GSOC Monthly Meeting

Abstract

Horizontal Drilling Of Deep Granite Wash Reservoirs in the Anadarko Basin of Oklahoma and Texas

Since 2002, over one-hundred horizontal gas and condensate wells have been drilled in Wheeler Co., TX and in Roger Mills, Beckham, Custer and Washita Counties, OK. These wells produce from Desmoinesian and Atokan Granite Wash reservoirs at depths between 12,000 and 15,000 feet. Most of the horizontals have been development wells in reservoirs already defined by vertical wells, but in a large area of Washita County many of the horizontal wells were exploratory tests that have now merged into a single field. The Granite Wash bearing portion of the Desmoinesian Series ranges in thickness from 1,800 to 3,100 ft across the area. It is comprised of a lower carbonate rich sandstone interval referred to as the “Skinner Wash”, a middle interval of silty marine shale, and an upper series of arkosic sandstones known as the “Marmaton Wash”. The initial fifteen horizontal gas wells were drilled in the Skinner Wash in southern Roger Mills County, Oklahoma between 2002 and 2006. Since late 2006 nearly one-hundred Marmaton Wash horizontal gas and condensate wells have been drilled, mainly in Washita County, Oklahoma and in Wheeler County, Texas. Horizontal wells typically demonstrate much higher initial rates than nearby vertical wells and also see a 3X to 5X improvement in ultimate recoveries. Greater recovery efficiencies and better economic profiles can be achieved in these reservoirs through horizontal drilling rather than vertical drilling. Lateral lengths and reservoir stimulations techniques have varied among operators, with four or more fracture stages being applied along laterals as much as 5,000 feet long.

Biography

John Mitchell is a professional petroleum geologist with thirty-one years of experience.  He received his M.S. in Geology in 1978 from the University of Arkansas.  His career has been spent exploring for oil and gas in the U.S. and western Canada with emphasis on the Rocky Mountains and Mid-Continent.  Over the years he has worked in Houston, Oklahoma City, Billings, MT, Kingsport, TN and Tulsa for a variety of companies.  He spent seventeen years in Billings, Montana where he worked for Meridian Oil and had his own exploration and consulting business.  For the past five years he has spent the majority of his time working on the Granite Wash play in the deep Anadarko Basin.  He is currently employed as exploration manager for St. Mary Land & Exploration Co. in St. Mary’s Mid-Continent office in Tulsa.  John served as president of the Montana Geological Society and as program chair for the Tulsa Geological Society.  He is a member of the Tulsa Geological Society and the Montana Geological Society as well as AAPG.  Recently he served as oral session chair for the 2009 AAPG Mid-Continent section meeting in Tulsa. 

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