Reduced-impact land disturbance techniques for natural gas production

Abstract

Traditional drill pad construction techniques for natural gas production involve a cut-and-fill procedure that displaces existing plant communities and results in costly soil remediation and revegetation procedures. At the Jonah natural gas field, Sublette County, Wyoming, EnCana Oil and Gas (USA), Inc. is evaluating use of oak mats during drilling and completion activities to minimize disturbances to soil and plant resources. In this study, changes in vegetation and soil attributes were evaluated as a result of oak mat use. Overall, oak mats tended to protect plant resources, minimize weedy forb establishment and maintain the plant community in a condition similar to adjacent rangeland. On average when compared to native range, grass growth improved, forbs remained similar, and shrubs were negatively impacted in oak matted areas. Vegetative results suggest that the success and timeliness of reclamation following the use of oak mat drill pads is superior to that obtained at reclaimed cut and fill locations. Following mat removal, mean soil bulk density values changed-2.9, 2.2 and 3.7 percent for the 0 to 5.1, 0 to 15.3, and 0 to 30.5 cm depth increments. All soil bulk density values remained below recommended thresholds for rangeland environments. A cost-benefit discussion indicates that in this setting, construction costs associated with oak mats are similar to those incurred by traditional cut-and-fill techniques. Drilling procedures using oak mats are more costly due to the need for a closed system for treatment of drill cuttings. However, this expense may be offset by lower reclamation costs associated with oak mat use.