US3395759A

US3395759A - Well tool pumpable through a flowline

Info

Publication number: US3395759A
Application number: US578247A
Authority: US
Inventors: Jr William A Talley
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1966-09-09
Filing date: 1966-09-09
Publication date: 1968-08-06
Anticipated expiration: 1985-08-06
Also published as: GB1198461A

Description

Aug. 6, 1968 w. A. TALLEY, JR

WELL TOOL PUMPABLE THROUGH A FLOWLINE Filed Sept. 9, 1966 66 lllll l FIG. 2

INVENTOR WILLIAM A. TALLEY, JR.

ENG/(6AA. PQM/ ATTORNEY United States This invention relates to a tool designed to remove paraflin and scale deposits from flowlines in oil, water, and gas wells. More particularly, the tool is designed to be pumped down into a tubing string of a well, by fluid pressure applied behind the tool, to scrape off the paraflin accumulated on the inner walls of the tubing string.

Since its inception, the offshore oil and gas industry has utilized bottom-supported above-surface platforms as the principal mechanism for the installation and support of the equipment necessary for the drilling and operating of subaqueous oil and/ or gas fields. As the industry has developed over the years, it has extended its search for offshore oil and gas production from its birthplace in the shallow coastal waters of California and the Gulf of Mexico into areas where, because of excessive water depth or other local conditions, the bottom-supported platform is neither economically nor technologically feasible, as in the relatively shallow waters in the Gulf of Mexico where such facilities are rather commonplace. While, theoretically, there is no limit to the depth for which a bottom-supported platform can be designed and installed, experience to date has illustrated that platform costs increase almost exponentially with the increase in water depth. Thus, the presently estimated cost of a platform to carry the production facilities for a field located where the water is much more than 300 feet deep is so high as to indicate that such an installation cannot be justified economically for any but a very productive and prolific field.

In many areas of the world, local conditions other than water depth impose critical limitations on the use of bottom-supported production platforms. One such area is the Arctic, as exemplified by Cook Inlet in Alaska, where a bottom-supported platform must be built to withstand the forces imposed by the ice that forms on the water surface during the winter months of the year. While any above-surface production platform is subject to forces attributable to wind and waves, especially during hurricanes and other violent storms, in the Arctic areas, these forces, due to wind and waves, can be exceeded by the forces exerted against the platform by the movement of the thick ice layers that freeze on the surface of the water.

In still other areas, it is not adverse natural conditions but man-made prohibitions which restrict the use of above-surface production platforms. Among such conditions could be listed government and/ or public objections to oil production facilities near public recreational or residential areas and the presence of heavy marine traflic, as in harbors, channels, rivers, or other navigable bodies of water, which may make it necessary or advantageous to install as much of the production equipment below the water surface as possible.

To overcome the problems associated with producing offshore oil and gas from above-surface platforms, subsea production systems have been designed. These subsea systems generally consist of pluralities of subsea wellheads grouped around bottom-mounted satellites. The wells are either directionally drilled from within an area on the marine bottom very close around the satellite or are spread out over a large acreage spacing, depending on whether they are gas or oil wells, the depth of the producing formations, and the permeability of the producing formations. In either case, the various routine workover atent G 3,395,759 Patented Aug. 6, 1968 and maintenance operations that must be performed on an above-surface installation must be performed here also. When operations, such as scraping the parafiin from the walls of the production tubing, need be repeated at short intervals, as often as twice a week in some areas, this presents a major problem. Such an operation is usually accomplished in above-surface installations by a Wireline unit utilizing a paraflin scraping tool having valving which permits the tool to move down, under the impetus of its own weight, from the platform deck, through a lubricator, and into the well while the flowing gas or oil passes through it. The wireline then is reeled in, pulling the tool up while the tool scrapes the wall of the well. While such a unit is quite simple to use and is effective with above-surface platform installations, this is not true with a submarine production system where the tool either must be somehow transferred from a subsea storage and injection location to the well through horizontal or upwardly inclining sections or must be extended down from a floating ship on the surface, in which case guidelines must be extended from the well to the surface to locate the well with all of the Well-known attendant problems.

Therefore, it is an aspect of the present invention to provide a tool which can be pumped through the flowlines connecting a satellite and a well and then down through the production tubing string of the well to scrape the paraffin from the wall thereof, the tool returning to a storage point under the impetus of the flowing well fluid.

It is another aspect of the present invention to provide a tool that can be directed down the production tubing string of a well against upwardly flowing fluid by a greater fluid pressure applied from above, and which may be lifted back to the surface by the flowing well fluid.

It is still another aspect of the present invention to provide a pressure-actuated tool having a fail-safe device for permitting the pressure applied behind the tool to be routed through the tool if the tool should become stuck in a tubing string of a well.

It is still a further aspect of the present invention to provide a tool that can be driven down a tubing string of a Well by fluid pressure applied therebehind, and which when becoming stuck in deposits the tubing string will open a passage therethrough to permit a solvent to pass through the tool to dissolve the deposits accumulated on the wall of the encircling tubing string adjacent the tool to free the tool so that it may descend further into the tubing string.

Other aspects and advantages of the present invention will become readily apparent from the following description, when taken in conjunction with accompanying drawings that illustrate useful embodiments in accordance with this invention.

In the drawings:

FIGURE 1 is an elevational view of a paraflin scraping tool of the present invention; and

FIGURE 2 is a sectional view of the paraffin scraping tool of FIGURE 1 taken through lines 2-2 of FIGURE 1.

Referring to FIGURE 1, the illustrated paraflin scraping tool, generally designated 10, designed to be driven through flowlines and/ or tubing strings under fluid pressure (in the art referred to as a TFL tool), consists of a nose section 11, a tubular body section 12, a hydraulic piston section 14, and a valve and receiver section 16. The cylindrical body section 12 is provided with a plurality of spiral scraping blades 18 extending outwardly of the body section 12. The spiral scraping blades 18 are formed with a variable pitch to prevent thread cutting through the deposits on the inner wall of a flowline or tubing string, in this instance, a tubing string 20 through which the tool 10 travels. Breaks or discontinuities 22 in the scraping blades 18 permit the flow of fluids fully along the body section 12. Smooth tungsten carbide buttons 24, spaced around the lower end of the body section 12, are designed to center the forward end of the tool 10 in the tubing string 20 to prevent the tubing string 20, or any internal coating thereon, from being damaged by the scraping blades 18 while the tool 10 moves through the tubing string 20 scraping the paraflin and other deposits from the wall thereof.

The body section 12 of the tool 10 is threaded into a collar 26 forming the forward end of the piston section 14. A rigid barrel portion 28, underlying the length of the piston section 14, is sweated into the collar 26 at its forward end and is internally threaded at its rearward end to accept the necked down externally threaded forward portion of the valve and receiver section 16. An oversize resilient cylinder 30, preferably of some rubber composition, is mounted on the barrel portion 28 and has smooth tungsten carbide inserts 32 vulcanized into the surface thereof to form a slidable seal between the inner wall of the tubing string 20 and the paraflin scraping tool 10.

The nose section 11 (FIGURE 2) comprises a conical nose portion 33 which is normally biased rearward against a circumferential Teflon seal 34, fixed to the forward edge of the body section 12 and functioning as a valve to close the forward end of a bypass passage 13 extending axially through the tool 10. The conical nose portion 33 is biased toward the seal 34, by a conical compression spring 36 acting between an internal flange 38 located within the tubular body section 12 and a rearward flange plate 49 connected to one end of a central shaft 42 threaded at its other end into the nose portion 33 and extending centrally through the portion of the hollow bypass passage 13 formed in the hollow body section 12 and the spring 3 there- Within. A snaplatch collet 44 encircling the central shaft 42 consists of a ring portion 4 located between the compression spring 36 and the circular flange 38, and a plurality of calibrated spring latch fingers 48, coming together at one end to form the ring portion 46 and extending through the circular flange 38. The forward separate ends of the plurality of latch fingers 48 are spring biased inwardly to grip the shaft 42 around a beveled ridge 50 formed between the main shaft portion and a necked down forward end 52. One or more washers or shims 54 may be included between the forward end of the compression spring 36 and the rearward face of the ring portion 46 of the snaplatch collet 44 for reasons to be discussed subsequently. To alleviate any fluid restriction caused by the assembled elements in the forward end of the bypass passage 13; a plurality of ports 56 are drilled through the flange plate 40; a relatively large annular space is provided between the washer or shim 54 and the central shaft 42; and a further annular space is provided between the ring portion 46 of the snaplatch collet 44 and the main portion of the shaft 42, particularly in between the rearward ends of the plurality of spring latch fingers 48.

Looking back to FIGURE 1, the valve and receiver section 16 consists of a tubular valve cage 58 having a necked down forward section 60 externally threaded to mate with the internal threads in the rear end of the piston section 14, and a rearward conical receiver head 61 for locking the tool 10 in a storage compartment between runs in an automatic system. A central cylindrical cavity 64, forming a portion of the bypass passage 13, extends axially through the valve cage 58 of the valve and receiver section 16 from the forward end thereof and terminates in a coaxial port 66 connecting the rearward end of the cavity 64 with the interior of the tubing string 20 rearward of the paraflin scraping tool 10. A valve seat 68 is press fitted into the rearward end of the cylindrical, cavity 64 and coacts with a ball valve element 7 biased rearward against a central spherical depression in the seat 68 by a coil spring 72 held in compression in the cavity 64 by a retainer plate 74 fixed to the forward end of the valve cage 58 by a plurality of screws 76 extending through registering counterbored holes in the plate 74 and tapped holes in the end of the valve cage 58. A central port 78 in the spring retainer plate 74 completes the bypass passage 13 extending the length of the araflin scraper tool 10, the interior of the barrel section 28 being connected to the interior of the body section 12 through the collar 26.

To use the tool 10, it is inserted, nose first, manually or automatically in the tubing string and is driven therethrough by fluid pressure applied through the tubing string 20 behind the tool. The tungsten carbide inserts 32 in the face of the piston section 14 permit the closely fitting piston section 14 to slide down through the tubing string 20 without binding against the wall thereof as would be inherent in its action if the rubber surface was directly against the inside of the tubing, while permitting a substantially fluidtight seal between the resilient cylinder and the inner wall of the tubing string 26. Should the tool 10 become stuck in the tubing string 20 due to excessive buildup of deposits within the tubing string 20, fluid pumped into the tubing string 20 behind the tool 10 enters the bypass passage 13 through the port 66 moving the ball 70 forward so the pressure would be applied against the rearward face of the nose section 11. The pressure, when above the minimum prescribed pressure, will cause the snaplatch collet 44 to unlatch, by spreading the forward ends of the fingers 48, before pipe burst pressure is reached. The moving forward of the nose section 11 will permit fluid to travel completely through the tool and not allow an excessive buildup of pressure behind. The pressure at which the nose section 11 opens can be regulated by the number of washers or shims 54 inserted forward of the spring 36. By utilizing the snaplatch collet 44 in conjunction with the spring 36, the opening of the nose section is accomplished at a definite minimum predetermined design pressure, rather than gradually, as would be the case if only the spring 36 was used. The design pressure is, of course, the differential pressure acting on the nose portion, the difference between the pumping pressure and the pressure in the tubing section 20 ahead of the tool 10.

A parafiin solvent is injected into the tubing string 20 directly behind the tool during a paraflin removing operation, and if the tool should become stuck and the nose section 11 unlatches and moves forward, the solvent flows through the tool 10 and out the forward end thereof between the front end of the body section 12 and the nose portion 33, the solvent dissolving the portion of the deposits ahead of the tool causing the tool 10 to stick. When the deposits have been dissolved and the tool 10 again can move down through the tubing string 20, the pressure behind the tool 10 will lessen and under the bias of the compression spring 36 the nose portion 33 will move back inwardly into conjunction with the Teflon seal 34. The spring fingers 48 of the snaplatch collet 44 will re-engage the beveled surface of the shaft 42 and the tool 10 again will move down the tubing string 20 without any fluids passing through the bypass passage 13. When the tool 10 has traveled a predetermined distance through the tubing string 20, the pump (not shown) supplying fluid under pressure behind the tool 10 ceases to operate and the tool 10 returns to the downstream end of the tubing string 20 by well flow pressure.

If for some reason the nose portion 33 does not reseat on the Teflon seal 34 to close the bypass passage 13, the valve and receiver section 16 is a fail-safe device to insure the returning of the paraffin cutting tool 10 to the surface. The one-way ball valve illustrated in FIGURE 1 allows fluid to be pumped down through the tool 10 but will close if fluid should attempt to flow rearwardly through the tool 10. Therefore, when the pressure is greater ahead of the forward end of the tool 10, as will be the case when the tool 10 is to be driven back out of the tubing string 20, the possibility of the nose portion 33 not closing presents no serious problem since the fluid entering the bypass passage 13 of the tool 10 through the nose section 11 is blocked in the valve and receiver section 16.

It is envisioned that the tool can be inserted into a submerged well through an extended rigid or flexible line connecting the wellhead at the mudline with a surface or submerged production satellite or the tool 10 can be stored in an underwater wellhead module and released automatically at intervals or by a signal from the satellite or a surface station into the well.

The tool 10, although primarily designed for cutting paraffin in flowing oil wells, can be used for flowing gas and water wells, and also nonflowing wells by the use of an added pump, or service, string of pipe and a standing valve in the bottom of the tubing string below a crossover between the pump or service string and the tubing string. The crossover must be below the furthest point that the tool 10 can be driven into the tubing string. Furthermore, the tool could be used for scraping cement, or the like, left inside a casing from the previous cementing operation, and for removing burrs resulting from perforating a casing. Specialized TFL tools for removing sand or setting chokes may also be designed around the novel aspects of the present invention.

Although the present invention has been described in connection with details of specific embodiments thereof, it is to be understood that such details are not intended to limit the scope of the invention. The terms and expressions employed are used in a descriptive and not a limiting sense and there is no intention of excluding such equivalents, in the invention described, as fall within the scope of the claims. Now having described the apparatus and method herein disclosed, reference should be had to the claims which follow.

What is claimed is:

1. A tool adapted to be reciprocatively pumped through a flowline under pressure comprising: a piston section for slidably sealing said tool in a flowline to permit said tool to be pumped through a flowline by fluid pressure applied at either end of said tool; a longitudinal bypass passage fully within said tool for bypassing said piston section; first valve means associated with said bypass passage for permitting a fluid flow through said bypass passage of said tool in a first direction, said first valve means including means for the automatic closing thereof against fluid flow through said bypass passage of said tool in a second direction; and second calibrated valve means associated with said bypass passage, in series with said first valve means, for permitting fluid flow of at least a minimum predetermined pressure through said bypass passage of said tool, in said first direction, said second valve means including means for the automatic closing thereof against fluid flow through said bypass passage of said tool in said second direction; said second valve means being Openable by fluid, of above said minimum predetermined pressure, having passed through said first valve means whereby fluid is permitted to flow through said tool as said tool moves through a flowline in a first direction if pressure builds up above a predetermined minimum pressure in a flowline between a source of fluid under pressure and said tool as said tool is pumped through a flowline in said first direction, while permitting no fluid to bypass said tool while said tool moves through a flowline in said second direction; said first valve means preventing fluid from bypassing said tool when said tool is returning through a flowline regardless of whether said second valve means is open.

2. A tool adapted to be reciprocatively pumped through a flowline under pressure comprising: a piston section for slidably sealing said tool in a flowline to permit said tool to be pumped through a flowline by fluid pressure applied at either end of said tool; a longitudinal bypass passage through said tool for bypassing said piston section; first valve means associated with said bypass passage for permitting a fluid flow through the bypass passage of said tool in only one direction, said first valve means comprising a biased ball valve; and second valve means associated with said bypass passage, said second valve means comprising a releasable nose section at one end of a body section of said tool, a calibrated release means for allowing said nose section to move axially out from said one end of said tool body section to form a fluid path between said bypass passage within said tool and the interior of a flowline at said one end of said tool body section, and means biasing said nose section toward said one end of said tool body section, said second valve means being in series with said first valve means, for permitting fluid flow of at least a minimum predetermined pressure through said tool; said second valve means being actuatable by fluid, of above said minimum predetermined pressure, having passed through said first valve means whereby fluid is permitted to bypass said tool, situated in a flowline, in said one direction, if said tool should become stuck, said nose section moving away from said tool body section into an open position when fluid of over said minimum predetermined pressure passing through said ball valve acts on said tool nose section so that a flowline is prevented from bursting due to a pressure buildup caused by the sticking of said tool in a flowline as said tool is pumped in a first direction through a flowline and whereby, when said tool is being pumped in a second direction through a flowline, said ball valve acts as a failsafe device, preventing fluid pressure from bypassing said tool even if said nose section should not move back toward said tool body section and close said bypass passage.

3. A tool adapted to be reciprocatively pumped through a flowline under pressure comprising: a piston section slidably sealing said tool in a flowline to permit said tool to be pumped through a flowline by fluid pressure applied at either end of said tool; a longitudinal bypass passage through said tool for bypassing said piston section; first valve means associated with said bypass passage for permitting a fluid flow through said tool in only one direction; and second valve means associated with said bypass passage, in series with said first valve means, for permitting fluid flow of at least a minimum predetermend pressure through said tool, said second valve means comprising a releasable nose section, at one end of a body section of said tool, a shaft connected to said nose section at a first end and extending into said bypass passage in said tool body section, a spring means fixed within said bypass passage and operatively connected to the second end of said shaft to bias said nose section toward said tool body section, and a calibrated snaplatch collet fixed within said bypass passage and releasably operatively connected to said nose section to retain said nose section against said tool body section until there is a predetermined fluid pressure in said bypass passage acting on said nose section.

4. A tool adapted to be reciprocatively pumped through a flowline as recited in claim 3 wherein there is a means for changing the predetermined pressure required to release said snaplatch collet including a circumferential internal flange within said bypass passage in said tool body section, said shaft extending through said internal flange; a flange plate fixed to the end of said shaft spaced from said nose section, said spring means being a coil compression spring located between said internal flange in said bypass passage and said flange plate fixed to said shaft; and shims of various thicknesses insertable between said internal flange and said flange plate whereby said spring is further compressed or relieved to change the collet release pressure.

5. A tool adapted to be reciprocatively pumped through a flowline as recited in claim 3 wherein said snaplatch collet connector comprises a ring portion loosely encircling said shaft and fixedly located on an internal flange in said bypass passage; a plurality of inwardly biased calibrated spring fingers connected at the inner ends of each of said fingers at spaced intervals around said ring; and the outer ends of each of said spring fingers being biased into a decreased diameter circumferential section of said shaft adjacent said nose section whereby said nose section is held tightly to said tool body section prior to the application of a fluid pressure greater than said predetermined pressure from within said bypass passage.

6. A tool adapted to be reciprocatively pumped through a flowline under pressure for scraping deposits from the inner wall of a flowline comprising: a piston section for slidably sealing said tool in a flowline to permit said tool to be pumped through a flowlineby fluid pressure applied at either end of said tool; a cylindrical body section in axial alignment with said piston section, said body section being provided with a plurality of variable pitch spiral scraping blades whereby thread cutting through the deposits on the inner wall of a flowline is prevented; a longitudinal bypass passage through said tool for bypassing said piston section, first valve means associated with said bypass passage for permitting a fluid flow through said tool in only one direction; and second valve means associated with said bypass passage, in series with said first valve means, for permitting fluid flow of at least a minimum predetermined pressure through said tool, said second valve means being openable by fluid, of above said minimum predeterminted pressure, having passed through said first valve means whereby fluid is permitted to bypass said tool as said tool, moves through a flowline in a first direction if said tool should become stuck in deposits on the inner wall of a flowline and pressure builds up above a predetermined minimum pressure, while permitting no fluid to bypass said tool while said tool moves through a flowline in a second direction.

7. A tool for scraping deposits from the inner wall of a flowline as recited in claim 6 wherein there are dis continuities in said scraping blades whereby fluid flow along said body section is permitted.

8. A tool for scraping deposits from the inner wall of a flowline as recited in claim 6 wherein there are smooth, hard, radially spaced, upstanding buttons fixed to said body section, said upstanding buttons being so located that said scraping blades are axially positioned between said piston section and said upstanding buttons whereby said upstanding buttons function in association with said piston section to center said tool in said flowline to prevent damage to the inner wall of said flowline from which deposits are to be scraped.

9. A through-the-flowline tool comprising:

(a) a valve and receiver section comprising: a tubular valve cage and a conical receiver head, said valve cage having an axial cylindrical cavity, a first port means extending from a first end of said axial cylindrical cavity through said conical receiver head to a first end of said tool to form a portion of a bypass passage extending through said too], a ball valve element in said axial cylindrical cavity, a ball valve seat fixedly located in said first end of said axial cylindrical cavity to block said port means when said ball valve element is in said valve seat, a retainer plate fixed across a second end of said axial cylindrical cavity, a coil compression spring located in said axial cylindrical cavity and compressed between said ball valve element and said retainer plate, and a second port extending through said retainer plate to extend said bypass passage from said valve and receiver section toward a second end of said tool;

(b) a piston section comprising: a rigid barrel portion, a resilient cylinder mounted on said barrel portion and smooth, hard inserts in said surface of said resilient cylinder, and a radial collar fixed over an end of said barrel portion between said resilient cylinder and said second end of said tool;

(c) a tubular body section axially located between said piston section and said second end of said tool, said tubular body section being provided with a plurality of discontinuous spiral blades of variable pitch, a circumferential seal on a first end of said body section toward said second end of said tool, and an internal circumferential flange within said tubular body section axially spaced from said first end of said body section toward said second end of said tool; and

(d) a nose section comprising: a nose portion adapted to act in conjunction with said seal on said first end of said body section to sealably close said second end of said tool, a central shaft connected at a first end to said nose portion, extending into said body section, and through said internal circumferential flange, a flange plate connected to a second end of said central shaft between said circumferential flange and a second end of said tubular body section, a coil compression spring located between said flange plate and said internal circumferential flange in said body section to bias said nose section toward said circumferential seal to close said bypass passage extending through said hollow piston and body sections at said second end of said tool, a snaplatch collet having a ring portion located between said internal circumferential flange and said flange plate, and spaced collet spring fingers connected to said ring portion and extending through said internal circumferential flange and into a circumferential necked down portion of said central shaft adjacent said nose portion, said ring portion of said snaplatch collet being fixedly located against said internal circumferential flange by said compression spring located between said flange plate and said internal circumferential flange in said body section, and shim means being adapted to be inserted between said ring portion of said suaplatch collet and said coil compression spring to set a desired nose section opening pressure.

10. A tool adapted to be reciprocatively pumped through a flowline under pressure for scraping deposits from the inner wall of a flowline comprising a piston section for slidably sealing said tool in a flowline to permit said tool to be pumped through a flowline by fluid pressure applied at either end of said tool; a cylindrical body section in axial alignment with said piston section, said body section being provided with a plurality of variable pitch spiral scraping blades whereby thread cutting through the deposits on the inner wall 0 a flowline is prevented; a longitudinal bypass passage fully within said tool for bypassing said piston section, first valve means associated with said bypass passage for permitting a fluid flow through said bypass passage of said tool in a first direction, said first valve means including means for the automaticclosing thereof against fluid flow through said bypass passage of said tool in a second direction; and second calibrated valve means associated with said bypass passage, in series with said first valve means, for permitting fluid flow of at least a minimum predetermined pressure through said bypass passage of said tool, in said first direction, said second valve means including means for the automatic closing thereof against fluid flow through said bypass passage of said tool in said second direction; said second valve means being openable by fluid, of above said minimum predetermined pressure, having passed through said first valve means whereby fluid is permitted to flow through said tool as said tool moves through a flowline in a first direction if said tool should become stuck in deposits on the inner wall of a flowline causing pressure to build up above a predetermined minimum pressure, while permitting no fluid to bypass said tool while said tool moves through a flowline in a second direction regardless of whether said second valve means is open.

(References on following page) 9 References Cited 3,056,156 3,070,167 UNITED STATES PATENTS 3,070,169 7/1942 Edwards et a1. 15-10406 3 171 4 7 11/1958 Matheny 15104.06 10/1961 Corley et a1. 166-170 X 9/1962 Von Rosenberg 308-4 Immel 15104.06 Loy et a1. 166153 Hilton et a1. 15-10406 X Ault 166-170 X 5 CHARLES E. OCONNELL, Primary Examiner.

IAN A. CALVERT, Assistant Examiner.

Claims

1. A TOOL ADAPTED TO BE RECIPROCATIVELY PUMPED THROUGH A FLOWLINE UNDER PRESSURE COMPRISING: A PISTON SECTION FOR SLIDABLY SEALING SAID TOOL IN A FLOWLINE TO PERMIT SAID TOOL TO BE PUMPED THROUGH A FLOWLINE BY FLUID PRESURE APPLIED AT EITHER END OF SAID TOOL; A LONGITUDINAL BYPASS PASSAGE FULLY WITHIN SAID TOOL FOR BYPASSING SAID PISTON SECTION; FIRST VALVE MEANS ASSOCIATED WITH SAID BYPASS PASSAGE FOR PERMITTING A FLUID FLOW THROUGH SAID BYPASS PASSAGE OF SAID TOOL IN A FIRST DIRECTION, SAID FIRST VALVE MEANS INCLUDING MEANS FOR THE AUTOMATIC CLOSING THEREOF AGAINST FLUID FLOW THROUGH SAID BYPASS PASSAGE OF SAID TOOL IN A SECOND DIRECTION; AND SECOND CALIBRATED VALVE MEANS ASSOCIATED WITH THE SAID BYPASS PASSAGE, IN SERIES WITH SAID FIRST VALVE MEANS, FOR PERMITTING FLUID FLOW OF AT LEAST A MINIMUM PREDETERMINED PRESSURE THROUGH SAID BYPASS PASSAGE OF SAID TOOL, IN SAID FIRST DIRECTION, SAID SECOND VALVE MEANS INCLUDING MEANS FOR THE AUTOMATIC CLOSING THEREOF AGAINST FLUID FLOW THROUGH SAID BYPASS PASSAGE OF SAID TOOL IN SAID SECOND DIRECTION; SAID SECOND