Geological Characteristics and Production Performance of Ultra-Deep Naturally Fractured Tight Sandstone Gas Reservoirs

Geological characteristics and production performances of ultra-deep naturally fractured tight sandstone gas reservoirs are different from those of conventional gas reservoirs; it is difficult to develop such gas reservoirs. Taking Dabei and Keshen gas fields in Kuqa foreland basin, for example, based on seismic, logging, core, well testing, and production dynamic data, we comprehensively analyze the geological and development characteristics of ultra-deep naturally fractured tight sandstone gas reservoirs by means of structural interpretation, reservoir evaluation, gas reservoir engineering, and well test analysis. These characteristics include the following: (1) Reservoirs have tight matrix, naturally developed fractures, strong heterogeneity, and complex gas–water relationships. (2) Gas deliverability of individual wells is quite different, and fractures are the key factor to determine gas deliverability. (3) Internal connectivity of gas reservoir is good, and percolation of gas well has the characteristics of fracture flow regime. (4) During the early stage of production appraisal, dynamic reserves are much lower than geologic reserves evaluated by volumetric method. (5) Some gas wells produce water and sands, which reduce gas deliverability dramatically. According to these characteristics of ultra-deep naturally fractured tight sandstone gas reservoirs, some development countermeasures are put forward in order to realize the efficient development of this kind of gas reservoirs .