Three dimensional FEM-based simulation of hydraulic fracturing - key to understand the process and improve economics

Johannes Will

Gas and oil production from unconventional reservoirs using hydraulic fracturing is one of the key technologies for Gas and oil companies in the 21th century. Starting more than 10 years ago developing and improving hydraulic fracturing for shale gas production in the BARNETT gas field, the USA became the word largest gas producer. But economical production is a challenge to all players in shale gas. Therefore the need of simulation to better understand and finally optimize the stimulation of reservoir rock is urgent. But simulating of hydraulic fracturing is a real challenge. Most commercially available hydraulic fracturing simulators from oil and gas industry using simplifications which are not suitable to represent the physics of fracture growth good enough to be used as forecast tool. Numerous R&D teams in Industry and Universities today are searching for the best way to result in sufficient forecast quality to be able to understand and optimize hydraulic fracturing. Dynardo started in 2008 by using homogenized FEM-based continuum mechanics to address the problem. The paper will introduce and discuss the challenges we faced and the solutions we developed using ANSYS software and Dynardo’s ANSYS add on multiPlas to setup a commercial hydraulic fracturing simulator. Today the simulator is used successfully in multiple US gas fields to simulate hydraulic fracturing. Part of the discussion will be the necessary to calibrate the simulator to the reservoir conditions using all available measurements from cores, geology exploration and fracture jobs including micro seismic measures. Only after successful calibration the simulator represents all important physic to understand and finally optimize the hydraulic fracturing setup. Of course the ability to simulate and understand hydraulic fracturing gives valuable inside to possible environmental risks of hydraulic fracturing and is the key to develop “green” fracturing techniques.