--> --> The Wolfcamp Horizontal Play of Midland Basin, West Texas

AAPG Pacific Section and Rocky Mountain Section Joint Meeting

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The Wolfcamp Horizontal Play of Midland Basin, West Texas


A total of 116,302 wells have been drilled for oil and gas in the Midland Basin of West Texas, including 96,894 oil and gas producers, a success rate of 83%. Productive portions of the Basin are in the south and center of the Basin; the northern portion has had comparatively little production. The Wolfcamp Formation (Wolfcampian-Leonardian) exists across the entire Midland Basin and was first drilled as a vertical oil play in the 1950's. Various operators experimented with horizontal wells in the Wolfcamp during 1990 — 2001, and the results of these early efforts were inconsistent. No wells were drilled in the play until 2007-2010 when six wells were drilled. Activity accelerated in 2011 when 57 wells were drilled in this resource play, and with the success of those wells, interest in the play has increased dramatically. Stratigraphically the Wolfcamp Formation is complex, consisting of mostly shale and argillaceous carbonates, with sand and sandy intervals near the basin edges, and facies that exhibit abrupt lateral changes. The Wolfcamp has stacked pay potential, with six possible target zones in which to direct horizontal wellbores, designated top-down as the A, B, C (upper and lower), and D (upper and lower) zones. The most drilled targets to date are the A and B zones in the section. Depths to the Wolfcamp in the Midland Basin vary from 4,000 feet in the east along the Eastern Shelf to 10,000 feet along the basin axis near the western basin edge. Gross thickness varies from about 700 feet to over 4,000 feet thick, with an average thickness of 1,663 feet. Structure does not appear to be an influence in this play. The total number of horizontal wells in the Midland Basin is 5,114, with 3,017 completed in the Wolfcamp interval. Wolfcamp horizontal wells can exhibit substantial initial potentials. To date, 24 wells have had IP's greater than 2,000 BOPD, with an average IP of all Wolfcamp horizontal wells of 680 BOPD. Although this play is still in the juvenile stage, cumulative production to date is 181 million BO. Porosity of the Wolfcamp Formation varies between 4% and 12% and averages 7%. Permeability is as low as 10 mD, necessitating multistage fracs. The Wolfcamp Shale has excellent shale rock properties; it fractures well and has a good range of total organic carbon, between 2% and 7%. The Wolfcamp horizontal wells were drilled and completed by 61 operators, with the top three being Pioneer Natural Resources, Apache Corporation, and Laredo Petroleum; 20% of these 61 operators have drilled 80% of the Wolfcamp horizontal wells. Recent drilling has increased lateral lengths to 13,000 feet, with Pioneer leading this effort. Average lateral length for the Wolfcamp horizontal wells is 7,107 feet, and 122 wells have laterals greater than 10,000 feet. Estimated ultimate recovery is greater than 500,000 BOE per horizontal well, which increases with increasing lateral length. Based upon areal extent, thick and abundant source rocks, and multiple producing horizons, the Wolfcamp Play is one of the largest resource plays in the world, particularly when combined with the overlying Spraberry Formation. Total recoverable reserves may exceed 35 billion BOE for the Wolfcamp horizontal play.