Characterisation of naturally fractured reservoirs using geological well-testing
Egya, David Oka
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In naturally fractured reservoirs (NFR), fractures often constitute the main heterogeneities, yet the pressure responses observed in the wells may not show the conventional well-test signatures for NFR. In order to better characterise a reservoir with well-test data, it is important to properly analyse and understand the diagnostic signatures of fracture ﬂow. Dual-porosity model is the underlying concept for interpreting well-tests data from NFR. However,pressure behaviours in real fractured reservoirs defy the simulated pressure responses corresponding to the dual-porosity model. To overcome the limitations of this model, this thesis applies a geoengineering workﬂow using discrete fracture-matrix modelling approach and unstructured-PEBI grid to simulate ﬂow behaviour in fractured reservoirs. The workﬂow allows for a systematic correlation of the pressure responses observed in the reservoir to the known geological features in the reservoir model. Using this approach, the thesis presents new insights into why the classical dual-porosity V-shape is observed in some NFR and absent in others; explains why different unconventional pressure transient responses emerge in NFR for scenarios where fracture conductivities differ and locations of the producer within the fracture network varies; and success fully applied the theoretical ﬁndings from this research work to provide new understanding about the ﬂow system in a newly discovered fractured offshore carbonate reservoir. Overall, this thesis provide novel reference solution for interpreting well-test data from NFR.