This paper is an evaluation of massive hydraulic fracturing and dendritic fracturing applied to four tight gas sands of the Eastern United States. A total of ten fracturing treatments were performed in the Berea, Benson, Clinton and Medina formations. The objective of this program was to determine whether a meaningful productivity increase could result from the application of new fracturing techniques over that of conventional hydraulic fracturing and/or explosive shooting. The small number of test wells, coupled with a wide range of test results and other geological factors make it difficult to draw definitive conclusions.
This paper describes work done under the sponsorship of Columbia Gas System Service Corporation, U.S. Department of Energy and Ohio Department of Energy. It was part of a major effort by the U.S. Department of Energy and private industry to increase the nation's gas supply from sources in the Northeastern section of the nation. The tight formations of this region are known to be potentially significant sources of natural gas. Shales in the Appalachian, Michigan and Illinois basins were studied along with some tight sandstone formations in the Appalachian areas. When the program began, shale production appeared to be a longer term development program. Increase production from the sandstones by applying new stimulation techniques held promise for quicker results. The work described in this promise for quicker results. The work described in this paper is the result of the stimulation tests performed paper is the result of the stimulation tests performed in the sandstone wells tested. Four wells are in Ohio and two each in Virginia, West Virginia and New York. Location, formation stimulated and stimulation type are listed in Table 1.
An attempt was made to test formations and areas which have some proven production. Two new stimulation techniques, massive hydraulic fracturing (MHF) and dendritic fracturing, were tested in the sandstone wells. The dendritic or Kiel stimulation is a patented pulsating version of hydraulic stimulation. Patent rights pulsating version of hydraulic stimulation. Patent rights belong to Othar Kiel of Houston, Texas. MHF test plans involved use of remote sensing techniques where possible to locate the well sites. Core data and well logs were used to help pick the zones for stimulation. Reservoir testing and production analysis were used to evaluate the effectiveness of each treatment.
Figure 1 shows the general location of the ten test wells. Table 2 contains some data pertaining to each well. The following is a brief summary of each formation tested.
Benson Sandstone. The Benson is a sandstone of Upper Devonian age. It is commonly brown, fine grained tightly cemented and generally water free. The sand is primarily composed of quartz and albite with silica cement. The Benson sandstone can be differentiated into two zones. A lower unproductive sandstone, 15–35 feet thick, and an upper productive sandstone, called the "producing Benson". It is 6–25 feet thick with an intervening, less readily identifiable middle silty unit, 5–20 feet thick. The porosity ranges from 2 to 10.5 percent and permeability is from 0.2 to 0.8 millidarcies.
Berea Sandstone. The Berea Sandstone in Dickenson and Buchanan Counties, Virginia is a tight, argillaceous siltstone of basal Mississippian age. The average porosity ranges from 3 to 10 percent. Permeability is porosity ranges from 3 to 10 percent. Permeability is generally less than 0.1 millidarcies. The pay thickness varies from 30–100 feet. Columbia's production in the area is from the Haysi Field. Because of the tightness of the formation, production is believed to be from natural fractures developed by faulting associated with the Pine Mountain Overthrust System.
Clinton Sandstone. The Clinton Sandstone is a traditional gas producing formation in Ohio. It is of Lower Silurian age and is a fine grained, dense quartzitic sandstone. Grain size is usually uniform with the majority of the grains in the 0.1 to 0.3 millimeter diameter size. Permeabilities are generally greater than 0.2 millidarcies. Porosities range from 2 to 9 percent. The thickness of the Clinton is from 100–200 percent. The thickness of the Clinton is from 100–200 feet.