Optimization of the Multi-stage Hydraulic Fracture Geometry for the Tight Carbonate Reservoir

Abstract

The tight carbonate oil resources are abundant, normally characterized with low permeability, poor pore connectivity and large flow resistance through the production area. Proper stimulation treatments and an optimal design for the hydraulic fracture geometry is of great importance for economic production. Since natural fractures are developed in some parts of the reservoir, the effective fracture network and efficient conductivity of the natural fractures and micro fractures for the long term is critical to improve the oil recovery. In this study, the hydraulic fracture geometry was optimized and the micro-proppant was incorporated for the long term fracture conductivity. A triple-porosity-permeability model was first established and three geometric models of hydraulic/acidizing fractures including multistage fractures, branch fractures and complex fracture network were proposed and compared in terms of daily and accumulative oil production. In addition, the influence of governing geomechanical and fracture parameters on the production performance and the ultimate oil recovery was analyze for the fractured horizontal well through numerical simulations. Moreover, the conductivity increase through the placement of micro-proppant in the micro and natural fractures and their effect on the long-term production improvement was investigated. The results show that the effective communication between the natural and hydraulic fractures results in significant improvement in the production performance. Specifically, the daily oil production rate from the complex fracture network is as high as 1.5 times compared to that from the branch fractures. In addition, the production is positively correlated with the half-length of the hydraulic fracture and conductivity of both natural and hydraulic fractures, which increases gradually in the first half year and decreases considerably afterwards. However, there is an optimal value for each parameter in terms of the NPV. This study improves the understanding of the uncertainties associated with hydraulic fracture geometry in the reservoir stimulation. The optimization of the fracture geometry and fracture parameters contribute to high production rates during the production build-up and the maximization of the long-term oil/gas recovery.