In-situ stress plays an important role in keeping borehole stability and designing the appropriate completion technique. Ultra-deep horizontal wells are adopted to exploit marine carbonate gas reservoirs in northeast Sichuan, which are sour gas reservoirs with high sulfur content. To recommend the appropriate completion method for horizontal well in sour gas fields in northeast Sichuan, in-situ stress should be precisely gained at first. Based on care in method and induced facture method, imaging logging data of 16 wells was used to determine the stress direction. Statistical results indicated that the maximum horizontal principal stress extended nearly east-westward. Rock mechanical parameters were calculated from density logging and crossdipole acoustic logging data based on the relationship between rock strength and acoustic slowness. Layering earth stress calculation model combined with imaging logging data and well stability information during drilling were used to calculate magnitude of in-situ stress of marine reservoir. Then, the influence of marine in-situ stress on horizontal borehole stability during production was studied, which gave an insight on ultra-deep horizontal wellbore completion optimization in northeast Sichuan.
Marine carbonate gas reservoirs in northeast Sichuan are characterized as deep buried depth, high temperature and high pressure, high H2S and CO2 content. A few numbers of horizontal wells were deployed; natural depletion development and multiple zones production strategy were used. In order to enhance recovery and keep long-term safety and high production, optimum well completion method should be chosen for ultra-deep horizontal well in northeast Sichuan. In engineering view, well completion optimization is mainly considering the well trajectory direction, borehole stability during production and stimulation methods. But all of these factors are related to in-situ stress. So, accurate evaluation of insitu stress for marine pay zones in northeast Sichuan is the fundamental work.
