Development of a model for estimating the hydraulic breakdown pressure in carbonate rocks of Iranian oil wells

Due to the increasing demand for more production rates and output from oil reservoirs, the re-activation of oil wells in Iran is a vital task. Oil production reduces overtime because of a decrease in reservoir's pressure and also as a results of the closure of cracks and microscopic holes. Hydraulic fracture, as a method for stimulating oil reservoirs related to various factors, including characteristics of the environment in which the fracture grows. Mechanical properties of layers has been recognized as one of the most effective parameters on the progress of hydraulic fracture and its geometry. In this study, the primary rock was considered as non-cracked. In this research, numerical modeling was done by ABAQUS software in 21 different cases for which the effect of each input parameters on the hydraulic fracture pressure was investigated by performing sensitivity analysis. The input parameters were well's data and included Young's modulus, minimum and maximum horizontal stress, vertical stress, tensile strength, Poisson''s ratio and pore pressure. The required data is obtained from the excavated wells in carbonate rocks in Iran. The results showed minimum horizontal stress has the highest impact on the hydraulic fracture pressure. Finally, using SPSS software and by performing multivariate regression analysis, a formula was made using the numerical modeling data to estimate the hydraulic fracture pressure. The results of statistical analysis corroborate the precision of regression line and consequently the suggested formula. In this formula, the parameters such as minimum horizontal stress, the difference between minimum and maximum horizontal stresses, pore pressure and tensile strength, have the most effect on the hydraulic fracture pressure respectively. Using the presented formula in this study, the hydraulic fracture pressure in carbonate wells with different properties could be obtained. Gaining this pressure will help to determine the proper pump and case to reduce operating costs.