ABSTRACT

A significant quantity of oil is left in reservoirs after conventional oil recovery techniques have been applied. In West Virginia and Pennsylvania alone, this oil has been estimated at over 4.5 billion barrels (0.72 billion m3). Conventional recovery methods are already being used when applicable. But a new recovery method is needed for use in reservoirs that have been abandoned. One alternative method for recovery of the residual oil is known as â??oil recovery from underground drill sitesâ?¿. This recovery technology is a combination of proven methods and equipment from the petroleum, mining, and civil construction industries.

Underground oil recovery can be an economically viable method of producing oil. This has been shown in producing fields, field tests, and feasibility studies. Faced with decreasing domestic oil production, the petroleum industry should give serious consideration to the use of oil recovery from underground drill sites as a safe, practical, and environmentally sensitive alternative method of producing oil from many reservoirs.

INTRODUCTION

Historically, oil from domestic reservoirs has been produced using primary and enhanced recovery techniques. As a field matures, more oil is produced using various means, including closer well spacing and advanced forms of enhanced oil recovery. Yet, 50 to 80 percent of the original oil in most reservoirs is unlikely to be recovered with currently used technology. The remaining oil is either too difficult to produce or is unproducible by conventional techniques. Other potential oil resources cannot be produced efficiently, if at all, due to urban development, legal restrictions, or environmental concerns.

This means that huge amounts of oil remain in known reservoirs. The Department of Energy (DOE) estimates that there will be 300 billion barrels of oil (45 billion m3) that will not be recovered under current economic conditions using existing technologies1. Another concern is that oil production in the United States is declining, with a nine percent decrease since 19552. The trend toward decreasing production is expected to continue and perhaps accelerate in the future. Faced with increasing dependence on imported oil, innovative solutions must be found to produce efficiently more of the oil that exists in known reservoirs.

Oil reservoirs are abandoned for economic reasons - not because reservoir forces have been totally depleted or eliminated. Although many once prolific oil fields are no longer productive, they still contain many millions of barrels of oil.

Why is it difficult to produce more oil from these reservoirs? Conventional solutions such as closer well spacings, are restricted by limits on the surface area disturbance and the drilling and pumping costs as each well recovers a lower volume of oil. For many of the oil fields in West Virginia and other states in the Appalachian region, the fields were originally developed before 1900. The techniques used at that time make it difficult to apply enhanced oil recovery techniques, such as fluid drives, because of interconnection of strata through poorly abandoned wells. Other fields contain micro-heterogeneities or other properties that make recovery of much of the oil difficult.

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