Patent Grant
7172026
1. Field of the Invention
The present invention is directed to apparatus and methods for removing sand and/or other fill material located in a wellbore ahead of a coiled tubing tractor and displacing the material behind the tractor. More particularly, the apparatus and methods of the present invention allow a coiled tubing tractor to drive forward in a wellbore by the removal of fill material in front of the tractor thereby allowing the wheels or traction pads of the tractor to remain in contact with the wellbore.
2. Description of the Related Art
Operators are drilling an increasing number of long reach horizontal wells to better access remote reserves of oil and/or gas. Many of these “extended reach” wells have passed the limit where unaided re-entry to the bottom of the wellbore is possible with practical sizes of coiled tubing. The industry has responded by developing hydraulically powered tractors that can be attached to the bottom of the coiled tubing for the purpose of pulling the coiled tubing along the horizontal section of the well. This technology is relatively new with only a few coiled tubing tractor jobs having been attempted to date but there is concern that the reliability of the technology could be seriously compromised by significant quantities of sand or fill on the low side of the hole. The unanswered question is how reliably can the different tractor types perform when they are trying to drive their wheels or traction pads through a substantial sand bed. Sand beds on the low side of the wellbore represent a potentially significant obstacle. For example, a 3 inch deep sand bed in a 6¼ inch hole could cause a tractor to begin pushing the sand ahead of it until a point is reached where the tool becomes stuck in the wellbore. Thus, there is a need for a way to clear the wellbore of sand or fill in the immediate vicinity ahead of the tractor so the tractor does not have to attempt to negotiate through and/or over such an obstacle. Although sand typically is the most prevalent wellbore fill material, it shall be understood that use of the term “sand” hereinafter shall also include any other wellbore particulates such as drill cuttings, metal shavings and wellbore fines.
The present invention employs a series of forward and rearward angled jetting assemblies that can be attached to or configured within the coiled tubing tractor itself. The leading assembly has forward angled nozzles to fluidize the sand bed ahead of the tractor plus a series of rearward angled nozzles that maintain the sand in turbulent suspension for a sufficient distance to ensure that the sand settles behind the tractor. The objective is to remove sand from the specific area in the well where the tractor is situated and allow it to deposit behind the tractor. The tractor itself would thus be operating in a portion of the wellbore that is largely unobstructed by any sand bed. Depending on the tractor length it may be necessary to include several rearward jet nozzles at strategic intervals along the tractor length to ensure that sand is carried the required distance. The addition of polymers in the circulating fluid may aid in the temporary suspension of sand and thus reduce the requirement for multiple rearward nozzle assemblies.
An alternative embodiment uses a jet pump to suck in the fluidized sand and vigorously expel the sand in the rearward direction. The fluidized sand discharge would either be directly into the annulus around the tractor or preferably through a separate return fluid passageway running substantially the full length of the tractor. Preferably this return fluid passageway is engineered within the tractor itself but, if wellbore and tractor dimensions permitted, it may be attached to the outside of the tractor.
The tractor would in effect “burrow” along the well while pulling the coiled tubing behind it. Any in-line, pump-through tool having rearward facing jetting nozzles, such as the Tornado™ tool offered by BJ Services Company, could be run behind the tractor without compromising the washing action around the tractor. When the drag of the sand on the coiled tubing reached the pull limit of the tractor, a wiper trip would be initiated and the sand beds behind the tractor could be swept out of the hole by the rearward facing nozzles of the pump-through tool after which forward progress along the wellbore could be re-initiated.
One embodiment of the present invention is directed to a wellbore tractor comprising a tractor body, a central fluid passageway extending through the length of the tractor body, a return fluid passageway and a means for driving the tractor through the wellbore. The return fluid flow passageway further comprises one or more flow conduits that may extend longitudinally through at least a portion of the wall of the tractor body. Alternatively, the one or more flow conduits may comprise one or more external flow channels extending along at least a portion of the outer surface of the tractor body. Preferably, the external flow channels are attached between the means for driving the tractor.
In an alternative embodiment of the invention, a wellbore tractor is provided having a tractor body, a central fluid passageway extending through the length of the tractor body, one or more rearward facing jet nozzles extending through the tractor body and in fluid communication with the central fluid passageway, and a means for driving a tractor through the wellbore.
A method of moving a coiled tubing tractor through a wellbore is also provided comprising the steps of running a coiled tubing tractor assembly on a coiled tubing into the wellbore, wherein the tractor assembly comprises one or more forward facing nozzles, a jet pump and the tractor. The method further comprises removing one or more sand beds ahead of the tractor by fluidizing the sand particles with the one or more forward facing jet nozzles to create a sand-ladened slurry, pumping the sand-ladened slurry via the jet pump past the trailing end of the tractor and driving the tractor through a portion of the wellbore that previously contained one or more sand beds. The method further comprises circulating and/or sweeping the sand out of the wellbore, preferably while pulling out of the hole with the coiled tubing tractor assembly with one or more rearward facing nozzles located between the tractor and the coiled tubing.
Another method of moving the coiled tubing tractor to the wellbore comprises the steps of running a coiled tubing tractor assembly on a coiled tubing into the wellbore, the tractor assembly comprising one or more forward facing jet nozzles, the tractor and one or more rearward facing jet nozzles. The method further comprises the steps of removing one or more sand beds ahead of the tractor by fluidizing the sand particles with the one or more forward facing jet nozzles, maintaining the sand in fluid suspension with the rearward facing jet nozzles until the sand particles settle behind the tractor and driving the tractor through the portion of the wellbore that previously contained the one or more sand beds.
Another embodiment of the invention is directed to a coiled tubing tractor assembly comprising a forward jetting assembly operable to fluidize sand beds ahead of the coiled tubing tractor, the coiled tubing tractor having a tractor body, a central fluid passageway and a return fluid passageway. The assembly also comprises a jet pump connected between the forward jetting assembly and the tractor, wherein the jet pump is operable to pump the fluidized sand through the return fluid passageway to expel the fluidized sand past the trailing end of the tractor. The assembly may further comprise a rearward facing jetting tool operable to circulate or sweep the sand behind the tractor out of the wellbore. The assembly may comprise a fluid manifold in fluid communication with the return fluid passageway.
An alternative assembly comprises a forward jetting assembly operable to fluidize sand beds ahead of a coiled tubing tractor, the coiled tubing tractor having a tractor body, a central fluid passageway extending through the tractor body, and one or more rearward facing jet nozzles extending through the tractor body and in fluid communication with the central fluid passageway wherein the rearward facing nozzles are operable to maintain the sand in fluid suspension until the sand travels past the tractor.
The present invention could also be used to move a coiled tubing tractor through a flowline, such as a water or petroleum pipeline, that contains particulate matter. The particulate matter in the flowline would be moved from in front of the tractor and displaced to a position behind the tractor in a similar manner as described in a wellbore.
The following figures form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these figures in combination with the detailed description of specific embodiments presented herein.
While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
It is difficult to pick up solids from a sand bed at the bottom of a wellbore with a conventional jet pump alone. It is better to fluidize the sand particles of the sand bed such that the sand particles are suspended in the liquid. The sand slurry is then sucked into the jet pump and pumped up the wellbore. Accordingly, a preferred embodiment of the present invention utilizes a jet pump connect to and in fluid communication with a forward facing jetting assembly. The jet stream from nozzles 22 stir up the sand, fluidize the particles 14a and then the jet pump sucks the fluidized material into the fluid intake of the pump and pumps the slurry up the wellbore and past the tractor. The power fluid can be water, drilling mud or any other suitable liquid. The power fluid may include polymers to aid in temporarily suspending the sand particles as the sand is transported from an area ahead of the tractor to an area behind the tractor. The transported sand 17a may form new sand beds 17 behind the tractor assembly.
Tractor 30 is connected to jet pump 25 in the tractor assembly illustrated in
In an alternative embodiment, the coiled tubing tractor includes a pair of hydraulic grippers and a telescopic hydraulic cylinder as the means for driving the tractor, and the coiled tubing it is pulling, into a wellbore. The All-Hydraulic Intervention Tractor™, offered by Western Well Tool, Inc., is a commercial example of the caterpillar-type wellbore tractor. Other examples of caterpillar-type tractors are disclosed in U.S. Pat. Nos. 6,003,606, 6,286,592, 6,230,813, 6,601,652, 6,241,031, 6,427,786, 6,347,674, 6,478,097 and 6,679,341, all of which are incorporated herein by reference.
In a preferred embodiment, tractor 30, shown in
Unlike the prior art tractors, tractor 30 also includes a novel return fluid passageway 65. The return fluid passageway 65 is in fluid communication with the discharge of jet pump 25. Thus, the sand-ladened slurry is pumped from jet pump 25 into the return fluid passageway 65 of tractor 30. The return fluid passageway may comprise one or more flow conduits. In one embodiment, the one or more flow conduits extend longitudinally through at least a portion of the wall of the tractor body, wherein the wall of the tractor body is defined as the area between the central passageway and the outer surface of the tractor body.
Alternatively, the one or more fluid flow conduits may comprise one or more external flow channels 85 extending along at least a portion of the outer surface of the tractor body. Preferably, the one or more flow conduits extend substantially the entire length of the wellbore tractor so that the fluidized fill may be pumped by the jet pump through the tractor and exhausted or expelled behind the wellbore tractor. In a preferred embodiment, a fluid manifold 80 is in fluid communication between the one or more flow conduits and the discharge of jet pump 25. In one embodiment, one or more inlet ports 82 in manifold 80 receive the sand-ladened slurry from jet pump 25.
For caterpillar-style tractors, such as the one illustrated in
In operation, a power fluid is pumped down the coiled tubing to the coiled tubing tractor assembly. The power fluid powers the tractor so that the means for driving the tractor is activated. A portion of the power fluid continues through the central passageway of the tractor and exits the forward facing jetting assembly to stir and break up the sand beds in front of the tractor and fluidize the sand particles. At the same time, another portion of the power fluid will exit the one or more rearward facing fluidizing jet nozzles in the tractor body, the rearward facing fluidizing nozzles being a fluid communication with the central passageway of the tractor. The rearward facing nozzles 135 maintain the sand particles 14a in turbulent fluid suspension and move the sand back past the trailing end of the tractor, whereafter the sand 17a will eventually form new sand beds 17 up the wellbore. Like the jet pump method, the rearward facing fluidizing jetting method cleans the wellbore substantially of sand in the immediate vicinity of the tractor so the tractor may be driven in a substantially sand-free section of casing or wellbore.
By way of example, using the present invention may create a clean section of casing or wellbore, for instance, extending about three feet in front of and about three feet behind the tractor. Obviously, the length of the clean section of wellbore will be a function of many factors, such as flow rate, tractor size, hole size, jet sizes, and rheological properties of the power fluid.
Using the assembly illustrated in
Upon reaching the end of the wellbore or reaching a point where it is no longer possible to move the coiled tubing string through the sand beds behind the tractor assembly, the sand is circulated out of the wellbore. There are several ways of removing the sand behind the tractor assembly out of the wellbore. The simplest method is to rely on pure fluid velocity and flow rates to clean out the wellbore behind the tractor assembly. Typically, this method is practiced with the coiled tubing in a stationary position to keep from prematurely fatiguing the coiled tubing. Although simpler, this method may require several hole volumes to be circulated at high fluid velocity to remove the sand from the wellbore and thus tends to be more time consuming and more expensive.
In a preferred embodiment, a pump through, in-line jetting tool 35 having rearward facing jet nozzles may be inserted between the coiled tubing and the coiled tubing tractor. The preferred jetting tool is described in U.S. Pat. No. 6,607,607 (incorporated herein by reference), assigned to BJ Services Company, and available commercially as the Tornado™ tool. The Tornado™ tool uses one or more rearward facing jet nozzles that may be selectively activated to re-entrain sand particles that have settled into beds 17 into the cleanout fluid. Operationally, the power fluid is circulated down through the Tornado™ to the tractor and the forward facing jetting tool. The rearward facing nozzles of the Tornado™ are actuated by increasing the flow rate through the tool to a predetermined level. This causes an inner mandrel inside the tool to shift, thereby closing off forward flow and directing flow through the rearward facing nozzles of the tool. The rearward nozzles may be larger than the forward facing nozzles so less pressure drop occurs through the rearward facing nozzles, thus providing a surface indication that the rearward facing nozzles have been activated. By activating the rearward facing nozzles, circulating a cleanout fluid through the nozzles and controlling the pull-out-of-hole speed, the sand can be swept out of the hole with near 100% efficiency. Smaller circulation volumes are required with the Tornado™ tool. The Tornado™ tool allows an operator to move the coiled tubing and to sweep the solids out of the wellbore at lower pressures and flow rates, thereby providing a more efficient clean up process with less fatigue on the coiled tubing.
In another embodiment, larger nozzles may be included in the back of the tractor. By increasing the flow rate through the tractor, sand could be swept out of the hole while pulling the tractor out of the hole without the use of a pump through, in-line jetting tool 35.
While the apparatus, assemblies and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the process described herein without departing from the concept, spirit and scope of the invention. By way of example, the described apparatus and methods may also be used to remove particulate matter in flowlines. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as it is set out in the following claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5565633 | Wernicke | Oct 1996 | A |
| 6003606 | Moore et al. | Dec 1999 | A |
| 6230813 | Moore et al. | May 2001 | B1 |
| 6241031 | Beaufort et al. | Jun 2001 | B1 |
| 6286592 | Moore et al. | Sep 2001 | B1 |
| 6296066 | Terry et al. | Oct 2001 | B1 |
| 6347674 | Bloom et al. | Feb 2002 | B1 |
| 6427786 | Beaufort et al. | Aug 2002 | B2 |
| 6478097 | Bloom et al. | Nov 2002 | B2 |
| 6601652 | Moore et al. | Aug 2003 | B1 |
| 6607607 | Walker et al. | Aug 2003 | B2 |
| 6679341 | Bloom et al. | Jan 2004 | B2 |
| Number | Date | Country |
|---|---|---|
| WO 03067016 | Aug 2003 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20050217861 A1 | Oct 2005 | US |
