Well test analysis of a low-thickness Cenomanian gas reservoir with permeable shale layer

Background. Effective oil and gas field development requires understanding of the drainage of the reservoir both by area and by vertical direction. This task is especially relevant for low-thickness objects underlain by bottom water, such as the gas-saturated reservoir of the Pokur suite (PK-1 formation) considered in this work. Objective. To identify the permeability of the siltstone thin layer separating the PK1-1 and PK1-2 cyclites. Materials and methods. The article uses well testing methods: analysis and interpretation of the actual data of the pressure build-up curve registration and interference testing and their comparison with the results of numerical and analytical modeling performed in the Saphir module of the Kappa Workstation software. Results. Pressure build-up behavior was identified, allowing to establish the drainage through a low-permeability layer of an untapped productive layer. We found that the drainage covers the entire productive interval in a fairly short period of time: within 1 hour for a vertical well and 10 hours for a horizontal one. These estimations are proved by the data of interference testing. Conclusions. The permeable nature of the siltstone thin layer was established, through which the whole productive interval is drained during well production. The obtained results are necessary for reserve recovery and water influx dynamics estimation and calculation of well operation parameters.