Wells – Processes – Separating material entering well
Reexamination Certificate
2000-05-25
2003-03-25
Suchfield, George (Department: 3672)
Wells
Processes
Separating material entering well
C166S267000, C166S272300, C166S272700, C166S303000, C203S010000, C203S025000, C203SDIG008, C210S747300
Reexamination Certificate
active
06536523
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a highly efficient water distillation process and an apparatus thereof and more particularly, the present invention is directed to a highly efficient water distillation process used in the thermal recovery of heavy oil which minimizes fouling and scaling of operating equipment over long periods of operation.
BACKGROUND OF THE INVENTION
Throughout the many regions in the world, heavy oil, a hydrocarbon material having much higher viscosity or lower API gravity (less than 20° API, typically 7° to 12° API) than conventional petroleum crude, is more difficult to recover and requires enhanced thermal stimulation techniques of the subsurface reservoir to produce. More particularly, in areas of Western Canada heavy oil producers use a technique of injecting high pressure steam into the reservoir at typical pressures of about 1,500 to 3,000 psig, and in some cases as low as 150 psig. The steam heat energy is generated by an apparatus known as a steam generator to a 60 to 80% steam quality and injected into vertical or horizontal well arrangements to reduce the heavy oil viscosity. The flowable heavy oil is collected in adjacent producing wells and a combination of heavy oil, oil/water emulsion, condensed steam and formation brackish water (known as produced water) is produced to the surface. Using surface facilities, heavy oil is separated from the production fluids and recovered for commercial sale. The produced water, typically recovered at water/oil ratios of 2 to 5, is currently disposed of in subsurface disposal wells. Makeup water from an authorized ground water source is used to makeup the steam generator feed water demand. Typically the makeup water receives minimum treatment to reduce hardness and silica compounds to avoid scaling of the steam generator heat exchange surfaces and prevent a safety hazard. In some facilities, the concentrated brine water from the steam generator discharge is separated from the reservoir injection steam and disposed of in suitable deep disposal wells. This concentrated brine water can also be referred to as high pressure blowdown. This prevents excess and unnecessary hot water from being injected into the reservoir during the steam stimulation operation. Typical current heavy oil recovery practices using the steam injection technique are referred to as Cyclic Steam Stimulation (CCS or Huff n' Puff), Steam Assisted Gravity Drained (SAGD) and Steam Assisted Gas Pushed (SAGP) methods.
Public and regulatory pressures require that heavy oil producers implement water recovery and reuse practices and in some facilities a zero effluent discharge is required. This means that 100% of the water used be recovered and reused and the elimination of offsite disposal of effluent streams. The produced water, recovered from the oil separation facility and the HP (high pressure) steam separators, contains hardness components, dissolved and suspended silica and colloidal compounds (clay) and dissolved solids such as sodium chloride. If this brackish water is recycled without treatment, the operation of the steam generators is at risk due to fouling and scaling.
A further problem encountered with the current heavy oil recovery practices using steam injection, is that as the operating temperatures of producing reservoirs are increased from 230° F. to greater than 400° F. to enhance the heavy oil recovery, the temperature of the recovered production fluids (oil and water) increase. To facilitate the common practice of atmospheric oil and water separation, significant quantities of steam is created when the fluid pressure is reduced. This steam is typically condensed by an external means, such as an air cooler to recover the condensed water. The heat energy of the condensing steam is discharged to the atmosphere and wasted.
Until the advent of the present invention combining the recovery of waste heat energy with a highly efficient and non-scaling water distillation process, the recycle of heavy oil produced water and concentrated brine disposal streams has been technically and commercially restricted.
Generally speaking, water distillation is a highly effective method of vaporizing a pure water distillate and recovering a concentrated liquid or solid containing a large quantity of non-volatile components. This process method can be an effective means to recover clean pure water from contaminated sources. However, water distillation processes typically have several problems not the least of which can be fouling or scaling of the apparatus with minerals or other components from the fluid being distilled. Common scaling compounds consist of calcium, magnesium and silicon. Fouling, or to a greater extent, scaling of the heat transfer surfaces have a detrimental effect on the capacity of the heat transfer components, causing conventional distillation processes to become inoperable.
In the prior art, Tsuruta, in U.S. Pat. No. 4,566,947, issued Jan. 28, 1986, taught a general distillation process, but did not recognize the key factors necessary for the prevention of fouling or the applicability of the process for treating produced water from heavy oil recovery. The most important passage in the Tsuruta reference is at column 7, beginning at line 55, with respect to FIG. 4, which states:
“The method which employs a vapor compressor 307 in this manner is advantageous in a case where the feed liquid gives rise to precipitation of solid upon condensation of its volatile component or clogging with pitch-like material which would cause dangerous accidents or troublesome maintenance and service of the compressor. With the above-described arrangement, only the vapor from the evaporator passes the compressor 307, thus preventing the occurrence of such troubles. The interiors of the line 350 and the reboiler 352 can be maintained in a clean state by the use of a suitable washing means. The foregoing method is advantageous especially when the bottom liquid is water, since it is possible to replenish through the line 353 cheap process water which does not require recovery. When the water which is collected at the tower bottom of 306 does not contain substances which foul the inside of the compressor 307, it may be fed to the evaporator though the line 353 to keep the liquid level in the evaporator constant.”
FIG. 4 of Tsuruta has been reproduced hereinbelow as well as an additional figure, (Revised FIG. 4), which substantially corresponds to FIG. 4 of Tsuruta, which incorporates Applicant's apparatus to effect its method.
As is evident from a review of FIG. 4 from the Tsuruta reference, if a forced circulation reboiler circuit were added to U.S. '947 and a specific vapor ratio defined, the bottom liquid water would contain fouling substances and operate without fouling or scaling the heated surfaces.
In the FIG. 4 illustration of Tsuruta, lines 340 and 353 are not connected. There is no connection from bottom 306 to line 353. Section 306 in the tower is defined as the tower bottom containing bottom liquid with a pre determined ammonia concentration. Tsuruta highlights the fact that the method is advantageous especially when the bottom liquid is water.
Tsuruta clearly states, in the passage noted above and to which emphasis has been added, that as long as the water which is collected in the bottom of the tower does not contain substances which foul, the water may be fed to the evaporator. The instant application is unconcerned as to the nature of the feed stream for fouling the evaporator. The water contaminated with contaminants can be fed directly to the evaporator without any fear or fouling or other damage to the heat exchanger. In effect, this is an exact opposite to what Tsuruta teaches. By consideration of the circuit loop in FIG. 4 of Tsuruta, all of the heated surfaces related to the bottoms liquid in the apparatus never come in contact with anything other than water substantially free of fouling contaminants, which water is used as the primary medium for stripping ammonia out of a mixture of ammonia and
Braun Alex
Kresnyak Steve
Aqua Pure Ventures Inc.
McFadden Fincham
Suchfield George
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