Periodic Reporting for period 2 - BESTOFRAC (Environmentally best practices and optmisation in hydraulic fracturing for shale gas/oil development)
Berichtszeitraum: 2019-01-01 bis 2022-10-31
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.
Concerning exchanges and activities inside the consortium, we notice that all workshops have been carried out as intended though the secondments are delayed for several reasons including visa issues. The first workshop training the ESRs and ERs has been held successfully in Udine as intended. The mid-term meeting was held in June at Leibinz University Hannover (LUH) as requested by the project officer. The external expert evaluated the progress positively and requested minor revisions to the progress report and deliverables. These have been incorporated and resubmitted.
1. One of the first (stochastic) 3D discrete crack models for hydraulic fracture taking into account the interaction between deformation and fluid.
2. One of the first 3D multiphysics HF models implemented in COMSOL.
3. One of the first platform for sharing knowledge, expertise and data of HF activities.
4. One of the first HF model quantifying the influence of uncertain input parameters with respect to a predicted (uncertain) output.
2012 World Energy Outlook special report on unconventional gas exploitation concluded that the potential for contamination of surface and groundwater must be successfully addressed. The existence of both cons and pros for the HF method making it highly controversial. The European scene on SGD is totally split: there are a number of countries who seem to be quite enthusiastic, like Poland or the UK. Germany remains conservative and uncertain while France is skeptical. Even as a favourable country, the UK has undergone changes in its position. Its government announced in December 2012 to resume HF activities after a temporary moratorium following small seismic tremors. Research on HF is often funded by these government bodies. The debates on the HF induced consequences require a clear look and consultation where scientific and effective modelling tools predicting HF consequences is in urgent need. European Commission is making plans for developing a legal framework for shale gas exploration in Europe. The research methods developed by this project are expected to provide scientific modelling results supporting decision making in future energy development.