A comprehensive model for after-closure analysis of DFIT by considering natural fractures
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2018 Offshore Technology Conference. For unconventional wells, diagnostic fracture-injection/falloff tests (DFIT) has become the standard well testing approach. However, very limited work has considered the natural fractures. The objective of this study is to develop a comprehensive model for after-closure analysis (ACA), which may help the operatorsto perform a more successful DFIT design. The comprehensive model is based on a semi-analytical model, which can simulate the DFIT by considering natural fractures. The semi-analytical approach is verified by a numerical simulator. We use the proposed model to analyze the DFIT data of a complex fracture case, namely complex fracture networks. The impacts of fractures on pressure behaviors are also studied with sensitivity analysis. It is found that the flow regime is not a single simple bilinear/linear flow during DFIT, and the pressure behaviors exhibit a dual-porosity feature "V-shape" in which pressure derivatives decrease rapidly until they reach a minimum. It is demonstrated that the standard well test analysis based on bilinear/linear flow may need improvements for ACA. Its applicability and robustness are demonstrated by using examples from a synthetic DFIT tests in unconventional reservoirs. This work may shed light on a more successful estimation of DFIT data in unconventional reservoirs.
