Journal of Southwest Petroleum University(Science & Technology Edition) ›› 2024, Vol. 46 ›› Issue (2): 65-76.DOI: 10.11885/j.issn.1674-5086.2023.09.02.01

• OIL AND GAS ENGINEERING • Previous Articles     Next Articles

Effect of Supercritical CO$_2$ on Mechanical Properties of Tight Carbonate Rocks

GOU Bo1, WANG Kun1, LI Xiao1, ZHAN Li2, LIU Chao3   

  1. 1. National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China;
    2. Downhole Service Company, CCDC, Chengdu, Sichuan 610052, China;
    3. Research Institute of Yanchang Petroleum(Group) Co. Ltd., Xi'an, Shaanxi 710065, China
  • Received:2023-09-02 Published:2024-05-11

Abstract: The supercritical CO$_2$ fracturing has the characteristics of low fracture pressure and easy formation of complex fractures in tight carbonate rock, but the mechanical mechanism of the effect of supercritical CO$_2$ on tight carbonate rocks is not clear. The physical properties, acoustic response, rock mechanical properties and fracture morphology of the tight dolomite samples from Majiagou Formation were studied by using the high temperature and high pressure supercritical CO$_2$ saturated fluid method, namely the samples were immersed in supercritical CO$_2$ + formation water for different time. The results show that with the increase of soaking time, the dissolution pore size and the porosity and permeability of the rock sample increase due to chemical corrosion, and the corresponding acoustic velocity, dynamic and static rock mechanical parameters all decrease. When the soaking time is longer than 1.0 d, the physical property parameters of the rock sample increase and the mechanical strength decreases obviously. With the increase of soaking time, the fracture morphology of rock samples develops from single low angle shear joint to high angle shear joint, conjugate joint and shear and tension composite joint. In short fracturing time($\leqslant$1.0d), the weak acid formed by supercritical CO$_2$ + formation water has limited deterioration degree to rock mechanical strength.

Key words: tight carbonate rock, supercritical CO2, pre-acid fracturing, mechanical strength, fracture pattern

CLC Number: