Three-Year Study in the Green River Formation of the Uintah Basin Optimizes Completion Technology
Authors: Larsen D.G. , Zellitti J. 
Published: December 2007

The cooperative effort of Equitable Resources Energy Company (EREC) and BJ Services (BJS) in the Monument Butte Field of the Uintah Basin has led to the optimization of the completion and production of the Green River Formation there.

Over the course of three years; 92 new wells; and over 200 fracture stimulation treatments a comprehensive database has cataloged most all significant criteria in the selection, preparation, completion and production of the various lenticular sands of the Green River.

The study has been conducted mostly in the Townships 8S 16E and 9S 16E, 17E, 18E along the countyline border of Uintah and Duchesne Counties, Utah. The area is in the heart of a massive secondary recovery project of the challenging Green River crude oil produced from multiple lenses ranging in depth from 4000' – 6200'. Lithologically the producing sands have limited aerial extent and communication; and, in addition to the high pour point of the oil (95 F.), a unified effort of geologists, reservoir engineers, production engineers and service company specialists has been necessary to explore, understand and, finally, optimize the completion of this reservoir.

This paper will demonstrate the various methods of data collection, data analysis, production tracking and decision-making that has contributed to the financial success of this project and continues to contribute to the improvement processes necessary in a long-range undertaking such as this.

Introduction

The Green River Formation has long been a source of black wax crude in this part of the Uintah Basin. Its paraffinic nature has been desireable in some refineries and has commanded a premium above WTI prices in the past. It produces from at least 22 different horizons identified across a 2200' interval from 4000' to 6200'. These horizons are lenticular sands with limited aerial extent and questionable horizontal and vertical communication. Primary production in the area has at times been dismal and left the field a marginally economic venture.

In spite of its many inherent limitations, the Monument Butte Field has been a favorite of operators as a secondary recovery project ever since Lomax Exploration conducted a pilot waterflood beginning in 1992 with the assistance of the DOE (Fig, 1). EREC first began developing its own waterflood in 1993 and entered into an alliance with BJS to provide its stimulation, cementing and miscellaneous pumping services in 1994.

This is an attempt to chronicle the events that have been the development of the various flood Units of EREC in the area by discussing the overall response to production of the drilling and water injection programs; describing the various optimization techniques tested and their benefit, if any, to the overall project; and the databasing of some 49 criteria as they relate to the 232 fracs performed in this operator's field.

History of the Waterflood

The Monument Butte Field was discovered by the Diamond Shamrock Company, presently Maxus Exploration, in 1964 when they drilled the Walton Federal #1-11 well located in S11, T9S, R17E. This well was completed May 11, 1964 with an initial production of 1973 STBO and 100 MSCFG per day with zero water. The discovery of oil in this area stimulated drilling activity and an additional 12 oil production wells were drilled in 1964 and 1965 in the surrounding sections. Drilling came to a near stop for over 15 years, when in 1981 the Diamond Shamrock Company began an aggressive drilling program to develop the remaining oil reserves of the Monument Butte Field. Drilling again slowed to a stop with the coming of late 1980's oil prices. P. 171^