Engineering Geological Condition Evaluation Technology Of Coalbed Methane Horizontal Well

China has rich coalbed methane,large scale development of coalbed methane can effectively solve the problem of gas shortage in China,at the same time reduce the oil and gas dependence on foreign,ensuring the national energy security.Comprehensive evaluation technology of engineering geological conditions for CBM horizontal well is an important support technology in the development of CBM.carrying out this research has important scientific research value and practical guiding significance.In this paper,the engineering geological evaluation of CBM horizontal well is studied from four aspects: geological structure impact assessment,analysis and evaluation of basic characteristics of coal seam,research of reservoir damage assessment method and key engineering geological problems evaluation method.Geological structure condition is the key to the successful implementation of CBM horizontal well engineering,the faults,the coal bed elevation,the structure of the direction and the formation tendency are the main factors.The coal seam depth,coal structure and coal quality are the three main factors of the CBM horizontal well engineering geology,the strong coefficient of coal is a comprehensive reflection of the mechanical properties of coal,it can be used as a simple and practical index to evaluate drilling efficiency and borehole stability.The reservoir damage evaluation technology of CBM horizontal well is based on the sensitivity evaluation of conventional oil and gas reservoirs,but the particularity of coal reservoir should be fully considered.The influence of intermediate principal stress should be taken into consideration on the stability of the borehole wall in coalbed methane horizontal well.Due to the strong stress sensitivity of coal reservoir,the effect of effective stress change should be taken into consideration in the evaluation of fracturing fluid in fracturing fluid.