Experimental Investigation on the Evolution of Tensile Mechanical Behavior of Cement Stone Considering the Variation of Burial Depth

Bohang Liu, Lei Wang (), Yintong Guo, Jing Li and Hanzhi Yang
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Bohang Liu: School of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao 266580, China
Lei Wang: State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China
Yintong Guo: State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China
Jing Li: School of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao 266580, China
Hanzhi Yang: State Key Laboratory for Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China

Energies, 2022, vol. 15, issue 19, 1-16

Abstract: The cement sheath is an annular structure between casing and formation, which is crucial to the integrity of the wellbore system. Considering that the temperature and pressure environment is changing continuously with increasing burial depth, the micro-structure and macro=mechanical properties of the in-situ cement sheath will change accordingly. To investigate the variation of burial depth on the evolution of the tensile mechanical behavior of oil cement stone, five temperature-pressure curing and testing conditions (25 °C—0 MPa, 50 °C—10 MPa, 80 °C—20 MPa, 110 °C—30 MPa, and 140 °C—40 MPa) are set to approximately simulate an in situ temperature-pressure environment at five typical burial depths (0 m, 1000 m, 2000 m, 3000 m, and 4000 m). The in situ tensile behavior, micro-structure and pore size distribution of the cement stones at each condition are tested and comparatively analyzed. Results show that with increasing temperature and pressure, the brittleness of the cement stone reduces and its ductility strengthens accordingly. The tensile strength experiences rapid growth at first, then increases at a slower rate and finally decreases. The failure mode of the cement stone gradually transforms from tensile splitting to tensile-shear composite fracture, accompanied by increasing fracture surface roughness. Microscopically, with increasing curing temperature and pressure, the pore structure of cement stone gradually transforms from closely stacked laminated sheets to interconnected fiber networks. The dense structure of cement stone gradually becomes loose and porous. The porosity also increases from 15.96% to 29.46%.

Keywords: cement stone; burial depth; high temperature; high pressure; tensile property; roughness; microstructure (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: 2022
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