Marathon Oil Company

Other

Eugene E Wadleigh

David E Ellwood

Douglas E Kenyon

James L Bowzer

Albert C Compton

This invention relates to the recovery of oil from an oil-bearing formation having a natural fracture network with substantial vertical communication and wherein gravity drainage is the primary means of recovery. A downwardly inflating gas-cap is pressured up with a chase gas having a density less than that of CO.sub.2. CO.sub.2 is injected and a CO.sub.2 -rich displacing slug is formed at the gas-liquid hydrocarbon contact. The chase gas is injected to facilitate displacing downwardly the CO.sub.2 -rich displacing slug to recover hydrocarbon from the reservoir. CO.sub.2 is replaced in the displacing slug as the CO.sub.2 is solubilized into the oil, including matrix oil, to facilitate recovery thereof. The oil is recovered through production wells in fluid communication with the reservoir, preferably the inlet to the well is below the water-liquid hydrocarbon contact at such a level to prevent free-gas production. The chase gas has a density less than that of the CO.sub.2 and is comprised mostly of nitrogen; however, it can contain other gases such as methane, ethane, CO.sub.2, and miscellaneous gases. The chase gas is injected at a rate to minimize mixing of the chase gas with the CO.sub.2 and to facilitate gravity segregation of the CO.sub.2 from the chase gas. The CO.sub.2 in the CO.sub.2 -rich displacing slug can be replenished by incorporating CO.sub.2 into the chase gas and permitting the CO.sub.2 to gravity segregate downwardly while the less dense gases move upwardly.

Gravity concentrated carbon dioxide for process

A process for recovering hydrocarbons from a subterranean formation having low permeability matrix blocks separated by a well-connected fracture network. Hot light gas is injected into the formation to heat the matrix blocks and create or enlarge a gas cap in the fracture network. The flowing pressure in one or more production wells is maintained at a value slightly less than the free gas pressure at the gas liquid interface, causing gas coning near the production well or wells. Both liquid and gas are recovered from below the gas/liquid interface in the fractures.

Process for recovering hydrocarbons by thermally assisted gravity

A downhole burner that economically generates hot inert gas and injects this gas into a subterranean formation. The burner has a nipple attached to a first tubing string that carries an oxidizer to the burner. The first tubing string also contains a coil tubing string that carries fuel to a movable nozzle inside the nipple. A small orifice in the nozzle increases the velocity of the fuel, and the nozzle extends out through a small orifice in a burner shroud that increases the velocity of the oxidizer flowing around the nozzle. The high velocity of the fuel and oxidizer keeps the flame front below the shroud and nozzle. A second tubing string supplies coolant gas around the burner shroud. Injection of an oxygen containing coolant gas provides a method for enhancing in situ combustion reactions through superheating the oxygen containing mix of coolant and exhaust gas.

Growing community of inventors

Midland, TX, United States of America

Eugene E Wadleigh