Discrete fracture network (DFN) modeling and hydraulic fracturing (HF) simulations in FracMan for tight sandstone and gas shale unconventional reservoirs of thrace region

Abstract

The thesis primarily aims to develop and validate Discrete Fracture Network (DFN) models for hydraulic fracturing (HF) simulations in unconventional reservoir rocks, specifically in the Trace region's tight sandstone and gas shale formations. This research is crucial in the field of petroleum engineering and rock mechanics as it seeks to provide a deeper understanding of hydraulic fracturing processes in complex geological settings. It addresses the challenges posed by the heterogeneous nature of rock formations and the intricate network of natural fractures that impact fluid flow and fracturing behavior. The methodology employed in this study is multifaceted. It begins with the collection and processing of high-quality outcrop images using Image J software for precise fracture identification. These images are digitized in AutoCAD, allowing for the accurate mapping of fractures and extraction of key geometric parameters. These parameters are then used to create and optimize DFN models for hydraulic fracturing simulations in the high-tech software FracMan. The study also encompasses comprehensive geological analysis, fieldwork, and laboratory experiments to validate these models and understand the geological structure of the Thrace region. The geological analysis focuses on the Thrace region's unique stratigraphy and sedimentation history. This involves a detailed description of the geological characteristics of the region, including the study of various formations, their composition, and their significance in terms of hydrocarbon potential. DFN models were developed using a state of art software FracMan, integrating geological, and in situ data. The study emphasizes enhancing the understanding of hydraulic fracturing processes within these complex settings. The models are validated through extensive fieldwork and laboratory experiments, which include analyzing rock samples for their physical and mechanical properties through Brazilian and uniaxial compression tests. The research involved simulating hydraulic fracturing within a 600x600x600 meter reservoir, examining vertical and horizontal well configurations aligned with the maximum and minimum horizontal stress directions. In the vertical well, induced fractures followed a trend/plunge of 225/0, with an average aperture of 0.0316 meters. These fractures covered an area of 5400 m2 and had a total volume of 134 m3. Horizontal wells aligned with SHmax exhibited 140 induced fractures spanning 1400 square meters, with a volume of 26.45 cubic meters. In the case of SHmin alignment, 144 induced fractures had an average aperture of 0.024 meters, covering 1440 square meters and totaling 27.16 cubic meters in volume. Inflation resulted in 80, 115, and 112 fractures for the vertical well, horizontal well aligned with SHmax, and horizontal well aligned with SHmin, respectively. Inflation predominantly occurred on fractures near perforation sites. The combined count of inflated and non-inflated fractures precisely equaled the total fractures identified in the Discrete Fracture Network model for each scenario. The outcomes of this research are expected to contribute to optimizing hydraulic fracturing designs and improving hydrocarbon recovery efficiency. By advancing DFN modeling techniques and integrating them with empirical data, the study aims to bridge the gap between theoretical models and real scenarios. The insights gained could be pivotal in determining possible future exploration and recovery strategies in similar geological settings. This study marks a significant contribution to understanding and optimizing hydraulic fracturing in complex geological settings. The comprehensive approach undertaken in this research is expected to influence the development of more effective fracturing practices and contribute to the broader field of geological research and exploration strategies.