English

Abstract

Traditional drill pad construction techniques for natural gas production displace the existing plant community and result in surface disturbances requiring costly soil remediation and revegetation procedures. At the Jonah natural gas field, Sublette County, Wyoming, EnCana Oil and Gas (U.S.A.), Inc. is evaluating the use of oak mats to minimize disturbance to soil and plant resources by facilitating drilling and completion activities atop continuous 15.2 centimeter thick oak platforms. One concern with both traditional and oak mat drill pad construction techniques is the potential for increases in soil bulk density. In this study, dry soil bulk density was measured before-and-after oak mat drill pad construction at 17 drill pad sites for 0-5.1, 0-15.2 and 0-30.5 centimeter depth increments to quantify changes in soil bulk density in relation to growth limiting bulk densities described in the literature. Similar bulk density measurements were taken at six conventional-reclaimed drill pads to allow comparison between the construction techniques. Of the 17 oak mat locations, four drill pad areas exhibited no statistically significant change in bulk density as a result of the oak mat procedure. Of the 13 remaining oak mat drill pads, one or more depth increments had significant soil bulk density increases of 0.06 to 0.17 g/cm 3 as a result of drilling on top of the oak mats. Literature review indicated plant growth may be impaired when the dry soil bulk density is greater than 1.5 g/cm 3 . Of the oak mat soil profile depths measured, 95 % remained below this value, while a substantially higher proportion of conventional-reclaimed drill pad soil profile depths exceed this threshold.