吐哈盆地中低阶深部煤储层地质特征及有利层段优选——以柯新1H井为例

Geological characteristics and optimal selection of favorable reservoir of deep and middle-low rank coal reservoirs in Turpan-Hami Basin—a case study of Kexin1H well

  • 摘要: 吐哈盆地首口煤层气风险探井柯新1H井目标煤储层埋深在3 163~3 350 m,对该煤储层进行地质特征分析与有利层段优选对后续滚动勘探开发意义重大。本文通过煤岩煤质、煤体结构、含气性现场测试与等温吸附、孔渗及应力敏感、岩石力学等12项270余次系统测试分析,揭示了柯新1H井西山窑组主力煤岩储层地质特征,并优选了有利层段。研究结果表明:①柯新1H井西山窑组煤岩镜质组反射率介于0.64 % ~1.02 %,镜质组含量介于63.40 % ~89.57 %,目标煤储层为长焰煤或不黏煤储层;②基于密闭取心与等温吸附实测,煤岩储层含气比介于1.47~1.98,煤岩三轴弹性模量在3.594~7.795 GPa,泊松比介于0.17~0.27,煤体结构主要为碎裂煤和碎粒煤,煤岩储层属于过饱和、中低阶、碎软、低渗、强应力敏感储层;③基于模糊层次分析建立了囊括3大类一级指标和12类二级指标的单井深部煤储层有利层段优选评价指标体系,认为柯新1H井第三段煤岩储层具备高产潜力,但须在工程作业中注意煤粉的影响。

     

    Abstract: The optimal selection of favorable reservoir is a fundamental and necessary task after logging and before fracturing operations, which can help improve the success rate of coalbed methane exploration. The target coalbed reservoir of the first coalbed methane exploration well, Kexin1H, in the Turpan-Hami Basin is located at a depth of 3 163~3 350 meters. The geological characteristics analysis and optimal selection of a favorable reservoir of coalbed methane are of great significance for subsequent exploration and development. This study conducted more than 270 tests on coal quality, coal structure, in-suit gas content, as well as isothermal adsorption, porosity, permeability, stress sensitivity, rock mechanics, and other parameters, providing a comprehensive understanding on the deep coalbed methane reservoir in the Turpan-Hami Basin and a deep analysis on optimal selection of favorable reservoir. The results show that: ① coals in the Xishanyao Formation drilled by Kexin1H well have a vitrinite reflectance ranging from 0.64 % to 1.02 %, with vitrinite content ranging from 63.40 % to 89.57 %. Based on the industrial analysis results of coal-rock, it is believed that the main coal seam is a long-flame coal or non-caking coal reservoir; ② based on the measurements of closed-core and isothermal adsorption, the gas saturation of coal rock reservoir ranges from 1.47 to 1.98. The three-axis elastic modulus and Poisson's ratio of coal rock are between 3.594 GPa to 7.795 GPa and 0.17 to 0.27, respectively. The coal structure is mainly fractured coal and granular coal. The coal rock reservoir belongs to the over-saturated, medium-low rank, fractured-soft, low-permeability, and strong stress-sensitive reservoir; ③ an evaluation index system for the optimal selection of a favorable reservoir in a single well based on fuzzy analytic hierarchy process was developed, which includes three main categories of primary indicators and twelve secondary indicators. It is believed that the producibility of the coalbed reservoir in the third section of Well Kexin 1H is high in production potential. However, attention should be paid to the impact of coal fines during engineering operations.

     

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