Wells – Processes – With indicating – testing – measuring or locating
Reexamination Certificate
1998-06-29
2004-04-13
Shackelford, Heather (Department: 3673)
Wells
Processes
With indicating, testing, measuring or locating
C166S265000
Reexamination Certificate
active
06719048
ABSTRACT:
This invention relates to the separation of oil-well fluid mixtures, and concerns in particular the down-hole separation of the multi-phase oil/gas/water mixtures produced by an oil well.
BACKGROUND OF THE INVENTION
Most oil wells produce what is basically a mixture of oil and/or gas together with water (usually in the form of “brine”, carrying quite large amounts of dissolved minerals, mostly common salt). Somewhere in the production process the ingredients have to be separated, the oil/gas to be stored and then delivered to a refinery for subsequent treatment, the water to be disposed of (often by pumping it back into the ground, perhaps in some borehole neighbouring the one it was removed from so as to replace the liquid removed from the formation, and maintain the associated pressure). For the most part this separation takes place above ground, and once the oil/gas/water mixture has been pumped up to the surface, but there are a number of good reasons why it would be highly advantageous—regardless of what actually then happens to the water—to effect the separation down-hole, even near the very earth formation out of which it has flowed into the borehole. Specifically, down-hole separation could result in a lighter liquid column within the borehole, it could permit a reduction in the separation equipment on surface, and it could facilitate the possibility of re-injecting the water directly down-hole, back into the formation (or a neighboring one) from which it originated. Other benefits of down-hole separation could be the easier separation before the mixture emulsifies, a reduced build-up of scale and corrosion, a minimizing of the risks from hydrogensulphide (a toxic gas often found in solution in oil well fluids), and a reduction in operating costs by reducing intervention in the well.
SUMMARY OF THE INVENTION
The invention relates to a method, and apparatus, for the separation of the water from the oil/gas in the well itself, down-hole. As explained in more detail hereinafter, the invention involves the combination of two ideas: the use of a gravity separator, and the utilization of controlling sensors positioned down-hole which identify the fluid components and then regulate the system accordingly. It is expected that this combination could be incorporated into an intelligent completion, in which the separated water is re-injected, resulting in an essentially water-free producing well.
In essence, the invention concerns a method of (and apparatus for) separating down-hole the two main components of an oil- (or gas-)well fluid, namely the oil/gas and the water, in which gravity is allowed to work on the mixture in a deviated section of pipe (a section that is not vertical, and then using physical separator means—smaller pipes, baffles and the like—the gravity-separated components are lead to individual pumps that will bring them to the surface (or wherever: as noted, the water can be injected back into the formation). This is the gravity separator. The crucial point, though, is to organize the pumping correctly, so as to keep the unsettled/unseparated mixture away from the separator means “inlets”, and this requires that there must be positioned downhole, right next to the inlets, sensors/detectors that can distinguish between the two components, and then cause the pumping rates to be modified so as to keep the mixture away from the inlets, and thus keep the inlet feeds “pure”—the one or the other component, not the mixture—or at least “purer” than the fluid actually issuing from the producing formation.
In one aspect, therefore, the invention provides a method of separating down-hole the main components (water and oil/gas) of a multi-phase oil- (or gas-)well fluid emanating from an underground formation into which a well has been drilled, in which method:
in a deviated, non-vertical section of the borehole the fluid is allowed to separate under gravity, aided by the flow regime imposed by the deviation, into separate streams or layers each being one (or mostly one) of its main components;
each stream is allowed to enter a conduit or pipe positioned to receive that stream only, and though which the component may be pumped away as required; and
component detector means are situated close to the effective mouth of each conduit/pipe, and are operatively linked to the relevant pump to alter the pump rate in dependence upon the actual nature of the material reaching the mouth.
In a second aspect the invention provides apparatus for use in a method of separating down-hole the main components (water and oil/gas) of a multi-phase oil- (or gas-)well fluid emanating from an underground formation into which the well has been drilled, which apparatus comprises, for location in a deviated, non-vertical section of the borehole within which the fluid is allowed to separate under gravity, aided by the flow regime imposed by the deviation, into separate streams or layers each being one (or mostly one) of its main components:
divider means by which the borehole is effectively divided into separate conduits or pipes each positioned to receive one respective fluid component stream only;
pump means associated with each such conduit/pipe and by which the relevant component may be pumped away as required; and
component detector means situated close to the effective mouth of each conduit/pipe, and operatively linked to the relevant pump to alter the pump rate in dependence upon the actual nature of the material reaching the mouth.
The invention concerns the down-hole separation of the main components of a multi-phase well fluid emanating from an underground formation into which the well has been drilled. These components will normally be oil and/or gas (the lighter) and water (the heavier). The proportions of oil/gas and water may vary very widely depending upon the field from which the oil/gas is coming. Indeed, the ratios vary widely not only between fields but also within a field—a range of likely ratios could be from 1:100 to 100:1 and still be valuable; the invention is useful for all of these.
Hereinafter the well fluid is for convenience referred to as though it were merely a two-phase oil/water mixture, resulting in two streams. This, it will be understood, is a handy simplification; in reality the fluid could be oil/water or gas/water, or even three-phase oil/gas/water (resulting in three streams).
In the first stage of the invention's method the oil/water mixture emanating from the formation is passed into a deviated—non-vertical—section of the borehole, and there the fluid is allowed to separate under gravity into two streams or layers each being one of its two main components. Oil being lighter than water, a mixture of the two will tend to separate if allowed to do so—if left alone, or moved only slowly—with the oil rising to the top. In a horizontal pipe (borehole) the mixture would thus stratify, forming two quite distinct layers each moving along with the other but not mixing, whereas in a pipe/borehole at an angle to the vertical—for example, at 45°—there will be a tendency for the oil to move up along the upper side of the pipe while the water moves up along the bottom side (it is even possible for the water to try to move down along the bottom side of the pipe). The slip velocity between the several components plays a significant role in determining what angles of deviation give the best practical separation for the purposes of the invention, and it has been found that in general an angle of 40° to 60° to the vertical seems most satisfactory.
In the deviated, non-vertical section of the borehole the fluid is allowed to separate under gravity into two streams or layers each being one of its two main components. In a horizontal section it is evident that given the chance the fluid will stratify, the oil and water separating due to their differences in density, but—and perhaps surprisingly—even in an angled section gravity can be used quite effectively to separate oil and water. In this type of separation the efficiency of the process is mainly controlled by the velocity o
Bryant Ian David
Murphy William F.
Ramos Rogerio Tadeu
Reischer Andrew J.
Theron Bernard Elie
Batzer William B.
Ryberg John J.
Schlumberger Technology Corporation
Shackelford Heather
Singh Sunil
LandOfFree
Separation of oil-well fluid mixtures does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Separation of oil-well fluid mixtures, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Separation of oil-well fluid mixtures will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3204187