Progress of geophysical well logging in shale gas reservoir evaluation

Shale gas is mainly comprised of the adsorbed and free gas which accumulated in black organic-rich and extremely low-permeability shales.Shale gas reservoirs have the characteristics of autochthonous generation,continuous charging and accumulation.China have superior geological conditions for shale gas accumulation,favorable shale gas resource prospects and development potentials.Compared with the North America,formation and development of.China's shale gas have obvious particularity and many geological and development problems need to be solved urgently In general,the gas-bearing shale layers in China possess high TOC,high thermal maturity and a high degree of later reformation.The spot in shale gas exploration and development is a section of high quality and core reservoir area,which determines the shale gas reservoir evaluation as the key to find out sweet spot in organic-rich shales.Geophysical well logging is one of the significant methods for identification and evaluation of shale gas reservoirs,which is throughout the process of shale gas exploration and development.Shale gas exploration,development and reservoir evaluation in China is at a initial stage.In order to use geophysical well logging effectively and efficiently to evaluate shale gas reservoirs in China and with a combination of literature,geological and well log data,this paper firstly introduces commonly used well logging series in different type of wells in shale gas exploration and development.And the logging response of shale gas reservoir is compared and analysed.Secondly,the main well logging methods and parameters' calculation of shale gas reservoir evaluation are introduced from the aspects of mineral composition,geochemical parameter,physical parameter,gas content and fracability.In particular,the emphases of shale gas reservoir evaluation are mineral composition,geochemical parameter,gas content and fracability,which determines whether a shale has potentials for further development.Besides,the equations of calculating TOC and brittleness index are improved by a combination of methods and actual data.Lastly,this paper puts forward several main problems,trends,understandings and suggestions about the geophysical well logging evaluation of shale gas reservoir in China.