高—中煤阶煤层气井生产特征及影响因素分析——以樊庄、韩城矿区为例

在层序地层学理论指导下,通过对大量单井及野外露头资料的分析,依据岩性、电性、古生物特征等,确定川中、川南寒武系各层组的对应关系,提出川中—川南寒武系地层划分与对比的新方案,并以此为基础,研究四川盆地中南部寒武纪不同时期的沉积相特征.研究表明,川南九老洞组基本对应川中的筇竹寺组,川南遇仙寺组基本对应川中沧浪铺组、龙王庙组、高台组,川南与川中洗象池群基本对应.川中—川南寒武系自下而上分为筇竹寺组、沧浪铺组、龙王庙组、陡坡寺组和洗象池群,长期受加里东运动形成的古隆起控制和影响,经历了滨岸—陆棚、局限台地—蒸发坪—陆棚染潟湖、局限台地等3个演化阶段.龙王庙组和洗象池群的砂屑白云岩、鲕粒白云岩、岩溶白云岩等是该区碳酸盐岩油气资源勘探的目标.

Production characteristics and affecting factors of high-mid rank coalbed methane wells: Taking Fanzhuang and Hancheng mining areas as examples

Production characteristics of coalbed methane wells in Fanzhuang and Hancheng mining areas, which are typical high and mid rank coal fields, are analyzed, compared, and summarized. And the effects of perforating thickness, layer number of perforating, unloading technology and stimulation treatment on gas production are analyzed. Coalbed methane wells in Fanzhuang and Hancheng mining areas are divided into four categories: high gas-production wells, middle gas-production wells, low gas-production wells and little gas-production wells. High gas-production wells have gas production of more than 3000 m3/d, and, long stable production period, slow and smooth declining rate, high peak production and short unloading period. Middle gas-production wells have gas production between 1000 m3/d and 3000 m3/d, and, shorter stable production period and longer unloading period and quick declining rate at the early stage. Low gas-production wells have gas production of less than 1000 m3/d, and, short stable production period, high water output and long unloading period and discontinuous production. Little gas-production wells have large water output, slow reducing rate of liquid level and low or zero surface casing pressure. Based on the production characteristics, three types of production modes of coalbed methane wells are summed up. In view of specific examples, it is discussed quantitatively and qualitatively how different factors affect the gas production of coalbed methane wells. It turns out that, generally, the perforating thickness of coalbed methane wells should be larger than 5 m and the layers of perforation should not exceed 3 layers. In addition, proper unloading system is needed to maintain stable and persistent high gas production, and secondary stimulation treatments can bring about significant production increase.