Abstract

Successful development of the Frontier formation in southwest Wyoming begins with the hydraulic fracture treatment design and implementation. Without a design to effectively stimulate the Frontier formation and a proper implementation of that design in the field, production rates will be limited. This paper will detail the efforts of the authors in the development by Bannon Energy Incorporated of a significant number of Frontier completions.

Information from over 100 fracture treatments and the production response from over 400 wells will be used to demonstrate the significant improvement in gas production resulting from the fracture treatment designs and implementation methods employed. A first year gas recovery improvement of over 50% was achieved when compared to offset production. The use of intermediate strength proppants along with other design and implementation methods have significantly improved production from this "tight" gas sand.

Introduction

The Moxa Arch area Frontier formation has been under steady development since the mid 1970's. Over 500 Frontier completions have been made in the study area of this paper. This study area includes Township's 18N to 23N and Ranges 111W to 113W in southwest Wyoming. Figure 1 indicates the current productive sections of the Frontier within this area. Production is centered along the axis of the Moxa Arch which plunges north to south.

The geology of the Frontier formation has been described in great detail in previous publications and studies. We have not conducted an independent geological study with the exception of performing detailed log analysis on the majority of the well completions. We have found that the Frontier formation is very heterogeneous and pay quality can change rapidly between wells. However, we have noted, in both log analysis and production analysis, that north-south offsetting wells have a much greater tendency to be similar than east-west offsetting wells.

The Frontier formation in this area has been designated as a "tight" gas sand and typically requires a massive hydraulic fracture treatment for commercial production. Figure 2 indicates the completion history of the study area. The early development was a result of high gas prices, while the most recent development was initiated by the incentives provided "tight" gas development. The economic success of recent wells has furthered development of the area beyond the "tight" gas incentive deadline due to reduced costs and increased productivity through modern fracturing techniques.

The wells completed in the late 1970's and early 1980's were fracture treated primarily with crosslinked water based polymers and sand as proppant. While some wells were successful, the production history did not exhibit the type of decline associated with a stimulated "tight" gas sand. This unexpected production response was attributed to formation clay swelling and damage caused by the water based fracturing fluids. This conclusion led to the use of obtained fluids to reduce the amount of water injected into the fracture and formation. Intermediate strength proppants were also used in many of the foam treatments of the late 1980's and early 1990's. The production response from these treatments was, on average, poorer than the original treatments. This led to a return to water based fluids and the use of sand as proppant.

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