Influence of Volume Fracturing on Casing Stress in Horizontal Wells

Jingpeng Wang, Youming Xiong, Zongyu Lu, Jiangang Shi and Jiwei Wu
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Jingpeng Wang: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
Youming Xiong: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
Zongyu Lu: Engineering Technology Research Institute of Xinjiang Oilfield Company, Karamay 834000, China
Jiangang Shi: Engineering Technology Research Institute of Xinjiang Oilfield Company, Karamay 834000, China
Jiwei Wu: Engineering Technology Research Institute of Xinjiang Oilfield Company, Karamay 834000, China

Energies, 2021, vol. 14, issue 8, 1-14

Abstract: In horizontal wells, the casing string is affected by the gravity effect, temperature effect, swelling effect, bending effect, friction effect and other mechanical effects. In view of this situation, the mathematical models of casing swelling effect and temperature effect caused by volume fracturing are established. The case analysis shows that the length of the unsealed section in the vertical section has a great influence on the axial shortening of the casing during fracturing. With the increase of the unsealed section length, the axial shortening of the casing increases gradually under the same wellhead pressure. In the process of fracturing, repeated squeezing and pressurization lead to periodic changes of the wellhead pressure, casing deformation and load, which leads to fatigue damage and even fracture of casing. At the same time, a large amount of fracturing fluid is continuously injected through the casing during the fracturing process, which makes the wellbore temperature change greatly. The additional stress caused by the temperature change reduces the casing strength, which has an important impact on the wellbore integrity. The mathematical model of temperature stress and its effect on the casing strength during volume fracturing is established. With the increase of the temperature stress acting on the casing, the casing collapse strength decreases gradually. When the temperature stress reaches 200 MPa, the casing collapse strength decreases to 84% of the original. The research results can provide a reference for the casing integrity design and control in the horizontal well fracturing process.

Keywords: casing deformation; bulging effect; temperature effect; volume fracturing; casing strength (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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