Maintaining a stable borehole and optimizing drilling are still considered to be vital practice for the success of any hydrocarbon field development and planning. The present study deliberates a case study on the estimation of pore pressure and fracture gradient for the recently decommissioned Volve oil field at the North Sea. High resolution geophysical logs drilled through the reservoir formation of the studied field have been used to estimate the overburden, pore pressure, and fracture pressure. The well-known Eaton’s method and Matthews-Kelly’s tools were used for the estimation of pore pressure and fracture gradient, respectively. Estimated outputs were calibrated and validated with the available direct downhole measurements (formation pressure measurements, LOT/FIT). Further, shear failure gradient has been calculated using Mohr-Coulomb rock failure criterion to understand the wellbore stability issues in the studied field. Largely, the pore pressure in the reservoir formation is hydrostatic in nature, except the lower Cretaceous to upper Jurassic shales, which were found to be associated with mild overpressure regimes. This study is an attempt to assess the in-situ stress system of the Volve field if CO2 is injected for geological storage in near future.
Ganguli, Shib Sankar (National Geophysical Research Institute (NGRI Library)) | Vedanti, Nimisha (National Geophysical Research Institute (NGRI Library)) | Dimri, V. P. (National Geophysical Research Institute (NGRI Library))
Reservoir characterization using integrated studies is beneficial to avoid exploration risk, and perhaps most useful to understand CO2-enhanced oil recovery (EOR) and storage process in mature oil fields, where reservoir variations must be taken care for engineering decisions such as well placement, well completion, etc. In the present work, integrated analyses of reservoir flow simulation and rock physics for effective reservoir characterization for feasible CO2-EOR and storage in an Indian mature oil field are explored.
Based on the results from reservoir flow simulation, we identified a suitable black oil model with 50 m grid resolution which is in good agreement with comparatively fine grid compositional model. During the rock physics study, we identified the residual oil zones which are potential target for CO2-EOR followed by its geological sequestration. Further, based on the rock physics model, a 4D seismic feasibility study has been conducted to estimate the change in elastic properties as a result of CO2-EOR, and we envisaged two scenarios of CO2 saturations, i.e. uniform and patchy saturation models at 20% of CO2 saturation. We found a small amount of CO2 changes the Vp and AI dramatically, suggesting a reasonable CO2 response on surface seismic data. The combined study suggests that the field under study i.e. Ankleshwar in Cambay Basin (western India), has great potential for CO2-EOR and storage.
Presentation Date: Wednesday, October 19, 2016
Start Time: 1:30:00 PM
Presentation Type: ORAL