CROSS-REFERENCE TO RELATED APPLICATION
The present application is based on and claims priority to European Patent Application No. EP08170190, filed Nov. 28, 2008.
The present disclosure relates generally to a borehole tool assembly for use in depositing materials in boreholes drilled in an underground formation. More particularly, but not by way of limitation, the present disclosure relates to dump bailers for use in boreholes such as oil and gas wells.
Dump bailers have been developed to remove debris or solids deposits from the wellbore prior to completing some other task, or to obtain a sample of the fluid from the area of a downhole device, by utilizing a suction action similar to a bicycle pump. Later developments of bailers became available to deposit cements or chemicals into a wellbore by simply reversing the action. However, these bailers do not positively displace their contents in the true sense, typically relying on gravity.
A dump-bailer tool normally includes a tubular chamber for storing the cement slurry and a ported valve for the slurry to discharge from the dump-bailer into the subterranean wellbore. Dump-bailer tools are well known in the oil and gas industry. They essentially include a thin walled concentric fluid chamber consisting of threaded bailer tube sections. The upper end of the tubes is connected mechanically to an armored or solid cable that is spooled on a surface winch. The lower end of the tool consists of electrical and/or mechanical dump release mechanisms, for example a bull-plug which supports and confines the cement slurry during conveyance into the wellbore. The bull-plug consists of a valve device or rupture plug, which is initiated at the proper dump depth by human interface, either electrically, hydraulically, or mechanically initiated.
In one example, the dump bailer method expels the cement slurry at a bridge plug or other barrier device in the well casing, possibly above perforations to the reservoir formation through the casing, prior to making new perforations. The slurry volume capacity of the dump-bailer device is limited by the length and internal diameter of the bailer tubes. Typical dump-bailer volumetric capacities range from one to six imperial gallons (four to twenty-eight liters). After each dump of slurry, the dump bailer is retrieved to the surface and prepared for subsequent dump-bail operations.
Of the gravity feed systems available, most use a glass or ceramic disc to retain the cement which is either broken with an explosive charge or by a pin when the tool is set-down. Gravity feed systems are not as desirable as they tend to leave some cement in the tool which then “strings” out as the tool is pulled out of hole. More runs might be needed to achieve the correct amount of cement for the desired plug strength (differential strength).
Positive displacement dump bailer systems have been previously proposed. These typically run on electric line and release a weight onto a piston which applies a pressure shock through the cement which shears a pin at the bottom of the bailer which allows the cement to fall out the bottom of the bailer either under its own weight or with the additional weight of the actuating system. One known device uses a motor to release the weight and another uses a solenoid. One variation uses an explosive bolt which has a similar function as the solenoid. Another known bailer is activated either by a timer or by a pressure transducer, but again only uses gravity to displace the contents to the wellbore.
Examples of various prior art documents in this field, include U.S. Pat. No. 2,591,807; U.S. Pat. No. 2,689,008; U.S. Pat. No. 2,696,258; U.S. Pat. No. 2,725,940; U.S. Pat. No. 2,994,378; U.S. Pat. No. 3,187,813, U.S. Pat. No. 3,202,961; U.S. Pat. No. 3,208,521; U.S. Pat. No. 3,273,647; U.S. Pat. No. 3,318,393; U.S. Pat. No. 3,379,251; U.S. Pat. No. 6,966,376; and, EP 1,223,303.
It is to rectifying these and other shortcomings of the current art that the present invention is directed. Therefore, the present disclosure is directed to providing a wireline tool assembly which provides true positive displacement of its contents into the borehole and that does not rely on gravity alone in which to do so.
BRIEF DISCLOSURE OF THE INVENTION
In view of the foregoing disadvantages, problems, and insufficiencies inherent in the known types of methods, systems and apparatus present in the prior art, exemplary implementations of the present disclosure are directed to a new and useful dump bailer.
In at least one aspect, the dump bailer comprises: a tool body defining a chamber for containing a material to be deposited; an outlet in the tool body through which the material can be deposited; and a piston assembly slideably mounted in the chamber and comprising a swabbing piston, a supply of pressurized fluid, and a valve for releasing the pressurized fluid to act on the swabbing piston to drive it along the chamber to expel material contained therein through the outlet.
In one embodiment, the valve is operable to direct pressurized fluid to act directly on the swabbing piston. In this case, the supply of pressurized fluid can comprise a reservoir carried on the swabbing piston so as to be moveable therewith.
Another embodiment further comprises an intermediate mechanism through which the pressurized fluid can act on the swabbing piston.
The piston assembly can comprise a first stage piston slideably mounted in the tool body, and a second stage piston that is slideably mounted in the first stage piston, the second stage piston being connected to the swabbing piston, the valve operating to release pressurized fluid between the first and second stage pistons to drive the swabbing piston along the chamber.
Preferably, a sliding seal is provided on an inner wall of the tool body, and the first stage piston comprises a head end that seals against the inner wall of the tool body, and a tail end that has a smaller diameter than the head end and seals in the sliding seal.
The supply of pressurized fluid can comprise a reservoir defined between the head end of the first stage piston and the sliding seal on the tool body and sliding movement of the first stage piston in the tool body can cause the reservoir to change in volume.
It is preferred that there is an opening in the tool body such that the interior of the tool body below the sliding seal is open to ambient pressure. The interior of the tool body above the head end of the first stage piston can open to ambient pressure or a supplementary supply of pressurized fluid can be connected to the interior of the tool body above the head end of the first stage piston by means of a valve. Preferably the pressurized fluid is pressurized by the effect of the ambient pressure acting on it.
The second stage piston is typically mechanically connected to the swabbing piston, and the first stage piston defines a cylinder in which the second stage piston is mounted and into which the valve can release pressurized fluid to drive the second stage piston along the cylinder which in turn drives the swabbing piston along the chamber.
In this case, the portion of the cylinder below the second stage piston can be maintained at an internal pressure that is less than the pressure of the fluid in the supply when the tool is in an ambient operating pressure environment.
The outlet typically comprises a relief valve that is normally held in a shut position until the pressure in the chamber rises above an opening pressure due to the action of the swabbing piston.
In one preferred embodiment, the outlet comprises an end fitting having an opening in a predetermined azimuthal position on the tool circumference. In another, the end fitting has a number of openings at azimuthal positions on the tool circumference. The end fitting can be freely rotatable. In which case a drive mechanism to rotate the end fitting powered by the flow of fluid from the chamber can be provided.
The piston system of the present invention is preferably driven by pressure differentials, for example between ambient operating pressure and reduced pressure in the tool, or elevated pressures in to tool.
Further aspects of the invention will be apparent from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
Certain embodiments of the present invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:
FIG. 1 depicts one embodiment of a dump bailer according to an aspect of the invention utilizing ambient pressure as a drive force;
FIG. 2 depicts an alternative embodiment of a dump bailer according to the invention utilizing compressed gas as a drive force;
FIGS. 3 and 4 depict variations of the embodiment of FIG. 1 having different end fittings at the outlet;
FIGS. 5 and 6 depict an alternative embodiment of an embodiment of the invention comprising an actuator which utilizes compressed gas; and,
FIG. 7 depicts a triggering device according to an aspect of the invention.
MODE(S) FOR CARRYING OUT THE INVENTION
One embodiment of the invention is shown in FIG. 1, in which the dump bailer comprises a ram assembly is designed to operate by using the difference between surrounding wellbore fluid pressure and a void volume in the tool to apply force to a piston.
The dump bailer of FIG. 1 comprises a tool body 10 that can be connected to a conveyance system (not shown) such as a wireline cable, coiled tubing or drill pipe, and lowered into a well. The tool body comprises a lower section defining a chamber 12 for containing the fluid to be deposited in the well, and an upper section 14 comprising an actuating mechanism that will be discussed in more detail below. An outlet 16 is formed at the lower end of the chamber 12 and is held normally closed by a spring loaded relief valve 18 or other means such as a shear pin. A swabbing piston 20 is mounted in the chamber so as to be slideable along the chamber to drive any fluid contained therein through the outlet 16.
A sliding seal 22 is formed on the inner wall of the tool body 10 and defines the top of the chamber 12 and the bottom of the upper section 14.
A vent 24 is provided in the tool body 10 below the sliding seal 22 and above the swabbing piston 20 so that there is pressure communication between this space and the ambient pressure surrounding the bailer.
The actuating mechanism in the upper section 14 comprises a two-stage piston that is mechanically connected to the swabbing piston 20. A first stage piston 26 is mounted so as to be slideable inside the upper section 14. The first stage piston 26 has a head end 28 that seals against the inner wall of the tool body 10, and a lower end 30 that is reduced in diameter with respect to the head end and defines a cylinder 32. The lower end 30 projects through the sliding seal 22. A second stage piston 34 is mounted slideably in the cylinder 32 and is connected to the swabbing piston 20 by means of a connecting rod 36.
The space around the lower end 30 and delimited by the head end 28 and the sliding seal 22 defines a reservoir 38 for a working fluid. A passageway 40 connects the reservoir 38 to the upper end of the cylinder 32. A valve 42 is provided in the passageway 40.
A further vent 44 is provided in the tool body 10 above the head end 28 so that there is also pressure communication between this space and the ambient pressure surrounding the bailer.
Alternatively the valve 42 can be positioned at the point where the vent 44 is described above, and the passageway 40 will remain as an open channel.
The space in the cylinder below the second stage piston 34 is not filled with working fluid, but contains either air or another gas at or near atmospheric pressure, or, in an alternative can be completely or partially evacuated.
As will be appreciated, pressure communication through the vents 24, 44 means that the difference in areas at 22 and 26, on which ambient pressure is acting, causes the working fluid within reservoir 38 to be higher than the ambient pressure around the tool. At a downhole location, this will be substantially above atmospheric pressure. With the second stage piston 34 at the top of the cylinder 32 and with the valve 42 closed, the second stage piston 34 moves little, if at all, to adopt an equilibrium position in which the pressure above the second stage piston 34 is the same as that below it. As all pressures in the various sections are balanced and there is no way for the different pressure to equalize (the valve 42 being closed), the swabbing piston 20 does not move.
When it is desired to evacuate the chamber 12, the valve 42 is opened. This allows working fluid from the reservoir 38 at ambient pressure to enter the cylinder above the second stage piston 34. Since this is a substantially higher pressure than is found below the second stage piston 34, it is driven downwards, pushing the swabbing piston along the chamber 13. The pressure exerted on the fluid in the chamber 12 by the swabbing piston 20 overcomes the force of the spring in the relief valve 18 and the fluids are deposited in the well.
As fluid passes from the reservoir 38 into the cylinder 32, the first stage piston 26 advances along the upper section 14 to accommodate the reduction in volume of fluid in the reservoir while maintaining ambient pressure. This will continue until either the second stage piston 34 reaches the bottom of the cylinder 32, the swabbing piston 20 reaches the bottom of the chamber 12 (or some other such mechanical stop point is reached), or until a pressure equilibrium between the fluid above the second stage piston 34 and the gas below it is reached.
FIG. 2 shows a variant of the embodiment of FIG. 1. The same numbers have been used for corresponding parts. In this case, the vent in the upper section 14 (44 in FIG. 1), is replaced by a gas reservoir 50 and a valve 52. The gas in the reservoir is held at a pressure higher than the ambient pressure of the well at the depth of use. In use, both valves 42 and 52 are opened and operation continues as described previously. The use of a pressurized gas allows a higher driving pressure to be applied where the operation is at relatively shallow depth such that the pressure differences are low, or where an extra ‘boost’ is needed to overcome static friction, or some mechanical blockage.
FIG. 3 shows another variant of the embodiment of FIG. 1. In this case, the outlet 16 is provided with an end fitting 54 having an outlet passage 56 terminating in an exit port 58 that directs flow from a side part of the end fitting 54. This particular embodiment of the invention can be useful where the chamber 12 is filled with acids and chemicals suitable for de-scaling and cleaning operations within the wellbore. The basic operating principle is the same as described above to generate the force to displace the contents of the bailer tube. The exit port 58 can be configured to have a fixed single or multiple exit orifice which may be oriented to a particular azimuth within the well bore using a muleshoe or other mechanical device (typically used within well completions such as are used to deploy or retrieve gas-lift valves from side pocket tools) to direct a pressure stream or jet of cleaning agent from within the apparatus during the displacement stroke of the ram. The tool could then be vertically oscillated from the well surface to direct the stream as required over a longitudinal section of the well trajectory.
With reference to FIG. 4, another embodiment of the apparatus used for clean up purposes has an end fitting 60 with multiple exit jets 62 arranged equally around its periphery to direct pressurized streams or jets of cleaning agent around an axial section of the wellbore. The end fitting 60 also be made to freely rotate around the longitudinal axis of the apparatus using the pressure and flow of displaced fluid from the tube as a driving mechanism whilst the hydraulic ram is displacing the contents. This arrangement could be used to clean a landing nipple profile or seal area of a wellbore or tubing completion.
FIGS. 5 and 6 show another embodiment of the invention that uses a supply of pressurized gas as the principal driving force. In this case, the dump bailer comprises a tool body 70 that defines a simple chamber 72 running along it whole length. The swabbing piston 74 is able to slide along the whole length of the chamber 72. The swabbing piston 74 has an extended piston body 76 extending from its rear surface to project through a sliding seal 78 at the top of the chamber 72. The piston body 76 includes a reservoir of pressurized gas (e.g. nitrogen) 80 and a passage 82 connecting the reservoir 80 to an outlet disposed in the chamber 72 just above the swabbing piston 74. A valve 84 is provided in the passage 82. In use, the valve 84 is operated to allow pressurized gas to enter the chamber 72 above the swabbing piston 74 which is forced down the chamber 72 expelling any fluids through an outlet 86. As the swabbing piston 74 advances, the piston body is drawn through the sliding seal 78 until the swabbing piston 74 reaches the bottom of the chamber 72 (FIG. 6).
A trigger section that can be used with the present invention that essentially corresponds to a slickline firing head of the type currently used for slickline explosive applications or to trigger cutters and set packers and plugs. The trigger is operated by a coded sequence of tension pulses on the slickline wire. This coded sequence is converted to pressure pulses by a strain sensor in the tool. This unique combination of pulses creates the special signature required to communicate with the firing head, or in this case with the dump bailer actuator.
A pressure transducer in the tool detects a command from the surface (pull on the slick line). Two separate processors in the controller module are required to independently verify the unique command. In addition to the safety of the unique command signature of the pressure pulses, the tool must be enabled by a preset hydrostatic pressure, followed by an arming command sent from the surface, before it will accept a firing command.
The trigger works by interpreting changes in downhole pressure as instructions to perform specific operations during a job. Pressure changes detected by a pressure gauge result from two sources: deviations in ambient hydrostatic pressure (i.e. depth in the well) and changes in line tension, which are translated into pressure changes by the strain head. Completion of the firing sequence requires suitable signals from both sources. The tool will not fire unless it reaches a preset minimum pressure specified by the operator. In addition, jerking on the slickline causes tension changes detectable by the pressure transducer through the action of the strain head. The signal produced by the jerk has unique characteristics that can be recognized. Detection of this signal is a slickline trigger event. The tool detects fire commands by searching for a predefined sequence of trigger events with specific time spacing.
Each event has an associated type, reference pressure and reference time. These events, each with its own reference time and pressure, are used to locate command sequences. The tool typically takes a pressure measurement every 200 ms for use in locating these events. Each sample is used for command analysis and saved in memory.
The trigger section of the tool (refer to FIG. 7) comprises a cylindrical tube housing 90, upper 92 and lower 94 connectors which allow the trigger to be mounted concentrically to both the slickline trigger and telescopic ram/actuator section of the tool. Contained within the housing is an interface electronics assembly 96 which will obtain and interpret electrical signals from the trigger tool at the appropriate time and operate an electric motor or other electro-mechanical actuator 98. The motor or electro-mechanical actuator will in turn operate an output shaft or rod 100 to operate the valves 42, 52, 84 of FIGS. 1, 2, 5 and 6.
Alternatively the tool may be triggered via electric line with a direct or indirect electrical connection to the surface, or by a built-in timer which is powered by an internal battery and where the delay is set at the surface.
Further, those skilled in the art should appreciate that the parameters and configurations described herein are exemplary and that actual parameters and/or configurations will depend on the specific application in which the systems and techniques of the invention are used. Those skilled in the art should also recognize or be able to ascertain, using no more than routine experimentation, equivalents to the specific embodiments of the invention. It is therefore to be understood that the embodiments described herein are presented by way of example only and that, within the scope of the appended claims and equivalents thereto; the invention may be practiced otherwise than as specifically described.
Moreover, it should also be appreciated that the invention is directed to each feature, system, subsystem, or technique described herein and any combination of two or more features, systems, subsystems, or techniques described herein and any combination of two or more features, systems, subsystems, and/or methods, if such features, systems, subsystems, and techniques are not mutually inconsistent, is considered to be within the scope of the invention as embodied in the claims. Further, acts, elements, and features discussed only in connection with one embodiment are not intended to be excluded from a similar role in other embodiments. Rather, the systems and methods of the present disclosure are susceptible to various modifications, variations and/or enhancements without departing from the spirit or scope of the present disclosure. Accordingly, the present disclosure expressly encompasses all such modifications, variations and enhancements within its scope.