--> --> An Outcrop Based Integrated Reservoir Model of the Frontier Formation Hybrid Play in the Powder River Basin, Wyoming, U.S.A.

2018 AAPG International Conference and Exhibition

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An Outcrop Based Integrated Reservoir Model of the Frontier Formation Hybrid Play in the Powder River Basin, Wyoming, U.S.A.

Abstract

The quantification of reservoir heterogeneities and their effect on reservoir behavior is becoming an increasingly important aspect to predict reservoir performance in low permeability plays. However, it is notoriously difficult to capture the stratigraphic architecture from the tools available for subsurface evaluation. Outcrops can serve as an excellent tool to improve the understanding of the reservoir behavior, in particular in a setting where outcrops are close to the producing fields, and stratigraphic architecture observed in outcrop is representative of the subsurface reservoir heterogeneity. Here we present the results of an integrated outcrop to geocellular modeling to reservoir simulation study to better understand the reservoir behavior of the tight oil reservoirs of the Frontier Formation in the Powder River Basin, Wyoming, USA. To capture and understand the effect of thin beds and drapes in this heterolithic reservoir, we first created representative geomodels at a centimeter resolution for all facies observed in outcrop. Although the architecture was captured from outcrop, the facies properties were taken from nearby well locations to have the best representation of the subsurface reservoir conditions. Flow simulations on these models resulted in anisotropic flow properties (Kx, Ky, Kz) that then were used to upscale to a full field geocellular model. In this latter model stratigraphic architectures were again captured from 3D outcrop models. Simultaneously we defined the reservoir properties through a single horizontal well flow simulation model to estimate the reservoir properties to use as input parameters for the outcrop geocellular models. Historical production data was matched by modifying the initial fluid saturation and the rock physics parameters such as relative permeability and capillary pressure. Our results suggest that of all the variables tested the presence or absence of mud drapes and low permeability thin beds within heterolithic deposits is the most fundamental and critical parameter in the effective permeability of the Frontier Formation. Other important parameters but secondary to the former, are bed geometry and continuity, facies variability on the parasequence scale, and structural complexity. This integrated multi-step study aids with development and completions strategies including optimization of well and fracture spacing in tight oil reservoirs.