Wells – Processes – Cyclic injection then production of a single well
Reexamination Certificate
1998-09-21
2001-04-24
Bagnell, David (Department: 3672)
Wells
Processes
Cyclic injection then production of a single well
C166S270100, C166S304000, C166S312000
Reexamination Certificate
active
06220352
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for increasing the permeability of a subterranean formation that produces a low-gravity, viscous asphaltene-based crude and has no reservoir drive with gravity drainage as the only production mechanism and is partially plugged with asphaltene precipitate accumulation, by using a micelle treating fluid thereby restoring a well penetrating a subterranean formation.
BACKGROUND OF THE INVENTION
Hydrocarbons are conventionally produced from a subterranean hydrocarbon-bearing formation to the surface via a well penetrating and in fluid communication with the formation. Usually, a plurality of wells are drilled into fluid communication with a subterranean hydrocarbon-bearing formation to effectively produce hydrocarbons from a particular subterranean reservoir. Approximately 20 to 30 percent of the volume of the hydrocarbons originally present within a given reservoir in a subterranean formation can be produced by the natural pressure of the formation, that is, by primary production. In the case of reservoirs which produce a low-gravity, viscous asphaltene-based crude and have no reservoir drive, that is, water or gas, or a combination of both, it is estimated that less than 5 percent of the original oil in place is produced during a primary recovery.
Thereafter, additional quantities of hydrocarbons can be produced from most subterranean formations by means of secondary recovery processes such as water or steam flooding. To accomplish secondary recovery of the hydrocarbons present in the subterranean formation, one or more wells are converted to, or drilled as, injection wells. A drive fluid such as water or steam is injected into the subterranean formation via the injection wells to drive the hydrocarbons present to one or more wells that are designated as production wells. Hydrocarbons are produced to the surface from the designated production wells by conventional production equipment and practices.
A successful secondary recovery process may result in the recovery of about 30 to 50 percent of the original hydrocarbons in place in a subterranean formation. In the case of reservoirs that produce a viscous low gravity asphaltene-based crude and have no reservoir drive, such as, water, gas, or a combination of both. Water injection has little or no effect moving this viscous oil through the subterranean formation. With regards to steam injection, higher molecular weight asphaltenes will form and precipitate because of the removal of the light weight ends which act as naturally occurring asphaltene solvents. Another problem associated with steam contacting low gravity aspaltene-based crude is that asphaltene coking will occur and plug the formation.
Tertiary recovery processes have been developed to produce additional quantities of hydrocarbons from subterranean hydrocarbon-bearing formations. Such tertiary recovery processes include the addition of a surfactant and/or a polymer to a drive fluid, such as water. A surfactant reduces the interfacial tension between formation hydrocarbons and reservoir rock, whereas a polymer, such as a polyacrylamide or a polysaccharide, increases viscosity of the drive fluid to substantially reduce fingering or channeling of the drive fluid through the formation so as to produce a more uniform injection profile that results in increased hydrocarbon recovery. In the case of reservoirs which produce a viscous low gravity asphaltene-based crude and have no reservoir drive, such as, water, gas, or a combination of both, surfactant and/or polymer injection has little to no effect on moving this viscous oil through the subterranean formation. Surfactant injection has a tendency to cause emulsion blocks in the formation reducing fluid movement through the reservoir and polymers tend to increase the viscosity of the already viscous crude also reducing fluid movement through the reservoir. With the use of surfactants and/or polymers, the fluids produced to the surface have a tendency to be heavily emulsified, such that demulsification is expensive when there are high concentrations of the crude in the water phase.
Accordingly, a need exists for a process to restore the productivity of a production well in fluid communication with a subterranean formation, the permeability of a near well bore environment being reduced by asphaltene precipitate accumulation, low gravity, viscous asphaltene-based crude produced, and lack of a reservoir drive mechanism with only gravity drainage governing fluid migration through the formation that is inexpensive and effective.
Therefore, it is an object of the present invention to provide a process for restoring the productivity of a well penetrating a subterranean formation and having an asphaltene-based precipitate accumulation in the well bore by effectively increasing the permeability of a subterranean formation.
It is another object of the present invention to provide a process for the reduction of the viscosity of low gravity asphaltene-based crude, allowing for easier migration through the subterranean formation.
It is also an object of the present invention to provide a process to establish a drive mechanism within the subterranean formation allowing the asphaltene-based crude to be produced either from the well into which fluid and gas are injected or produced from wells offset to wells into which fluid and gas are injected.
Additionally, it is an object of this invention to provide a process for restoring productivity of a well in fluid communication with a subterranean formation which is effective and relatively inexpensive.
SUMMARY OF THE INVENTION
This invention is directed to a method for increasing production, or returning to production, oil wells having no reservoir drive and only gravity drainage as a production mechanism, and producing a heavy asphaltene-based crude. An increase in production or return to production is accomplished by treating a production well with a non-aqueous solution of an oxyalkylated phosphate ester surfactant, 2 percent potassium chloride water, and thereafter injecting a gas at a surface pressure of less than 200 PSIG to displace the resulting solution, a colloidal micelle solution, into the formation—a distance of 3 to 20 feet from the well bore. The resulting micelle solution containing the phosphate ester surfactant is allowed to remain in the formation for an effective period, generally for several hours, preferably for 24 hours to a week, after which the oil is recovered using a pump, tractor mounted swab unit, or alternatively using a conventional fluid drive mechanism whereby water and/or micelle treating fluid or air, or both, are injected into an offset injection well to displace the oil or gas. The micelle treating fluid comprises 2 percent potassium chloride water and a mutual solvent, which is mixed in a volumetric ratio of from about 1 to 1 to about 2 to 1 and injected via the well into contact with the accumulation of asphaltene precipitate and asphaltene-based crude. Air is injected at a surface pressure of less than 200 PSIG for a period of one hour and provides the drive mechanism for moving the micelle treating fluid out into the formation. It should be noted that normally exposure to air will cause asphaltene-based crude to cross link and precipitate, however, this does not occur in the presence of the micelle treating fluid. The mutual solvent comprises alcohol, aromatic hydrocarbon, and alkyl or alkylaryl polyoxyalkylene phosphate ester surfactant The treating fluid degrades and disperses the asphaltene precipitates as well as reduces the viscosity of the asphaltene-based crude.
REFERENCES:
patent: 3599716 (1971-08-01), Thompson
patent: 3653440 (1972-04-01), Reisberg
patent: 3998743 (1976-12-01), Maly et al.
patent: 4278129 (1981-07-01), Walton
patent: 4393935 (1983-07-01), Walton
patent: 4541483 (1985-09-01), Walton
patent: 4775489 (1988-10-01), Watkins et al.
patent: 4813482 (1989-03-01), Walton
patent: 4863618 (1989-09-01), Falls
patent: 4886609 (1989-12-01), Walton
patent: 5038864 (1991-08-01), Dunleav
Bagnell David
Dougherty Jennifer R.
ETechMM
Scott F. Lindsey
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