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.