Description GeoResources has been expanding geographically to increase its oil and gas resources. The company, once a regional explorer in Montana and North Dakota only, has grown to incorporate exploration acreage in the Southwest, the Gulf Coast, and the Williston Basin. In 2009 GeoResources reported proved reserves of 141.4 billion cu. ft. of natural gas equivalent. That year it reported a portfolio of about 484,000 gross acres and 234,000 net acres. Its Southern Bay Energy unit operates out of Houston, while G3 Operating is based in Denver.