A case study for HCL-based fracturing and stress determination: A Deformation/Diffusion/Thermal approach

作者：Haghi A H^*; Kharrat R; Asef M R

来源：Journal of Petroleum Science and Engineering, 2013, 112: 105-116.

DOI：10.1016/j.petrol.2013.10.013

• acid stimulation
• reservoir geomechanics
• present day in-situ stress
• re-opening pressure
• bi-linear flow

In this research, attempts were made to estimate the in-situ stresses acting on a hydrocarbon reservoir based on routine activities of acid fracturing in carbonate reservoir. A triple DDT (Deformation/Diffusion/Thermal) full solution was introduced to the estimate maximum horizontal stress magnitude by using rock mechanics and poroelastic equations for the circular underground cavities, fluid diffusivity equation through porous media and thermal stress. To eliminate errors in recognition of the breakdown pressure, it was replaced by re-opening pressure with some modifications. Accordingly, for the first time in this study bilinear flow equation was presented to simulate acid flow through the fracture. Furthermore, this approach was introduced as a good indicator of stress direction in open hole wells while the chemical reaction between HCL-based acids and carbonates caused enlargements of induced fracture and wellbore. Accordingly, this new stress indicator promoted some weaknesses from the old fracturing technologies, such as less fracture initiation pressure by producing heat at the borehole wall, easily defining fractures with caliper and image logs, introducing a triple full solution for direct estimation of S-H and so on. This study was then applied successfully to an offshore well, and completed in Triassic carbonate reservoir in Persian Gulf, South Iran. Vertical stress at 2900 m depth was found to be 7800 psi from density log. Maximum and minimum horizontal stresses were calculated by employing the presented method and they were 8730 and 7180 psi respectively. Calculated field stress, noticed fracture and fault%26apos;s strike direction and maximum horizontal stress orientation worked together and proved strike-slip faulting regime as the present-day stress field. The significance of this approach may be distinguished at both the local and global scale by enabling better correlation and development of in-situ stress data in oil-rich states around the world.

• 出版日期2013-12
• 单位中国石油大学（北京）