A New Dynamic Analysis Method for Hang’s Mudding-Off Technique based on Circulation Loss in Return

¹ National Joint Local Engineering Research Center for Shale Gas Exploration and Development, Chongqing Institute of Geology and Mineral Resources, Chongqing 400042, China ;
² Key Laboratory of Shale Gas Exploration，Ministry of Natural Resources, Chongqing Institute of Geology and Mineral Resources, Chongqing 400042, China ;
³ Chongqing Fuling Shale Gas Environmental Protection R & D and Technical Service Center, Chongqing 408000, China ;
⁴ Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China.
⁵ Key Laboratory of Mine Geological Hazards Mechanism and Control Xi'an, Shaanxi 710054, China.

^* Corresponding author, Pu Liu *. E-mail address: 248161979@qq.com.

Abstract

Hang’s mudding-off technique is a well control measure used to maintain the dynamic balance of the pressure inside a well and thus ensure safe operation when there is circulation loss in the return. Given the lack of a dynamic analysis method that reflects the principles of annulus liquid level changes in a well shaft, there has been no analytical basis for applying Hang’s mudding-off technique in practice, and as a result, the technique is typically applied as a “blind Hang”. In this study, a dynamic analysis method was employed to model well shaft leakage loss, based on actual engineering conditions under which Hang’s mudding-off technique is used, and models were developed for the effective height of the well shaft annulus liquid level in Hang’s mudding-off technique and for a safe operation time after the application of the technique. The calculation of variations in the cross-sectional area of the annulus was also addressed. The reliability of the proposed models was evaluated using calculation examples. The error in the calculated effective liquid level height was 1.22% when dynamic leakage loss was considered, and the error in the safe operation time calculation was 3.58%. These results illustrate the accuracy of the models. The analysis method proposed in this paper can be used to solve problems related to calculation of the engineering parameters involved in Hang’s mudding-off technique and averting the risks of well control safety under conditions of circulation loss in the return, thereby optimising Hang’s mudding-off technique and reducing project costs.