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Interest in tight gas reservoirs (TGR) has quickly spread worldwide. Most researches on the permeability stress-sensitivity of tight gas reservoirs mainly concentrated on experimental approach, physical modeling or pressure behavior analysis, while transient production rate performance does not attract much attention. This study developed a dual-porosity model of a horizontal well in fractured tight gas reservoirs considering the stress-sensitivity effect. The solution methods include variable substitution, perturbation technique, Laplace transformation, Sturm-Liouville eigenvalue theory, orthogonal transformation and numerical inversion. The results showed that the production rate decreases with the increasing of permeability modulus and the derivative curve will be warped up during the whole system late radial flow stage. The influences of other parameters are also analyzed. The work undertaken here has both theoretical and practical significance in predicting production performance and evaluating underground fluid transport in such formations. [ABSTRACT FROM AUTHOR]

Abstract On the basis of the seismic data volume of a certain well group unit of the Tahe fracture–vuggy reservoirs, the similarity theory is adopted, and a numerical model with geometric, kinematic, dynamic, and fracture–cavity characteristic parameter similarities is designed. Moreover, a large–scale three–dimensional physical karst cave model is built with the carving technology. The model is used in the experimental study of two–phase flow of oil/water during waterflood development and in the analysis of relevant influencing factors. Results show that the displacement efficiency of low–high mode is obviously superior to the case of high–low mode. A high crude oil viscosity is found to equate to a low ultimate recovery. High–velocity water flooding improves ultimate recovery but results earlier water breakthrough. Well shutdown improves recovery factor and well shutdown during middle water cut stage achieves optimum effects. Bottom water energy benefits oil reservoir exploitation to some degree. Highlights • A large–scale three–dimensional physical karst cave model is built to study the two–phase flow of oil/water. • Displacement efficiency of low–high mode is obviously superior to the case of high–low mode. • A high crude oil viscosity is found to equate to a low ultimate recovery. • High–velocity water flooding improves ultimate recovery but results earlier water breakthrough. • Well shutdown during middle water cut stage achieves optimum effects. [ABSTRACT FROM AUTHOR]

Multi-stage hydraulic fractured horizontal wells (MHFHWs) are used to develop low permeability reservoirs. A flow model of the MHFHW is proposed based on tree-shaped fractal fracture networks (TFFNs) considering the tree-shaped fractal network and the hydraulic theory of fracture. Then, a physical model of the MHFHW is established by several TFFNs, including the physical model, generating rules, and numbering rules of the TFFN. A coupling mathematical model is presented by combining the flow and seepage models for the TFFN of the MHFHW. The iterative method is used to solve the mathematical model, and the distributions of pressure, flow rate, and seepage rate in the MHFHW are obtained. The proposed model provides a new method to simulate the flow of the MHFHW considering the tree shape and the fractal characteristics of fractures in the MHFHW. [ABSTRACT FROM AUTHOR]