AN ANALYSIS OF FACTORS AFFECTING SINGLE WELL DELIVERABILITY OF COALBED METHANE IN THE QINSHUI BASIN

The Qinshui basin is rich in coalbed methane resources.The latest round of coalbed methane resources evaluation shows that coalbed methane resources in coal bed with a burial depth shallower than 2000 m is up to 3.98 tcm.Although several companies such as CUCMC,CNPC and NANYAN have built certain coalbed methane deliverability in several blocks in the southern part of the Qinshui basin,such as Panzhuang,Sizhuang and Fanzhuang,the current annual production potential of a single well is still below 2 bcm in this basin,indicating a very long way from large scale commercial production of coalbed methane.Factors influencing recovery of coalbed methane are very complex,resulting in relatively great differences of performance between wells,and large variations of stable production period and deliverability.Therefore,this paper focuses on analysis of the main factors influencing production potential of single coalbed methane well.It is concluded that the high-productivity wells are mainly distributed in regions where the thickness of coal beds is larger than 5 m,the gas content is over 19 m3/t,the gas saturation is above 70%,the permeability is around 1.0×10-3 μm2,critical desorption pressure is higher than 1.8 MPa,and the hydrodynamic conditions of formation water is relatively poor.