Well Wutan 1 is a wildcat well deployed in the DazhoueKaijiang paleo-uplift,eastern Sichuan Basin and its design depth is 7570 m.The Cambrian and Sinian strata are its main exploration targets,and the strata below the...Well Wutan 1 is a wildcat well deployed in the DazhoueKaijiang paleo-uplift,eastern Sichuan Basin and its design depth is 7570 m.The Cambrian and Sinian strata are its main exploration targets,and the strata below the Silurian in this well are geologically uncertain with a high risk.A large section of gypsum-salt layer may be encountered in the Cambrian and the longitudinal pressure system is complex.It is predicted that the bottom hole temperature is up to 175 C,and the bottom hole liquid column pressure exceeds 140 MPa,and there is hydrogen sulfide.As a result,the casing program design is confronted with great challenges.In this paper,the difficulties and risks of drilling engineering were analyzed.Then,a casing program was designed and optimized referring to the successful drilling experience of subsalt ultra-deep wells at home and abroad,combined with the pressure system characteristics of Well Wutan 1 and the creep performance of gypsum-salt layers.Finally,the casing program was applied on site.And the following research results were obtained.First,in order to prevent lost circulation,blowout and differential pressure induced stuck pipe in the open hole section,it is determined that the casing program shall be in the pattern of six-section casing with 5 setting points.Second,no setting point is needed in the Carboniferous pressure depleted reservoir for it is lithologically tight and differential pressure induced stuck pipe and lost circulation are less risky.Third,to better isolate the salt layer,one section of casing is specially designed for the Cambrian gypsum-salt layer and its collapse strength is 160 MPa to prevent collapse by salt creep.Fourth,Well Wutan 1 is drilled successfully to the expected strata and its total depth is 8060 m.In conclusion,the unconventional six-section casing program with 5 setting points to ensure the subsalt drilling safety in the eastern Sichuan Basin is rational.The successful drilling of Well Wutan 1 provides experiences and references for the follow-up exploration of deep-seated gas in the DazhoueKaijiang paleo-uplift.展开更多
基金supported by Major Science and Technology Project of PetroChina Company Limited“Research and application of key exploration and devel opment technologies to achieve 30-billion-m3 production in Southwest Oil and Gas Field”(No.:2016E-0608)Major Science and Technology Project of Southwest Oil&Gas Field Company“Research and application of key gas exploration and development technologies for Eastern Sichuan Basin”(No.:2016ZD01).
文摘Well Wutan 1 is a wildcat well deployed in the DazhoueKaijiang paleo-uplift,eastern Sichuan Basin and its design depth is 7570 m.The Cambrian and Sinian strata are its main exploration targets,and the strata below the Silurian in this well are geologically uncertain with a high risk.A large section of gypsum-salt layer may be encountered in the Cambrian and the longitudinal pressure system is complex.It is predicted that the bottom hole temperature is up to 175 C,and the bottom hole liquid column pressure exceeds 140 MPa,and there is hydrogen sulfide.As a result,the casing program design is confronted with great challenges.In this paper,the difficulties and risks of drilling engineering were analyzed.Then,a casing program was designed and optimized referring to the successful drilling experience of subsalt ultra-deep wells at home and abroad,combined with the pressure system characteristics of Well Wutan 1 and the creep performance of gypsum-salt layers.Finally,the casing program was applied on site.And the following research results were obtained.First,in order to prevent lost circulation,blowout and differential pressure induced stuck pipe in the open hole section,it is determined that the casing program shall be in the pattern of six-section casing with 5 setting points.Second,no setting point is needed in the Carboniferous pressure depleted reservoir for it is lithologically tight and differential pressure induced stuck pipe and lost circulation are less risky.Third,to better isolate the salt layer,one section of casing is specially designed for the Cambrian gypsum-salt layer and its collapse strength is 160 MPa to prevent collapse by salt creep.Fourth,Well Wutan 1 is drilled successfully to the expected strata and its total depth is 8060 m.In conclusion,the unconventional six-section casing program with 5 setting points to ensure the subsalt drilling safety in the eastern Sichuan Basin is rational.The successful drilling of Well Wutan 1 provides experiences and references for the follow-up exploration of deep-seated gas in the DazhoueKaijiang paleo-uplift.
