Completion Design for Deep, Sour Norphlet Gas Wells Offshore Mobile, Alabama

Abstract

Abstract Producing gas from the Norphlet formation in the Mobile Bay Area presents many unique completion design challenges. The Mobile Bay Area Norphlet, a consolidated aeolian sandstone, is estimated to contain an ultimate natural gas resource base of 20 TCF1. Proved reserves of 4 - 6 TCF have been discovered to date with hydrogen sulfide concentrations ranging from 50 ppm to 10% and carbon dioxide concentrations up to 4%. Production may also include brine and elemental sulfur. Formation intervals below 20,000′ have bottomhole temperatures in excess of 400°F and initial bottomhole pressures from 10,000 psi to 20,000 psi2. Wells can cost upwards of thirty million dollars to drill and complete due to the extreme depth, the highly corrosive nature of the gas, and the close proximity to environmentally sensitive areas. Economics dictate development with a minimum number of wells on wide spacing, therefore, completions are designed for maximum rate and maximum life. This paper describes the evolution of design concepts and equipment innovations utilized in the completion of Norphlet gas wells in the Lower Mobile Bay - Mary Ann and Mobile 823 Fields.