Project Title: Key Technologies and Large-Scale Application of' Stuck Pipe Prevention in Multi-Stage Fractured Shale Horizontal Wells

Participating Enterprises: Engineering Technology Research Institute of PetroChina Southwest Oil and Gas Field Company, Southwest Petroleum University, Sinopec Southwest Oil and Gas Branch Unconventional oil and Gas Exploration and Development Management Department, Sichuan Changning Natural Gas Development Co., Ltd, Sichuan Shale Gas Exploration and Development Co., Ltd

Award Received:Scientific and Technological Progress Award - Gold Award

Achievement Level: International Advanced Level

Project Number: ECF-2025-SET-1018

Main Participants: Wang Xudong, Chen Ye, Hu Xihui, Dai Feng, Liu Wei, Zhang Peiyu, Fan Xiangyu, Zhang Qiangu i, Xia Chengyu, Liu Lu, He Haikang, Liu Houbin, Huang Danchao, Wang Zhiqiang, Wang Qiren

Expert Review Comments:
International advanced level. Targeting the global technical challenge of borehole collapse and sticking in fractured–brittle shale horizontal wells, the project systematically proposes a collaborative stuck-prevention theory of “inhibitive sealing and rock consolidation, mechanical support against collapse, and efficient wellbore cleaning and sand control.” It develops multigrade particle stacking and nano-flake sealing technologies, builds a high-performance anti-collapse oil-based drilling fluid system and a coupled wellbore stability evaluation model, and delivers wellbore cleaning tools, rapid purification techniques, and an intelligent early-warning system—forming a multi-dimensional, collaborative, safe well-construction technology for collapse and stuck prevention. The achievements enabled a leap from “unable to drill” to “drilling completed” and further to “drilling well” in shale horizontal wells. With large-scale application in demonstration areas such as Changning–Weiyuan, the project has supported the construction of China’s largest shale gas production base, significantly improving drilling success and safety, delivering remarkable economic and social benefits, and providing an important demonstration for efficient and safe shale gas development in China.

Main Innovations:

Addressing the key technical problems of safe well construction in fractured–brittle shale horizontal wells, the project proposes a collaborative stuck-prevention theory of “inhibitive sealing and rock consolidation, mechanical support against collapse, and efficient wellbore cleaning and sand control,” together with multigrade particle stacking and nano-flake sealing techniques for micro/nano-scale fractures. It develops a high-performance anti-collapse oil-based drilling fluid system suitable for fractured–brittle shale formations; a structural–thermal–mechanical–chemical coupled wellbore stability evaluation technology; cam-type and helical-drive wellbore cleaning tools; a high-speed “conveyor-belt” wellbore purification technology for long horizontal sections; and a stuck-pipe intelligent early-warning system—achieving major breakthroughs in key technologies for collapse and stuck prevention during drilling.

Main Uses and Technical Principles:

The project resolves key technical issues such as unclear mechanisms of wellbore collapse and sticking in fractured–brittle shale horizontal wells, poor anti-collapse performance of drilling fluids, inaccurate collapse pressure prediction, insufficient wellbore cleaning capacity, and difficulty in stuck-risk early warning. By overcoming bottlenecks in “mechanisms, materials, processes, tools, and systems,” it establishes a multi-dimensional, collaborative, safe well-construction technology system for collapse and stuck prevention in fractured–brittle shale horizontal wells—enabling the transition from “unable to drill” to “drilling completed” and then to “drilling well.” Records include a 3,150 m horizontal section and an 18.83-day drilling period, minimizing downhole complex events. The project supports the Changning–Weiyuan National Shale Gas Demonstration Zone to achieve an annual output of 15.95 billion m³, building the largest shale gas production base in China and contributing to the national energy strategy and “dual-carbon” goals.

Technical Applications:

The project has broken through core theoretical methods, tools, and process barriers in key technologies for collapse and stuck prevention in fractured–brittle shale horizontal wells, forming a suite of proprietary technologies including strong-sealing, high-performance anti-collapse oil-based drilling fluids; stability evaluation technologies for fractured–brittle shale horizontal wells; high-speed “conveyor-belt” wellbore purification technologies for horizontal wells; and stuck-pipe early-warning systems.

As of October 2024, the results have been successfully scaled across 800 wells in PetroChina’s Changning, Zigong, and Luzhou blocks, and in Sinopec’s Yongchuan and Weirong blocks—effectively resolving problems of chip-off, collapse, and sticking in fractured–brittle shale horizontal wells, greatly reducing stuck and buried pipe rates, ensuring safe and efficient drilling of shale gas horizontal wells, strongly supporting capacity construction in the Changning–Weiyuan National Shale Gas Demonstration Zone (achieving an annual output of 15.95 billion m³), and building the largest shale gas production base in China, thereby laying a solid technical foundation for the construction of the Sichuan–Chongqing trillion-cubic-meter natural gas capacity base.

(1) Application in Sichuan Changning Natural Gas Development Co., Ltd.

The Changning shale gas reservoir has undergone multiple tectonic evolutions; the shale is hard and brittle, and micro/nano fractures are developed in some blocks, exhibiting typical fractured–brittle characteristics. Conventional oil-based drilling fluids cannot effectively seal the formation, and blocks tend to chip off under external forces. The reservoir is tight and must be developed by well-pad clusters with long horizontal sections, resulting in complex 3D trajectories; the ~2,000 m long horizontal sections make cuttings transport difficult, creating a dual cause of “wellbore instability + settled cuttings” that induces stuck and buried pipe problems.

In the Daba East area, prior to application, 11 wells were drilled and rotary steerable tools were stuck/buried in 10 wells, earning the label “forbidden zone for rotary steerables,” with huge losses. The project achieved four innovations—“mechanism of wellbore instability and chip-off sticking in fractured–brittle shale horizontal wells,” “strong-sealing, high-performance anti-collapse oil-based drilling fluid,” “stability evaluation technology for fractured–brittle shale horizontal wells,” and “high-speed conveyor-belt wellbore purification technology and stuck-pipe intelligent early warning system for long horizontal wells”—laying a solid technical foundation for safe and efficient drilling in Changning.

Since 2020, the project results have been fully promoted and applied in the Changning block, guiding the compilation of the Changning Block Drilling Guidance and the Anti-Stuck Drilling Guidance for Shale Gas Horizontal Wells in Sichuan–Chongqing, and supporting exploration and development in Changning. From January 2020 to October 2024, 269 wells were completed using the project results, reducing the stuck rate from 10.28% to 0.7%, strongly supporting capacity construction in the Changning–Weiyuan National Shale Gas Demonstration Zone and providing technical assurance for high-quality production ramp-up.

(2) Application in Sichuan Shale Gas Exploration and Development Co., Ltd.

In the southern Sichuan Luzhou block, the shale gas reservoir has undergone multiple tectonic evolutions; the shale is hard and brittle with developed natural fractures, causing severe wellbore instability and chip-off during drilling. Under complex 3D trajectories and long horizontal sections, wellbore cleaning is difficult, leading to frequent stuck and buried pipe incidents with long handling times and heavy losses—seriously constraining safe and efficient capacity building.

Targeting the major engineering challenge of frequent stuck and buried pipe incidents in Luzhou deep shale gas horizontal wells, the project carried out research on stuck mechanisms, anti-collapse drilling fluid systems, and wellbore cleaning processes through theory, lab experiments, and process development, yielding four innovations:

① Clarified the mechanisms of wellbore instability and cuttings-bed transport/deposition-induced sticking in fractured–brittle shale horizontal wells;

② Developed a stability evaluation technology for fractured–brittle shale horizontal wells;

③ Developed a strong-sealing, fully inhibitive, high-performance anti-collapse oil-based drilling fluid system;

④ Developed a high-speed “conveyor-belt” wellbore purification technology for long horizontal wells and a stuck-pipe intelligent early warning system—building a multi-dimensional collaborative key technology for stuck prevention in fractured–brittle shale, and realizing “density support + wellbore strengthening + wellbore cleaning” multi-dimensional collaboration for stuck prevention.

Since 2020, the results have been fully promoted and applied in the Luzhou block, guiding the compilation of Drilling Guidance 2.0 for Lu 203 and Yang 101 Well Areas and the Anti-Stuck Drilling Guidance for Shale Gas Horizontal Wells in Sichuan–Chongqing, and supporting exploration and development in Luzhou. From January 2020 to October 2024, 301 wells were completed using the project results, reducing the stuck rate from 8.57% to 1.2%, strongly supporting deep shale gas capacity construction in Luzhou and providing technical assurance for the company’s “50 bcm production” goal.

(3) Application in Sinopec Southwest Oil & Gas Company

Confronting wellbore instability, inadequate cleaning, and stuck/buried pipe issues in deep shale gas drilling, the project formed a key technology for safe well construction based on the core of “density support + wellbore strengthening + wellbore cleaning,” which has been promoted in Sinopec’s Weirong and Yongchuan blocks, efficiently supporting capacity construction.

From January 2020 to October 2024, 159 wells were completed (119 in Weirong and 40 in Yongchuan) with the project technologies. Compared with 2019, the failure rate decreased from 6.20% to 0.60%, average lost time per well dropped from 6.20 days to 0.45 days, drilling costs were reduced by 118.915 million RMB, and economic benefits reached 77.2947 million RMB. Based on diesel consumption of enhanced ZJ50D and ZJ70D rigs (5.0 and 7.0 tons/day) and a conversion of 1 ton of diesel ≈ 1.4571 tons of standard coal (burning 1 kg of coal emits 0.075 kg SO₂, 2.5 kg CO₂, 0.0375 kg NOₓ, 0.68 kg carbon dust), the completion of 159 wells from January 2020 to October 2024 resulted in reductions of 278.84 tons SO₂, 9,294.52 tons CO₂, 139.42 tons NOₓ, and 2,528.11 tons carbon dust, delivering significant social benefits.

(4) Application in the Development Division of PetroChina Southwest Oil & Gas Field Company

With increasing development depth and expanding areas, geological–engineering conditions have become more complex. Shale gas reservoirs generally exhibit strong heterogeneity, with developed natural fractures and bedding weakness planes, and pronounced brittle characteristics—leading to frequent wellbore instability and chip-off. To maximize benefits, pad well groups and long horizontal sections are adopted, reducing cuttings transport efficiency; after chip-off, sticking becomes more likely, with frequent stuck/buried pipe incidents posing severe challenges to safe and efficient shale gas production.

Addressing the major safety issue of stuck/buried pipe incidents in horizontal wells in the Zi 201 area, the project conducted research on stuck mechanisms, anti-collapse drilling fluid systems, and wellbore cleaning processes through theory, lab experiments, and process development, achieving four innovations—“mechanism of wellbore instability and chip-off sticking in fractured–brittle shale horizontal wells,” “strong-sealing, high-performance anti-collapse oil-based drilling fluid,” “stability evaluation technology for fractured–brittle shale horizontal wells,” and “high-speed conveyor-belt wellbore purification technology for long horizontal wells and stuck-pipe intelligent early warning system.”

This formed a multi-dimensional, collaborative key technology for stuck prevention in fractured–brittle shale, realizing “density support + wellbore strengthening + wellbore cleaning” multi-dimensional collaboration for stuck prevention, and laying a solid technical foundation for safe and efficient drilling of shale gas horizontal wells.

Since 2020, the results have been fully promoted in the Zi 201 area, guiding the compilation of the Zi 201 Area Drilling Guidance and the Anti-Stuck Drilling Guidance for Shale Gas Horizontal Wells in Sichuan–Chongqing, and supporting exploration and development in the Zigong block. From January 2020 to October 2024, the Development Division completed 71 wells using the project results, reducing the stuck rate from 11.92% to 1.4%, strongly supporting capacity construction in the Zigong block and providing technical assurance for the Southwest Oil & Gas Field’s “50 bcm production” plan.

This achievement has greatly reduced stuck-pipe and rotary steerable drop-in rates in shale gas horizontal wells, shortened the time to address complex failures, accelerated production ramp-up, and supported large-scale, cost-effective shale gas development and the establishment of the country’s largest shale gas production and integrated utilization base. It strongly supports the Southwest Oil & Gas Field Company’s strategic plan to reach 50 bcm, offers important guidance and reference for similar stuck-prevention efforts in shale plays at home and abroad, has cultivated a high-level team for complex failure prevention and control, and shows broad application prospects with huge overall social benefits.