This work discusses reservoir pressure gathering relevance in tight gas sands description. Data validation and interpretation procedures are outlined, as well as the impact of using this kind of data in reservoir characterization and optimum completion design.
A workflow to gather reservoir pressure values within an acceptable certainty range for the description of these low permeability reservoirs is presented. The proposed methodology is based on the analysis of historical data obtained according to traditional standards, with the aim of improving the pressure data acquisition efficiency.
The workflow considers the characteristics of most of the commercially available tools (i.e. snorkel geometry and size, flow rate ranges, etc.). Optimum zone selection and tool placement points based in log interpretation is also described.
The proposed workflow proved to be helpful in optimizing pressure data obtained through wireline formation testers. Data are in good agreement with pressures estimated by DFIT. These results encourage the continuous improvement of the technic.
In addition, some conclusions were drawn from the analysis of the DFITs obtained.
From the data analyzed, the tight sands of Cuyo Group can be best described as low porosity – low permeability reservoirs, in the micro Darcy (μD) range. Deeper zones can reach pressures and temperatures of up to 80 MPa (11600 psi) and 165°C (HPHT). Both normally and overpressurized sands can be found.
We propose a workflow to guide pressure acquisition with formation tester, to deal with the challenge of low permeability sands. Even though the results are presented in relatively wide ranges, those are suitable for better reservoir description and well completions.