Coiled tubing well tool and method of assembly

Abstract

A long, well tool which effectively performs as an integral part of a typical coiled tubing string and accordingly can be ran continuously into a pressurized wellbore with the same deployment equipment as used with known coiled tubing. The tool is comprised of a plurality of elements (e.g. perforating charges or logging sensors such as hydrophones, geophones, gamma ray sensors, gravity sensors, etc.) fixed at spaced, known distances from each other within a flexible housing, e.g. a length of coiled tubing.

Description

1. TECHNICAL FIELD

The present invention relates to a downhole well tool which is effectively incorporated into the lower end of a string of coiled tubing and in one of its aspects relates to running a long well tool having a plurality of elements (e.g. logging sensors, perforating charges, etc.) into a pressurized wellbore without the need of specialized, pressure deployment equipment or procedures.

2. BACKGROUND OF THE INVENTION

It has long been routine to run a long well tool into a wellbore to carry out a particular operation. For example, it is routine to “log” a well after or during drilling to determine various characteristics of the subterranean formations traversed by the wellbore. That is, a well may be logged to determine the presence and location of any oil/gas deposits that may lie adjacent the wellbore. Some of these logging operations require taking measurements at several spaced points within the wellbore and then collating the collected data to produce the desired log.

Typically, in the past a particular type of sensor (e.g. geophone, hydrophone, gamma ray sensor, gravity meter, etc.) was lowered on a wireline or string of tubing to a first point in the wellbore and a measurement was taken. The sensor was then raised or lowered to a second point where a second measurement was taken and so on until the desired number of measurements was made. Not only is this operation time consuming, it can also lead to inaccuracies in the final log since, in many instances, it is critical not only to know the depth at which each measurement is taken but also the exact distances between the respective measurement points.

More recently, logging tools have been proposed wherein a plurality of sensors are fixed at known spaced intervals within a defined housing. Not only does this allow multiple measurements to be taken with a single positioning of the tool but it also maintains an exact, known distance between the fixed sensors at each measurement point. For example, see the tool disclosed in U.S. Pat. No. 6,671,057 B2 wherein a plurality of gravity sensors are spaced within a housing which, in turn, is lowered into a wellbore on the end of an armored electrical cable, drill pipe, or coiled tubing string. However, since the sensors are fixed in a rigid cylindrical housing (e.g. length of pipe, casing, or the like), the number of sensors that can be mounted in the rigid housing is limited since the overall length of the tool (i.e. housing) has to be kept relatively short in order to transverse deviated and horizontal wellbores typically encountered during the logging operation.

Also, there are problems in deploying “long” tools into pressurized wells; i.e. going from atmospheric pressure to the substantial higher pressures in the wellbore. This is true for not only logging tools but for other types of long well tools, e.g. casing perforating tools having a plurality of explosive charges spaced within a housing. Normally, a long length of pipe, riser, or “lubricator” is supported on the valved wellhead or “tree”. A typical lubricator has a pack-off, grease seal, or other annular sealing element that allows well pressure to be contained inside the lubricator. With known “shorter” logging tools, the entire length of the rigid housing which is attached to the end of a wireline, pipe, or coiled tubing string is positioned within the lubricator with the tree valves closed to block the well pressure. The lubricator is then pressured to well pressure and the tree valves into the well are opened. The annular sealing element on top of the lubricator holds a seal between the well pressure and the atmosphere and allows the wireline or coiled tubing to lower the tool into the pressurized wellbore.

Problems arise when deploying long tools which will not fit within the lubricator. Presently, this is done by making the tools in shorter components and sequentially lowering each respective component a short distance down the wellbore. As will be understood by those skilled in this art, slips and rams of a blow-out preventer (BOP), which has been installed on the tree, are closed on the component being lowered. The pressure in the lubricator is bled down above the sealing rams and the lubricator is lifted off the BOP while back stripping the lowering means (e.g. wireline, coiled tubing, etc.).

The lowering means is then disconnected from the tool component being held by the rams and the next component is attached thereto. The next component is then positioned in the lubricator which, in turn, is swung back over the wellhead and the next component is mated with the previous component held by the rams. The next component is mated up to the previous component and the lubricator is pressure tested to at least wellbore pressure. The rams are then opened and the assembled components are lowered some distance into the wellbore before the process is repeated as many times as necessary to deploy the respective long tool.

This deployment procedure is both a time intensive and tedious job with risks associated with the rams not holding the well pressure, the slips not keeping the tool from being ejected from the wellbore, etc. Each step must have pressure containment to keep from flooding the tool during pressure deployment, or from wellbore fluids flowing up through the components while they are in the rams. Unfortunately, logging tools using geophones, hydrophones, or multi-component gravity sensors are typically “long” tools requiring many repetitions of the above described deployment steps.

Accordingly, a need exists for a long well tool having a relatively large number of elements (e.g. logging sensors, perforated charges, etc.) mounted therein in a fixed, spaced relationship (i.e. known exact distance between elements) which can be used in vertical, deviated, slanted and/or horizontal wellbores and at the same time be capable of being easily run into and out of a pressurized wellbore in a continuous operation.

SUMMARY OF THE INVENTION

The present invention provides a long well tool (e.g. logging tool, perforating tool, etc.) which can be ran into a pressurized wellbore without requiring the time consuming and tedious operating steps typically required in such operations. Basically, the tool is one which performs as an integral part of a typical coiled tubing string and accordingly can be ran continuously into a pressurized wellbore by merely using the same deployment equipment as that used in running a standard coiled tubing string into a well. The housing of the tool is relatively flexible as is the mounting of the elements (e.g. logging sensors) within the housing so the tool, itself, can easily be coiled onto and off of a typical reel of known coiled tubing systems.

More specifically, a plurality of elements (e.g. shaped charges or logging sensors such as hydrophones, geophones, gamma ray sensors, gravity sensors, etc.) are spaced at known distances and are coupled together with a spacer (e.g. individual, known lengths of prima cord, cable, or a hollow rod or the like) to form an array of spaced elements. In the logging tool, the sensors are coupled together with power/transmission wire(s), preferably through the hollow spacers, and the fixed array of sensors is positioned within the flexible housing. This housing may be any material which is durable enough for this purpose while at the same time is compatible with coiled tubing spooling technology; e.g. a length of the coiled tubing, itself.

The actual position within the housing of each element is determined from the outside of the housing and each element (e.g. sensor) is then secured to the housing at that position by any appropriate means, e.g. dimpling the housing at each element location. The housing, if not already a part of the lower end of the coiled tubing string, is attached to the coiled tubing string and effectively becomes an “integral” part of the “spoolable” string.

By effectively incorporating the plurality of elements into the coiled tubing, itself, long tools (e.g. 500 feet or more) can easily and quickly be run into a pressurized well using only the same deployment equipment and techniques used in running any typical coiled tubing string into a well. This eliminates the several tedious steps previously required with the running of long well tools where the tools had to be made up by joining components as the tool is being lowered through the wellhead.

BRIEF DESCRIPTION OF THE DRAWINGS

The actual construction operation, and apparent advantages of the present invention will be better understood by referring to the drawings, not necessarily to scale, in which like numerals identify like parts and in which:

FIG. 1 is a perspective illustration of a typical coiled tubing surface unit and an enlarged, sectional view of the lower end of a wellbore having the well tool of the present invention positioned therein; and

FIG. 2 is a further enlarged sectional view of a portion of the present well tool taken within lines 2-2 of FIG. 1.

While the invention will be described in connection with its preferred embodiments, it will be understood that this invention is not limited thereto. On the contrary, the invention is intended to cover all alternatives, modifications, and equivalents that may be included within the spirit and scope of the invention, as defined by the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, FIG. 1 illustrates a well 10 having a wellbore 11 and a wellhead 12. As will be understood, wellbore 11 can be cased (as shown), lined, open, or otherwise completed and can be vertical, slanted, and/or horizontal. A typical, coiled tubing system 13 is positioned on the surface for running a coiled tubing string 14 into and out of the wellbore 11 through wellhead 12. As will be understood in the art, the term “coiled tubing”, as used herein is a continuous length of a relatively small diameter (up to 6 inches), thin-walled relatively flexible metal tubing (e.g. steel or other high-strength alloy tubing such as titanium alloy, chrome alloy, or composite material) 14 which can be wound or coiled onto reel or spool 15 which, in turn, can be mounted on a mobile trailer 15a or the like.

Reel 15 may include a “level wind” mechanism 16 or the like to align the continuous length of tubing in relatively uniform layers as the tubing is reeled onto/off reel 15. The tubing is moved into/out of wellbore 11 by injection unit 17, which uses a pair of endless chains 19 to grip the tubing. Being continuous, no joints of pipe have to be made-up or broken-out as the tubing 14 is run into/out of the well. Coiled tubing units such as that described are well known and are commercially available in the industry.

In accordance with the present invention, a long element or plurality of elements 21 are fixedly positioned within a relative flexible length of tubing or the like which, in turn, forms a pressure housing 22 for the present well tool 20. Housing 22 can be formed from a length of common coiled tubing which, in turn, is typically formed of steel, corrosion resistant alloy, titanium, fiberglass, composite materials or other suitable material compatible with coiled tubing spooling technology. The housing 22 may be slightly more rigid than the coiled tubing used on reel 15 if it is still within the standard back tension capacity of the reel required to bend the tubing string as it is coiled onto the reel. Preferably, pressure housing 22 is substantially the same nominal diameter as that of the coiled tubing 14 but, it should be recognized that it may be slightly larger or smaller when used with known externally upset coiled equipment and techniques.

Also it is known that that there is little difference between standard 80 ksi (i.e. 1000 psi) jointed pipe and 80 ksi coiled tubing. The two tubulars are extremely similar in forces required to bend them, load capacity, and in almost every other ‘macro scale’ test results. The only known real difference between the two is their respective crystal structures which allows standard coiled tubing to bend more times without breaking. Precise control of the alloying materials (e.g. nickel) in the respective tubulars help maximize the amount of bending before breaking.

Elements 21, as illustrated in the Figures, are intended to be merely representative of known explosive charges or, in logging tools, may be any of the different, known sensors routinely used in every day logging operations and are not intended to illustrate the details of any one particular type of sensor. In perforating tools, elements 21 represent shaped, explosive charges such as used in known perforating tools and are connected by lengths of prima cord 26 or the like. When well tool 20 is a perforating tool, it is preferably connected to the lower end of coiled tubing string 14 by any type of known disconnect coupling 14a (FIG. 1), e.g. manual overpull, pressure or electrically actuated, etc., so the well tool can be left in the hole. Also, a disconnect coupling, such as 14a, can be used where tool 20 is a logging tool so that the tool can be released if it should become stuck in the hole. Further, though not shown but well understood in the art, coiled string 14 may include check valves, vents, etc. to control flow into or out of the string during lowering and/or raising the tool.

Where elements 21 are comprised of logging sensors, they may be selected from any known type of sensors, e.g. hydrophones, geophones, gravity measuring devices, gamma ray sensors, or any other commonly used logging sensors where a plurality of the respective measurements are to be made at fixed distances from each other in a single operation. That is, a predetermined number of hydrophones 21 may be fixed at known, spaced intervals within a flexible housing 22 to thereby form a hydrophone logging tool 20 in accordance with the present invention while, in another instance, a number of gamma ray sensors 21 may be fixed in a known spaced relationship within a flexible housing 22 to form a gamma ray logging tool in accordance with the present invention, and so on.

While various techniques may be used to position and fix the plurality of selected elements 21 in a spaced relationship within a flexible housing 22 without departing from the present invention, the following describes what is considered as being the easiest known technique for doing this. A length of coiled tubing which is to form flexible housing 22 is reeled out and laid onto the ground. Since the tool 20 will be flexible and reelable onto and off of reel 15, tool 20 (i.e. flexible housing 22) can practically be of any length (e.g. 500 feet or more and can contain 10 elements 21 (e.g. sensors) or more when spaced at a distance of 50 feet from each other). However, it should be realized that flexible housing 22 may be comprised of the entire length of coiled tubing 14 on reel 15 thereby allowing substantially any length of element spacing.

In logging tool 20, a plurality of the desired sensors, e.g. hydrophones, are first coupled together in a spaced relationship by respective, known lengths of a substantially rigid but relatively flexible spacer means (e.g. spacer members 25). Preferably, spacer members 25 are formed of known lengths of a hollow rod or tubing or the like which are coupled between two adjacent sensors 21. Since the diameter of rod 25 is much smaller than that of flexible housing 22, bending of tool 20 will have very little detrimental effect on the connecting rods, themselves. Once assembled and electronically connected (e.g. wire 26, fiber-optics, etc. within rod 25, see FIG. 2), the assembly of sensors are slid into housing 22. This allows the sensors to be easily removed and serviced and/or replaced if and when needed and the housing to be replaced if it should wear out. It should also be noted that communication from and between sensors may also be by electromagnetic wave propagation powered by batteries (not shown), by vibrational energy through tool components, or by fluid pressure pulses in the coiled tubing string.

Elements 21 may also be installed within the housing 22 by first hanging off the entire reel of coiled tubing into a well and the lowering the string of elements into the coiled tubing. The coiled tubing and elements are then reeled back onto the reel as a unit and then can be used for the respective intended logging or perforating operation. Further, it is possible that the elements may be pumped into a spooled reel of coiled tubing using available pumping techniques, e.g. “pressure capstan drive”. In these instances, the lengths of rod 25 may not be necessary wherein a wireline of wrapped fiber-optic cable (not shown) will be used for support and communication back to the surface.

Once the elements are spaced within the housing, their exact location is determined and marked on the outside of the housing. The locations of the elements inside housing 22 can be determined by running a common metal detector along its length or can be determined more precisely by placing a small radioactive pip tabs (i.e. very low energy gamma ray sources) on each element and then locating the pip with a Geiger tube or crystal gamma ray detector from outside the housing. A dimpling tool of a type well known in this art, is then either slid over the housing 22 or if constructed in two halves, is bolted around the housing sequentially at each element location.

As known in the art, this type of commercially-available tool has one or more round nosed bolts which are either threaded or slidable within openings in the wall of the tool. The bolts are then manually threaded inwardly or are forced inwardly by cooperating hydraulic pistons to effect indentations or “dimples” 27 (FIG. 2) in the wall of housing 22 on either side of each element to thereby hold the respective elements against longitudinal movement within the housing 22. The exact location of the dimples does not have to be precise as long as the exact distances between the adjacent dimples are known. Elements 21 can also be anchored at their respective locations within housing 22 by sending a signal through wireline 30 or by pressuring up the coiled tubing to trigger individual anchors (not shown) built into each element 21.

Next the uppermost element 21a (FIG. 1) is coupled to a wireline 30 (i.e. power and/or signal transmission line) which passes down through the coiled tubing 14. As known in the art, there are several ways to deploy wireline 30 into coiled tubing 14 while the tubing is on reel 15. For example, as will be understood in the art, a slickline (not shown) can be pumped through the entire length of the coiled tubing by using a swab cup or the like attached to the end thereof. The slickline is then attached to end of the wireline 30 which is then pulled back through the coiled tubing by the slickline. This pulling operation can be assisted by pumping the wireline back through the coiled tubing, if necessary. More recent methods for installing the wireline or fiber-optic cable into a coiled tubing string is to use flow tubes (e.g. “Grease Injection Head”) to allow the wire to be pumped into the coiled tubing with the flow tubes controlling the pressure similar to a labyrinth seal. Also, a known pressurized “capstan drive” unit can be used to pull the wire into the pressurized system and then driving it into the flow being pumped through the reel of coiled tubing.

Once the tool 20 is assembled and connected to the wireline or communication cable 30, and if a separate component, flexible housing 22 is connected to the lower end of coiled tubing string 14 by any number of techniques, e.g. disconnect coupling 14a, spoolable connectors, dimpled connectors, roll-on connectors, or weld-on connectors, none shown but all of which are known and commercially-available, and tool 20 effectively becomes an “integral” part of the spoolable coiled tubing string. Of course, as stated throughout, housing 22 may actually be an integral part of the coiled tubing string 14, itself.

Again, the tool 20 of the present invention is comprised of a plurality of known elements 21, e.g. logging sensors, perforating charges, or the like, which are fixed at known distances from each other in a relatively flexible housing 22. Where the elements are hydrophones, the required coupling to the formations to be logged will be provided by the well fluids that are normally present in the wellbore 11 or which may be introduced into the wellbore 11 by pumping through coiled tubing 14 or through tree 12. Where the elements are geophones, it may be necessary to mount “spoolable anchors” or the like on the housing 20 to provide the acoustical coupling normally required for the operation of the geophones. As to orienting gravity sensors, if used, see U.S. Pat. No. 6,671,057 B2.

By effectively incorporating the plurality of elements into the coiled tubing, itself, long tools (e.g. 500 feet or more) can easily be run into a pressurized well in a routine and fast operation. The pack-off on top of the relative short lubricator (e.g. a few feet long) seals around the coiled tubing in the same way as it would in any coiled tubing deployment operation. The tool 20 (i.e. flexible housing 22 and elements 21 inside housing 22, FIG. 1) are actually spooled onto and off the reel 15 and the pack-off in the wellhead sees the housing 22 as merely part of a typical coiled tubing string.

Claims

1. A well tool comprising:

a flexible housing adapted to be connected to the end of a string of coiled tubing to become a part thereof, said housing being flexible enough to be wound onto a reel of a standard coiled tubing system; and

a plurality of elements fixed within said housing at known distances from each other.

2. The well tool of claim 1 wherein said housing is formed from a length of the same coiled tubing to which said housing is to be attached.

3. The well tool of claim 1 wherein said housing is formed from a the entire length of the same coiled tubing.

4. The well tool of claim 1 wherein said elements comprise:

perforating charges.

5. The well tool of claim 1 wherein said elements comprise:

logging sensors.

6. The well tool of claim 5 wherein said logging sensors comprise

hyrdophones.

7. The well tool of claim 5 wherein said logging sensors comprise:

gamma ray sensors.

8. The well tool of claim 5 wherein said logging sensors comprise:

geophones.

9. The well tool of claim 5 wherein said logging sensors comprise:

gravity sensors.

10. The well tool of claim 1 wherein said flexible housing is comprised of material selected from the group: steel, steel alloys, corrosion resistant alloy, titanium, fiberglass, or composite materials which are compatible with coiled tubing spooling technology.

11. The well tool of claim 1 wherein said flexible housing has the same nominal diameter as that of the coiled tubing string to which it is to be attached.

12. The well tool of claim 1 wherein including:

spacer means for spacing said elements at said known distances from each other with said flexible housing.

13. The well tool of claim 12 where said spacer means comprises:

individual flexible members of known lengths which are respectively coupled between two adjacent said elements.

14. The well tool of claim 13 wherein each of said flexible members comprises:

a known length of a flexible hollow rod.

15. The well tool of claim 1 including:

means for connecting said elements together for transmission of power and signal transmission to and/or from element.

16. The well tool of claim 14 wherein said means for connecting said sensors comprise:

individual lengths of wire passing through respective said lengths of said hollow rod and connecting said two adjacent elements together.

17. A method of assembling a well tool for use with a coiled tubing string, said method comprising:

coupling at least two elements together which are spaced from each other at a known distance from each other to thereby fix said elements in a fixed array;

positioning said array in a flexible housing; and

fixing said array of said elements within said flexible housing whereby said housing and said elements effectively form an integral part of said coiled tubing string which can be reeled onto and off of a coiled tubing reel.

18. The method of claim 17 wherein said at least two elements comprises:

a plurality of perforating charges wherein adjacent charges are coupled and spaced from each other at a known distance.

19. The method of claim 17 wherein said at least two elements comprises:

a plurality of logging sensors wherein adjacent sensors are coupled and spaced from each other at known distances.

20. The method of claim 17 wherein said array of said elements is fixed within said housing by dimpling said flexible housing at each of said elements to thereby secure said respective element to said housing at that point.