Safe drilling method when high and low pressure coexist in marine and continental facies

Abstract

The present invention provides a safe drilling method when high and low pressure coexist in marine and continental phases, and the safe drilling method when high and low pressure coexist in marine and continental phases comprises: step 1, using a composite salt strong inhibition drilling fluid system to start drilling; step 2, when drilling to a high-pressure fractured gas layer, using a fine pressure control device to monitor overflow in real time and increase the density of the drilling fluid; step 3, using a pressure control drilling technology to achieve safe drilling in a long open hole with a narrow pressure window; step 4, performing air release and pressure reduction to effectively release the pressure of the gas layer; step 5, taking special pressure-bearing squeezes to improve the pressure bearing capacity of the formation; step 6, performing special sand cleaning operations; step 7, using a high-wear-resistant PDC + high-performance screw to achieve rapid drilling through complex formations. The safe drilling method when high and low pressure coexist in marine and continental phases specifically solves the problem of safe drilling when high and low pressure coexist in marine and continental phases, and forms a set of comprehensive matching drilling technology for high and low pressure coexistence in marine and continental phases.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield development, and in particular to a safe drilling method when high and low pressure coexist in marine and terrestrial phases. Background Art

[0002] The porous reservoirs of the volcanic rock strata in the deep-earth engineering in western Sichuan are well developed, and the preliminary predicted reserve level is hundreds of billions, with huge gas reservoir potential. In order to achieve the special drilling of the target layer, the upper well section will bear more footage, and the "mixed drilling" of high and low pressure coexisting in the marine and terrestrial phases has become a normal design mode. The technical difficulties of drilling in the marine and terrestrial phases are mainly manifested in three points:

[0003] 1. High and low pressure leakage coexist

[0004] There are long open holes and multiple pressure systems with large differences in height. For example, the safety density window of the Xujiahe Formation to Leikoupo Formation section is narrow or even negative. There are many vertical oil and gas display layers in the continental strata, reservoir fractures and pores are well developed, and the well control risk is high, which poses new challenges to the fine pressure control drilling technology.

[0005] 2. Fault development, block drop and drill jam

[0006] The continental strata are unstable, with many blocks falling off in the well, and it is difficult to prevent the long open hole from getting stuck. For example, the second drilling of Gudian Well 1 encountered a reverse fault, and leakage occurred many times during the construction. The Xujiahe Formation strata broke and fell off quickly, causing the drill to get stuck and backfilled. Finally, the well was drilled to a depth of 4630.35m (Xu 2), and a technical temporary closure was implemented due to the difficulty of construction.

[0007] 3. Speed ​​up in high abrasive formations

[0008] For example, the thickness of the Xujiahe Formation to Xiaotangzi Formation in western Sichuan exceeds 2,000 m, with well-developed quartz sandstone and frequent interbedded sandstone and shale. The formation has poor drillability, low mechanical drilling speed, and difficulty in selecting drill bits. The construction of wells in the surveyed area and ultra-deep wells in the Pengzhou block shows that the drill bit failure rate of the Ziliujing Formation-Xujiahe Formation is high and the average mechanical drilling speed is low. Summary of the invention

[0009] The purpose of the present invention is to provide a safe drilling method when high and low pressures coexist in marine and terrestrial phases, which solves the problem of safe drilling when high and low pressures coexist in marine and terrestrial phases.

[0010] The object of the present invention can be achieved by the following technical measures: a safe drilling method when high and low pressure coexist in the sea and continent, the safe drilling method when high and low pressure coexist in the sea and continent comprises:

[0011] Step 1, start drilling using a composite salt strong inhibition drilling fluid system;

[0012] Step 2: When drilling into a high-pressure fractured gas layer, use precise pressure control equipment to monitor overflow in real time and increase the density of the drilling fluid;

[0013] Step 3: Use the controlled pressure drilling technology to achieve safe drilling in a long open hole with a narrow pressure window;

[0014] Step 4, deflate and reduce pressure to effectively release the gas layer pressure;

[0015] Step 5: Take special pressure-bearing and plugging measures to improve the pressure-bearing capacity of the formation;

[0016] Step 6, carry out special sand cleaning operation;

[0017] Step 7: Use highly wear-resistant PDC + high-performance screw to achieve rapid drilling through complex formations.

[0018] The purpose of the present invention can also be achieved by the following technical measures:

[0019] In step 1, the drilling fluid formula used is: upper well slurry + 0.1%-0.2% hydrolyzed potassium polyacrylate + 0.1-0.2% zwitterionic polymer coating agent + 0.5-1.0% polyanionic cellulose + 1-1.5% polyamine + 2-5% resin fluid loss reducer + 2-5% lignite fluid loss reducer + 1-2% ultrafine calcium carbonate + 1-3% temperature-resistant and saturated salt-resistant lubricant + 1-3% graphite solid lubricant + 2-3% multi-softening point asphalt + 1-3% modified paraffin plugging agent + 1~2% film-forming plugging agent + 5-7% potassium chloride + 0.5-0.8% quicklime + barite.

[0020] In step 2, a precise pressure-controlled precision flowmeter is used to detect changes in the outlet flow rate, determine overflow, and appropriately close the outlet valve to form wellhead back pressure, balance the formation pressure, prevent formation fluid from continuing to invade the wellbore, and keep the liquid level from rising; at the same time, a precise pressure-controlled MPD monitoring and control system is used to calculate the formation pore pressure and obtain the density of the well-killing fluid. The well-killing fluid inlet density is maintained through circulation and weighting, and the gas layer is stabilized after 1-2 weeks of circulation.

[0021] In step 3, the pressure-controlled drilling technology is used. The core technology is to accurately control the micro-balance of wellbore pressure through fine four-pressure profile reconstruction + ECD while-drilling prediction + wellhead back pressure, improve the advanced evaluation of downhole leakage risk and the ability of fine wellbore pressure control while drilling, and realize safe drilling of long open holes with narrow pressure windows.

[0022] In step 3, a detailed geomechanical profile is established based on the data from adjacent wells and seismic data, and a safe density window for the entire well section is determined. During the actual drilling process, the drilling fluid density is adjusted in real time based on the geological collapse and well leakage risk point prompts; ECD calculations are performed in real time to monitor and evaluate wellbore risks. The annular pressure of the operating well section is controlled, including drilling fluid density adjustment, displacement adjustment, and pressure control value adjustment, to maintain a slightly over-pressured wellbore for balanced drilling.

[0023] In step 4, after encountering the gas layer, a fine pressure-controlled surface process, a liquid-gas separator, a blowdown pipeline and an outlet ignition equipment are used to exhaust gas and evaluate the wellbore pressure within a controllable risk range, including bottom hole ECD equivalent calculation, gas logging total hydrocarbon value monitoring, oil and gas return velocity test, and outlet flame height. Depending on the position of the high-pressure gas layer from the low-pressure layer, if the distance is close, a special circulating exhaust gas reduction method is used; if the distance is far, pressure-controlled drilling exhaust gas reduction method is used to successfully reduce the wellbore ECD, creating basic conditions for reducing density and safely uncovering the low-pressure formation.

[0024] In step 5, in order to improve the stability of the wellbore in the broken formation, special pressure-bearing plugging methods are adopted, such as pressure-controlled drilling and well shut-in plugging, and dynamic and static pressure-bearing are combined to carry out multiple pressure-bearing plugging to improve the pressure-bearing capacity of the formation.

[0025] In step 5, preferred inhibitory plugging materials such as film-forming plugging agents, ultrafine calcium carbonate, and natural asphalt are used in combination with fine-grained rigid plugging to enhance the sealing and plugging while drilling, thereby achieving low-permeability reinforcement of the wellbore wall in the fractured formation; the core treatment agent is a wellbore enhancer, which uses micro-nano particles to reduce permeability and protect the wall while drilling, achieves multi-component composite plugging, enhances the stress around the well, and forms a low-permeability sealing plugging layer with the ability to protect the wall and prevent collapse and seal and plug while drilling.

[0026] In step 6, special sand cleaning operations are carried out regularly to remove the fallen blocks in the broken formation. A simplified conventional drilling tool combination is used, and the drilling tool does not have large outer diameter flow-blocking tools such as stabilizers. After drilling to the bottom, high-density, high-viscosity and heavy slurry is injected to ensure that the injection volume exceeds the length of the wellbore section at one time. Large-displacement and high-speed circulation sand cleaning are adopted to ensure the sand cleaning effect.

[0027] In step 7, the highly wear-resistant personalized PDC drill bit design features are: 5 blades with 16mm composite pieces, double-row teeth, inner cone carbide, enhanced diameter protection design, and inverted eye tooth design, which are used to crush and discharge the blocks and improve the drill bit's ability to prevent sticking; screw design: for the composite salt drilling fluid system, a highly salt-resistant internal rubber structure is selected to improve the screw's salt resistance, and a multi-rotor high-torque screw is selected to improve the drill bit's working stability; finally, the drilling parameters are strengthened, high speed + large displacement is used, the screw function is fully utilized, and the pre-bent drill tool anti-deflection effect is combined to release the drilling pressure, realize the coordinated optimization of the drill bit + tool + parameter, and improve the drilling efficiency.

[0028] The safe drilling method for coexistence of high and low pressure in marine and terrestrial phases in the present invention adopts a fine pressure-controlled drilling process, changes the concept of wellbore pressure control, and transforms the conventional "pressure drilling" into "controlled release". The wellhead back pressure is used to compensate for the static liquid column pressure, gradually release the pressure of the terrestrial high-pressure fracture gas layer, and appropriately reduce the drilling fluid density before entering the marine low-pressure layer. At the same time, in the face of the risk of wellbore instability caused by density reduction, the supporting strong inhibition composite salt drilling fluid system + drill string optimization design effectively prevents drill jamming accidents, and uses high wear-resistant PDC + high-performance screws to achieve safe and rapid drilling through complex layers, specifically solving the problem of safe drilling for coexistence of high and low pressure in marine and terrestrial phases, and applying it to the Hexing 1 well and conducting on-site effect evaluation, forming a set of comprehensive supporting drilling technology for coexistence of high and low pressure in marine and terrestrial phases. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a flow chart of a specific embodiment of a safe drilling method when high and low pressure coexist in marine and terrestrial phases. DETAILED DESCRIPTION

[0030] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0032] like Figure 1 As shown, Figure 1 The present invention is a flow chart of a safe drilling method when high and low pressure coexist in marine and terrestrial phases.

[0033] Step 1, start drilling using a composite salt strong inhibition drilling fluid system;

[0034] Drilling fluid formula: upper well slurry + 0.1%~0.2% hydrolyzed potassium polyacrylate (KPAM) + 0.1~0.2% zwitterionic polymer coating agent + 0.5~1.0% polyanionic cellulose + 1~1.5% polyamine + 2~5% resin fluid loss reducer (SMP-3) + 2~5% lignite fluid loss reducer + 1~2% ultrafine calcium carbonate + 1~3% temperature and saturated salt resistant lubricant + 1~3% graphite solid lubricant + 2~3% multi-softening point asphalt + 1~3% modified paraffin plugging agent + 1~2% film-forming plugging agent + 5~7% potassium chloride + 0.5~0.8% quicklime + barite.

[0035] Step 2: When drilling into a high-pressure fractured gas layer, use precise pressure control equipment to monitor overflow in real time and increase the density of the drilling fluid;

[0036] Use the fine pressure control precision flowmeter to detect the change of the outlet flow, quickly and accurately judge the overflow, close the outlet valve appropriately to form the wellhead back pressure, balance the formation pressure, prevent the formation fluid from continuing to invade the wellbore, and keep the liquid level from rising. At the same time, use the fine pressure control MPD (fine pressure control drilling technology) monitoring and control system to accurately calculate the formation pore pressure, obtain the well killing fluid density, and maintain the well killing fluid inlet density through circulation weighting, and circulate for 1-2 weeks to stabilize the gas layer.

[0037] Step 3: Use managed pressure drilling. The core technology is to accurately control the micro-balance of wellbore pressure through fine four-pressure profile reconstruction + ECD (bottom hole annulus circulation pressure) while drilling prediction + wellhead back pressure, improve the advanced evaluation of downhole leakage risk and the ability of fine wellbore pressure control while drilling, and achieve safe drilling in long open holes with narrow pressure windows;

[0038] Based on the data of neighboring wells and seismic data, a fine geomechanical profile is established to determine the safe density window of the entire well section. During the actual drilling process, the drilling fluid density is adjusted in real time according to the geological collapse and well leakage risk point prompts. ECD calculation is performed in real time to monitor and evaluate the wellbore risks. Through the annular pressure control of the operating well section (including drilling fluid density adjustment, displacement adjustment, and pressure control value adjustment), the wellbore is kept slightly over-pressured and balanced during drilling.

[0039] Step 4, deflate and reduce pressure to effectively release the gas layer pressure;

[0040] After encountering a gas layer, we use a fine pressure-controlled surface process, a liquid-gas separator, a blowdown line, and an outlet ignition device to exhaust gas and evaluate the wellbore pressure (including bottom hole ECD equivalent calculation, gas logging total hydrocarbon value monitoring, oil and gas return velocity test, outlet flame height, etc.) within a controllable risk range. According to the location of the high-pressure gas layer from the low-pressure layer, if the distance is close, a special cycle exhaust is used to reduce the pressure, and if the distance is far, pressure-controlled drilling is used to reduce the pressure, successfully reducing the wellbore ECD, creating basic conditions for reducing density and safely uncovering the low-pressure formation.

[0041] Step 5: To improve the stability of the wellbore in the broken formation, special pressure-bearing plugging methods are adopted, such as pressure-controlled drilling, well shut-in plugging, etc., and dynamic + static pressure-bearing is combined to perform multiple pressure-bearing plugging, which significantly improves the pressure-bearing capacity of the formation:

[0042] Film-forming plugging agents, ultrafine calcium carbonate, natural asphalt and other inhibitory plugging materials are selected, and fine-grained rigid plugging is used to strengthen the "sealing and plugging" while drilling, so as to achieve low-permeability reinforcement of the wellbore wall in the broken formation. The core treatment agent is a wellbore strengthening agent, which uses micro-nano particles (particle size 1-10μm) to reduce permeability and protect the wall while drilling, realize multi-component composite plugging, strengthen the stress around the well, and form a low-permeability sealing plugging layer, which has the ability to protect the wall and prevent collapse, and seal and plug while drilling.

[0043] Step 6: To remove the fallen blocks in the broken formation, special sand cleaning operations are carried out regularly.

[0044] A simplified conventional drilling tool combination is used, and the drilling tool does not have large outer diameter flow-blocking tools such as stabilizers. After drilling to the bottom, high-density and high-viscosity heavy slurry is injected to ensure that the injection volume exceeds the wellbore section length of more than 200m. A large displacement (60-70L / s) and high speed (100-120rpm) circulation sand cleaning is adopted to ensure the sand cleaning effect.

[0045] Step 7: To prevent periodic stress collapse of the wellbore wall, a highly wear-resistant diamond drill bit (PDC) + high-performance screw is used to achieve rapid drilling through complex formations.

[0046] The drill bit adopts the following personalized design features: 5 blades, 16mm composite pieces, double-row teeth (the second row of teeth adopts Mercedes-Benz tooth design to enhance wear resistance), inner cone carbide, enhanced diameter protection design, and inverted eye tooth design, which are used to crush and discharge the blocks and improve the drill bit's ability to prevent jamming. The screw design is jointly developed with Petrochemical Machinery to tackle the low-speed and high-torque screw. For the composite salt drilling fluid system, a high-salt-resistant internal rubber structure is selected to improve the screw's salt resistance. Finally, the drilling parameters are strengthened, using a high speed of 110rpm + a large displacement of 60L / s to give full play to the screw function, and with the anti-deflection effect of the pre-bent drill bit, the drilling pressure is released to 140KN-180KN, realizing the coordinated optimization of the drill bit + tool + parameters and improving the drilling efficiency.

[0047] In a specific embodiment of the present invention, the safe drilling method for coexistence of high and low pressure in marine and terrestrial phases is introduced by taking the example of Hexing 1 well as an example. The method comprises:

[0048] 1. Preparation before drilling

[0049] Regarding the three core technologies of safe high and low pressure drilling in marine and terrestrial facies: precise pressure control, exhaust and pressure reduction technology, anti-stuck technology in broken zones, and efficient rock breaking technology, corresponding equipment and material preparations must be carried out before drilling.

[0050] 1) Fine pressure control

[0051] A. The main equipment for fine pressure control are: Southwest MPD includes four core parts: automatic throttling control system, MPD monitoring and control system, special liquid-gas separator for pressure control and high-pressure wellhead rotary sealing device.

[0052] B. Installation location: The rotary control device is installed at the uppermost end of the wellhead blowout preventer of the drilling team; at the inlet of the automatic throttle manifold and downstream of the throttle manifold of the drilling team, and a manual flat valve is installed.

[0053] C. Pressure test standard: The pressure test of the rotating control head (or rotating blowout preventer) shall be conducted with clean water to 70% of the rated static pressure, and the dynamic pressure test shall be no less than 70% of the rated dynamic pressure, provided that the pressure does not exceed 80% of the casing internal pressure resistance and the rated working pressure of other equipment at the wellhead. The pressure stabilization time shall be no less than 10 minutes, and the pressure drop shall not exceed 0.7MPa.

[0054] D. Application scenario: Under pressure operation (such as changing the rotating assembly), establish a connection and balance between the upper and lower pressures of the shut-in blowout preventer; under shut-in conditions, the rotary blowout preventer is not available, but it can still be connected to the pressure control throttling manifold through the well team manifold to implement pressure control operations.

[0055] 2) Anti-stuck preparation

[0056] A. Anti-stuck drill bit: The anti-stuck drill bit is prepared on site. The anti-stuck structure at the diameter-protected end adopts the diameter-protected inclined surface to arrange the inverted eye teeth and conical teeth to achieve active crushing of blocks; the separated blade anti-stuck structure establishes blades and diameter-protected inclined surface flow channels to improve the fluid chip return effect.

[0057] B. High-torque screw: High-torque screws are prepared on site, and 7L244mm high-torque screws are used to increase the torque upper limit of anti-jamming treatment and also improve the stability of the drill bit.

[0058] C. Drilling jar: The site is equipped with high-performance imported jars, which are made of high-strength and tough materials. Key components are specially processed to extend fatigue life and can withstand high temperature and high pressure environments.

[0059] D. Spiral drill collar: The use of spiral drill collar can increase the flow area and improve the annulus permeability, and reduce the contact area between the drill collar and the well wall to prevent sticking.

[0060] E. Drilling fluid preparation: Use a composite salt strong inhibition drilling fluid system, with the idea of ​​"overall inhibition, plugging and strengthening" to increase the overall concentration of drilling inhibition and plugging agents to achieve the purpose of wellbore strengthening.

[0061] 3) Efficient rock breaking

[0062] A. Personalized drill bit: Personalized PDC is prepared on site, with 5 blades, 16mm composite pieces, double-row teeth (the second row of teeth adopts Mercedes-Benz tooth design to enhance wear resistance), inner cone carbide, enhanced diameter protection design, and inverted eye tooth design, which are used to crush and discharge fallen blocks and improve the drill bit's ability to prevent sticking.

[0063] B. Screw selection: United Petrochemical Machinery has tackled the problem of low-speed, high-torque screws. For the complex salt drilling fluid system, a highly salt-resistant internal rubber structure is selected to improve the salt resistance of the screw.

[0064] C. Parameter enhancement: Ensure that the equipment is in good working condition before drilling, conduct test runs on key equipment such as drilling pumps and top drives, and test their working stability at high displacement and high speed.

[0065] 2. Specific steps of drilling

[0066] 1) Use a composite salt strong inhibition drilling fluid system, drill at a density of 1.60g / cm³, and use fine pressure control equipment to monitor overflow in real time;

[0067] Drilling fluid formula: upper well slurry + 0.1%~0.2% hydrolyzed potassium polyacrylate (KPAM) + 0.1~0.2% zwitterionic polymer coating agent + 0.5~1.0% polyanionic cellulose + 1~1.5% polyamine + 2~5% resin fluid loss reducer (SMP-3) + 2~5% lignite fluid loss reducer + 1~2% ultrafine calcium carbonate + 1~3% temperature and saturated salt resistant lubricant + 1~3% graphite solid lubricant + 2~3% multi-softening point asphalt + 1~3% modified paraffin plugging agent + 1~2% film-forming plugging agent + 5~7% potassium chloride + 0.5~0.8% quicklime + barite.

[0068] 2) When drilling to a well depth of 3398m (Required 5), a high-pressure fractured gas layer was encountered. The density of the drilling fluid was increased from 1.65g / cm³ to 1.86g / cm³ to stabilize the pressure. The additional circulating pressure consumption ECD calculated the equivalent density of the bottom hole to be 1.91g / cm³;

[0069] 3) Use managed pressure drilling. The core technology is to accurately control the micro-balance of wellbore pressure through fine four-pressure profile reconstruction + ECD prediction while drilling + wellhead back pressure, improve the advanced evaluation of downhole leakage risk and fine wellbore pressure control while drilling, and achieve safe drilling in long open holes with narrow pressure windows;

[0070] 4) After more than 40 days of degassing and depressurization, the gas layer pressure was effectively released, the drilling fluid density was reduced to a minimum of 1.75g / cm³, and the low-pressure formation at Leikou Slope was safely uncovered;

[0071] 5) During the decompression period, the density reduction aggravated the well wall chipping and spalling. During the actual drilling of Hexing 1 Well, the drill was stuck 174 times, stopped 67 times, and the drill was stuck twice in a short time in Xujiahe.

[0072] 6) The composite salt strong inhibition drilling fluid technology + drill string optimization design is adopted. On the one hand, the overall concentration of drilling inhibition plugging agent is increased to 16% to achieve the purpose of strengthening the wellbore. On the other hand, in complex well sections such as Xuer and Xiaotangzi fragmentation concentrated zones, the drill bit combination is simplified, the screw and the stabilizer are thrown out, and a mixed drill bit / PDC + conventional tower inverted drill bit combination is adopted, and high-performance imported jars are added to improve the anti-stuck ability of the drill bit.

[0073] Table 1 Simplified drilling tools for the complex formation of the second drilling of Hexing 1 well

[0074] Use well section Stratigraphic characteristics Drilling Tool Assembly 4969-5217 Xiaotangzi Formation, unstable strata, many shale and sandstone blocks fall off, prone to drill jams 333.4mm mixed drill bit + 630*730 double drill bit + 2 731*730 back pressure valves + 9 241.3mm drill collars + 731*630 conversion joints + 3 203.2mm drill collars + 203mm jar + 6 203.2mm drill collars + 631*520 conversion joints + bypass valve + 9 139.7mm weighted drill pipes + 139.7mm drill pipe 5217-5489 In the fourth section of Leikoupo, gypsum is well developed, drilling torque fluctuates abnormally, and gypsum shrinkage and drilling sticking are prone to occur. 333.4mm PDC drill bit + 630*630 double mother + 631*730 variable buckle + 2 731*730 back pressure valves + 9 241.3mm drill collars + 731*630 conversion joints + 3 203.2mm drill collars + 203mm jar + 6 203.2mm drill collars + 631*520 conversion joints + bypass valve + 9 139.7mm weighted drill pipes + 139.7mm drill pipes

[0075] 7) In order to improve the stability of the wellbore in broken formations, special pressure-bearing and plugging measures were adopted, using methods such as pressure-controlled drilling and well shut-in and plugging, combining dynamic and static pressure-bearing. During the second opening of the Hexing 1 well, pressure-bearing plugging was carried out 5 times in total, and the pressure-bearing capacity of the formation was significantly improved.

[0076] Table 2 Statistics of the “drilling and sealing immediately” pressure plugging in the second opening of Hexing 1 well

[0077] well deep Strata Mud density Pressure bearing method Pressure conditions Plugging slurry performance Plugging well section 2585 Xiashaxi Temple 1.40g / cm³ Static The wellhead was gradually pressurized to 13.90MPa, and the pressure was stabilized for 10 minutes. The pressure drop was 0.03MPa, which was equivalent to an equivalent density of 1.95g / cm³ at the casing shoe. The formation was not broken. none none 2965 Thousand Buddha Cliff 1.55g / cm³ Static <![CDATA[The wellhead is gradually pressurized to 11.5 MPa, the pressure is stabilized for 10 minutes, the pressure drop is 0.1 MPa, which is equivalent to a casing shoe density of 2.02 g / cm 3 , equivalent to a bottom-hole equivalent density of 1.96 g / cm³, and the formation is not broken]]> A total of 56m³, well slurry + 3% graphite + 4% superfine + 3% asphalt 2582-2965 4693 Suji 1.80g / cm³ dynamic After the plugging slurry was injected, the heavy slurry cap + pressure-controlled drilling method was adopted, and the comprehensive conversion of the bottom hole equivalent density was 1.97g / cm³ A total of 10m³, well slurry 20m³ + 3% superfine + 4% asphalt + 4% acid soluble 4 type 4500-4650 4844 Suji 1.82g / cm³ dynamic After the plugging slurry is injected, the heavy slurry cap + pressure-controlled drilling method is adopted, and the comprehensive conversion of the bottom hole equivalent density is 2.00g / cm³ A total of 24m³, well slurry + 3% superfine + 4% asphalt + 4% acid soluble 4 type 4540-4844 5081 Suji 1.40g / cm³ Static The wellhead pressure is 3.5MPa, and the pressure is stabilized for 30 minutes without pressure drop. The equivalent density at the casing shoe is 2.02g / cm³, and the equivalent density at the bottom of the well is 1.95g / cm³. A total of 38m³, well slurry + 2% wellbore enhancer + 3% film-forming plugging agent + 3% graphite + 3% natural asphalt + 2% ultrafine + 3% rigid 4 type 4650-5081

[0078] 8) In order to remove the fallen blocks in the broken formation, special sand cleaning operations are carried out regularly. The second opening of Hexing 1 Well carried out 14 heavy slurry sand carrying operations, and a total of 10m³ of fallen blocks were removed, with obvious wellbore cleaning effect.

[0079] 9) In the construction of high-abrasive formations in Xujiahe and Xiaotangzi, we innovatively selected personalized PDC drill bits + high-torque screws to fully release the drilling parameters (110rpm high speed + 60L / s large displacement, giving full play to the function of the screw), enhance the wear resistance and aggressiveness of the PDC drill bits, and cooperate with high-torque screws to improve the working stability of the drill bits, realize the coordinated optimization of drill bits + tools + parameters, improve drilling efficiency, quickly drill through complex broken zones, avoid the complex risks of underground wells caused by periodic collapse of broken zones, and achieve safe and rapid drilling completion.

[0080] In a specific embodiment of the present invention, the Hexing 1 well was drilled on December 30, 2023, and the well was fully drilled on September 3, 2024. The designed drilling cycle was 278 days, and the actual drilling cycle was 247.27 days, 30.73 days earlier than the lean cycle, and the efficiency was improved by 11%. In addition, the average mechanical drilling speed of the Hexing 1 well was 3.59m / h, setting 23 records such as the shortest regional construction cycle, the fastest mechanical drilling speed, the deepest drilling depth in the same sea and land, the deepest large-size casing, the largest hanging weight, and the longest small hole continuous coring section, which were unanimously affirmed by Party A.

[0081] In terms of economic benefits, through technological innovation, the project cost was significantly reduced. The project was completed 30.73 days ahead of schedule, saving 2.714 million yuan in drilling rig costs; wellbore strengthening technology saved 600,000 yuan in mud costs; anti-stuck technology avoided the complex situation similar to Gudian 1 well; speed-up technology reduced the number of drilling times to 14 times, compared with the 22 times required for Yongsheng 1 well, saving another 1.23 million yuan. The total cost savings were about 4.544 million yuan.

[0082] In terms of promotion value, the successful application of the safe drilling technology of high and low pressure coexistence in the marine and terrestrial phases of western Sichuan in the Hexing 1 well not only provides a new technical idea for speeding up and improving the efficiency of large-size wellbores in the upper part of ultra-deep and extra-deep well drilling projects, but also provides scientific evidence for the optimization of the wellbore structure of similar ultra-deep wells in the region and the next step of efficient exploration and development. It also provides economic feasibility proof for the industrial application of ultra-deep and extra-deep oil and gas exploration and development technology, which has far-reaching promotion value and social significance.

[0083] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0084] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. A safe drilling method when high and low pressure coexist in marine and terrestrial phases, characterized in that: The safe drilling method for coexistence of high and low pressure in marine and continental phases includes: Step 1, start drilling using a composite salt strong inhibition drilling fluid system; Step 2: When drilling into a high-pressure fractured gas layer, use precise pressure control equipment to monitor overflow in real time and increase the density of the drilling fluid; Step 3: Use the controlled pressure drilling technology to achieve safe drilling in a long open hole with a narrow pressure window; Step 4, deflate and reduce pressure to effectively release the gas layer pressure; Step 5: Take special pressure-bearing and plugging measures to improve the pressure-bearing capacity of the formation; Step 6, carry out special sand cleaning operation; Step 7: Use highly wear-resistant PDC + high-performance screw to achieve rapid drilling through complex formations.

2. The safe drilling method for coexistence of high and low pressure in marine and terrestrial phases according to claim 1, characterized in that: In step 1, the drilling fluid formula used is: upper well slurry + 0.1%-0.2% hydrolyzed potassium polyacrylate + 0.1-0.2% zwitterionic polymer coating agent + 0.5-1.0% polyanionic cellulose + 1-1.5% polyamine + 2-5% resin fluid loss reducer + 2-5% lignite fluid loss reducer + 1-2% ultrafine calcium carbonate + 1-3% temperature-resistant and saturated salt-resistant lubricant + 1-3% graphite solid lubricant + 2-3% multi-softening point asphalt + 1-3% modified paraffin plugging agent + 1~2% film-forming plugging agent + 5-7% potassium chloride + 0.5-0.8% quicklime + barite.

3. The safe drilling method for coexistence of high and low pressure in marine and terrestrial phases according to claim 1, characterized in that: In step 2, a precise pressure-controlled precision flowmeter is used to detect changes in the outlet flow rate, determine overflow, and appropriately close the outlet valve to form wellhead back pressure, balance the formation pressure, prevent formation fluid from continuing to invade the wellbore, and keep the liquid level from rising; at the same time, a precise pressure-controlled MPD monitoring and control system is used to calculate the formation pore pressure and obtain the density of the well-killing fluid. The well-killing fluid inlet density is maintained through circulation and weighting, and the gas layer is stabilized after 1-2 weeks of circulation.

4. The safe drilling method for coexistence of high and low pressure in marine and terrestrial phases according to claim 1, characterized in that: In step 3, the pressure-controlled drilling technology is used to accurately control the micro-balance of wellbore pressure through fine four-pressure profile reconstruction + ECD while-drilling prediction + wellhead back pressure, thereby improving the advanced evaluation of downhole leakage risks and the ability of fine wellbore pressure control while drilling, and achieving safe drilling in long open holes with narrow pressure windows.

5. The safe drilling method for coexistence of high and low pressure in marine and terrestrial phases according to claim 4, characterized in that: In step 3, a detailed geomechanical profile is established based on the data from adjacent wells and seismic data, and a safe density window for the entire well section is determined. During the actual drilling process, the drilling fluid density is adjusted in real time based on the geological collapse and well leakage risk point prompts; ECD calculations are performed in real time to monitor and evaluate wellbore risks. The annular pressure of the operating well section is controlled, including drilling fluid density adjustment, displacement adjustment, and pressure control value adjustment, to maintain a slightly over-pressured wellbore for balanced drilling.

6. The safe drilling method for coexistence of high and low pressure in marine and terrestrial phases according to claim 1, characterized in that: In step 4, after encountering the gas layer, a fine pressure-controlled surface process, a liquid-gas separator, a blowdown pipeline and an outlet ignition equipment are used to exhaust gas and evaluate the wellbore pressure within a controllable risk range, including bottom hole ECD equivalent calculation, gas logging total hydrocarbon value monitoring, oil and gas return velocity test, and outlet flame height. Depending on the position of the high-pressure gas layer from the low-pressure layer, if the distance is close, a special circulating exhaust gas reduction method is used; if the distance is far, pressure-controlled drilling exhaust gas reduction method is used to successfully reduce the wellbore ECD, creating basic conditions for reducing density and safely uncovering the low-pressure formation.

7. The safe drilling method for coexistence of high and low pressure in marine and terrestrial phases according to claim 1, characterized in that: In step 5, in order to improve the stability of the wellbore in the broken formation, special pressure-bearing plugging is adopted, using the pressure-controlled drilling and well shut-in plugging methods, combining dynamic and static pressure-bearing, and performing multiple pressure-bearing plugging to improve the pressure-bearing capacity of the formation.

8. The safe drilling method for coexistence of high and low pressure in marine and terrestrial phases according to claim 7, characterized in that: In step 5, film-forming plugging agents, ultrafine calcium carbonate, and natural asphalt are selected in combination with fine-grained rigid plugging to enhance the sealing and plugging while drilling, thereby achieving low-permeability reinforcement of the wellbore wall in the fractured formation; the treatment agent is a wellbore strengthening agent, which uses micro-nano particles to reduce permeability and protect the wall while drilling, achieves multi-component composite plugging, enhances the stress around the well, and forms a low-permeability sealing plugging layer with the ability to protect the wall and prevent collapse and seal and plug while drilling.

9. The safe drilling method for coexistence of high and low pressure in marine and terrestrial phases according to claim 1, characterized in that: In step 6, special sand cleaning operations are carried out regularly to remove the fallen blocks in the broken formation. A simplified conventional drilling tool combination is used, and the drilling tool does not have a large outer diameter flow-blocking tool. After drilling to the bottom, high-density, high-viscosity and heavy slurry is injected to ensure that the injection volume exceeds the length of the wellbore section at one time. Large-displacement and high-speed circulation sand cleaning are adopted to ensure the sand cleaning effect.

10. The safe drilling method for coexistence of high and low pressure in marine and terrestrial phases according to claim 1, characterized in that: In step 7, the high wear-resistant PDC personalized drill bit design features are: 5 blades 16mm composite piece, double row teeth, inner cone carbide, enhanced diameter protection design, inverted eye tooth design, which are used to crush and discharge the blocks and improve the drill bit's anti-stuck ability; the screw design is: for the composite salt drilling fluid system, a high salt-resistant internal rubber structure is selected to improve the screw's salt resistance, and a multi-rotor high-torque screw is selected to improve the drill bit's working stability; finally, the drilling parameters are strengthened, high speed + large displacement is adopted, the screw function is fully utilized, and the anti-deflection effect of the pre-bent drill tool is combined to release the drilling pressure, realize the coordinated optimization of the drill bit + tool + parameter, and improve the drilling efficiency.

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