New Analytical Approach for Reservoir Stress Approximation Based on Acid Fracturing Data

Recently, rock mechanics contribution in petroleum industry has significantly increased. Examples of these applications are wellbore stability analysis in horizontal wells, and sand production problem while extracting hydrocarbon from sandstone reservoirs. However, determination of the magnitude and orientation of the in-situ stresses is an important parameter for implementation of such kind of studies. The matter is so important that recently global endeavor for sharing practice to determine such expensive data is formed, and world stress map is being developed based on information provided by individuals around the world.In this research attempts were made to estimate the in-situ stresses acting on a hydrocarbon reservoir based on routine activities of acid injection in oil reservoir. It was found that the relation between the re-opening pressure of fracture and principal in-situ stresses can be estimated using rock mechanics equations for the circular underground cavities. An appropriate relation between the maximum and minimum horizontal principal in-situ stresses and reservoir parameters such as permeability, reservoir pressure, Young’s modulus, acid viscosity, injection flow rate and etc, was developed by using the well-known Darcy equations for fluid flow in porous media. Accordingly, knowing the flow rate of acid injection during well stimulation operations and some other reservoir parameters, in-situ stresses may be estimated. This approach is innovatively creating further significant knowledge regarding the reservoir mechanics, using the routinely available acid fracturing data. The method was then successfully applied to a giant carbonate reservoir in SW of Iran. Maximum and minimum effective horizontal stresses were calculated by employing the presented method. The significance of this approach may be distinguished at the local and global scale by helping for better correlation and development of in-situ stress data at oil-rich states around the world.