Current HF practices of unconventional hydrocarbon extraction are based on the emergence of several key technologies: the development of directional drilling, the use of high volumes of fracturing fluid, improvements in fluid lubrication as well as the use of multi-well pads. Lately, the use of HF in unconventional oil and gas extraction has generated a lot of controversy. Opponents of HF claim that its use poses severe environmental risks such as contamination of groundwater resources, that it depletes freshwater supply and induces seismic activity. There are serious environmental issues, which include possible groundwater contamination as well as risk of spills of chemicals and wastewater during vehicular transport and from on-site storage equipment. This is complicated by the fact that full disclosure of chemicals used in HF has not yet been achieved in industry despite intense public demand, so that monitoring of surface contamination is made difficult in the sense that monitoring personnel do not know exactly what substances to test for.
It is apparent that successful optimization of HF process variables requires a good understanding of the mechanics of HF treatment operations in NFRs such as shale. These variables include fluid injection pressures and rates, chemical compositions of the HF fluid, well lateral orientations and spacings, number and distance between HF stages. Ideally, we want to maximize stimulated volumes while minimizing the volume of HF fluids as well as their chemical content. Successful optimization is predicated on the ability to accurately model the physics of the HF process as well as the ability to do proper sensitivity analyses with respect to the process variables. Direct monitoring evidence suggests that fracture in an NFR evolves in a complicated manner according to the presence of local heterogeneities, layering and natural fractures. Therefore, it is also important to be able to take into account existing natural fracture networks in the numerical model.
This project aims to bring together the complementary expertise of research groups to gain a better understanding of the physics in hydraulic fracturing (HF) with the final goal to optimize HF practices and to assess the environmental risks related to HF. This requires the development and implementation of reliable computational models of HF and laboratory experiments to validate these models. The scientific objectives can be summarized as follows:
1. To generate new models to the HF analysis and control problems through exposure to different methodologies.
2. To validate the models in a stochastic sense and carry out uncertainty analysis (UA) to identify the key input parameters (such as tectonic stress, material parameters etc.) of the underlying model with respect to (w.r.t.) a pre-defined output such as the crack density, fracture volume or pressure drop.
3. To build a database and experience sharing platform for the current HF models, geological data and operating conditions.
