CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is based on and claims priority to GB Application No. 0722818.2, filed 22 Nov. 2007; and International Patent Application No. PCT/EP2008/009696, filed 17 Nov. 2008. The entire contents of each are herein incorporated by reference.
This invention relates to a system for borehole cleaning. In particular the invention relates to a system for using mechanical and hydraulic means to remove debris.
In the drilling and completion of oil and gas wells debris can accumulate in the well. This debris may come from drilling cuttings, formation debris due to wellbore instability during drilling, debris from formation fluids deposited during production, scales from pipes, swarfs produced by window milling or other pipe machining. Accumulation of debris can be particular severe where lateral wells are being drilled. Deposits that can accumulate in these lateral regions can result in plugging reducing the effective cross section of the well resulting in a corresponding decrease in flow area and/or excessive wear on producing equipment can occur. In order to maintain the flow of fluid through the well and prevent wear, the debris has to be removed.
Conventional methods of cleanout involve high pressure jetting through coiled tubing to mobilize the debris around the cleanout tool and using the flow of jetting fluid or production to carrying the debris to the surface, or a foam column is used to sweep the debris up the well. EP1852571 describes one system using coiled tubing and a downhole electrical pump to perform cleaning by withdrawing material from the borehole and pumping it into the tubing up to the surface.
This invention aims to provide an alternative to conventional borehole cleaning techniques that rely on coiled tubing and instead can be used with wireline drilling equipment to remove debris from the well while still maintaining efficient transport of the debris with the fluid flow.
DISCLOSURE OF THE INVENTION
Accordingly a first aspect of the invention comprises an apparatus for removing debris from a well comprising: a tool body having a head, the head having a conduit opening and comprising protrusions extending from the outer surface of the head for moving debris in the well; a chamber in the tool body to store debris; a connector for attaching the tool body to a drilling system; a conduit connected to the opening in the head to convey debris and fluid from the well to the chamber; and a filter in the tool body to limit the size of the particles that can pass into the drilling system from the chamber; wherein in use fluid flow and the protrusions move the debris from the well and into and through the apparatus.
By using a combination of both mechanical means and hydraulic flow means the apparatus is able to efficiently collect debris from the well and transport the debris up the drilling system.
Preferably the apparatus is attached to a drilling system. The drilling system can be a bottomhole drilling assembly (BHA).
The drilling system can comprise a pumping system operable to circulate fluid through the tool and drilling system. Fluid can be pumped through the apparatus in any direction. The drilling system can also comprise a rotary mechanism operable to rotate the apparatus.
The drilling system may also comprise an orientation mechanism operable to direct the apparatus in a predetermined direction.
In one embodiment of the invention the apparatus is integrated into the drill bit of a BHA of the drilling system.
The conduit opening of the apparatus can be located in the centre of the head. This allows debris from the bottom of the well to be collected. Alternatively the conduit opening is offset from the centre of the head. This helps in collecting debris deposited on the side walls of the well.
The head can include rigid protrusions, flexible protrusions and/or protrusions that are cutting elements.
The conduit of the apparatus can be rotatable within the apparatus. This helps the flow of the debris through the conduit and packing of debris in the chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
The present embodiments may be better understood, and numerous objects, features, and advantages made apparent to those skilled in the art by referencing the accompanying drawings. These drawings are used to illustrate only typical embodiments of this invention, and are not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness.
FIG. 1 shows a cross section view of the cleaning apparatus according to the invention;
FIG. 2 shows a detailed view of part of the system of FIG. 1;
FIG. 3 shows embodiments of the conduit that can be used for the invention;
FIG. 4 shows a cross section view of an embodiment of the invention for handling large amounts of debris; and
FIG. 5 shows an embodiment of the invention integrated into a drilling bit.
MODE(S) FOR CARRYING OUT THE INVENTION
Referring to FIG. 1 the borehole cleaning apparatus 10 according to the invention comprises a connector 12, a tool body 14 and a conduit 16. The connector 12 allows the apparatus to be connected to a wireline drilling system (not shown). The connector 12 includes a filter 18 which will separate particles in the fluid flowing through the apparatus. The tool body 14 is attached to the connector 12 at one end and at the other end comprises a cleaning head 20. The cleaning head 20 has an opening 22 to allow debris to enter the cleaning apparatus. The conduit 16 runs from the opening 22 to the chamber 24 to convey the particles through the apparatus.
The apparatus is mounted on the lower end of the wireline lateral drilling equipment (WiLD) (not shown) and uses the functionalities of the bottom hole assembly (BHA) of the wireline drilling system to operate. The cleaning apparatus can be placed anywhere in the well using the wireline cable or the crawler system of the BHA. The drilling section of the BHA is used to rotate the cleaning apparatus, i.e. as if it was the drill bit, and can be used to deflect and orientate the apparatus using continuous and adjustable displacement. While the pump system of the BHA is used to pump fluid around and through the apparatus to facilitate the removal the debris from the well. The apparatus can be used to collect debris from the bottom end of the borehole before a drilling operation using WILD.
Debris in the well is agitated by protrusions on the outer surface of the head 20 as the apparatus is rotated by the rotational means of the drilling system, and the protrusions help convey the debris into the apparatus from the well. The debris enters the apparatus via the opening 22 in the head along with fluid flowing through the well. Fluid is pumped around the outside of the apparatus 10 so as to flow to the head 20 into the conduit 16. The fluid flow conveys the debris along the conduit 16 to the chamber 24, where the fluid is pumped through the filter 18 and up through the wireline drilling equipment. As the fluid passes through the filter 18 larger particles present in the fluid will be separated from the smaller particles in the fluid. Smaller particles in the fluid are able to pass through the filter mesh and continue up the drilling system while larger particles remain behind and will be collected in the chamber 24.
The pump system can be activated in reverse circulation mode or in direct circulation mode to move fluid through the apparatus in any direction depending on the conditions in the well. In reverse circulation mode particles smaller than the filter mesh are able to pass through the filter and be pumped through the wireline drilling system with the fluid while the larger particles are trapped by the filter and stored in the chamber. If the filter gets plugged the pumping direction can be reversed and fluid can be pumped through the system in a direct circulation mode. This will dislodge the filter cake from the filter, so that the filter cake will get trapped in the chamber.
The debris is moved and loosened from the borehole by a combination of mechanical and hydraulic mechanisms. The head 20 of the tool body comprises elements 26 protruding from its front and lateral surface as shown in FIG. 2. These elements can be rigid, i.e. teeth or ribs, or soft like i.e. brushes or fingers. The choice of elements protruding from the cleaning head will depend on the debris targeted. Protrusions such as paddles 26 or teeth extend from the head to agitate and move the debris from the well into the apparatus. In some situations the protrusions can include cutting elements. For example if scale or adhesive deposits need to be moved the appropriate cutter mechanisms can be used instead of paddles, so the scale or adhesive deposits are grinded or milled.
The mechanical effort to move the debris provided by the protruding elements is helped by the hydraulic flow through the apparatus and well. The hydraulic flow is provided by the pumping system of the drilling system and conveys the debris along the outside surface of the apparatus to the opening in the head and into the conduit. Using both mechanical and hydraulic mechanisms together maximizes the efficiency of debris removal from the well.
The cross area of the central conduit is selected to provide enough flow speed to convey debris safely along using known design rules for such transportation of debris and the pump characteristics. The conduit can be made of rigid material, for example metal or plastic, or a deformable material, for example rubber which allows larger debris to be caught. Using a deformable material the cross section of the conduit can take the form of a flattened cylinder or a star as shown in FIG. 3. Alternatively the cross section of the conduit could be a circle.
When the bottom of the borehole is to be cleaned the shape of the front surface of the tool is designed to provide a constant and controlled cross area between the front surface of the collector and the bottom of the well to maximize the efficiencies of the operation.
While the conduit opening 22 can be in the centre of the head 20 of the tool to collect debris from the bottom end of the borehole, if debris on the side of the well is to be collected, the conduit opening 22 can be positioned off-centered in the head, as shown in FIG. 2.
In one configuration of the invention the apparatus can be integrated into the BHA of a drilling system. If it is expected that a large amount of debris is going to be collected, then to obtain a greater chamber capacity for the cleaning apparatus the chamber can be placed above the rotating and orientation mechanism of the wireline drilling system, as shown in FIG. 4. The chamber 28 comprising the filter 30 is positioned between the pump unit 32 and the orientation unit 34, with the rotation unit 36 located between the orientation unit 34 and the cleaning head 38. The conduit 40 conveys debris 42 from the opening in the head 38 through the rotation unit 36 and the orientation unit 34 to the chamber 28. The size of the chamber can be extended by adding sections between the pump module 32 and the orientation module 34. Although FIG. 4 exemplifies the system having an orientation unit 34, rotation unit 36 and a pump unit 32 it is not necessary to have all three units in all cleaning operations. The hole cleaning system can be operated using only the rotation unit 36 and the pump unit 32 of the drilling system and not using an orientation unit 34.
The central conduit 40, connecting the chamber 28 to the cleaning head 38, can have a screw shape on its external surface and can be rotated to help transport the debris along the conduit 40 and help pack the debris in the chamber 28 that is not able to pass through the filter 30 with the fluid flow. This is particularly useful for configurations using multiple chamber units to increase the debris holding capacity of the apparatus.
The cleaning apparatus can be integrated into the BHA in order to catch any debris above a predetermined size before it has traveled far up the drilling system, and allow larger amounts of debris to be collected. However the chamber and filter can be placed at the bit level to minimize risk of plugging further up the bottomhole assembly.
Referring to FIG. 5 a further embodiment of the invention comprises integrating the cleaning apparatus into a drill bit of the drilling system to allow removal of debris while drilling. The drill bit 44 comprises openings 46 which lead to a conduits 48 which conveys debris to the chamber 50 and filter 52. Particles are separated by the filter 52 and larger particles remain in the chamber 50 in the drill bit. While particles smaller than the filter mesh size can pass through the filter 52 and be pumped up the drilling system 54.
As the drill bit is rotated by its rotary mechanism cuttings are generated and moved into the opening of the bit with the reverse circulation flow of fluid that also is generated by the pumping unit of the drilling system.
When the cleaning tool is integrated into the bit, the collector chamber that collects the debris is limited in size and could get filled up quickly. However by reversing the direction of the flow the large cuttings can be expelled back out the bit into the well where they can be grinded between the bit and rock face. These initial larger cutting particles are grinded to a smaller size where they are then able to pass through the filter as they are a small enough size to be efficiently transported up the flow channel of the BHA.
When drilling in reverse circulation, various factors determine the efficiency of cutting transport through the inner flow channel of the BHA and umbilical, such as: fluid rheology, fluid velocity, inner tube profile and dimensions. Therefore particles with a size above a given value will not be transported effectively up the flow channel and may plug the flow channel leading to an increase in pressure losses as well as plugging.
The cutting distribution can be controlled by controlling the depth of cut (DOC); however large cuttings may still be generated either by the drilling itself or from debris or scales falling from above the bit. These large cuttings will not be transported with the flow through the drilling system and may accumulate in the well or drilling system.
While limiting the DOC will limit the maximum cutting size generated, this can also limit the drilling efficiency and rate of penetration. Therefore to maintain the drilling efficiency that is achieved with higher DOC the cleaning apparatus of the invention can be used to allow drilling with a higher DOC and yet still maintain the cutting transport efficiency that would be achieved when small cutting are generated with a small DOC. The filter of the cleaning apparatus filters all the particles above the maximum size for achieving efficient cutting transport. The smaller particles that can be transported efficiently with the fluid flow up the bottomhole assembly pass through the filter with the fluid, while the larger particles will remain in the chamber.
While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible.
Plural instances may be provided for components, operations or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter.