Unconventional casing programs for subsalt ultra-deep wells with a complex pressure system: A case study on Well Wutan 1 in the Sichuan Basin

被引：0
作者：
Zou L. [1 ]
Mao Y. [2 ]
Liu W. [3 ]
Wang H. [1 ]
Guo J. [3 ]
Deng C. [3 ]
Zheng Y. [3 ]
Huang H. [1 ]
Li J. [3 ]
Yue H. [3 ]
Chen G. [3 ]
机构：
[1] CNPC Engineering Technology Research Institute Co., Ltd., Beijing
[2] PetroChina Exploration & Production Company, Beijing
[3] PetroChina Southwest Oil &Gasfield Company, Chengdu, 610051, Sichuan
来源：
| 2018年 / Natural Gas Industry Journal Agency卷 / 38期
关键词：
Casing program; Complex pressure system; Dazhou-Kaijiang paleo-uplift; Eastern Sichuan Basin; Gypsum-salt layer; Hydrogen sulfide bearing; Sichuan Basin; Ultra-deep well; Well Wutan 1;
D O I：
10.3787/j.issn.1000-0976.2018.07.010
中图分类号：
学科分类号：
摘要：
Well Wutan 1 is a wildcat well deployed in the Dazhou-Kaijiang paleo-uplift, eastern Sichuan Basin and its design depth is 7 570 m. The Cambrian and Sinian strata are its main exploration targets, and the strata below the Sinian 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 bottomhole temperature is up to 175℃, and the bottomhole 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 leakage, blowout and pressure difference induced pipe sticking in the open hole section, it is determined that the casing program shall be in the pattern of six-section casing with 5 setting positions. Second, no setting position is needed in the Carboniferous pressure depleted reservoir for it is lithologically tight and pressure difference induced pipe sticking and leakage is less risky. Third, for achieving salt layer specialization, 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 8 060 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 deep-seated gas exploration in the Dazhou-Kaijiang paleo-uplift. © 2018, Natural Gas Industry Journal Agency. All right reserved.
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页码：73 / 79
页数：6
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