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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]

Transient rate decline analysis (TRDA) is an important analysis in modern reservoir engineering and applications. Most studies have focused on the threshold pressure gradient (TPG) of low permeability reservoirs and have placed an emphasis on the transient pressure response or steady productivity, whereas transient production decline has not been a focus. This paper presents a transient production decline analysis model of a horizontal well in low permeability gas reservoirs considering the threshold pressure gradient. An accurate solution is determined by employing the Laplace transformation, Sturm-Liouville eigenvalue method, and orthogonal transformation. The bi-logarithmic type curves of dimensionless production and the derivative are plotted by the Stehfest numerical inversion method. Five different flow regimes were recognized, and the effects of the influencing factors, such as the threshold pressure gradient, wellbore storage coefficient, skin factor, horizontal section length, and formation thickness, are discussed. This research contributes to the understanding of transient flow behavior and provides the theoretical basis for efficiently exploiting low permeability reservoirs. [ABSTRACT FROM AUTHOR]

Horizontal well (HW) was divided into several elements after acidizing. In each element, there would exist a composite zone that was made up of damage zone (DZ) and acidizing zone (AZ). Local skin factor after acidizing was used to describe the resistance in each composite zone. The models for local skin factor and productivity of HW were created using the method of equivalent filtration resistance and displacement between two similar flow modes. According to the solution of the models, type curves of skin factor and production-increasing ratio after acidizing were illustrated, and the effect of different parameters in DZ and AZ on distribution of skin factor and production-increasing ratio after acidizing were discussed. The present model has a significant guide on the practice of acidizing technology. [ABSTRACT FROM AUTHOR]

After multistage fracturing, the flowback of fracturing fluid will cause two-phase flow through hydraulic fractures in shale gas reservoirs. With the consideration of two-phase flow and desorbed gas transient diffusion in shale gas reservoirs, a two-phase transient flow model of multistage fractured horizontal well in shale gas reservoirs was created. Accurate solution to this flow model is obtained by the use of source function theory, Laplace transform, three-dimensional eigenvalue method, and orthogonal transformation. According to the model’s solution, the bilogarithmic type curves of the two-phase model are illustrated, and the production decline performance under the effects of hydraulic fractures and shale gas reservoir properties are discussed. The result obtained in this paper has important significance to understand pressure response characteristics and production decline law of two-phase flow in shale gas reservoirs. Moreover, it provides the theoretical basis for exploiting this reservoir efficiently. [ABSTRACT FROM AUTHOR]