Description Earthstone Energy (formerly Basic Earth Science Systems) taps into some of Planet Earth's basic energy sources -- oil and gas. It is involved in exploration, production, operation, and development activities, exploiting crude oil and natural gas assets in Colorado's Denver-Julesburg Basin, the Williston Basin of Montana, North Dakota, and along the Gulf Coast. The company drills about 48 net wells a year and has proved reserves of 638,000 barrels of oil and 936 million cu. ft. of gas. Most of Earthstone Energy's productive wells are in Montana, North Dakota, and Texas.