, characterized in that, If the drill bit is above the target housing and the well inclination angle α < 90°, then the drill bit is below the downward-sloping target housing.

18. The method for optimizing and accelerating drilling in the horizontal section of a shale gas well as described in claim 17, characterized in that, If the adjustment method is determined to be the use of a rotary steering system, then the rotary steering system will increase the drilling inclination at a target well inclination angle of (90-β+(2~4))° until the drill bit re-enters the target box.

19. The method for optimizing and accelerating drilling in the horizontal section of a shale gas well as described in claim 17, characterized in that, If the adjustment method is determined to be using a downhole motor, then the downhole motor is used to perform directional drilling with a tool face angle of 0° for 0.3~0.5m, followed by compound drilling. After the compound drilling has reached a predetermined distance, it is determined whether the drill bit has entered the target box. The directional drilling, compound drilling and determination steps are repeated until it is determined that the drill bit has entered the target box.

20. The method for optimizing and accelerating drilling in the horizontal section of a shale gas well as described in claim 9, 10, 15, or 16, characterized in that, Once it is determined that the drill bit has entered the target box, the drill bit is controlled to drill at a steady inclination angle α≤(90+β±1)°.

21. The method for optimizing and accelerating horizontal well drilling in shale gas as described in claims 12, 13, 18, or 19, characterized in that, Once it is determined that the drill bit has entered the target housing, the drill bit is controlled to drill at a steady inclination angle α≤(90 -β±1)°.

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