Modeling Migration Pathways in Washover Fans Using Analyses of Modern Fan Morphologies and Subsurface Data

Hudock, Jessica¹; Wood, Lesli; Flaig, Peter; and Massingill, Gary
¹[email protected]>

Washover fan (WOF) deposits are part of a larger group of highly heterolithic barrier and shoreline-margin deposits, which form notoriously hard-to-produce conventional and heavy oil reservoirs (e.g. vast quantities of hydrocarbons are typically stranded in these systems, steam breakthrough is unpredictable, etc.). For this study we analyzed both modern and ancient WOFs. Results were combined with a detailed examination of subsurface data (core, log, seismic and production history) from a relatively large, late Cretaceous WOF in the McMurray Heavy Oil Belt of Canada in order to develop an improved method for producing these prolific but complex reservoirs.

A spatial analysis on 118 modern WOFs employed satellite imagery to quantify various morphometric characteristics of WOFs. Results show that WOFs that resemble the classic model of a point-sourced, channelized, fan-like geometry are actually rare, and this model may be unsatisfactory for reservoir development plans. Contrary to the classic model, WOFs predominantly occur as line-sourced, non-channelized features and typically do not extend to form back-barrier lagoon micro-deltas. Fan length increases exponentially, and fan throat width increases linearly, with total fan area.

Core, log, seismic and production data from a WOF in the McMurray Formation of Alberta, Canada show the deposit to be an amalgamated feature up to 20 meters thick. Core descriptions are used to identify facies and correlate facies to log motifs. Additionally, our data analysis of modern fans is compared to McMurray Formation isopach maps to help improve predicted geometries and architectures of this heavy oil reservoir. Surfaces and barriers to flow are described and a new static reservoir model is proposed. We believe that this study will help to improve modeling and recovery in other petroleum systems containing producible WOF deposits.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013