Arrangement used in oil field wells for lifting hydrocarbons

The present invention relates to an arrangement for the lifting of hydrocarbons in oil field wells, comprising a lifting assembly formed by a fluid collecting hose and a fluid suction tube being lowered, filled and raised within a well casing.

FIELD OF THE INVENTION

The present invention is directed to an arrangement used in oil field wells for lifting hydrocarbons, and more particularly it is directed to a new arrangement of elements placed within production wells for safely lifting liquid or gaseous hydrocarbons, avoiding gas venting and thus allowing for an increase in productivity of the facility, among other important advantages.

BACKGROUND OF THE INVENTION

Lifting of hydrocarbons from oil fields involves introducing into the well a casing that extends down sufficiently to reach the hydrocarbon-containing strata, so that any oil, gas and water found therein may flow upwardly to the surface through the casing to be then separated, stored or channeled to its next destination. The oil, gas and water from the strata enter the casing and, because of their different densities, they segregate from each other so that water remains at the bottom of the casing, while oil floats over it and gas flows up through the casing.

Conventional oil lifting requires the use of pumping units disposed on the surface of the field ground and on the wellhead, which include, among other components used for fluid extraction, a pump lever, a suction rod and a pump placed downhole within the casing at the deepest possible production position. For operating the suction rod, its lower end is connected to the pump, while its upper end is connected to the pump lever disposed on the ground surface. By means of a mechanical arm lever, the pump lever drives the upwards and downwards reciprocating movement of the suction rod, thus performing the pumping work in the production well.

Another widely known type of pumping system consists in using a bailing system disposed on the ground surface adjacent to the production well, using a bailer mechanism disposed on the ground surface adjacent to the production well, comprising a bailer type (tube and hose) system, a pulling strip or cable which extends along an admission tube or arm, and a hoist mechanism. In this system for lifting hydrocarbons, the bailing system is operated by spooling and unspooling a pulling cable from a hoisting mechanism, to which one end of the wireline is attached, while the other end is attached to the upper end of the bailer-type mechanism placed within the well casing. During operation of the hoist mechanism by spooling and unspooling the wireline or cable, the latter makes a reciprocating movement and undergoes considerable stresses when it is spooled to lift the bailer or unspooled for lowering it to the oil-containing section of the well casing. When the bailer is submerged into the oil-containing section, it collects some oil and gets filled with it. Then, the bailer is lifted up to the surface and the oil is poured into a storage dam.

In these conventional systems for lifting hydrocarbons, fluid discharge from the hose that extends along the borehole is achieved by the action of gravity. These systems have disadvantages that must be overcome. In fact, during the lowering operation, the hose may stick to the tube due to the presence of viscous or paraffin hydrocarbons. These conditions may be affected by external temperatures and the tubes may be worn off by friction with the hose, which may cause ecological damage. In addition, the hose must have thicker walls in order to withstand the strain caused by the rollers over the curvature of the header when entering into the PVC tube. Furthermore, the hose diameter is limited by the header's entrance hole and the recovery capacity of the hose is limited by the length of the tubes, all of which leads to a reduction in productivity. Another disadvantage is that the hose detection system is external and has no protection. In addition, harsh environmental conditions (temperatures, wind, sunlight), the presence of animals, mishandling, etc. can damage the tube joints and cause leaks. The presence of gas pockets may damage PVC tubes and cause environmental damage. In addition, the horizontal tube where the fluid is discharged is made of plastic and can only withstand low gas pressure. Consequently, the gas cannot be transferred by its own pressure and requires permanent venting.

In order to solve the above mentioned drawbacks of conventional hydrocarbon-lifting facilities, the inventors have developed the arrangement of the present invention, which provides outstanding improvements over the prior art. In fact, the arrangement to be used in oilfield wells for lifting hydrocarbons is capable of capturing gas from the well and thus avoid venting, which increases productivity of the lifting equipment. One of the most important factors favoring productivity is the use of the gas pressure from inside the casing for draining the hose. The hose length may be made proportional to gas pressure at a ratio of 10 ml per 1 kg/sq. cm. of gas pressure, without modifying the length of the surface equipment. In addition, there will be less tubing on the surface and all the moving elements of the arrangement will remain within the casing, thus avoiding possible leaks of fluid at surface level and providing greater safety to the lifting process. It should also be underlined that equipment, mounting and operation costs are lower than those of conventional arrangements, no “pulling” is needed, it is easily maintained and consumes less power, among other advantages.

SUMMARY OF THE INVENTION

The present invention discloses an arrangement for the lifting of hydrocarbons, which is used in oil field wells, and comprises a lifting assembly having a fluid collecting hose and a fluid suction tube within the well casing. The suction tube extends along the collecting hose, which has an open upper end, through which passes the upper section of the suction tube having an end attached to the pulling cable of the “collecting hose/suction tube” assembly, and a lower end closed by means of a one-way check valve, through which the fluid flows into a space comprised between the hose and said tube. The upper section extending beyond the open upper end of the collecting hose has a laterally-conformed fluid discharge opening. When the “hose/suction tube” assembly is risen by action of the pulling cable to reach the end of its travel, said discharge hole is positioned within a sealed chamber in the wellhead, which is defined between a pair of sealing rings, and in this way the fluid is discharged with the assistance of the suction pump and/or the inner gas pressure from the casing.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A to 1Cshow that the hydrocarbon lifting arrangement placed within oil field wells of the invention comprises a lifting assembly formed by a suction tube1and a fluid collection hose2, said assembly extending along the well casing3. The hose2has an open upper end4and a lower end5closed by means of a one-way check valve6which opens into the hose2to let the fluid flow into it. In turn, the suction tube1, which extends from the proximity of the check valve6and beyond the upper end4of the collecting hose2, has a lower section7and an upper section8having a laterally positioned discharge opening10for the fluid being lifted. The upper section8of the suction tube1has a closed end9, to which the pulling cable11is connected to cause the upwards and downwards movement of the lifting assembly defined by the suction tube1and the collecting hose2.

The upper section8of the suction tube1is of a length such that, during operation of the facility, when the “tube-hose” assembly reaches the end of its upwards travel, the discharge hole10is positioned between a pair of sealing rings—a lower ring12and an upper ring13—which are placed in the lower section15of the wellhead14, a sealed chamber16being formed between said rings, where said chamber has a discharge opening coupled to a fluid outlet duct17connected to a suction pump18.

The pulling cable11, attached to the upper end9of the suction tube1, passes through a cable guide bushing19and an actuating device that senses the sealed chamber16. The bushing19is part of a member having a lower section20, which defines the bushing itself and an upper section21having a larger diameter than said lower section20and defining a guide and an abutment on the sealing ring13within the upper section22of the header14. As shown in the drawing, the bushing19passes through said pair of sealing rings12and13during the travel of the “tube-hose” assembly. In addition, the pulling cable11passes though a cable seal23positioned next to the upper section22of the wellhead14.

As shown in the operation sequence represented inFIGS. 1A to 1C, when the “tube-hose” assembly is pulled up by the cable11until it reaches the end of the travel, the upper section8of the suction tube1, and consequently the discharge opening10, are positioned within the sealed chamber16defined between sealing rings12and13. Immediately after the discharge opening10connects with the sealing chamber16, the suction pump18begins to force the circulation of the fluid contained in the collecting hose2towards the outlet duct17, passing through the discharge opening10. Liquid flow, and consequently, oil production, is maintained during the parts of the cycle comprising ascending and descending of the “tube-hose” assembly, as long as the discharge opening10is in communication with the sealed chamber10and until the hose2is drained. In this part of the lifting process the check valve6remains closed.

During the descending travel of the “tube-hose” assembly, when the end5of hose1is submerged again into the fluid content of the well, the check valve6is opened by the pressure exerted thereon by the fluid, and consequently the hose2is filled again until the “tube-hose” assembly reaches the end of its descending travel, to be subsequently discharged in each “up/down” cycle of the “tube-hose” assembly. In gas-containing wells, the pressure exerted by the gas, depending on its intensity, will cause discharging of the hose2, thus contributing to an increase in the fluid flow rate from the suction pump18.

FIG. 2shows an exemplary embodiment of the present invention, in which the outlet duct17comprises a flow-rate control24, which, by means of a one way check valve25, is fluidly connected to the corresponding flow line, together with the outlet duct of pump18, so that the produced gas will be driven to the storage facilities under its own pressure. The figure also shows that the pulling cable11goes through a pulley mechanism26and extends along a tube27to enter a motor driven equipment28where it is spooled on a drum29.

FIG. 3shows a further embodiment of the present invention, which includes a device30designed to lower gas pressure within the well casing3whenever it is deemed convenient. Said device30comprises a storage tank31having an inlet32connected to the suction pump18outlet, a first outlet33connected to a screw pump34, and a second outlet connected to the corresponding fluid transportation line. The outlet of the screw pump34is connected to an auxiliary inlet of the suction pump18. In addition, in this exemplary embodiment the sealed chamber16of the wellhead14has an attached pressure switch36and a positioning sensor37.

When the tube-hose assembly is in its discharge position as detected by sensor37, the device30suctions the fluid to discharge hose2. On the other hand, when the tube-hose assembly is not in position—during the upwards and downwards movements—if gas pressure is higher than desired, the pressure switch36actuates the device30, allowing only gas to flow out.