Downhole well access line cutting tool

A cutting tool for cutting a wireline, slickline, coiled tubing, or other well access line stuck downhole in a well. The tool includes a host of features including a propulsion mechanism to aid in delivering the tool to a predetermined cut location of the line. In this manner, the risk of unintended uphole cutting of the line may be minimized.

FIELD

Embodiments described relate to oilfield well operations. In particular, applications for cutting and removing a well access line from a well that has been stuck downhole for any number of reasons. The well access line may be wireline, slickline, coiled tubing or any of a host of downhole conveyance mechanisms, generally with a tool or toolstring disposed at a downhole end thereof.

BACKGROUND

Exploring, drilling, completing, and operating hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of these expenses, added emphasis has been placed on well access, monitoring and management throughout its productive life. Well intervention and ready access to well information may play critical roles in maximizing the life of the well and total hydrocarbon recovery. As a result, downhole tools are frequently deployed within a given hydrocarbon well throughout its life. These tools may include logging tools to provide well condition information. Alternatively, these tools may include devices for stimulating hydrocarbon flow, removing debris or scale, or addressing a host of other well issues.

The above noted downhole tools are generally delivered to a downhole location by way of a well access line. A well access line may include a wireline or slickline cable, coiled tubing, and other forms of downhole conveyance line. Regardless, once delivered downhole, a well application may proceed employing the tool. Subsequently, a winch-driven drum at the surface of the oilfield may be used to withdraw the well access line and tool from the well. Unfortunately, however, the well access line and/or tool often become stuck in place downhole. This may be due to the presence of an unforeseen obstruction, unaccounted for restriction, differential sticking of the tool against the well wall, or a host of other reasons.

In the case of wireline cable, a weak-point is generally built into the cable head where the tool and cable are joined. Thus, when sticking occurs, the winch may continue to pull uphole on the line until a break occurs at the weak-point. Subsequently, a fishing operation may ensue to retrieve the stuck tool from the well. Unfortunately, slickline, coiled tubing, and other conveyances often lack a built-in weak-point. Thus, at best, continued pulling on the line will only result in an uncontrolled break, generally nearer the oilfield surface. Such an uncontrolled break may leave the well obstructed by thousands of feet of line that will only add to the time, effort, and expense of the follow-on fishing operation. Furthermore, even where a weak-point is built into the assembly, break failure of the weak-point often occurs. This may be due to a design or manufacturing flaw, or other reasons. Regardless the reason, failure of the weak-point to break may result in an uncontrolled break as noted above.

In the case of wireline or other non-tubing conveyances, cutting bars are often employed in an attempt to avoid uncontrolled breaking of the line. A cutting bar is a pipe equipped with an internal cutting mechanism. The bar may be positioned over the line and dropped vertically into the well. In theory, the bar will drop until it reaches the sticking location, at which point the sudden stopping of the bar will actuate the cutting mechanism and induce a break in the line.

Unfortunately, employing a cutting bar may still result in breaking the line at a location uphole of the sticking location. This is due to the fact that the described cutting bar technique proceeds blindly. So, for example, in the case of a deviated well, the cutting bar will stop dropping and cut the line as soon as a bend or deviation is encountered which may be nowhere near the targeted sticking location. Similarly, a slight narrowing in the well, or minimal obstruction unrelated to the sticking of the line, may be enough to stop the fall of the cutting bar. Either way, the cutting bar may stop uphole of the sticking location, induce a break in the line, and add tremendous time and expense to the follow-on fishing operation.

As an alternative to the cutting bar, a timed cutter may be deployed within the well. That is, a cutter equipped with a cutting mechanism that is activated based on a timer may be dropped into the well. In this way, temporary stopping of the cutter, for example, upon encountering a minor obstruction, may not result in activation of the cutting mechanism. Rather, the cutting mechanism may be activated only after a set period of time, presumably after bypassing any such minor temporary obstructions.

Unfortunately, the use of a timed cutter fails to overcome uncontrolled line breaks in circumstances of deviated wells or in the face of significant well obstructions. In such cases, the activation of the cutting mechanism is still likely to take place well uphole of the sticking location. That is, the mode of cutting remains blind and thus, susceptible to breaking the line well uphole of the targeted sticking location. Furthermore, in the case of coiled tubing, similar cutting mechanisms may be employed that generally involve the initial deployment of a cable interior of tubing so that follow-on cutting techniques may be carried out. However, such techniques remain blind and susceptible to inducing coiled tubing breaks uphole of the targeted sticking location. In fact, in the case of coiled tubing, the cutting techniques generally require cutting of the coiled tubing at the location of the drum in order to deploy the interior cable. As a result, large amounts of coiled tubing are rendered ineffective for future use. Thus, in many cases, the operator may ultimately be left with no better option than to run a blind attempt at cutting the line which runs a significant likelihood of adding several hundred thousand dollars of expense to future fishing and other operations.

SUMMARY

A cutting tool is provided for cutting a well access line downhole in a well. The tool includes a housing which accommodates an active propulsion mechanism for driving the tool along the well access line to a cut location thereof. A cutting mechanism is also accommodated by the housing in order to achieve cutting of the well access line at the cut location.

DETAILED DESCRIPTION

Embodiments are described with reference to certain downhole tool operations at an oilfield. For example, primarily wireline based tractor driven logging operations are described throughout. However, alternate downhole operations employing different types of well access line, including coiled tubing, may utilize embodiments of cutting tools as described herein. Of particular note, these cutting tool embodiments may be equipped with a propulsion mechanism configured to actively drive the cutting tools along the well access line to a deliberately targeted cut location.

Referring now toFIG. 1, a side overview of an oilfield105is shown with a well180running through a formation190thereat. The well180includes a vertical section181that transitions into a lateral section182as it rounds a bend195. In the embodiment shown, a downhole logging tool130is driven through the well180by way of a downhole tractor120to obtain diagnostic information relative to the well180. For example, pressure, temperature, flow and other readings may be obtained through such an application.

The above noted tractor120and logging tool130are delivered to the depicted downhole location by way of a well access line in the form of a wireline cable110. The wireline cable110may provide telemetric and powering capacity between the tractor120and/or logging tool130and surface equipment, such as a processing unit178and power unit179. As shown, the wireline cable110is delivered to the oilfield105by way of a wireline truck175accommodating the noted equipment along with a drum177about which the wireline cable110is wound. Additionally, as described in greater detail below, a cutting tool100is provided in the event that that the logging tool130and/or tractor120become stuck downhole in the well180.

The wireline cable110is run from the drum177to a rig150where it is strung about sheaves152,154and ultimately directed through well access and regulation equipment155, often referred to as a ‘Christmas tree’. This equipment155includes blowout prevention and other valve mechanisms to allow for the coupling downhole tools120,130to a cable head115at the end of the cable110. Such tools120,130may then be advanced through the well180. Indeed, as shown inFIG. 1, the tractor120may be employed to drive the logging tool130to the location shown. Thus, the cable110traverses the well180, eventually terminating at the in the lateral section182thereof.

However, in the embodiment ofFIG. 1, the logging tool130is shown stuck in debris197. In certain circumstances, this sticking may reach a point that the combined efforts of the tractor120and winch-powered drum177remain unable to dislodge the logging tool130. Thus, cutting of the cable110followed by fishing out of the downhole tools120,130may be in order. However, in cutting the cable110, it may be of significance that the cut take place as close to the cable head115as possible. In this manner, the well180may be substantially free of cable110during the subsequent fishing operation. Therefore, in order to help ensure that the cable110is cut close to the cable head115, the cutting tool100may be positioned about the cable110and directed into the well180toward the cable head115as detailed herein-below.

With added reference toFIG. 2, a side cross-sectional view of the cutting tool is depicted. The cutting tool100is equipped with a line or cable space215running there-through to allow the tool100to be positioned about the cable110and dropped into the well180. A blade240for cutting the cable110is provided for use once the tool100is properly positioned downhole. Along these lines the tool100is also equipped with an active propulsion mechanism in order to help properly position the tool100for the cutting. That is, as shown, the tool100includes wheels200disposed at the end of extension arms201. Thus, at the appropriate time, the wheels200may grab onto the cable110in the space215and drive the tool100to the proper downhole location for cutting.

Continuing with reference toFIG. 2, the above noted propulsion mechanism is housed within a main housing250of the tool100along with a clamping mechanism230as described further below. Additionally, a power source225and locator housing275are each coupled to the main housing250. The power source225may be a conventional battery such as an off-the-shelf lithium battery casing. In one embodiment, up to about 12 volts of power may be provided to the propulsion mechanism from the power source225so as to adequately drive the tool100downhole as described. Also, as detailed below, the clamping mechanism230may be activated to secure the tool100to the cable110in advance of the cutting thereof. Actuation of this clamping may be powered by the power source225or mechanically. Regardless, once clamping of the cable110is achieved at the location of the clamping mechanism230, cutting of the cable110downhole thereof will result in securing of the tool100to a portion of the cable110that is now retractable about the drum177at surface.

The above noted locator housing275may house a locator mechanism such as bearings277which are biased by springs278. As described below, the locator housing275may interface a cable head115as the tool100reaches a targeted location for cutting the cable110. As this interfacing of the locator housing275and the cable head115occurs, the bearings277may be laterally displaced in a manner that effects compression of the springs278. In the embodiments described herein-below, this compression of the springs278may be utilized as an indicator of tool location. Thus, signaling may be sent by conventional means throughout the tool100indicative of tool location. For example, spring compression may be employed as a trigger for actuation of the clamping mechanism230, immediately followed by actuation of the cutting of the cable110by the blade240.

As shown inFIG. 2, the blade240is retained within a chamber242by a membrane450(seeFIG. 4). However, once the tool100reaches the cutting location as indicated by the above-noted interfacing, the blade240may be fired from the chamber242to achieve cutting of the cable110. That is, a firing mechanism244such as an explosive charge, compressed gas or other conventional source may be employed to fire the blade240toward the cable110in order to attain cutting thereof. Once this process occurs as detailed below, the cable110with tool100clamped thereto may be retrieved from the well180and a follow-on fishing operation may ensue for retrieval of the cable head115and other downhole tools120,130.

Referring now toFIGS. 3A-3C, enlarged depictions of the cutting tool100making its way down the well180and through tortuous sections thereof are shown in greater detail. Of note is the fact that the tool100is guided through such well sections without prematurely triggering cutting of the cable110. Rather, as traversing the well180becomes more challenging, the propulsion mechanism is employed to drive the tool100therethrough and toward a proper cut location as shown inFIG. 4.

With particular reference toFIG. 3A, the cutting tool100is shown dropped through the vertical section181of the well180. At this point, the tool100freely drops with the cable110running through the cable space215. There is no engagement of the clamping mechanism230or the wheels200relative to the cable110. Indeed, in the embodiment shown, the tool100traverses the vertical section181of the well180without draining any power from the power source225(seeFIG. 2).

As shown inFIG. 3B, the tool100eventually reaches the bend195in the well180. In the embodiment shown, the impact of reaching the bend195may act as a trigger to activate the extension arms201of the propulsion mechanism. In this manner, the wheels200may engage the cable110and begin driving of the cutting tool100further through the well180. That is, as opposed to triggering a cut of the cable110as in the case of a conventional cutting tool, the impact of the sudden stoppage of the depicted cutting tool100is to activate engagement of the propulsion mechanism. That is, a conventional motion sensor202, best seen inFIG. 2, within the tool100may be employed to trigger engagement of the propulsion mechanism in lieu of cutting. Thus, premature cutting of the cable110may be avoided.

As shown inFIG. 3C, the wheels200of the propulsion mechanism may be powered by the power source225sufficiently to drive the tool100around the bend195ofFIG. 3B. In fact, it is worth noting that no downhole powering of the tool100is generally required for dropping the tool100through the vertical section181of the well180or for removing the tool100from the well entirely (seeFIG. 6). Thus, a conventionally available battery pack may sufficiently serve as the only downhole power source225for driving the tool100.

Eventually, as depicted inFIG. 4, the cutting tool100may come to the cable head115. Thus, a targeted location for cutting of the cable110has been reached. That is, a cut of the cable110made while the cutting tool100interfaces the cable head115may avoid leaving any significant amount of cable110in the well180following the cutting and retrieval operation. As described above, the wheels200may act to drive the tool100to interface the cable head115.

As shown inFIG. 4, the cable110may terminate at an extension400of the cable head115. Thus, the extension400may be received by the locator housing275at the cable space215thereof. When this occurs, the bearings277may be displaced as described above such that the springs278are compressed. As such, locating of the tool100at the cut location may be communicated throughout the tool100by conventional means. In particular, clamping of the cable110by the clamping mechanism230may be initiated followed by actuation of cutting. As shown inFIG. 5, this may include firing of the blade240from the chamber242and through a retaining membrane450toward the cable110. Such firing may be achieved through a firing mechanism244as described above. In an alternate embodiment, however, firing may be actuated when the propulsion mechanism is prevented from continued downhole advancement (e.g. when sticking is uphole of the cable head115). Nevertheless, the firing takes place following driving by the propulsion mechanism and thus, in a less blind manner than conventional cutting.

With reference toFIG. 5, an enlarged view taken from5-5ofFIG. 4is shown, revealing the cutting of the cable110by the blade240. In this view, the membrane450ofFIG. 4is eliminated as the blade240is fired from the chamber242. The firing results in the cutting of the cable110within the cable space215as defined by the main housing250of the tool100. Thus, while a small segment of cable110downhole of the cut may be left, the vast majority of the cable110is now free of any downhole sticking (seeFIGS. 1 and 6).

Referring now toFIG. 6, the drum177may be employed to remove the severed cable110from the well180. As such, the well180is cleared of any significant cable obstruction. With added reference toFIG. 4, the removal of the severed cable110also removes the cutting tool100from the well180due to the clamping of the clamping mechanism230about the cable110. By the same token, the engagement between the extension400and the locator housing275may be of a matching, however, not a locked fashion. Thus, pulling on the cable110by the winding drum177may be sufficient to disengage the extension400and locator housing275so as to allow cable110and cutting tool100removal from the well180. As such, follow-on fishing operations may proceed to remove the stuck downhole tools120,130without concern over cable interference.

Referring now toFIG. 7, an alternate embodiment of a cutting tool700is shown. In this embodiment, the tool700is particularly configured for cutting well access line in the form of coiled tubing710. That is, due to the larger diameter and hallow nature of the coiled tubing710, the tool700is deployed within the tubing710as opposed to being deployed thereabout. In fact, the cutting tool700may be configured small enough to allow for introduction to the coiled tubing710at a coiled tubing reel at the surface of the oilfield105. In this manner, cutting of the coiled tubing710at the surface may be avoided, thereby salvaging potentially several thousand feet of tubing710for future use.

Continuing with reference toFIG. 7, the main housing725is coupled to a drop line711and positioned within the coiled tubing710as shown. In the embodiment shown, the line711may have power delivering capacity built therein so as to meet power requirements of the tool700. Additionally, given the generally unobstructed nature of a coiled tubing interior, pump assisted driving of the tool700may be employed. Indeed, the generally unobstructed nature of the coiled tubing710may make premature cutting due to locating error less of a concern. Nevertheless, the main housing725is equipped with a propulsion mechanism in the form of tracks750which extend outward and engage the interior walls of the coiled tubing710. As such, the tool700may be stably driven to the downhole cut location.

Similar to the cutting tool100ofFIGS. 1-6, the tool700may be advanced through the coiled tubing710in a relatively passive manner. For example, depending on the architecture of the well180, pump assistance and gravity alone may be employed to drive the tool700through the majority thereof. However, motion sensing and/or other conventional mechanisms may also be employed such that the noted tracks750are deployed at some point in advance of the downhole cut location.

In one embodiment, the tool700is driven in this manner until a coiled tubing connector head is reached. At this point, an interfacing may be achieved similar to that detailed above for the cutting tool100ofFIGS. 1-6. For example, a smaller diameter or other recognizable feature of the connector head may be encountered and employed as a location indicator. Thus, cutting as described below may ensue.

The cutting tool700ofFIG. 7is also equipped with a cutting extension742and blade740for extending outward and cutting the coiled tubing710(see cut720). Due to the secure nature of the tracks710compressed against the tubing710, a stable cut720may be made therein as the extension742and blade740are rotated about the tool700. In an alternate embodiment, the blade740serves as a scoring device for scoring of the tubing710as opposed to complete cutting. Nevertheless, follow-on uphole pulling on the coiled tubing710may be employed to induce a coiled tubing break at the scoring location. Indeed, a corrosive chemical from a source741of corrosive chemical in the main housing725for example, may be sprayed from the extension742to enhance the breaking in the coiled tubing710. In yet another embodiment, a corrosive alone, without any prior scoring or cutting, may be employed in a manner sufficient to allow uphole pulling to induce the break in the tubing710.

Referring now toFIG. 8, a flow-chart is shown which summarizes embodiments of employing cutting tools as detailed hereinabove. The cutting tools are initially coupled to a well access line to be cut as indicated at810and then passively advanced into the well as indicated at830. In the case of wireline or other non-tubular well access this may involve coupling the cutting tool about the line and manipulating well access and regulation equipment such as blow out prevention valving. Thus, the cutting tool may then be dropped into a vertical portion of the well. In the case of coiled tubing, on the other hand, this may involve positioning the cutting tool within the tubing at a coiled tubing reel and employing pump assistance to advance the tool to the vertical portion of the well. Regardless, at this point, the advancement of the tool may be achieved without any active propulsion from the tool itself and thus, is considered herein as ‘passive’ advancement.

At some point, the tool may reach a bend in the well or other obstruction sufficient to halt passive advancement thereof. A conventional motion sensor within the cutting tool may be employed to detect such a halt. When this occurs, a propulsion mechanism of the tool may be deployed as indicated at850to engage the line. As noted above the propulsion mechanism may engage the line by either outward or inward extension, for example, depending upon the type of line and cutting tool involved. Regardless, the propulsion mechanism may thus be employed to drive the tool further downhole as indicated at870.

The tool may be advanced as described above until reaching a cut location. In the case of non-tubing access such as wireline, confirmation of the tool reaching the cut location may be particularly beneficial as detailed hereinabove. Thus, as indicated at880, such cut location may be confirmed, for example, based on an interface achieved between the cutting tool and a cable head. Of course, similar location confirmation techniques may also be employed where the well access line is coiled tubing. In any case, once the cut location is attained by the cutting tool, a break may be induced in the line as indicated at890.

Embodiments detailed hereinabove provide cutting tools and techniques that may be employed in manners that enhance certainty and accuracy of well access line cutting. The cutting tools may be employed in manners that need not rely exclusively on timers, motion sensors, or other blind mechanisms for triggering cutting of a well access line. This may be particularly beneficial in the case of non-tubular access cutting where actuation of cutting based on such mechanisms is prone to trigger cutting as a response to downhole obstructions or at a point in time that the cutting tool is caught on such an obstruction. Additionally, in the case of coiled tubing, cutting tools and techniques are detailed which may avoid the cutting of the tubing at the well surface, thereby saving potentially several thousand feet of coiled tubing.

The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. For example, a cutting tool for severing a non-tubular well access line may be employed with an outward extending propulsion mechanism similar to that described for use on coiled tubing. In such an embodiment, the propulsion mechanism may engage a well wall as opposed to the line interior thereof. By the same token, space permitting, a cutting tool for coiled tubing may be employed about the coiled tubing with inwardly extending propulsion mechanism similar to that described herein for use on non-tubular access lines. With modifications such as these in mind, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.