Analysis Of Geological Conditions Of Coalbed Methane In Linyi Block And Research On Development Countermeasures

Coalbed methane(CBM)as a kind of unconventional natural gas is playing an increasingly important role in the development of oil and gas.With the reservoir of Linfen Block,the coalbed is thick,and has stable distribution and rich hydrocarbon,thus this block has abundant of CBM resources.However,main CBM resources of Linfen block are generally deeper than 800m,which is defined as deep coalbed methane.Comparing with shallow CBM resources,the geological conditions,exploration and development technics of deep CBM are more difficult.Because of deep burying,although after years of exploration,Linfen block CBM development is still faced with unsatisfactory conformity of geological understanding,exploration and development results,big differences in production laws of gas well and shallow CBM wells,and low single-well production problems.This paper mainly discusses Linfen block deep CBM gas resources development.Unconventional oil and gas research method of integral geological,engineering,and production is used.Starting with the analysis on geologic conditions,comprehensive understandings of coal seam geological characteristics and CBM enrichment controlled factors are acquired.Based on CBM geological characteristics,researches of drilling,fracturing and production technology optimization were carried on,and deep CBM development countermeasures are put forward.Through the resources collection and regional geological survey,using the latest drilling results,the coal seam thickness,buried depth and upper layer lithology were assured.By core experiments,including mercury injection experiment,whole rock X-ray diffraction,thin section identification,and kerogen learnt technical means,coal rock,coal quality features and rock physical properties were measured.CBM gas content distribution,porosity and permeability of coal seam,isothermal adsorption feature were analyzed to have more understanding of the CBM reservoir geological conditions.By analysis all gas wells that have been put into production,combined with the coal seam and its upper and lower lithology,and distributed and comprehensive sampling produced water and output gas,the geological factors which affect CBM enrichment,like the fault zone,coal nature and its upper and lower lithology,and hydrogeology were studied.The block CBM reservoir characteristics are clear.Based on the analysis of the CBM geological factors,combined with gas production results,research of drilling,fracturing,and production were optimized,and the development well network deployment principles were specified.The drilling process was optimized by the well type,well bore quality,cementing quality,and reservoir protection.The fracturing technology was optimized by geological conditions,such as coal rock characteristics,gas saturation,upper layer’s aquosity,upper and lower layers’ rock mechanics parameter difference,coal seam sensitivity etc.At last,this paper summarizes equipment selection to adapt to various well conditions of Linfen block deep CBM,and comes up with the application of quantitative production in tubing design,critical desorption control,joint wells production,and pump inspection and workover afterwards,etc.And also did geological analysis and engineering prevention on abnormal water production.