Hydraulic Fracture Design Evaluation Through a Robust Geo-Mechanical Model, Tested in a Tight Gas Reservoir, North of Oman

Abstract

Abstract Natural gas plays an essential role in providing the world with a cleaner energy for possibly the next 50 years. Conventional gas resources are quickly declining and many countries (e.g. Oman) are investing in tight gas extraction. Such natural gases are usually accumulated in tight sand or shale formations, which have extremely low permeability. Thus, they don't flow at a commercial rate without implementing a hydraulic fracturing, which is an expensive and complicated technique. Therefore, proper fracturing design is a must to enhance well productivity and connectivity. In this study, the petrol physical logs and real field test data were used to construct an intensive rock mechanical model (RMM) for a specific tight gas field to be used in an economical simulator, to optimize the hydraulic fracturing design and strategy for the field. In this study, a rock mechanical model (RMM) was constructed to calculate the rock mechanical properties of the Formations, such as Poisson ratio, Young's modulus, uniaxial compressive strength (UCS), pore pressure and situ stresses. This was achieved by using the drilling data, wireline logs and core data of two wells from the field. The calculated properties from RMM were calibrated by inputting them in a specific constructed geo mechanical equation at which its trend was matched with the field caliber log trend. Some revision and modification were applied using an economical simulator to optimize the hydraulic fracture treatment. The simulation was run twice. In the first run, the simulator calculated the mechanical properties of the formation automatically by the built-in correlations of the simulator. In the second run, the outcome of constructed RMM were input in the simulator. The results from simulator were compared with the real fracture height from the radioactive tracer measured from the field test. The simulator's result shows the error percentage in the first run, which was done without the RMM, was 112%. While in the second run, where rock mechanical properties were entered in the software, it was 11%. As expected theoretically, building a fracturing model with calibrated data from RMM provides accurate and precise results that are close to the real measurements. However, the minor difference between the second run and the actual measurements can be because of uncertainties in the rock formation, and unavailability of some test data. In addition, the accuracy of the radioactive tracer to measure the real fracturing treatment should be considered. The outcome of this project would help to enhance and optimize the fracturing design and ultimately enhance the productivity of the newly fractured wells. Further, this study is considered an excellent guideline for current and new hydraulics fracture design to reduce the OPEX of the well and optimize production.