Fluid Flow Behaviors Under Architectural Controls of the Wall Creek Member in the Frontier Formation: Western Powder River Basin, Wyoming

Abstract

The Frontier formation in the Powder River Basin has been re-discovered for oil and gas potential with the development of long horizontal wells and multi-stage hydraulic fracturing. Over the last decade, the Wall Creek Member (WCM) of the Frontier formation has proven to be a successful hydrocarbon-producing target, yet a full understanding of this complex stratigraphic unit has not been fully achieved. Tisdale Anticline outcrop studies conducted by University of Montana have shown that thickening upward tidal bars within WCM play an important role in hydrocarbon production. Recent studies have analyzed the geometry and extent of muddy toesets within tidal bars to affect fluid flow behavior. Furthermore, the fluid and rock properties have uncertainty and are not well defined due to the low permeability rocks. This study aims to describe the fluid flow behaviors of these features and create a regional outcrop model (1 km by 1 km) that includes all the reservoir properties and geologic features to better understand hydrocarbon recovery.

This project consists of defining the reservoir properties and upscaling the permeability of defined geocellular models with different geologic features into the reservoir model for the WCM. A single horizontal well flow simulation model was created to estimate the reservoir properties. Using three offset well logs, a 32 feet interval was selected to represent the net pay zone of the Wall Creek. The porosity was estimated using well logs, and permeability was established by applying a correlation of porosity and permeability found from core data. The historical production was matched by modifying the initial fluid saturations and the rock physics parameters such as relative permeability and capillary pressure. As a result, representative fluid and rock physics models were obtained for regional model.

From the outcrop study, the defined geologic models (25m by 15m) of 2 to 3 meters thick WCM tidal bars were created to include abundances and orientations of mud drapes as the most effective features of tidal bars. A regional model captures fine heterogeneities of tidal bars using flow-based upscaling of the geologic models. The effective directional permeabilities of each geologic scenario were obtained to create the correlations between the mud drapes characteristics and effective permeability to create the regional model based on the outcrop observations. Results from the regional model are used to optimize field development.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018