Patent Grant
7647962
The present invention relates to an assembly and method for extracting fluids, preferably crude oil, from a drilled well within a geological formation by means of reciprocating pumping with hollow sucker rods. In particular, the system comprises the use of a string of hollow centered rods, which are able to transport/extract the effluents to the surface through their inner bore and, at the same time, to impart the reciprocating axial movement in relation to the subsurface pump.
The economical or strategic importance of oil, is evident, therefore the possibility of increasing the production, as well as the usable reservoirs, is extremely attractive. However, new oil fields have not been found, and oil and gas reservoirs have been reduced in the last three years. In addition, the cost reduction is a constant existing need in all industries in order to increase the competitivity and profitability of the companies. In the case of oil production, the cost reduction increases the economically exploitable reservoirs, since oil is extracted provided the income is higher than the operative costs. In Argentina, where there are many mature oil fields exploited by means of secondary recovery where the average cut (water ratio in the extracted fluids) is over 90%, the idea of a productive alternative for reducing costs is particularly attractive.
Typically, once an underground formation capable of containing oil and/or gas is located, a well is drilled, and depending on the type of ground to be passed through and the final depth to be reached, it may begin with a diameter of about 12.¼″ (311,15 mm) in the first 200/300 mts, of 8.½″ (215,9 mm) at a higher depth, capable of reaching a depth of 400 mts up to 4500 mts or more. The greater diameter allows placing a steel line (guiding line or security line) which will be fixed to the ground by means of a forced introduction of cement in the annular space between the tube and the ground. The blow out prevention (BOP) valve will be located above said tubing during the drilling with the smaller diameter. Following this drilling of smaller diameter, it is required to introduce a tubular steel lining, namely casing of about 5.½″ (139,7 mm) diameter extending along the whole well bore. As well as with the security line, the forced introduction of cement in the annular space between the casing and the walls of the borehole from the bottom to a height beyond the areas of interest will allow to fix the casing once the cement is forged.
Following the above operation, punctures are made at pre-selected depths, in accordance with the nature of the reservoir, which go through both the casing wall and the cement sheath, allowing a free access of production fluids from the formation to the well bore.
In some regions, the pressure of the reservoir fluids itself is sufficient to allow the natural lift of the fluids to the surface, rendering a flowing well. However, reservoirs are generally not eruptive, being necessary to extract the fluids entered into the well in an artificial manner by means of a pumping system.
A conventional reciprocating pumping well includes, in addition to the casing, the production line or tubing within which the produced fluids are passed from the bottom to the surface. At the bottom of the well and anchored in the production tubing, there is a reciprocating axial pump of barrel-rod type. This pump is mechanically actuated by an oscillating lever pivotally assembled on the surface, connecting in one end to a driving source and in the other to a series of solid steel rods connected each other to form a string which extends within the well, being connected by its lower end to the mobile part of the deep well pump and imparting it the reciprocating movement of the oscillating lever. In this way, the pumped fluids ascend to the surface trough the annular space defined between the production tubing and the rod string.
The solid rods movement within the production tubing involves a frictional contact between both, thus producing the rod and/or production tubing break and damages to the system. This problem increases in deviated or crooked holes. The high number of interventions in holes due to this problem generates high maintenance costs and increased production losses.
In such system, the production tubing cost is a significant part of the total investment.
The conventional pumping system with production tubing provides low pumping efficiency due to its stretching and shortening, which occurs with the change of direction of the rod string between ascending and descending movement.
Another relevant disadvantage of the system is that, whenever a service on the pump is needed in the fixed tubing system (when due to its size the pump is fixed to the production tubing) it is necessary to remove the rod string and the production tubing, thus increasing the hole intervention and interruption times, with the corresponding rise in costs, and loss of production.
Among the attempts to reduce costs, we can mention some patents that tend to reduce the rods' weight in order to require less energy for its operation, although the energy required in this system is not directly related to the loads, since these regenerate energy during the ascending movement. Among these patents, we can mention the following:
AR patent No. 230316 refers to a pumping rod, essentially made of fiber glass, with a significantly lower weight.
AR patent No. 234862 suggests the replacement of the rod string with a fiberglass rod string with no mutual contact, in order to achieve a lower weight of the rods.
Other attempts have proposed the use of continuous coiled tubing in order to replace the solid rod string. Among them, we can mention the following:
U.S. Pat. No. 5,667,369 (H. Cholet) proposes the replacement of the sucker rods with a continuous coiled tubing that has a PCP type pump rotor (progressive cavity pump) bound to its bottom end, and wherein the corresponding stator is bound to the base of a production tubing. In this case, the pump activation is carried out by means of a rotating movement of the continuous tubing, lower in weight and easy to handle, but the use of the production tubing is maintained.
The AR published application No. 0010430 (YPF S.A.), (U.S. Pat. No. 6,186,238) proposes to replace the combination of solid pumping rods and production tubing in the conventional reciprocating pumping system by a continuous coiled tubing. Among its advantages, this system has a fast downloading handling as well as a fast pump extraction. The great flexibility helps its coiling, however, it reduces the strength to absorb compression efforts and buckling during the ascending run, thus increasing the possibility of friction against casing walls, particularly in deep wells. Consequently, this system is successfully applied in shallow and low production wells. In addition, once broken, the continuous tubing must be bound by welding, thus reducing the resistance against weariness in said area. This reduction is enhanced by the amount of splices, considerably reducing the life of the continuous tubing that may derive in a total change of it. The continuous tubing system does not allow the use of vulcanized centralizers on the tubing body; only bayonet centralizers may be used, with no satisfactory results.
U.S. Pat. No. 4,476,923 (Walling), describes a coiled, composite tubing that allows the effluents to be conducted through its internal cavity. Such composite tubing supports, in its bottom end, a pump mechanically actuated by means of an electrical engine housed in the same deep well pump casing. The engine is electrically actuated from the surface by means of conductors extending along and across the composite tubing sheaths. Therefore, the composite tubing comprises a complex sequence of sheaths and wrappings made of different materials able to provide the resistance required to support this particular pumping system.
In U.S. Pat. No. 4,089,626, the hollow rods are used to inject chemical products to the bottom of the well. The possibility that the well fluids may be produced from its interior is not mentioned. Consequently, the production line (tubing) has not been removed in this patent.
U.S. Pat. No. 4,948,003 describes a method of taking crude samples wherein the hollow rods are used to inject chemicals, such as surfactants, that increase the viscous fluids mobility. However, a conventional solid rod tubing system is also used in this patent.
The Chinese Patent Application 95-104622.5 describes a production system with hollow rods that uses a flexible tube (hose) in the well head for the derivation of the fluids to the production tubing, accompanying the reciprocating movement of the rod string to the production tubing. This arrangement increases the environmental pollution risks due to the possibility of high pressure, several bent parts and harsh environments that may produce a malfunction in the flexible tube.
The main object of the invention is to provide an assembly and method for pumping, from the underground, an effluent produced by a drilled well within a geological formation that replaces the combination of solid sucker rods and production tubing of the conventional reciprocating pumping system with only one centered hollow sucker rod string, able to raise the effluents to the surface and at the same time, to transmit reciprocating axial movement to the deep well pump.
An important object of the invention is to provide a simple and robust bottom set, able to house and anchor reciprocating pumps of any size according to the casing diameter.
Another relevant object of this invention is to provide a rigid well bore head able to vent and pack the annular space formed between the rod string and the casing as well as to lubricate the external wall of a hollow rod in its reciprocating movement.
It is also an object of the invention to provide a safe production bridge to allow the distribution of the fluids produced from a well to the surface pipeline while simultaneously accompanies the axial reciprocating movement of the rod.
It is an important object of the invention to provide a robust device made from standard elements, easy to assemble, install and handle, able to raise high flow rates from very deep wells, such as 90 m3/day and 2500 m dynamic height, to totally replace the conventional reciprocating pumping system with solid rods and production tubing.
A further main object of the invention is to provide a device and method for producing an effluent from a well, preferably an hydrocarbon well, which by means of the replacement of a conventional combination of solid rods and production tubing with a centered hollow rod, reduces the disadvantages of the prior art and allows a reduction in operative costs and capital.
The assembly and method of the invention have the following advantages with respect to the prior art:
The present invention relates to an assembly for extracting a fluid from a drilled well within a geological formation, which walls are secured by means of a casing that is perforated to pre-selected depth levels, wherein the assembly comprises:
According to a preferred embodiment of this invention, it is hereby provided an assembly to pump fluid, such as, preferably a hydrocarbon, comprising:
In addition, a method is provided to extract a fluid from a drilled well within a geological formation which walls are secured by means of a casing, perforated at selected depth levels, by the assembly of the present invention, wherein the stationary bottom set is lowered into the well upon its termination in an independent run, once the desired depth is reached. Next, once the stationary bottom set is fixed to the bottom, the deep well pump, centered coupled to the centered hollow rod string, is carried down in one run in a concentric position with respect to the casing walls until the stationary bottom set is reached where, due to the weight of the tool itself, it enters and is attached to its respective seats within the set. Subsequently, a hollow polished rod is connected to the free end of the hollow rod string above which a surface head is placed that provides a gasket between the polished rod and the casing while lubricating it. The polished rod is connected to a production bridge and is driven according to a reciprocating axial movement, recovering the fluid pumped by the inside of the hollow rod string and the hollow polished rod and delivered through the production bridge to the driving pipeline.
In general, as shown by the scheme of
The stationary bottom set is attached to the casing 1 by means of the anchor 3. The anchor has the necessary attachment means of the type to allow the free flow of fluid, so that the fluid entering the well through the layers placed above the anchor may access the admission opening 2. The mechanical and in cups seating shoes 4 and 5, respectively, are located immediately above the anchor and forming part of the bottom set. Then, the bottom set comprises a pump housing tube 6 and, above it there is a centralizer 7 that together with the anchor 3 keeps the bottom set in concentric position with respect to the casing 1 in all its extension. Finally, in the upper part of the bottom set, there is a connecting set 8, that is connected by its upper end to a tubing used for the descending run. Said connector has a “J” pin and slot system, as shown in
The deep well pump illustrated in
The pump mobile member pull tube 15, is connected to the rod string 18 by means of the flow linking and drain tube 17 (nipple) that allows the pumped fluid to pass from the inside of the pump to the interior of the hollow rod string. Said linking tube provides a drain plug 41 as described below referring to
The upper free end of the hollow rod string 18, is connected to the hollow polished rod 24 that extends outside the well. The connection between both is carried out by means of the connecting sleeve 20. Such hollow rod 24 driving the fluid along the inner part, is suspended by the clamp and crosspiece set 25 of the system, which by means of a driving force (not shown) provides the reciprocating axial pumping movement.
The hollow polished rod 24 is connected by its upper end to the production bridge through a rotating joint 26. Said production bridge formed of rigid articulate tubes 27, is connected by its free end to the surface driving pipeline 28. The connection between both tubes to the driving pipeline is also carried out through the rotating joints 26 that allow the production bridge to accompany the reciprocating axial movement of the polished rod.
At the exit of the well at the surface, a rigid head 22 is threaded to the end of the casing tube 1. Said head provides a side exit 21 that allows the disposal of fluids, gases, etc. through a valve, that may spontaneously arise from the annular space formed between the hollow rod string 18 and the casing tube 1.
The pump housing tube 6 is formed by a portion of production tubing, for instance, about 2.⅞″ (73 mm) in diameter and about 6,5 pounds/inch (128 kg/m) in weight. The length of this tube will depend on the length of the pump to be lowered. When big pumps, above 2″ in diameter, that do not run through the interior of the housing tube 6 are used, this element and the next upper centralizer 7 are removed from the bottom set that is adapted to receive pumps of any dimension, which will depend on the size of the casing tube 1. When the size of the pump to be lowered is not known for certain, or when an increase in the future production is expected, it is recommended to use the reduced bottom set that comprises the anchor 3, the mechanical 4 and in cups 5 seating shoes, and the connecting set 8 as shown in
According to a particular embodiment, even when it is not limiting, the anchor 3 used in the stationary bottom set of the present invention, was obtained from the modification of a Lokset Baker® packing device. Such modification includes: the removal of the rubber section packing against the casing 1, the removal of the seal packing over the mandrel, the shortening of the mandrel 32 (due to the removal of the packing rubber) and the modification of the mandrel thread as well as the modification of the segments that actuate the attachment mechanism to avoid its interlock and blocking with sand. By this way, an anchor was obtained to allow the free fluid flow entering the well from the layers placed above said anchor, and the attachment force of which is trapped inside, therefore, it does not need to remain stressed as the majority of the anchors used in the conventional system. The ability of the anchor 3 to remain still and neutral allow to disassemble the connecting set 8 and recover the tubing 36 used for lowering the stationary bottom set, as shown in
According to a particular embodiment, the connecting set 8, used for this arrangement, shown in
Preferably, the seating shoes 4 and 5 used in the bottom set are standard API mechanical and in cups type, respectively.
The centralizers 7 and 16 are obtained from the centralizing block of the packing Lokset Backer® device, as shown in
The rod pump used for this embodiment is an API reciprocating axial pump with a hollow pull tube and double mechanical anchorage 9 and in cups 10. A centralizer 7 was added to such pump in its top part and integral to the stationary member 12, for guiding the descent into the well and for easing in the entry to the stationary bottom set, as shown in
According to an embodiment of the present invention, hollow rods and connecting sleeves made by Tenaris under the name of PCPRod® may be used, although not limited to them.
Although these rods have been developed to be used with PCP progressive openings pumps due to their higher torsion resistance and fatigue to flexo-torsion with constant axial load, they have also shown to be resistant to variable axial efforts. Recent fatigue analysis with variable axial loads carried out over the PCPRod® rod have shown that both the rod and the bond may stand more than 10 MM cycles without breaking. Hydraulic estimations for load losses through the interior of the hollow rods and their corresponding links for different flow rates up to a maximum of 90 m 3/day have also been made, the results of which showed to be similar to those of conventional reciprocating pumping for production tubings of 2.⅞″ (73 mm) diameter and API solid rod strings No. 76 (double telescopic strings of ⅞″ (22,2 mm) and ¾″ (19,05 mm) in diameter and No. 86 (triple telescopic strings of 1″ (25,4 mm), ⅞″ (22,2 mm) and ¾″ (19,05 mm) in diameter). Even though the hollow rod string is, in general, heavier than a solid string, the requests about the means that imparts the reciprocating axial movement to the rods are not significantly modified due to the lower weight of the fluid column (minor section) and the lack of relative movement between the rod and the fluid in the ascending run that eliminates the load losses thus compensating the higher string weight.
Preferably, the PCPRod® 1000 model without jump, with an external diameter of 48 mm (1.889″), internal diameter of 34,6 mm (1.362″), wall thickness of 6,7 mm (0.264″) and 6 Kg/m (4 pounds/feet) in weight may be used and, more preferably, the PCPRod® 1500 model with jump, external diameter of 50 mm (1.968″), body external diameter of 42 mm (1.653″), internal diameter of 32 mm (1.259″), wall thickness of 5 mm (0.196″) and 4,9 Kg/m (3.28 pounds/ft) in weight. The rod centralizers 19 may be, for example, Poli Phenylene Sulfide, (PPS) type, supplied by Tenaris, vulcanized over the rod in the requested amount and diameter, not being limited to them.
According to a particular embodiment, the rigid head type 22 used for this arrangement was obtained from the API DC 200 hanging head manufactured by ABB (ex DANCO) or similar, without clamps, to which an adaptor 44 was added. The seal box 23 with lubricating device 48 that is an adaptation of a box manufactured by TULSA@.
As can be seen from the above description, and in a comparative analysis in relation to the prior art, the total elimination of the conventional production tubing, as well as the elimination of the solid rod string as the axis actuating the reciprocating axial pump is emphasized first, for its replacement by a hollow rod string that performs both roles simultaneously. This novel configuration, built up from existing elements and simple modifications made therefrom allows to obtain a high performance reciprocating pumping system and most relevantly, easy to install and operate, that adapts to any casing and rod pump size, which makes it possible to perform drillings of significantly smaller diameter than those for conventional wells, which usually have a diameter of about 21,6 cm (8½ inches). This reduction in the well diameter will additionally mean a reduction in the casing tubing diameter, which entails a reduction in the drilling costs and the materials used.
According to an additional embodiment of the present invention, a method of extracting a fluid from a drilled well within a geological formation is provided, which walls are secured by a casing, perforated at selected depth levels, by means of the above disclosed assembly, comprising the following steps:
Considering that the minimum drilling depth for exploiting hydrocarbons is 400 mts, with the possibility of reaching up to 4500 mts, the cost reduction achieved by using the device of the present invention will be evident for those skilled in the art, even if the stationary bottom set is lowered in a separate run.
It has been found that the pumping assembly and method of the present invention may provide an efficient extraction service for oil wells of depths up to 2500 meters and with average flow rates of about 90 m3 oil/day.
Preferably, the pumping assembly and method of the present invention may provide an efficient extraction service for oil wells of depths up to 2200 meters.
Preferably, the pumping assembly and method of the present invention may be applied to pumping flow rates of about 80 m3/day of fluid, wherein the fluid is preferably oil.
It must be understood that the drawings and their detailed description are not intended to limit the invention to the particular described embodiment; but on the contrary, they intend to encompass all modifications, equivalents and alternatives comprised within the spirit and scope of the present invention, as defined in the annexed claims.
| Number | Date | Country | Kind |
|---|---|---|---|
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