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| A wellbore pressure calculation method considering gas entrapment in wellbore shut-in condition |
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DUAN Wenguang1,2, SUN Baojiang1, PAN Deng2, PAN Shaowei1, WANG Zhiyuan1, GUO Bing3, ZHANG Zhi1
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(1.School of Petroleum Engineering in China University of Petroleum (East China), Qingdao 266580, China;2.PetroChina Western Drilling Engineering Company, Karamay 830011, China;3.Foreign Cooperation Projects Department of Dagang Oilfield, Tianjin 300457, China)
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| Abstract: |
| After gas intrusion occurs during drilling, the invading gas is distributed in the wellbore in the form of bubbles. When the buoyancy of the bubble is insufficient to overcome the resistance caused by the yield stress, the bubble will be entrapped in the drilling fluid. The ultimate gas entrapment concentration under different yield stress and bubble geometry was carried out experimentally. By fitting the experimental results, a prediction model of ultimate gas entrapment concentration was obtained, and a wellbore pressure calculation method by considering the effect of gas entrapment under shut-in conditions was established. It is found that the error between model prediction and experimental results is less than 7％ when the yield stress ranges from 0 to 22.4 Pa. Compared with the field data, the relative error of the calculated peak casing pressure error is 1.51％ and of the casing pressure on the same time after shut-in is not exceed 3.5％. The wellbore pressure after shut-in can be accurately calculated by the established model. |
| Key words: yield stress gas entrapment ultimate gas entrapment concentration gas intrusion and well shut-in gas distribution wellbore pressure |
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