Restoring Sagebrush Habitat in the Pinedale Anticline Natural-Gas Field in Wyoming

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 120980, "Restoring Sagebrush Habitat in the Pinedale Anticline Natural-Gas Field in Wyoming," by H. James Sewell, Shell E&P, and Richard S. Carr, C-M Environmental Group, prepared for the 2009 SPE Americas E&P Environmental & Safety Conference, San Antonio, Texas, 23–25 March. The paper has not been peer reviewed. Disturbed areas in the Pinedale Anticline natural-gas field are being restored with native plant species that are beneficial in the sage grouse and ungulate habitat. A new seed mixture was developed to re-establish native plant species in reclaimed areas, replacing the grass-dominated seed mixes used in the past, thus returning these areas to productive habitat in a timelier manner. Introduction The Pinedale Anticline field is in the Upper Green River basin of southwestern Wyoming, near the town of Pinedale. The gas field was discovered in the mid-1930s and has estimated ultimate gas reserves of more than 25 Tcf. Land ownership in the field is more than 90% federal, and all aspects of the gas development are managed by the US Bureau of Land Management (BLM). New hydraulic-fracture-stimulation technology enabled further development of this resource, which accelerated after 2000. In an effort to limit the amount of overall land and habitat disturbance, the field is being developed with multiple-well drilling pads, with up to 32 wells drilled, completed, and produced from each pad location. Total land disturbance to date is estimated at more than 700 acres for Shell's operations on the Pinedale Anticline. Once the drilling on a pad is completed, pad size can be reduced by up to 70%. Full development of the field will have 12,885 acres of initial disturbance and 4,012 acres of disturbance remaining after interim reclamation activities are completed. The ecosystem in the area is considered a sagebrush-dominated steppe with mixed grasses and forbs. Elevation ranges from 7,200 to 7,400 ft above sea level, and annual rainfall averages less than 9 in./yr. Native soils range from sands and gravels to clayey loams. The native plants are a main source of forage, especially in the winter months, for large ungulate populations that include pronghorn antelope and mule deer. This sage-steppe habitat also is critical for populations of the greater sage grouse, a species that may soon be listed as endangered. Project Approach and Objectives The overall goal of this project was to restore native sage grouse habitat in as timely a manner as possible, to reduce the surface environmental effects of natural-gas development. Native-plant survival in harsh arid environments such as the Pinedale Anticline depends on interaction between soil microbial communities and the native shrub, forb, and grass species. Specifically, soil microbes, referred to as mycorrhizal fungi, are known to aid native plants in nutrient and water absorption, leading to improved plant growth and reproduction. Re-establishing microbial communities and healthy soils on disturbed sites is important in restoring native-plant habitats, particularly for the germination stage and first-year growth of the native shrubs, forbs, and grasses.