Abstract: In a dipping underground petroleum reservoir devoid of a natural gas cap, a mixture of gases soluble in petroleum is injected into a well positioned in an up dip location. Gases in the mixture are selected for their diverse solubility and diffusion characteristics. Gas injection is terminated followed by attic oil production wherein the gases accompanying the produced oil are separated and measured. The separated gases are then compared quantitatively with gases injected and the solubility capabilities of the produced oil. Results are used to estimate the size of the attic portion of the reservoir. Alternating cycles of gas injection and attic oil production are continued until the well is engulfed by the expanding artificial gas cap.

Abstract: Hydrogen is injected into an underground petroleum reservoir that is devoid of natural gas. Due to its high rate of diffusion, hydrogen disperses rapidly throughout the reservoir, including the tight portions that are relatively impermeable to the injection of water. Pressure is lowered in the reservoir when the crude oil is substantially saturated with hydrogen. Hydrogen then migrates from the tight portions of the reservoir, sweeping petroleum into the more permeable portions. Expanding hydrogen experiences a temperature rise which in turn heats the crude oil and further reduces the viscosity for added mobility. A water sweep displaces the oil to production wells. In an alternate embodiment hydrogen is injected into an underground petroleum reservoir as a prelude to fire flood techniques. The absorbed hydrogen dilutes the crude in place and provides a fuel with much wider flammability limits to sustain the underground fire.

Abstract: Hydrogen and other gases that are miscible in petroleum are injected into an underground reservoir to the extent that the volume of hydrogen exceeds the absorption capacity of the petroleum, thereby forming a gas cap composed substantially of hydrogen. Petroleum is withdrawn from the reservoir in part under the influence of gases absorbed into the petroleum and in part under the influence of increased reservoir pressure created by an artificial gas cap. Reservoir temperature is increased by establishing a combustion zone within the underground petroleum reservoir. Hydrogen is withdrawn from the artificial gas cap and is reinjected into the petroleum adjacent to the combustion zone with the resultant hydrogenation of the petroleum.