Tierney Field - A New Wamsutter Area Sweetspot, Greater Green River Basin,

Sweetwater County, Wyoming, USA

By

G. Earl Norris

BP America Production, Inc, Houston, TX

Debra H. Phillips

BP America, Inc, Houston, TX

Since 1998 over sixty producing wells have been drilled in the Tierney area, more than doubling the number of wells that were drilled prior to 1998. This field produces basin-centered gas from the Upper Cretaceous Almond Formation. The new sweetspot is located approximately four miles west of the Echo Springs-Standard Draw Field, currently the largest basin-centered gas sweetspot (1 TCF+) in this portion of the Greater Green River Basin. The existing Tierney area wells are expected to produce over 250 BCF from an area that is about a township in size. The main productive unit in the Almond Formation at Tierney field differs significantly from the main productive unit in the Echo Springs-Standard Draw field. In the Tierney area, the Middle and Lower Almond sands contribute the majority of the production. The Lower Almond sands here are thick, stacked fluvial regressive channel sands. The Middle Almond Formation is composed of transgressive, lagoonal deposits that generally consist of thin, discontinuous tidal sands, shales, and coals. The Upper Almond consists of marine tidal channels and some thin shoreface deposits which contribute only moderately to the production. The main production in the Echo Springs area, however, comes from thick Upper Almond shoreface sands with minor contributions from thin Middle and Lower Almond sands. Seismic attribute analyses including coherency and spectral decomposition have been useful in mapping these stratigraphic units outside of well control and identifying higher potential production fairways.

AAPG Search and Discovery Article #90004©2002 AAPG Rocky Mountain Section, Laramie, Wyoming