University of Wyoming-office of Research & Economic Development

Norman R Morrow

Nina Loahardjo

Koichi Takamura

Sheena Xina Xie

Winoto Winoto

Winoto

Zhengxin Tong

A method for residual oil recovery from oil reservoirs, and diagnostic tests for determining its efficiency using a single well are described. The method includes injecting oil into a well in a reservoir that has been previously waterflooded or an oil reservoir or zone of an oil reservoir which contains immobile oil at the time of discovery, and extracting the oil by waterflooding the charged zones by placing the injection well in production. The target zone from which oil is recovered may be increased by following injection of oil with injection of water to push an oil bank which grows in volume as a function of distance of propagation, because of the effect of waterflooding on residual oil. The well may then be placed in production and the oil bank volume will continue to increase in volume as it returns to the well, again because of the waterflooding effect. The oil bank is then produced at the surface. The double-sweep waterflooding process using a single well can be repeated by again charging with oil followed by waterflooding. Sequential injection of oil and water to generate more than one oil bank may also be used to increase oil recovery by multiple sequential waterfloods. Combinations of oil injection and sequential waterflooding also have application to reservoir diagnostics.

Single-well diagnostics and increased oil recovery by oil injection and sequential waterflooding

Methods for reducing the size of an oil slick on a water surface or on a water surface when ice is present are described. Spreading of oil can be reversed by reducing the surface tension of the seawater, for example, by using a low concentration of at least one water-soluble surfactant, such as a non-ionic surfactant. A controlled amount of the surfactant or surfactant mixture may be discharged over time at the inner-wall of a spill control boom surrounding the oil spill, or within the vicinity of the oil spill in the absence of control booms using a soaker hose or a floating polyethylene or polypropylene hose impregnated with surfactant, whereby the confinement and contraction of the oil slick is maintained by compensating for dissolved surfactant and surfactant moving away from the oil slick. Water-soluble surfactants are typically solids or gels at low temperatures when no organic co-solvent is added to the surfactant. The solid or gel form is advantageous for generating slow, but continuous release of surfactant, and thus there is no need for an organic co-solvent. This is not the situation for oil-soluble surfactants, which require an organic co-solvent to be successfully applied at low temperatures. Mixing oil-soluble surfactants with water-soluble surfactants may overcome the problem of dispersing oil-soluble surfactant without an organic co-solvent at low temperatures.

Contraction and confinement of oil slicks on water, including water where ice is present, using non-ionic surfactants

A method for retracting oil on a water surface, and a method for reducing the quantity of oil on an oil control boom are described. Spreading of oil can be reversed by reducing the surface tension of the seawater, for example by using a low concentration of a water-soluble surfactant, such as a non-ionic surfactant. A controlled amount of the surfactant may be continuously discharged at the inner-wall of a spill control boom surrounding the oil spill. The spilled oil is caused to retract away from the boom toward the center of the area encircled thereby, such that the oil layer becomes sufficiently thick to be more effectively removed mechanically. The surfactant also reduces the amount of oil on the spill control boom, whereby the boom can easily be removed from a remediated oil spill and reused at a later date without further cleaning.

Retraction of oil slicks using surfactants

A method for enhancing oil recovery from reservoirs is described. The method includes partially recharging zones of pore space in a reservoir that has been previously waterflooded to extract oil, in order to obtain increased ultimate oil recovery by re-waterflooding the recharged zones. The recharging may be achieved by either reinjection of oil or by change in injection scheme, such as changing an oil producing well to a water injection well. This procedure of recharging with oil followed by waterflooding may be repeated. Application of the present method to increase recovery from reservoirs producing dry (water-free) oil to mature reservoirs which produce at high water-to-oil ratios is anticipated.

Oil recovery by sequential waterflooding with oil reinjection and oil relocation

A method for reducing or eliminating water block around a well bore of a well bore region in a reservoir is provided. The method comprises removing the water from around the well bore, injecting crude oil around the well bore, and injecting precipitants causing surface precipitation of asphaltenes thereby altering formation wettability in the well bore and decreasing capillary forces of retention for water and/or gas condensates and increasing the flow of hydrocarbon fluids from the reservoir.

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Laramie, WY, United States of America

Norman R Morrow