The Permian Basin is one of the top five resource plays in the United States and consists of a number of stacked pay zones. Two of these formations, the Wolfcamp shale and Bone Spring (together referred to as the Wolfbone), deliver a pay zone thickness from approximately 1,000 to 1,500 ft. They are made up of several different layers of organic rich shales, intermingled with sandstone and siltstone. Horizontal completions in the shales are just beginning and have yet to be proven; however, operators are successfully exploiting the reserves through vertical wells.
While a mature exploration area, the completion of the thick shale intervals is a new target formation. To date, two vertical completion methods have been utilized to gain access to hydrocarbons: openhole multistage systems (OHMS) and the conventional cemented liner, “plug and perf” (CLPP) method. This paper compares 1 year production results from 12 vertical wells in Reeves County, Texas completed with OHMS systems and 56 offset wells completed with the CLPP method. The system details, fracture methods used, as well as the cost and operational differences are discussed.
By comparing these two methods, this paper highlights OHMS as a long-term solution for operators completing vertical wells in stacked pay. The production, operation and cost comparisons of the two completion methods will provide theoretical and practical arguments to assist in designing a completion. The results of this study contribute to the technical conversation of how to economically produce a vertical well.
The Permian system consists of three basins: Delaware Basin, Central Basin Platform, and Midland Basin (Fig. 1). The Permian Basin is an unconventional trend comprising a mix of fine sandstone and siltstone interbedded with various shale and carbonate layers. Early production targets in the Permian Basin were shallow formations on the basin edges to deeper deposits in the central Delaware (Avalon, Bone Spring, and Wolfcamp formations). The Delaware Basin encompasses three zones of the Bone Spring formation as well as the Wolfcamp shale below (Fig. 2). Since 2009, this play has been developed with vertical wells commingling the oil resource from the Third Bone Spring and Wolfcamp formations with conventional reservoirs.
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