Fracture Design Optimization Utilizing 3D Simulation Models & Sensitivity Analysis for Unconventional Reservoirs

Abstract

Hydraulic fracturing is the gateway for achieving new levels of unconventional resource production. However, hydraulic fracturing requires careful planning and optimized design for it to be profitable. There are multiple parameters that affect the performance of a hydraulic fracture design. One of the most important parameters that effect the performance of hydraulic fracturing is the fracture cluster spacing (FCS). FCS design is a complicated task especially for a new area due to the complexity of rock mechanics involved in unconventional reservoirs. We developed a novel sensitivity analysis approach to optimize the FCS using a 2D and 3D hydraulic fracturing models built with field data acquired from a well producing in the Eagle Ford. Our optimization criteria include fracture conductivity, fracture cluster length, fracture cluster width, proppant coverage, and fluid loss. The main optimization constraint during the fracture design was to avoid stress shadowing effects and screenout issues. This approach consists of two phases. Phase 1: Investigation of optimum clusters per stage number. Phase 2: Creation of the optimum fracture design. First step in our methodology is generating the simulation model by importing the log data to distinguish potential pay zone(s) and calculate the stress profile of these zone(s). Second step is to build a permanent 2D simulation model by selecting a perforation design, optimum proppant size, proppant type, pumping rate, and fluid type to finally attain an injection schedule for the 3D model. The final step is to optimize the 3D model’s performance by selecting the ideal FCS per stage. Our results show that the optimum cluster design is 3 fractures per stage with 200 feet spacing between fracture clusters (FCS). We observed that most cases outside the optimum design will cause stress shadowing which needs to be avoided for the sake of fracture efficiency and well productivity. Although, this FCS design is for a specific area, our comprehensive sensitivity analysis approach will be a guide to many operators to design fracture jobs more efficiently in the future because stress shadowing can happen for any area in the world. Our optimization study also revealed that we can get an efficient hydraulic fracture design with low number of clusters which will have a positive impact on the environment due to water preservation. It will also reduce the cost of the operation and the time it takes to complete the fracture job.