Abstract
Transient pressure analysis is a crucial tool to forecast the production performance during the exploration and production process in gas reservoirs. Usually, a regular shaped outer boundary is assumed in previous studies for well-testing analysis, which is just a simplification of practical cases and cannot reflect the actual boundaries of reservoirs. In this paper, a mathematical model is established to analyze the transient pressure behaviors of a horizontal well in an arbitrarily shaped gas reservoir. Dimensionless treatment, Laplace transformation, and boundary element method are applied in solving the model, which is verified by comparing with the results from the source function method. Based on the Stehfest numerical inversion method, the models of single-porosity media and dual-porosity media are solved respectively. Then, the time-domain curves of pseudo pressure and its derivative are obtained, and the flow regimes are identified. Finally, the impacts of some critical parameters on pressure transient behaviors are analyzed, including storativity ratio, interporosity coefficient, well length, and well orientation. This paper presents an effective way to handle complex external boundary problems in gas reservoirs.
Highlights
The exploration and development of natural gas plays an irreplaceable role in building a green and clean energy system (Zou et al, 2018)
Zhao et al (2016) used the boundary element method (BEM) to analyze pressure transient of multiple fractured horizontal wells (MFHWs) in the gas reservoirs with arbitrary outer boundary, and the solutions obtained by the BEM fit well with the solutions derived from the semi-analytical method and well testing software, respectively
The curves of pseudo pressure and its derivative are overlapped lines of a unit slope. › The second flow regime is the transition flow period, which is controlled by the skin factor. fi The third is the early linear flow period, where the pseudo pressure derivative curve appears a straight line with 0.5 slopes
Summary
The exploration and development of natural gas plays an irreplaceable role in building a green and clean energy system (Zou et al, 2018). Zhao et al (2016) used the BEM to analyze pressure transient of multiple fractured horizontal wells (MFHWs) in the gas reservoirs with arbitrary outer boundary, and the solutions obtained by the BEM fit well with the solutions derived from the semi-analytical method and well testing software, respectively. This method cannot handle seepage problems in reservoirs with complex outer boundaries, such as the arbitrary shaped outer boundary In this part, the transient pressure behavior of a horizontal well in a gas reservoir with a rectangular shaped outer boundary (seen in Figure 2) is used to verify our model. The calculation results of transient pressure behaviors of a horizontal well in box gas reservoir are in good agreement between the traditional source function method and our new boundary element method (See Appendix 1 for the original data). Our model will be used to conduct the identification of flow regimes and sensitivity analysis
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