Semi-Analytical Modeling of Fluid Flow in and Formation Evaluation of Unconventional Reservoir Using Boundary Integration Strategies
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Tight oil/gas has been increasingly playing a more and more important role in petroleum industry around the globe for the past two decades and accounting for more share of total production of oil/gas each year. Fractured vertical or horizontal wells contribute most of the tight oil/gas production. Understanding and analyzing fluid flow in the process of fracturing, therefore, become crucial in tight formation production. However, the resulting complexity of fracture propagation from fracture injection test in tight formation, which currently is one the most heated topics for unconventional reservoirs, and heterogeneity problems of tight oil/gas reservoir with non-uniform distribution of rock/fluid properties bring great difficulties in modeling of such complex well-reservoir systems so as to evaluate reservoir characteristics and simulate a variety of reservoir flowing behaviours. Using boundary integration strategies and source and sink function methodology, this dissertation tackles the problems of modeling fracture-propagation-and-closure process along with analyzing the fracture injection test data (mini-fracturing test) in homogeneous reservoir, and modeling of fluid flow in different types of heterogeneous reservoirs. In particular, they are: (1) Analytical Modeling of Fracture Propagation on Evaluation of Transient Pressure Behavior during Injection and after Shut-in: Minifrac Test Analysis by Model-Based Type Curves; (2) Modeling of Multi-stage Fractured Horizontal Well Producing in Multilayered Reservoir with Inter-layer Crossflow; (3) Semi-analytical Modeling of 2-Dimensional Heterogeneous Reservoir by Using Boundary Element Method. II What is presented is that a practical fracture-propagation-and-closure process is modeled, its solution in terms of pressure and leak-off rate behaviors in type curve format is generated and the model-based solutions are applied using curve matching strategy in analyzing field mini-fracturing testing data to evaluate the leak-off rate behavior along a fracture, in order to obtain the fracture geometry, attain an instantaneous shut-in pressure (ISIP), extract reservoir flowing capacity (kh) and detect closure pressure Pc. A reasonable set of parameter solutions can be obtained using the model developed in this study due to a proper modeling of the physical process. Robust analytical results on transient pressure behavior under constant rate and rate response under constant bottom pressure are presented in type curve format as well as inter-layer crossflow for the multilayered reservoir system. By applying boundary element method (BEM), pressure- and rate-transient behaviours of reservoir with multi-scale heterogeneities bounded by arbitrarily shaped boundaries/surfaces are also presented.