Critical drilling and completion techniques for deep coalbed methane in the Shenfu block and their applications
[Objective]Deep coal seams exhibit high in-situ stress,moderate to high temperatures,ultra-low permeabil-ity,high compressibility,and significant heterogeneity,leading to the absence of mature technical systems for their ex-ploitation presently.The complex geological characteristics of deep coal seams pose new technical challenges to their drilling and completion engineering,rendering it urgent to tackle theoretical and technical challenges in drilling and completion tailored to the geological characteristics of deep coal seam reservoirs.The purpose is to achieve the reserve growth and production addition of hydrocarbons in order to guarantee China's strategic energy security.[Methods]Based on the pilot tests for deep coalbed methane(CBM)production in the Shenfu block along the eastern margin of the Ordos Basin,a set of critical techniques have been developed for efficient drilling and completion.[Results and Con-clusions](1)Given the low wellbore stability,low drilling rates,and prolonged drilling cycles of deep coal seams,integ-rated and efficient drilling of deep coal seams has been achieved by optimization using a second-spud-in casing program,the optimal drilling fluid system,and"one-trip drilling"technique,combined with fine-scale control of borehole traject-ories.Such technology can boost the construction of innovative,optimized,and efficient well platforms.(2)To address the challenge posed by the complex geological characteristics and low hydrocarbon production through conventional fracturing of deep coal seams,a composite extremely large-scale fracturing technology system has been developed,which centers on directional perforation,pre-acid to reduce fracturing pressure,multi-cluster closely spaced fracturing within intervals,large-scale fracturing at high injection rates of fracturing fluids,integrated viscosity-variable slickwater,temporary plugging and diverting,and proppants with multiple grain sizes.(3)Following the work philosophy of one strategy for one block and global optimization,a factory drilling and completion operation mode for a stereoscopic well pattern has been designed,with the zipper fracturing mode manifesting the best performance at an optimal horizontal well spacing of 350 m.(4)The high industrial gas flow from the commingled production of deep CBM and tight gas proves that multi-gas commingled production serves as a significant measure to enhance the production efficiency of un-conventional natural gas along the eastern margin of the Ordos Basin.It is expected that the findings of this study will provide theoretical guidance and practical experience for the efficient drilling and completion techniques for deep coal seams in the Ordos Basin.
deep coalbed methane(CBM)Shenfu blockfactory drilling and completion operation modereservoir volume fracturingmulti-gas collaborative productiont
国家科技期刊平台
NSTL
万方数据
