Abstract

As with all mature petroleum fields, reservoir depletion becomes a factor, especially for wells drilled later in the life of the field. When the reservoir pressure becomes low, standard treatment fluids cannot be used effectively and other methods must be used to stimulate the reservoirs. The Arkoma Basin of Western Arkansas is no exception to this rule. This area of the basin is highly faulted and compartmentalized, which adds significantly to the reservoir complexity. Depending on well placement, there are several potential zones in each well exhibiting varying degrees of reservoir depletion.

The fracturing industry has gone through many technological advances over the years, and with these technological improvements have come many successes. Use of a low polymer energized fluid provides a good solution for these low reservoir-pressure reservoirs. These new style treatments provide faster cleanup, better flowback, better sand placement, and better production than conventional or previously utilized fracturing fluids.

The case studies will show that the low polymer energized fluid technique provides a positive response for these types of wells. Low polymer energized fluids can offer the qualities and properties to enhance completions and improve project and well economics.

Introduction

This study reviews the use of a new low polymer, energized fluid in the Arkoma Basin primarily in western Arkansas and its positive impact on these areas. A brief look at the basin, its geology, and stimulation history should give insight into the how's and why's of current stimulation techniques. While there are not many published studies in this area, a basic background of the types of reservoirs can be given. Fully characterizing each formation within the Arkoma Basin is beyond the scope of this paper. The intent of this paper is to make operators aware of what they can evaluate when making completion decisions on wells in this area.

Geology

The Arkoma Basin located in western Arkansas and extending into eastern Oklahoma, has become one of the largest and most productive petroleum areas in the United States. The basin extends for approximately 260 miles east to west and from 20 to 50 miles north to south Figure (1)1. The basin is bounded on two sides, by the Ouachita overthrust belt to the south and the Ozark uplift to the north. Because of the stresses that these boundaries incurred, the basin has undergone extreme folding and faulting, which created a sequence of east to west trending anticlines and synclines throughout the basin. These are again influenced by normal faults that run southward to the basin's dips1.

Most gas production from the basin is related to anticlinal or fault-trap structures where adequate porosity was preserved for hydrocarbon accumulation Figure (2)2. Today, more than 30 different producing zones have been discovered which range in age from the Cambrian to the Pennsylvanian2. In this study the Atokan series sands of the Pennsylvanian age will be the primary zones of interest.

The Atokan sands were deposited in a delta environment. Most reservoirs are lenticular sandstones, typically composed of fine to medium grains, and are described as shaley. The Pennsylvanian sands are bound by strong shale barriers that help limit fracture height growth. The Atokan sands thicken from east to west to the Oklahoma State line giving Arkansas more productive horizons than Oklahoma.

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