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贵州织金煤层气田地质特征及勘探开发关键技术

Geological characteristics and key technologies for exploration and development of coalbed methane in Zhijin Block of Guizhou Province

  • 摘要: 织金煤层气田累计钻井50余口,开展了不同井型、不同合采层位、不同压裂方式的攻关试验,已探明珠藏次向斜煤层气地质储量113×108 m3,是贵州境内龙潭组煤层气勘探程度最高的地区之一。为了评价该类型煤层气的勘探开发潜力,回顾了该区勘探历程,从构造、沉积、储层、保存、含气性、气藏特征等方面分析了气田的地质特征,评价了产气效果,总结梳理了勘探开发关键技术,分析了煤层气效益开发面临的挑战和攻关方向。结果表明:织金煤层气田龙潭组煤层具有层数多、单层薄、累厚大、含气量高、构造−煤体结构复杂的地质特点,主体为浅层、低压−常压、常温、不含硫化氢、干气煤层气藏;煤层气井生产整体表现出“解吸效率高、上产快、稳产能力强”的特征,增大动用煤层厚度、增大压裂规模,可显著提升单井产能,薄煤层水平井表现出高产稳产潜力;形成了多煤层平面选区、纵向合采层位优选、浅层大位移薄煤层水平井钻完井、多层分段压裂、多煤层精细控制排采等关键技术;多薄煤层气面临煤层气基础研究薄弱、储层表征技术不成熟、工程工艺技术适应性不强等问题,需加强煤储层微观特征及吸附−解吸−运移机理、裂缝扩展规律及煤储层可压性评价体系研究,攻关差异化有效支撑压裂技术、定量化智能化排采技术等。

     

    Abstract: Zhijin Block has drilled over 56 wells, conducting research and tests on various well types, commingled horizons, and fracturing methods. The proven geological reserves of coalbed methane (CBM) in the Zhucang Sub-syncline are 113×108 m3, making it one of the most extensively explored Longtan Formation coalbeds in Guizhou Province. To evaluate the exploration and development potential of this type of CBM, the exploration history of the area was reviewed. The geological characteristics of the gas field were analyzed from multiple perspectives including structural configuration, sedimentary environment, reservoir properties, preservation conditions, gas content characteristics, and gas reservoir features. The gas production performance was systematically assessed, while key exploration and development technologies were summarized and categorized. Additionally, challenges facing the cost-effective development of CBM were analyzed, along with corresponding research priorities and technical pathways. The results indicate that: Longtan Formation coal seams in Zhijin Block exhibit distinctive geological characteristics including multiple coal seams with thin individual layers yet significant cumulative thickness, high gas content, and complex structural and coal body structures. The reservoir is predominantly characterized as a shallow, low-pressure to normal-pressure, normal-temperature dry gas CBM reservoir with absence of hydrogen sulfide. Production characteristics of CBM wells demonstrate three key features: “high desorption efficiency, rapid production buildup, and strong sustained production capacity”. Significant per-well productivity enhancement is achieved through increased effective coal seam thickness utilization and enlarged hydraulic fracturing scale. Horizontal wells in thin coal seams exhibit high and stable production potential. Key exploration technologies have been developed, including multi-coal seam plane selection, optimized vertical commingled horizons, drilling and completion technologies for horizontal wells in shallow, large-displacement, thin coal seams, multi-stage fracturing technologies for multiple seams, and fine-control dewatering and gas production technologies for multi-coal seams. The issues faced in the evaluation of sweet spot targets and production enhancement technologies were analyzed, directions for tackling challenges were proposed, including deepening research on the enrichment and high-yield laws of multiple thin coal seams, making breakthroughs in low-cost production enhancement technologies, and optimizing development methods.

     

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