--> Straight to the Point: Drilling a Horizontal Well in the Upper Devonian Chipmunk Sandstone

Eastern Section Meeting

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Straight to the Point: Drilling a Horizontal Well in the Upper Devonian Chipmunk Sandstone


The availability to small operators of modern horizontal drilling technology used in the Appalachian Basin to develop the Marcellus and Utica unconventional reservoirs has provided them with an opportunity to test the economic viability of horizontal development of relatively shallow Upper Devonian sandstone reservoirs. In 2013 Dallas Energy and its joint venture partner undertook a drilling project in southeastern Cattaraugus County, New York on the western edge of the historically famous Bradford oil field consisting of a horizontal well drilled in the Upper Devonian Chipmunk sandstone which intersected a conventional vertical well drilled through the sequence of Bradford Group sandstones typically completed for oil and gas production in the area. The planned goal was to use the vertical borehole to recover oil and gas from zones completed in both the horizontal and vertical wells.

The Chipmunk in the project area is a fine to medium grained, light-grey to light brown sandstone ranging in thickness from 15 to 25 meters (50 to 80 feet) and occurs at a depth of 373 meters (1,225 feet). Based on analysis of core obtained from the vertical well, porosity ranges from 2 to 14 percent and maximum permeability is 0.22 millidarcies. Examination of thin sections prepared from the core shows the rock to consist of primarily monocrystalline quartz with minor amounts of plagioclase feldspar, potassium feldspar, polycrystalline quartz, chert and undifferentiated calcareous fossil fragments. Accessory minerals include muscovite, biotite, and heavy minerals. Minor amounts of dolomite and Fe-dolomite replaced unstable minerals and cement and minor amounts of quartz overgrowth cement are present. Porosity consists of primary intergranular pores with minor amounts of secondary intragranular and moldic pores.

Drilling operations lasted fourteen days, much longer than originally anticipated due to mechanical breakdown of the MWD equipment on a number of occasions, completing one sidetrack, and ultimate failure of the gamma ray tool used for geosteering. The well was drilled to a total measured depth of 1,042.7 meters (3,421 feet) with the distance from landing the curve to total depth being 545.6 meters (1,790 feet). The horizontal portion of the borehole was drilled at an average inclination of 89.5°. A rotating magnet ranging system was used to determine the final closure distance and direction to ensure successful intersection of the vertical well.

Due to the State of New York's restrictions on the volume of water that is allowed to be used in hydraulic fracturing, a relatively modest cased hole completion program was undertaken comprised of perforating five 3.3 meter (10 foot) intervals spaced equidistant apart along the lateral with 40 shots each and subsequently fracing each stage with 125 to 150 sacks of 20/40 frac sand. Following clean-up of both the horizontal and vertical wells, a conventional downhole pump and pump jack were installed on the vertical well and the combined wells were placed on production. To date oil and gas production has been disappointing. It is suspected that “porpoising” of the horizontal well has allowed fluids to accumulate in the lows and not allow steady drainage to the vertical well. A review is being undertaken to determine if changes to the equipment configuration and/or production procedures can improve the volumes of oil and gas produced.