Experience and Lessons of Dynamic Description of Naturally Fractured Tight Sandstone Gas Reservoir in Keshen Gas Field, Tarim Basin

Abstract

The Keshen gas field is the first successfully developed gas reservoir deeper than 8000 m in China. The ultra-high reservoir pressure brings challenges to the development mechanism analysis and dynamic monitoring. In the early stage, downhole pressure test was carried out in only a few wells during completion, but the data acquired were not ideal for dynamic reservoir characterization. Since 2014, the dynamic monitoring technique for ultra-deep and ultra-high pressure gas wells has been formed. It allows the downhole temperature and pressure data acquisition in wells with depth more than 8000 m and wellhead pressure greater than 90 MPa, thus facilitating the dynamic reservoir characterization, and providing a basis for well deployment in the productivity construction stage and development optimization in the stable production stage. Well test interpretation results show that the Keshen gas field is a naturally fractured tight reservoir with different levels of fractures. It is characterized as that local structure controls hydrocarbon accumulation, stress controls reservoir, fractures control production and faults control water influx. Well deployment in sweet spots at structural highs, moderate stimulation and water drainage will be the main countermeasures to efficiently develop ultra-deep and ultra-high pressure naturally fractured tight sandstone gas reservoirs.