GAS SEPARATOR
FIELD OF THE INVENTION This invention relates to a gas separator and in particular to a gas separator to be used as a tool within the pipeline at the bottom of the borehole for the drilling and maintenance of oil and gas wells. BACKGROUND OF THE INVENTION EXPOSITION OF THE PREVIOUS TECHNIQUE As described in the Latos et al patent No. 6,138,757, there are occasions in the oil and gas industry in which a gas is pumped into a well with a liquid. The pressure jet cleaning services deployed in coils are commonly carried out in depleted wells using energized fluids typically nitrogen and water. Underbalanced operation with energized fluids reduces the potential for damage to the well and helps transport fluids and debris from sounding to the surface. When nitrogen and water are injected as a two-phase fluid, the jet expands as it leaves the jet, reducing the pressure of the jet impact. The flow of two phases in the jet jet can also be regulated sonically by limiting the speed and effectiveness of the jet discharge. In addition, the jets
of fluid are rapidly dissipated in the fluid surrounding the well borehole. All these factors combine to reduce the effectiveness of a two-phase jet. Removal of the gas from the fluid stream would improve the performance of the cleanup by jet blasting for well maintenance. A single-phase water jet has a higher density and stagnation pressure than a mixed phase jet and would be more effective than a two-phase jet. Under the conditions found in oil and gas well maintenance operations, the fractions of gas in the fluid discharge from the separator must be less than 1 vol% to ensure effective cleaning by jet discharge. Coating the jets with the separated gas would reduce the jet dissipation and increase the effective raof the jet. Many well maintenance operations require pressure jet tools to pass through small diameter pipes and obstructions before cleaning the larger diameter pipe, the bottom drilling equipment on the side cavity mandrels, or the perforations of the well of non-tube wells, the raof cleaning to increased jet will increase the effectiveness of the tools of cleaning by discharge of jet under pressure compared to the cleaning by discharge of jet to pressure of fluids of a
single phase for these applications. The use of energized fluid with a gas separator will also increase the differential pressure and the hydraulic power of cleaning by jet discharge by reducing the circulating pressure of the bottom of the borehole. The increase in pressure and energy will allow the erosion of harder material such as mineral encrustations, cement and rock, while the increase in energy will improve erosion rates. An effective gas separator would maintain high efficiency over a relatively high raof inlet gas fractions. In a common application, enough nitrogen is added to reduce the bottomhole pressure to 50% of the hydrostatic. Under these conditions, the compressed gas represents 20 to 60% of the volume fraction of the flow inside the coil. The fraction of volume of gas entering the separator can vary substantially during a single run due to cha in pressure and temperature as the depth of the operation of the tool increases. The Latos et al patent (supra) describes a downhole phase separator for coil tubing using a cyclonic separator design. This tool provides less than 5% gas fractions for a supply fluid with 30% to 40% of
gas content. Cyclonic separators are used to turbulence the flow of fluid through a set of blades. This procedure generates very high radial accelerations, which provide the separation forces. In small diameter tools, the high flow rate generates high turbulent mixing forces that overcome the separation forces and limit the performance of the separation. Rotating gas separators are commonly used in the production of two phases to prevent gas from entering submersible electric pumps. The rotary gas separator is driven by the pump shaft and rotates at 3500 or 1750 rpm depending on the electric motor and the power supply. The system includes an inductor to pressurize the two-phase flow entering the separator. The flow enters a section of covered blades where the flow turns and the water or oil moves outward due to centrifugal forces. The cover rotates with the blades reducing the turbulence in the separator. A cross-linking distribution tube on top directs the flow of fluid to the pump and the flow of gas back to the well ring. The fractions of gas claimed are less than 0% for a wide range of flow rates and gas / liquid flow ratios. Rotary gas separators online also
They are used in pipes to remove small volumes of condensate from the gas flow. This style of separator uses a stator to induce to induce turbulent flow within a drum that includes rotor blades in the gas flow. The rotor provides power to rotate the drum. This type of separator is designed to remove all fluid from the gas stream as opposed to providing low fractions of gas in the fluid. Yahiro et al in the patent E.U. No. 4,047,580 discloses a method for covering a submerged jet by introducing compressed air through an outer ring of a concentric jet nozzle. The air cover increased the range of jet discharge by a factor of four. The construction of annular gas nozzles is complex, particularly for cleaning by jet discharge of high pressure fluids. GENERAL DESCRIPTION OF THE INVENTION There is still a need for a separator within the pipe to efficiently separate a gas from a liquid. An object of the present invention is to meet this need by providing a compact, relatively simple separator for removing gas from a gas / liquid mixture. Another object of the invention is to provide an apparatus that combines a separator to separate a gas from a
liquid and a pressure jet cleaning tool for operations inside the pipe, at the bottom of the borehole. Accordingly, the invention relates to an apparatus for separating a gas from a liquid under pressure comprising: a tubular housing having an inlet end and an outlet end; a stator at the inlet end of the housing to cause turbulence of the liquid containing gas introduced at the inlet end; a drum installed rotatably in the housing under the stator in the direction of liquid flow between the inlet and outlet ends of the housing; a rotor at an inlet end of the drum for causing the drum to rotate in the housing; a final wall at a downstream end of the drum in the direction of fluid flow through the housing; liquid outlet ports in the periphery of the final wall to discharge the liquid from the drum; a gas outlet port in the center of the final wall to discharge the gas from the drum; a liquid outlet passage in the housing
to receive the liquid from the liquid outlet port and discharge the liquid from the housing; a gas outlet passage in the housing to receive the gas from the gas outlet port and discharge the gas from the housing; a first restriction of flow in the liquid outlet to restrict the flow of liquid during discharge from the apparatus; and a second flow restriction at the gas outlet to restrict gas flow during discharge from the apparatus. In another embodiment, the invention relates to a pressure jet cleaning method comprising the steps of passing a two phase fluid stream through a pressure jet cleaning tool, removing the gas from the fluid stream. of two phases thus producing a phase rich in gas and a liquid phase containing less than lvol% gas. In a further embodiment, the gas-rich phase and the liquid phase are discharged from the tool and the gas-rich phase covers the discharge of the liquid phase. In yet another embodiment, the invention relates to a method for pumping a two-phase fluid containing a gas and a liquid in a well bore and separating the gas phase from the liquid phase by means of which the
The resulting liquid contains less than 100% gas. DESCRIPTION OF THE FIGURES The invention is described below in greater detail with reference to the accompanying drawings, wherein: Figure 1 is a schematic longitudinal sectional view of a combination of separator and pressure jet cleaning apparatus in accordance with the present invention; Figure 2 is a schematic longitudinal sectional view of a second embodiment of a combination of spacer and jet cleaning tool according to the present invention; Figure 3 is a schematic longitudinal sectional view of a combination of separator and rotary jet cleaning tool according to the invention; Figure 4 is a schematic longitudinal sectional view of a second embodiment of a combination of separator and rotary jet cleaning tool according to the invention; Figure 5 is a schematic longitudinal sectional view of a third embodiment of a separator and rotary jet cleaning tool combination according to the invention; Figure 6 is a longitudinal sectional view
schematic of a fourth embodiment of the separator and rotary jet cleaning tool combination according to the present invention; Fig. 7 is a schematic longitudinal sectional view of a fifth embodiment of a separator and rotary cutting tool combination according to the present invention; Figure 8 is a front view of the separator and the cutting tool of Figure 7; Figure 9 is an isometric view of a stator used in the tool of Figure 7; and Figure 10 is an isometric view of a rotor used in the tool of Figure 7; DETAILED DESCRIPTION OF THE INVENTION Referring to Figure 1, a separator according to the invention includes an elongated tubular housing containing a rotating drum 2. A liquid containing gas is introduced into the inlet end 3 of the housing 1 through a narrow diameter orifice 4. The liquid passes around the conical end 5 of a stator 6, which is installed in the housing. The stator 6 includes blades 7 connected to the housing 1 to cause fluid entering the housing 1 to spin. The spinning flow causes a rotor 9 to rotate. The rotor 9, which is connected to the drum 2, includes straight blades 10 that extend parallel
towards the longitudinal axis of the drum to ensure that the tangential flow of fluid in the drum 2 is small. The rotor 9 is rotatably supported on the stator 6 by a bearing 12. The fluid flow through the rotor 9 causes rotation of both the rotor and the drum 2. A final wall 25 of the drum 2 is rotatably connected to one end of unloading the housing 1 by a bearing 14 having a restriction. Bearings 12 and 14 are formed of low friction materials and have a small diameter to limit the bearing torque. The bearing 14 is a combination of plain bearing and thrust bearing, while the bearing 12 is a simple plain bearing bearing. A clearance seal 15 is provided between the rear end of the drum 2 and the rear end 16 of the housing 1. The gas in the liquid entering the drum 1 by means of the stator 6 and the rotor 9 is separated from the flowing mixture. beyond the tapered rear end 18 of the rotor
9 by centripetal acceleration, which forces the liquid 19 outwardly and the gas 20 towards the center of the drum 2. Because the tangential component of the fluid velocity is small, the total velocity of the flow is minimized
which minimizes turbulent mixing forces that oppose separation. Preferably, a balance pressure port 21 is provided in the rotor 9 for venting a chamber
Balance pressure 22, between the stator and the rotor. The reduced pressure in the chamber 22 reduces the thrust load imparted by rotating drum 2 on the thrust bearing 12. The ports 23 can also be provided in the drum 2 near the rear end thereof. Ports 23 are located in a region of low velocity liquid flow, which is at a higher pressure than the high speed region between the stator 6 and the rotor 9. The ports 23 result in the reverse circulation of the fluid, which counteracts gas seepage through the space between the housing 1 and the drum 2. The liquid 19 is discharged from the drum 2 through the ports 24 at the periphery of the end wall 25 of the drum 2. The ports 24 define the sections of a ring. The liquid flows through the passage 26 at the rear end 16 of the housing 1 to a restriction in the form of a nozzle 28. The gas is discharged through an axially extending central siphon tube 30 connected to the rear end wall. 25 of the drum 2 and a passage 31 and a hole 32 in the rear end 16 of the housing 1. Multiple gas outlets can be provided. The gas orifice at the inlet end of the passage 31 is preferably sized as a sonic nozzle which will pass the maximum volumetric flow rate of gas provided in a given operation. The dynamic equations of
Gas to give a gas orifice for a given pressure, temperature and flow rate is well known to those skilled in the art. The liquid nozzles 28 are dimensioned to provide the maximum hydraulic cleaning power with a pressure jet taking into account the frictional pressure losses in the coil. If the liquid flow rate is increased and the gas fractions are minimized, the differential pressure and the flow rate through the liquid jet nozzles and the gas orifice are increased. The liquid that enters the gas orifice causes it to regulate, which reduces the capacity of gas flow. The gas hole thus provides a simple and robust means of limiting the loss of liquid from the gas separator while maintaining the pressure and hydraulic power of the liquid jet as the gas flow rates decrease. The rear end of the housing 1 in the direction of fluid flow is closed by a pressure jet cleaning installation 34, which contains parts of the passages 26 and 31, the nozzle 28 and the holes 32. The jet cleaning installation Pressurized 34 is representative of a variety of more complex tools that include rotating jet blasting tools, drill motors and other tools that depend on a flow restriction.
fluid. In a preferred embodiment of the invention, the gas orifice 32 is sized to be slightly larger than that required for the maximum rate of gas flow provided in a given operation. The dynamic gas equations for sizing a gas orifice for a given pressure, temperature and flow rate are well known to those skilled in the art. The liquid nozzles 28 are sized for the pumped fluid flow rate at the desired pressure jet cleaning pressure, taking into account the loss of frictional pressure in the coil. If the gas fraction decreases, the fluid will begin to enter the siphon tube 30 and the orifice 32. The two-phase flow capacity of the gas orifice 32 is much smaller than the gas flow capacity. The gas port 32, therefore, provides a simple and robust means for limiting the loss of liquid from the gas separator due to variations in the fraction of the inlet gas that may occur during the operation. The gas separator benchmarks show that the liquid loss is 0.6% or less while the input gas fraction varies from 29% to 52%. The embodiment of the invention shown in Figure 2 is similar to that of Figure 1 except that the rotor 9 is cylindrical with no tapered rear end, and the upstream end 36 of the end wall 25 of the drum is conical
to accelerate the flow of liquid in the outlet ports 24 without introducing sudden changes in the flow direction that could trigger the turbulent re-mixing of gas and liquid. The nozzle axis 28 and the orifice 32 intersect outside the pressure jet cleaning installation 34 so as to form a gas cover around the liquid jet. In the embodiment of Figure 2, the orifice 32 is restricted in place of the bearing 14 as in the embodiment of Figure 1. Figure 3 shows an apparatus for applications requiring rotary cleaning with jetting of the liquid exiting the apparatus. The apparatus according to Figure 3 is similar to that of Figure 1 except that the liquid discharged from the drum 2 via the siphon tube 30 passes through the passages 38 at the rear end of the housing 1, and the central axial passages 39 and 40 through a brake installation 42 and a head 43, respectively. The brake installation 42, which includes a tube 46 carrying the head 43, is installed rotatably on the bearings 47 in the housing 1. The passage of the liquid through the nozzles 44, which move from the longitudinal axis of the head 43, ie, they are inclined with respect to the spokes of the head 43, causing the brake assembly 42 and the head 43 to rotate in the housing. The nozzles 44 are located beyond the
rear end of the housing 1, so that when deployed in an oil or gas production pipe 49, the fluid jets will remove the encrusted deposits 50. It will be appreciated that any rotary motor with an axial flow passage large enough to accommodate the Siphon tube 30 can be used in combination with the separator. For example, the U.S. Patent Application. de Marvin et al 2005/0109541 discloses a reaction turbine jet motor rotor with an unblocked, large diameter axial flow passage. The siphon tube 30 transports gas from the drum 2 to a central outlet hole 51 in the head 43. The inlet end of the siphon tube 30 is freely rotated in the end wall 25 of the drum 2. The outlet end of the tube 30 is fixed on the rotary head 43, which rotates at a speed different from that of the drum 2. Thus, a gas bubble is formed at the outlet end of the head 51 and the outlet end of the housing 1, so that the liquid is thrown from the nozzles 44 to the gas. The apparatus according to Figure 4 is similar to that of Figure 3 except that the gas discharged through the siphon tube 30 passes through the passage 54 and is discharged through a cylindrical passage 55 between the housing 1 and the end of discharge 56 of the head 43. The liquid discharged through ports 24 in the wall
end 25 of the drum 2 passes through the passage 57 in the rear end of the housing 1 towards the passages 39 and 40 and through the brake installation 42 and the head 42 to exit through the nozzle 44. Referring to Figure 5 , another embodiment of the rotary jet cleaning apparatus includes all the elements of the apparatus of Figure 3, except that the rear conical end 18 of the rotor 9 and the brake installation 42 and the cylindrical end wall 25 of the drum have been omitted. it has been replaced with a final wall having a conical entrance or upstream end 36. Furthermore, in the apparatus of Figure 5, the head 43 itself is installed rotatably at the rear end of the housing 1. The liquid is discharge through the passages 38 and 40 and a plurality of inclined nozzles 44 at the rear end of the head 43. The gas is discharged through the end wall 25 of the drum 2 through the siphon tube 30, a raisin 58 at the rear end of the head 43 and the inclined nozzles 59. The trailing end of the siphon tube 30 includes a restriction 60. The axes of the nozzles 44 and 59 intersect outside the head 43 so that the jets of liquid are they cover gas. The apparatus of Figure 6 is used to cut through a 60 formation. The apparatus is similar to that of the
Figure 4, except that the rotor 9 is cylindrical with no tapered rear end, the rear end wall 25 of the drum 2 has a conical front end 36 and the brake installation 42 is omitted. The liquid is discharged by means of the ports 24 in the end wall 25 of the drum, a passage 57 in the rear end of the housing 1, a central passage 40 in the head 43 and the holes 44. The gas passage 54 defining a siphon tube contains a restriction 62. With reference to the Figure 7, another embodiment of the combined separator and jet cleaning apparatus includes a separator that includes the housing 1 with internally threaded inlet and outlet ends 64 and 65, respectively to receive the connections 67 and 68. A stator 70 fixedly installed at the inlet end 64 of the housing 1. As best shown in Figure 9, the stator 70 includes a cylindrical body 71 with a generally hemispherical forward end 72. The arched blades Adas 74 extending outward from the body 71 connect the stator to a sheath 75, which connects the stator to the housing 1. A cylindrical rotor 77 is rotatably mounted on a bearing 78 at the rear end of the stator. The rotor 77 (Figure 10) includes a cylindrical body 80 with radially extending blades 81. The final wall 25 of the drum 2 is installed in a manner
rotating on a bearing 14 at the inlet end of a sheath 83 in the siphon tube 30. The bearing 14 is connected to the inlet end of the connection 68 by a sheath 84. The downstream end of the connection 68 is connected to a second housing 85 containing a speed regulator 87. The speed regulator 87 includes a tubular central shaft 88, which is installed rotatably on the bearings 89 in the coupler 68 and the bearings 91 in a coupler 92. The centralizers 93 in the axis 88 center the siphon tube 30 in the speed regulator. The segmented weights 94 about the axis 88 regulate the rotational speed of the shaft by sliding outwardly against the housing 85. The pressure jet cleaning system indicated generally at 96 is rotatably supported on the end of the connection 92 by the bearings 97, 98, 99, 100 and 101. The installation 96 includes a housing 102 carrying a rotating head 43. The bearing 97 includes a half-front vent 104, which vents toward the rotating head 43 and forms a front mechanical seal with the bearing 98. The bearing 100 is fixed to the rotating head 43. The bearing 100 forms a frontal mechanical seal with the bearing 101. The diameters of the contact surfaces of the bearing are dimensioned to minimize the mechanical contact load on the frontal seals. mechanics while maintaining a
effective sealing under high pressures. The liquid discharged from the drum 2 through the ports 24 in the end wall 25 flows through three jet nozzles 106 (shown one) in a cover 107 on the rotating head 43. The gas discharged from the drum 2 passes through of the siphon tube 30 and discharged through a gas orifice 109 at the end of the siphon tube 30 and through three discharge ports 110 (one shown) in the cap 107 to form covers around the liquid jets .