Influences of Fracturing Fluid Injection on Mechanical Integrity of Cement Sheath under Four Failure Modes

Energies

Bin Yang¹  Honglin Xu¹  Nian Peng¹  Tianshou Ma² 

[1] School of Petroleum and Natural Gas Engineering, Chongqing University of Science and Technology, Chongqing 401331, China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China;

关键词: cement sheath;    analytical model;    failure stress;    safety factor;    fracturing wells;   

DOI  :  10.3390/en11123534

来源: DOAJ

【 摘 要 】

The significant decreased wellbore temperature and increased casing pressure during fracturing fluid injection present a big challenge for the mechanical integrity of cement sheath in fracturing wells. Based on the theories of elastic mechanics, thermodynamics, and a multi-layer composed thick-wall cylinder, this paper proposed a new mechanical model of cement sheath for fracturing wells, coupling pressure, and thermal loads, which consider the failure modes of de-bonding, radial cracking, disking, and shear failure. The radial nonuniform temperature change and the continuous radial stress and radial displacement at two interfaces have been considered. With the proposed model, the radial distributions of failure stress and the corresponding safety factor for cement sheath during fracturing fluid injection have been analyzed and compared under four failure modes. Results show that the decreased wellbore temperature will produce significant tri-axial tensile stress and induce cement failure of de-bonding, radial cracking, and disking. The increased casing pressure will significantly lower the risk of de-bonding but also aggravate radial cracking and shear failure. For integrity protection of cement sheath, increasing the injected fluid temperature, maintaining higher circulation pumping pressures, and adopting cement sheath with a low elasticity modulus have been suggested for fracturing wells.

【 授权许可】

Unknown