Tidally Influenced Sedimentation in the Upper Cretaceous Almond Formation, Patrick Draw Field, Sweetwater Co, Wyoming: Come Look at the Cores

Beverly Blakeney DeJarnett, The University of Texas at Austin, Bureau of Economic Geology, Houston Research Center, 11611 W. Little York Road, Houston, TX 77041, phone: 713-983-9420, [email protected] and Alan J. Scott, Alan J. Scott and Associates and Anadarko Petroleum Corporation, 1201 Lake Robbins Drive, The Woodlands, TX 77380.

The Almond Formation has been a prolific hydrocarbon producer in the Green River Basin for over 50 years. In Patrick Draw Field, Sweetwater County, Wyoming, the Almond has produced approximately 60 MMBO and 130 BCFG since its discovery in 1959. Patrick Draw, made up of Monell and Arch Units, has undergone primary and secondary (waterflood) recovery efforts. Initial stratigraphic interpretations were based on cores taken in the 1960's and 70's. Most cores from Monell Unit were subsequently lost or destroyed, and most cores from Arch Unit reside at the USGS in Denver. The Almond reservoir sandstones in Patrick Draw were originally interpreted as two north-south trending barrier bars with fine-grained lagoonal sediments forming an updip trap to the west and the transition into marine mudstones defining the eastern extent of the reservoir.

Anadarko Petroleum Corporation has recently begun tertiary recovery of the oil in place through CO2 flooding of the Almond in Monell Unit. Improving efficiency of CO2 flooding in this significant oil reservoir is critical in light of the alternative costs of drilling all new wells and building new facilities. Over 10 recent cores have been taken in Monell, and new stratigraphic interpretations can be made by integrating these cores with earlier cores. The Almond deposits are now interpreted as flood tidal deltas, tidal inlets, tidal channels, tidal creeks, spit platforms, bay muds and oyster patch reefs. Understanding the complex stratal architecture of these lithofacies is critical to designing and operating a more successful CO2 flood for Monell Unit.