Patent Application
20060196658
This invention relates to devices and techniques for reducing or eliminating slugs in a tubular string within a well, such as liquid slugs in a gas well, or gas slugs in a liquid well or pipeline. More particularly, the device of the present invention is highly reliable and does not interfere with the passage of various tools through the tubular or pipeline.
Various types of devices have been designed for reducing or eliminating slugs in a flow line. Slugs in a flow line may cause serious problems to downstream equipment, such as blow-out preventers, flow control valves, and sensors. Most slug prevention devices are positioned within the bore of the tubular string, and thereby substantially interfere with the passage of wireline tools, coiled tubing tools, pigs, or other devices intended to pass through the tubular string or pipeline.
U.S. Pat. No. 5,698,014 discloses a spiral or auger type separator particularly intended for well production fluid flow. U.S. Pat. No. 5,431,228 discloses another version of a liquid-gas separator for use in downhole producing wells. An early version of an air-water separator is disclosed in U.S. Pat. No. 4,762,176. U.S. Pat. No. 5,570,744 discloses another version of a separator for well production fluids, including a spiral baffle.
The disadvantages of the prior art are overcome by the present invention, and an improved slug reducer for use along a flow line is hereinafter disclosed.
According to a preferred embodiment, a flow line for reducing axial separation of different density fluids passing through the flow line includes one or more grooves in a wall of the flow line and radially outward of a generally cylindrical bore of the flow line. Each of the one or more grooves forms a spiral along an axial length of the flow line, thereby swirling fluid passing through the flow line and causing lighter fluid to move toward a center of the flow line due to a created vortex and heavier fluid to move toward a radially outer portion of the flow line.
In another embodiment, a tubular for reducing axial separation of liquid slugs and gas slugs passing through the tubular in a well includes one or more grooves in the tubular, with the one or more grooves each forming a spiral along the axial length of the tubular. Swirling fluid passing through the tubular in the well causes gas to move toward a center of the tubular due to the created vortex and liquid to move toward a radially outer portion of the tubular.
According to the method of the invention, axial separation of different density fluids passing through a flow line having a generally cylindrical bore is reduced by forming one or more grooves in a wall of a flow line and radially outward of the generally cylindrical bore of the flow line. The recesses may be formed by one or more radially outward projections on a mandrel, such that when the flow line moves axially over the mandrel while rotating, the one or more grooves are formed in the flow line.
These and other features and advantages of the invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.
The size of the grooves in the pitch of the spiraling grooves which are preferred will depend to some extent upon the velocity of the fluid moving through the flow line. Higher velocity fluids will require less groove depth. In a preferred embodiment, the tubular may be of the type having a verified thickness, such as the thickness 42 of the tubular wall normally greater than conventional thickness of the tubular. In other applications, an increased wall thickness tubular may be utilized to maintain the desired strength of the tubular while still providing the spiraling grooves along the tubular.
According to a method of the invention, the grooves in the tubular may be formed by a machining operation. In a preferred application, however, the grooves may be formed when initially extruding the tubular. For this application, a mandrel may be provided with radially outward projections forming the grooves in the inner wall of the tubular. The tubular thus passes over the mandrel and is rotated at the desired rate to achieve the spiral pitch intended.
A flow line with a generally cylindrical bore having a bore internal diameter includes one or more grooves in the wall of the flow line according to a preferred embodiment of the invention. The grooves are thus radially outward of the generally cylindrical bore, with each groove forming a spiral along the axial length of the flow line, thereby causing fluid to swirl as it passes through the flow line and causing lighter fluid to move toward a radial center of the flow line due to the created vortex and heavier fluid to move toward a radially outer portion of the flow line. The improved flow line thus reduces axial separation of different density fluids, which in one embodiment may be liquid slugs or gas slugs passing though the flow line, and in another embodiment may be different density liquids. The grooves cause spiraling of the fluids passing through the flow line, and reduce axial separation of one type fluid from another type fluid. A slug of one fluid upstream of the spiral grooves which occupies all or substantial portion of the cross-section of the bore may thus be stretched by the spiral grooves, so that this fluid reaches a downstream facility and constitutes only a portion of the bore of the same diameter flow line. This axial stretching or separation of the fluid thus reduces the damage to the downstream equipment normally caused by a slug of one type fluid. In a preferred embodiment, two or more grooves are circumferentially spaced at substantially uniform circumferential spacing about the flow line. This spiraling of fluid in the flow line also has the potential benefit of improved separation efficiency for downstream equipment, since separation of, for example, the liquid and the gas passing through the flow line prior to arrival at the downstream facility may assist significantly in downstream separation, since substantially only liquid will be in the radially outer portion of the flow line, and substantially only gas will be in the radially inner portion of the flow line.
Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.
