Accurate Calculations of Stock Tank Oil Initially In Place (STOIIP) and Associated Uncertainties on High Resolution Geological Model
Guérillot, Dominique R.*1; Bruyelle, Jérémie 1
(1) Terra 3E, Rueil Malmaison, France.
Estimation of Oil Initially In Place (OIIP) is one of the priority tasks defining the reserves. An accurate method is proposed to calculate the volumetric using high resolution geological models taking advantage of huge improvements made last decade.
This paper proposes an innovative approach calculating initial oil and gas initially in place directly on these models equilibrating gravity and capillary forces. It provides 3D pressure and saturation maps. The physic is fully respected using, for each lithofacies, the most accurate available geological description with their 3D porosity distributions, their capillary pressure curves, and the thermodynamic data of oil and gas.
Moreover, uncertainties on these parameters are propagated to deliver the associated uncertainties on these volumetric calculations.
This method calculating oil in place in standard or reservoir conditions is the natural end point of any workflow devoted to the geological modeling of newly discovered or mature reservoirs, but particularly suited to highly heterogeneous reservoirs as for some carbonate reservoirs:
Being based on volumetric, it does not require dynamic data.
Using 3D maps, well designs can be improved at the early stages.
This step insure perfect consistency with the calculations done in the initialization stage of reservoir simulators on reservoir grid.
Results and conclusions
This method provides oil and gas in place in reservoir and standard conditions and 3D maps of the pressure and saturations of each phase: oil, gas and water.
These results can be compared to log extracted values to cross check the geological modeling for newly discovered reservoirs or to evaluate contact changes for mature reservoirs.
Uncertainty calculation gives to the deciders a better approach for the risk taken producing them and allows objective comparisons between several fields.
An innovative method calculating in a physically sounded manner the original or initial oil in place for reservoirs is proposed.
Dynamical data are not required allowing application to recent discoveries.
3D pressure and saturation maps help designing Maximum Recovery Contact (MRC), and intelligent or smart wells.
Uncertainties calculations allows better risk estimation.
AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain