The Wolfcamp shale has taken center stage and the full glare of the spotlight.

On November 15, 2016 the USGS released results of their resource assessment of the Wolfcamp. They concluded that the Wolfcamp shale in the Midland Basin portion of the greater Permian Basin contains an estimated 20 billion barrels of oil, 16 trillion cubic feet of associated natural gas, and 1.6 billion barrels of natural gas liquids; volumes that equate to 30 billion BOE. This estimate consists of undiscovered, technically recoverable hydrocarbons for continuous oil; i.e., unconventional oil. This number exceeds the 7 billion barrels of oil for the Bakken-Three Forks estimated by the USGS in their 2013 resource assessment. The 20 billion barrels of oil (or 30 billion BOE) for the Midland Basin Wolfcamp shale is the largest estimate of continuous oil that USGS has ever assessed in the United States. This greater oil assessment of the Wolfcamp compared to the Bakken-Three Forks is due to better geologic factors present in the Wolfcamp, including higher quality and thicker source rocks, plus several stacked shales throughout the Wolfcamp section.

The Wolfcamp Formation exists across the entire Midland Basin and was first drilled as a vertical oil play in the 1950's. Vertical drilling in the Wolfcamp continued into the 1990's, with some operators completing wells in both the Wolfcamp and the overlying Spraberry, labelled the "Wolfberry" play. Various operators experimented with horizontal wells drilled in the Wolfcamp during 1990 - 2001, and the results of these early efforts were inconsistent. Horizontal drilling activity in the Wolfcamp remained slow during 2007-2010 when only six wells were drilled. As operators learned more about the Wolfcamp shales, how to drill and hydraulically fracture and complete them, their results improved. Wolfcamp horizontal activity accelerated in 2011 when 57 wells were drilled in this resource play. The success of those wells created additional interest in the play, causing activity to increase 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 pay potential is stacked, with six possible target shale zones in which to direct horizontal wellbores, including, from the top down, the A, B, C (upper and lower) and D (upper and lower) zones.

There are several key factors that make the Wolfcamp formation an attractive resource play:

• Horizontal wells can exhibit substantial initial production (IP). To date, 24 wells have had IP's greater than 2,000 BOPD; all Wolfcamp horizontal wells IP's average 680 BOPD.
• Although this play is still in the juvenile stage, cumulative production to date has exceeded 180 million BOE.
• The individual shales of the Wolfcamp Formation have excellent shale rock properties. These shales fracture well and have a good range of total organic carbon (2-7%).
• Estimated Ultimate Recovery (EUR) values are encouraging; the average EUR is 400-500 MMBO.
• Based upon a large 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.

In mid-December 2016 IHS Geoscience hosted a webinar as part of our geoscience series, focusing specifically on the Wolfcamp Horizontal Play of the Midland Basin. This webinar presented an overview of the play including the geology, drilling and production results, operators, and the successes and challenges. In addition to the webinar, you will also have access to key resource materials that help illustrate why the Wolfcamp has become one of the largest and most active resource plays in North America. View on-demand webcast.

Peter Blomquist is a Technical Advisor and Geologist at IHS Markit.
Posted 14 February 2017

This article was published by S&P Global Commodity Insights and not by S&P Global Ratings, which is a separately managed division of S&P Global.