This paper presents the results of field trials conducted primarily to evaluate the efficacy of a new additive developed specifically for use in fracturing coal seams and shale wells. The case histories were carefully chosen so that the effects related to use of the new material could be isolated as well as possible. The data show that substantial production improvements may be achieved. This paper also presents results from laboratory tests which show that the new additive may also be useful in workover treatments.

The Berea Sandstone has long been and continues to be a favorite drilling target in many producing areas of the Appalachian Basin. However, its low permeability makes it necessary to fracture stimulate the Berea to obtain economic production rates. The Haysi Field located in western Virginia has responded well to various hydraulic fracture stimulations using a wide range of frac fluids and proppant densities. The initial fracture systems pumped utilized fresh water with linear gels as the fracturing fluid, these were followed by foams, and several massive fracture treatments. The foam treatments afforded quicker cleanup due to the nitrogen present. However, higher initial production rates with lower decline rates are the direct result of increased proppant densities in the fracture. This concept is supported by the production histories of the individual wells. Twenty-five (25) years of production data from twenty (20) wells has been analyzed and used as a basis for comparing the different types of fluids pumped and the various proppant densities achieved. Propped fracture lengths were also calculated to compare production results (Figure 5).

Generally, water saturations in the Devonian Shale are low. Production records indicate minimal, if any, water in the areas produci ng gas or gas and oil. This low water saturation appears to be the key to stimulating the shale, especially in the oil-producing areas.The introduction of water in the stimulation fluid appears to reduce the permeability to oil, which is reflected in poorer production.The relative permeabil ity reduction seems to be more of a problem than particle migration or clay swell ing. and ~ould explain the good initial results froo stralght nltrogen treatments. However, the lack of a proppant, even with low closure stress, leads to very rapid declines.Water-base stimulation fluids appear to increase water saturation in the Devonian Shale. Use of 90+ quality foam with sand should provide a method of minimizing saturation changes while creating a propped fracture.Initial results indicate this technique provides better sustained production increases in the Devonian Shale.This paper defines areas of production, describes the geology and presents physical data of the Devonian Shale. It also compares results of several types of treatments that have been used in the Devonian Shale. These results indicate 90+ quality foam with sand should provide an improved stimulation technique for this formation. RESULTSThe 90+ quality foam treatments to date have been done in Monroe and Noble counties, Ohio, and Ritchie and Raleigh counties in West Virginia.