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Abstract: Environmental Implications of a Gas Well Blowout in Northwest Louisiana - A Case Study
Michael S. Kline, David T. McKenzie, William H. Schramm
Oil and gas exploration in northern Louisiana has been ongoing since the 1920s. During this time occasional blowouts have occurred which have impacted the environment. In March, 1994, a Sligo Field well experienced an unusual blowout in that the event propagated to the surface through an adjacent abandoned well.
While drilling through the fractured Thompson-Pettet interval at a depth of 5000, a pressure kick, caused by a loss of drilling fluids, occurred. The well control devices activated and prevented loss of the well. However, the pressure front moved up the well's uncased annulus until reaching the base of the cemented surface casing where it dispersed laterally in the Nacatoch formation at a depth of approximately 1000. This was the uppermost portion of the uncased hole. The pressure front propagated through the Nacatoch until it encountered the poorly cemented annulus of the abandoned Hardman #1 well, located approximately 300 to the south of the drilling location. After moving up the annulus of the Hardman #1 well and charging the fresh water sands of the Wilcox system, local residential water wells and the drilling rig's water supply well became flowing artesian. Several hours later sands and fluids began erupting, creating a large cavity on the outside of the casing surrounding the Hardman #1 well. The artesian impact lasted approximately four days until the pressure front dissipated. Subsequent sampling of the rig supply well determined the well to be contaminated with benzene, a known human carcinogen.
The Louisiana Department of Environmental Quality, in conjunction with the operator, is currently investigating the extent of contamination with the goal of ensuring the health of the local residents and the protection of the environment.
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ACKNOWLEDGMENTS AND ASSOCIATED FOOTNOTES
Louisiana Department of Environmental Quality, Baton Rouge, LA
Copyright © 1999 by The Gulf Coast Association of Geological Societies