Abstract
The combined technology of perforation and hydraulic fracturing has been the main development method for unconventional oil and gas to date. However, perforation can cause crack damage to cement sheath or de-bonding of the cement interfaces, resulting in fluid channeling during hydraulic fracturing. From an operational perspective, it is thus critical to be able to characterize the degree and range of cement sheath damage after perforation. To achieve the objective, a numerical method of perforation is set up based on the ALE (Arbitrary Lagrange-Euler) algorithm in LS-DYNA software. The numerical results are verified by the ring target simulation test. The cement-interface damage zone shapes like a saddle after perforation, and there is a narrow range of damage around the perforation tunnel. The damage zone is minimized with the enhancement of cement compressive strength but conversely with shear modulus. Cements with lower shear modulus and higher compressive strength should be selected during well cementing for reducing cement sheath perforation damage. Additionally, a shaped charge with smaller liner diameter is more effective in enhancing the seal integrity during hydraulic fracturing.
