Do Fluid Compositions and Reservoir Pressure Tell Us the Same Thing About Reservoir Segmentation?

Abstract

A multitude of reservoir fl uid parameters (pressure, GOR, molecular composition, etc.) are usually available for reservoir segmentation interpretations. These parameters are controlled by multiple reservoir processes including, but not limited to, reservoir charge/fi lling, fl uid mixing through darcy fl ow/advection/diffusion, gravity segregation, biodegradation, fractionation, and differential leakage. The time scales for these processes to operate in reservoirs will be the key to understanding the relative signifi cance of fl uid data to reservoir compartmentalization studies.Numerical simulation provides us a platform to put these reservoir processes to test. Validation and prototyping of the miscible fl uid mixing simulation have generated results consistent with analytical solutions and other numerical simulations (Smalley et al., 2004). Preliminary results from simulation for simple geometrical reservoir models suggest that pressure equilibration is the fastest and is several orders of magnitude shorter in time scale than density/composition through convection or through diffusion processes. Thus same pressure gradients do not necessarily mean that fl uids have equilibrated in composition in reservoir compartments. We may need to attach different degrees of signifi cance to pressure and fl uid compositional data in reservoir segmentation assessment. Field case studies will be presented to apply the fl uid mixing simulations to explain fl uid data distribution and composition variations.This study will reduce the uncertainties associated with reservoir compartmentalization interpretation using fl uid property data and help to optimize oil fi eld development and production.