1. Introduction
CCTETG Xi’an Research Institute has constructed many coalbed methane wells in Liupanshui and surrounding areas of Guizhou Province. Major underground problems such as formation water inrush in well, repeat lost circulation, etc. was solved. Thus, a wealth of karst fracture developed strata drilling and underground complex treatment experience were accumulated.
2. Treatment solution
For CBM exploration wells, a set of soft coal seam coring technology is explored, and the core recovery rate is over 85%. In view of the malignant leakage caused by the development of Karst Cave and karst fissure in Guizhou, on the basis of summing up rich construction experience, a series of technical problems have been solved. A set of effective plugging methods and techniques have been summarized, thus shortening the drilling cycle, reducing cost of lost circulation control. These research results lays a foundation for low-cost development and utilization of coalbed methane.
3. Construction situation
4. Achieved accomplishment
Since 2015, a total of 6 CBM exploration wells and 29 CBM cluster wells have been constructed in Liupanshui area, Guizhou Province, with a cumulative footage of 34568m. Among these Coalbed methane wells, average single well depth is about 1000m. Drilling and completion cycle of a single well can be controlled within 15 days. The highest drilling efficiency is 486m footage per day. High-efficiency coalbed methane drilling in karst region is realized. Taking Zhong1-8-6 well as an example. As of the end of May 2019, average daily gas production exceeds 5000m3. Cumulative gas production is 1.8 million m3, which is still in a stable rising stage.
Three-dimensional trajectory map of Zhong 1-8-6 well
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