Embodiments herein related to apparatus and methods for clearing obstructions in wellbores during casing of the wellbores and more particularly to apparatus connected at a bottom of a typically non-rotating tubular string for clearing obstructions encountered in the wellbore as the tubular string is run into an open hole, such as prior to cementing.
In the oil and gas industry, following drilling of a vertical or horizontal wellbore into a formation for the production of oil or gas therefrom, the wellbore is typically cased and cemented to line the length of the wellbore to ensure safe control of production of fluids therefrom, to prevent water from entering the wellbore and to keep the formation from “sloughing” or “bridging” into the wellbore.
It is well known that during the running in of a tubing string, such as casing and particularly the production casing, the casing may encounter tight spots and obstructions in the open wellbore, such as that created by sloughing of the wellbore wall into the open hole or as a result of the casing pushing debris ahead of the bottom end of the casing along the open hole until it forms a bridge. Such obstructions prevent the advance of the casing and require the open hole to be cleared in order to advance the casing to the bottom of the hole. This is particularly problematic in horizontal wellbores.
Should the casing string become sufficiently engaged in a mud pack formed at the obstruction, differential sticking may also occur, making advancing or removal of the casing from the wellbore extremely difficult.
While casing strings have been rotated to assist with moving past or through an obstruction, high torque created by trying to rotate a long string of casing may result in significant damage to the threads between casing joints and may cause centralizers and the like to drag and ream into the wellbore. While rotation of casing may be a viable option in a vertical wellbore, albeit fraught with problems, it is extremely difficult, if not impossible in a horizontal wellbore.
One option is to employ a washing technique, pumping fluids through the casing while the casing is axially reciprocated uphole and downhole. The fluids exiting the downhole end of the casing bore act on the obstruction in the wellbore to wash out or erode the wellbore obstruction creating debris which is lifted or conveyed through the annulus to surface by fluid circulation therein. Should the washing technique be unsuccessful, it is known to trip out the casing and run in a mud motor on a drill string to drill out or ream the obstruction from the wellbore. Such repeated running in and tripping out of tubulars is time consuming, labor intensive and, as a result, very expensive. Alternatively, others have contemplated providing teeth on the bottom of the casing string or on a shoe at the bottom of the casing string to assist with cutting away the obstruction as the casing is advanced during running in. Typically, the casing is also reciprocated or stroked during the clearing operation, or, in some cases, at the same time as the casing is rotated.
Further, it has been contemplated to attach costly apparatus, such as mud motors, jetting or reaming tools, to the bottom of the casing string, however the apparatus is not retrievable thereafter from the wellbore and adds significantly to the cost of the casing operation.
Ideally, what is required is a relatively simple and inexpensive apparatus that can be incorporated into the casing string for clearing wellbore obstructions without the need for rotating the casing string. Ideally, the apparatus could be left downhole, after the casing and cementing operations are complete, without a significant increase in operational costs.
A wellbore obstruction-clearing tool is fit to a downhole end of a string of tubulars, such as a casing string or a string of coiled tubing (CT). The tool comprises a tubular mandrel having a rotatable tubular sleeve concentrically fit thereabouts. A helical drive is positioned between the mandrel and the sleeve, permitting the sleeve to reciprocate axially along the mandrel and to rotate relative thereto. The sleeve is driven to extend or retract axially and to rotate relative to the mandrel through axial reciprocation of the tubulars and the mandrel in the wellbore, commonly referred to as stroking of the tubulars within the wellbore. At least the rotation of the sleeve engaging the wellbore obstructions causes the obstructions to break up or erode, forming debris therefrom which is conveyed to surface by fluids circulated downhole through the string and uphole to surface in an annulus between the tubulars and the wellbore. The fluids can also aid in hydraulically extending the sleeve during the upstroke and fluidly eroding wellbore obstructions.
In a broad aspect, a wellbore obstruction-clearing tool is fit to a downhole end of a tubing string for advancing the tubing string through obstructions in a wellbore. The tubing string has an axial bore therethrough for communicating fluids to an annulus between the tubing string and the wellbore for circulation to surface. The obstruction-clearing tool comprises ad tubular mandrel a tubular sleeve and a helical drive therebetween. The tubular mandrel connects to the downhole end of the tubing string, the mandrel having a mandrel bore extending axially therethrough, and the mandrel bore being fluidly connected to the axial bore. The tubular sleeve has a sleeve bore extending axially therethrough and fit concentrically fit about the mandrel, the sleeve bore being fluidly connected with the mandrel bore, and a downhole end for engaging the wellbore obstructions. The helical drive arrangement acts between the mandrel and the sleeve for driving the sleeve axially and rotationally along the mandrel between a retracted position and an extended position in response to reciprocating axial movement of the tubing string and mandrel. The engagement of the downhole end of the sleeve creates debris from the wellbore obstructions, and wherein the fluids from the sleeve bore convey debris along the annulus to surface.
The obstruction-clearing tool enables methods for clearing obstructions in a wellbore and advancing a tubing string therein without rotation of the tubing string. Such method comprises running a wellbore obstruction-clearing tool on a downhole end of the tubing string, such as casing or CT, the wellbore obstruction-clearing tool having a tubular mandrel for connection to the tubing string and tubular sleeve which is axially and rotationally moveable therealong between a retracted position and an extended position; and when the wellbore obstruction-clearing tool encounters a wellbore obstruction. In operation, the method comprises stroking the tubing string uphole and downhole so as to drive the tubular sleeve to rotate and reciprocate axially between the retracted position and the extended position for engaging the wellbore obstruction and creating debris therefrom; and discharging fluid through contiguous bores in the tubing string, the mandrel and the sleeve for conveying debris to surface.
Embodiments of a wellbore obstruction-clearing tool are connected to a downhole end of a string of tubulars, such as casing or coiled tubing (CT), to aid in advancing or removing the tubulars within a wellbore. Thus, the obstruction-clearing tool obviates the need to rotate the casing thereby, substantially avoiding problems associated therewith, such as torque build up along the casing. For the purposes of the description which follows, Applicant has described the tool in the context of use with casing. Those of skill in the art will appreciate however, that embodiments disclosed herein are not limited for use with casing and are suitable for use with other tubulars having a bore formed therethrough and for which rotation is to be avoided.
In embodiments, a tubular sleeve is caused to rotate while extending and retracting along a mandrel connected to the downhole end of the casing. Axial reciprocation and rotation of the sleeve along the mandrel is initiated by axial reciprocation of the casing in the wellbore, commonly referred to as stroking of the casing. At least the rotation of the sleeve within the wellbore clears any obstruction, creating debris, the debris being conveyed to surface by circulation of fluids downhole through the casing and uphole to surface through an annulus between the casing and the wellbore. When the obstructions are removed from the wellbore, the casing can be lowered to a target depth such as prior to cementing the casing into place in the wellbore.
In embodiments, fluid, such as a drilling fluid, is injected or pumped downhole through the casing. The mud is circulated up the annulus for conveying the debris to surface. Further, extending or resetting of the tubular sleeve can be through hydraulic impetus from the drilling fluid and gravity depending on the wellbore orientation. The fluids discharging from the casing can also aid in clearing obstructions by fluidly engaging the wellbore obstructions, such as in a jetting action, fluidly eroding the wellbore obstructions for creating debris therefrom. A velocity of the fluids discharged can be increased for enhancing the fluid erosion. The downhole end of the sleeve can also physically disrupt the obstructions for creating debris therefrom.
In more detail, and having reference to
The obstruction-clearing tool 100 comprises a tubular mandrel 120, connected, such as by threading, to the downhole end 12 of the casing 10 and having a mandrel bore 121 which is fluidly connected to an axial bore 11 of the casing 10.
A tubular sleeve 110 having a sleeve bore 115 is fit concentrically about the tubular mandrel 120 and is axially displaceable therealong between a fully retracted position, wherein a downhole end 112 of the sleeve 110 is adjacent a downhole end 127 of the mandrel 120, and a fully extended position, wherein the downhole end 112 of the sleeve 110 is displaced axially away from the downhole end 127 of the mandrel 120.
In embodiments, fluid F is pumped through the contiguous bores of the casing's axial bore 11, the mandrel bore 121 and the sleeve bore 115. The fluid F discharges from the sleeve bore 115 and into the wellbore 14. The fluid F is circulated along an annulus 20, between the casing 10 and the wellbore 14, to surface through the annulus 20.
A drive arrangement 118, co-operates between the mandrel 120 and the sleeve 110, and permits the sleeve 110 to be rotated as the sleeve 110 is axially displaced along the mandrel 120. Thus, the sleeve 110 is axially and rotationally displaceable between the extended and retracted positions.
The tubular sleeve 110 engages obstructions 119 in the wellbore 14. Applicant believes that at least the engagement of the sleeve 110, and rotational movement thereof, aids in agitating or disrupting the obstructions 119. The fluids F discharged through the sleeve bore 115 convey the debris from the wellbore 14 as the fluid F is circulated to surface through the annulus 20. Fluid F, where discharged so as to contact the obstruction 119, further acts to fluidly erode the obstructions 119, enhancing the production of debris therefrom.
In greater detail, as shown in
Referring again to
With reference to
In an embodiment as shown in
Axial movement of the mandrel 120, fixed to the casing 10, causes the sleeve 110 to reciprocate along the mandrel 120. A downhole stroke of the casing 10 causes the sleeve 110 to rotate in one direction and an uphole stroke of the casing causes the sleeve 110 to rotate in the opposite direction. The downhole stroke causes the sleeve 110 to retract along the mandrel 120 and the uphole stroke permits the sleeve 110 to extend along the mandrel 120. The impetus to retract the sleeve 110 relative to the mandrel 120 is by resistance encountered at the sleeve, such as by the obstruction 119, or a tight wellbore 14. The impetus to extend the sleeve 110 relative to the mandrel 120 is by hydraulic force created by the fluid F on the downhole end of the sleeve and gravity depending on the orientation of the wellbore, being most effective in vertical wellbores.
In one method of manufacture the sleeve 110 is slipped over the mandrel 120 and the pins 111 are installed through the sleeve 110 to engage the helical grooves 122. The pins 111 are retained therein, such as by deformation of the installation hole, or use of a cap screw or welding.
In an embodiment of the invention, the mandrel 120 is threadably connected to a last joint of casing 10. The uphole end 128 of the mandrel 120 has a box end which is threaded to a conventional pin end at the downhole end 12 of the casing 10. A thickness of the tubular mandrel 120 is generally greater than a thickness of the casing 10 to permit machining of the helical grooves 122 therein.
As shown in
As shown in
Annular seals are positioned to fluidly seal between the sleeve 110 and the mandrel 120. A downhole annular seal 124 is positioned such that the downhole seal 124 becomes sandwiched axially between the mandrel's downhole stop 123 and the sleeve's uphole stop member 113 when the sleeve 110 is in the fully extended position. An annular seal 126 is positioned such that it becomes sandwiched axially between the uphole stop 125 and the sleeve's uphole stop member 113 when the sleeve 110 is in the fully retracted position.
In an embodiment, a shipping or shear pin 129 is employed to maintain the sleeve 110 in the axially retracted position during shipping. Depending on operator technique, the shear pins can also maintain the sleeve 110 in the axially retracted position running-in of the casing 10 and the tool 100. The shear pin 129 extends radially inwardly from the stop member 113 on the uphole end 114 of the sleeve 110 to engage the uphole end 128 of the mandrel 120. When removed after shipping, or if retained, when sheared in the wellbore, the sleeve 110 is freed to reciprocate as described herein in response to the axial reciprocation of the casing 10 and mandrel 120.
As shown in
Having reference again to
In vertical wellbores, stroking the casing 10 uphole permits gravity to act on the sleeve 110 for causing axial extension of the sleeve 110 along the mandrel 120. In the case of horizontal wellbores, there is little to no gravitational impetus to cause axial extension of the sleeve 110. In this case, the flow restrictor 140 further acts to create an uphole face or shoulder 141 upon which the fluid F pumped through the sleeve bore acts, creating a backpressure and an extending force or impetus for hydraulic extension of the sleeve 110.
Optionally, as shown in
Further, in the case of horizontal wellbores, the centralizing ribs 116 may engage and drag in the wellbore 14 during uphole stroking of the casing 10, assisting with axial extension of the sleeve 110 relative to the mandrel 120.
In an embodiment, as shown in
Similarly, as shown in
With reference to
As shown in
With reference to
In the case of horizontal wellbores 14, the teeth 161 formed about the open bore 162 can engage and ream the wellbore 14. An alternate embodiment of bit 179 is shown in
In some embodiments, there may be an objective to drill through the obstruction-clearing tool 100. In a conventional casing operation, casing is advanced into the wellbore 14 until the casing 10 is landed at the target depth. The casing 10 is cemented into place. In embodiments, for use where there is no expectation to extend the wellbore 14 after cementing the casing 10, the obstruction-clearing tool 100 is manufactured of robust 4140 steel.
In embodiments, for use where the depth of the wellbore 14 is to be extended following cementing of at least a first section of casing 10, at least portions of the obstruction-clearing tool 100 are made to be drillable. Due to the nature of the tool 100 to have relative rotatable components, accommodations are made to avoid reactive rotation of one or more portions of the tool 100 when drilling through the tool 100.
Generally, the drillable portions are made of less competent materials, such as aluminum and aluminum composites, which facilitate being drilled out. In such cases, the portions that are made drillable are generally internal components which would otherwise interfere with or retard passage of a drill string therethrough. The bit 150 can also be drillable or its design accommodates passage of a drill string therethrough, such as in the tubular drill bit 160 embodiment of
For example, the mandrel 120 may be formed of aluminum and the guide pins 111 may be made of bronze while the remaining components such as the sleeve 110 are made of 4140 steel. The bit 150 is also made of less competent materials permitting drilling therethrough.
In an embodiment, shown in
The bit body 170 is manufactured from robust 4140 hardened steel. The bit insert 173 and the flow restrictor 140 are manufactured from 6061 aluminum, which is suitable to withstand the rigors of the casing stroking operation yet are drillable.
The drillable embodiment of the obstruction-clearing tool 100 is connected to the downhole end 11 of the casing 10 and casing 10 is lowered to the target depth, the obstruction-clearing tool 100 acting as a landing tool. The casing 10 is thereafter cemented into with wellbore 14 using conventional cementing operations. Cement is pumped through the casing 10 and is discharged from the downhole end 112 of the sleeve 110 and into the annulus 20. The cement hardened about the sleeve 110 prevents any further axial or rotational movement of the sleeve 110 about the stationary mandrel.
In drill-through operations, a secondary drill string and drill bit can damage or drill out the helical drive connection between the mandrel 120 and the sleeve 110. Free rotation of the mandrel ahead of the secondary drill string nullifies the drilling operation. Several features are provided in one or more embodiments, to minimize problems when drilling through the tool 100.
In one embodiment, shown in
The mandrel 120 and the sleeve 110 may not be in the interlocked position when the drilling operation begins, such as when the sleeve 110 is in the axially extended position when cemented in. In such instances, when the mandrel 120 becomes free to rotate with the drill string, the remaining portion of the mandrel 120 having the first castellated profile 181 is pushed downhole by the secondary drill string. The first castellated profile 181 is caused to engage with the second castellated profile 183 of the sleeve 110 in the interlocked position preventing further rotational movement of the mandrel 120 and permitting the drilling operation to continue.
In an embodiment as shown in
In an embodiment which minimizes deviation of the extended wellbore when drilling through the tool, the mandrel and sleeve are provided with a casing shell 190 which guides the second drill through the tool 100.
Having reference to
As one of skill in the art will appreciate, the obstruction-clearing tool 100 can be sized appropriately depending upon the size of the casing 10 being utilized. That is, the obstruction-clearing tool 100 can be adapted to operatively and fluidly connect to tubulars commonly used in the industry, such as 4½ inch, 5½ inch, 7 inch, or 9⅝ inch casings and 2⅞ inch coiled tubing, or can be custom sized for any size casing 10 or CT.
As shown in
With reference to
Embodiments of the wellbore obstruction-clearing tool 100 are used during casing of an open hole or wellbore 14 which has been drilled in a previous drilling operation. A survey can log obstructions, including tight spots, requiring clearing. The wellbore obstruction-clearing tool 100 is connected to a bottom of a joint of conventional casing and the casing is run into the wellbore.
Some operators prefer to remove the shipping or shear pin or pins 129 and run the tool 100 in extended, possibly operating passively and periodically on the trip downhole. In other cases the shear pin or pins 129 remain in place to retain the sleeve 110 in the retracted position during tripping into the wellbore 14.
As shown in
Once the sleeve 110 is free to move axially and rotationally relative to the mandrel 120, the casing 10 and mandrel 120 are lifted or stroked uphole at (5) with sleeve 110 moving rotationally towards its extended position. The casing is stroked upwardly and the sleeve 110 reaches the extended position at (6). The stoke of the casing can be controlled and is not necessarily stroked to the full extension or the full retraction.
The stroking of the casing 10 continues uphole and downhole so as to drive the tubular sleeve to rotate and reciprocate axially between the retracted position and the extended position for engaging the wellbore obstruction, creating debris and is repeated until the obstruction is cleared and the tool 100 can be landed at target depth, or the next obstruction.
In a vertical wellbore, extension of the sleeve 110, as the mandrel 120 is stroked uphole, is largely under the influence of gravity and thus lifting of the casing 10 may be sufficient to cause the sleeve 110 to extend. Fluid F is typically used as well for removal of debris and for extension of the sleeve 110.
With reference to
With reference to
Thereafter, as shown from right to left in
The operation of
With reference to
An embodiment of the invention was tested during casing of a vertical wellbore in which normal casing operations were first attempted and had failed. Obstructions were encountered at about 1 kilometer downhole preventing passage of the casing to the target depth.
Previously, a drilling fluid was circulated through the casing and adjacent the obstructions in an attempt to hydraulically clear the obstruction. The process lasted three successive days, at great expense, and was ultimately unsuccessful in clearing a first obstruction. The casing was tripped out and a mud motor was run downhole to mechanically drill through the first obstruction. The conventional mandrel, drill bit and bottom sub of the expensive mud motor were eventually lost downhole without successfully clearing the first obstruction. The bottom sub of the mud motor was eventually recovered by a fishing operation. Several weeks were lost and the first obstruction was still not cleared.
Thereafter, an obstruction-clearing tool 100 was operatively and fluidly connected to the casing and run downhole. The obstruction-clearing tool was actuated when the first obstructions was reached. The casing and the tool were stroked fully, uphole and downhole, three times. The obstruction was successfully cleared and the casing advanced thereby.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/CA11/50032 | 1/20/2011 | WO | 00 | 7/30/2012 |
Number | Date | Country | |
---|---|---|---|
61297365 | Jan 2010 | US | |
61386291 | Sep 2010 | US |