The present invention is in the field of down hole so-called fishing equipment used in most on/offshore oil and gas wells. More particularly, the invention relates to removing magnetic objects and accumulated magnetic debris as well as other particles from the wellbore rapidly and efficiently. The device of the invention is normally run on a drill string.
During well operations such as drilling or running tools into and out of the wellbore, debris, including magnetic debris, is generated, generally mechanically, by tasks preformed, due to ubiquitous minor collisions and friction between metal components or between metal components and rock. This debris can cause problems for down hole equipment and operations. It is vital to the operations that debris, both non-magnetic and magnetic, is removed before or during operations to prevent potentially hazardous consequences to people, the environment and well components. In an event of equipment failure, parts may break/twist of and leave undesired magnetic objects in a wellbore. Such lost objects are commonly broken-off cones from drill bits, balls from valves. The broken off parts may prevent access to valves, may prevent the operation of valves, may block passages, etc. and need to be removed before operations can resume. Unremoved undesired objects can prohibit further well construction and a new costly well will have to be drilled.
The applicant has a so-called Tornar grab magnet which is a combined curl flow forming tool receiving axial flow from a drill pipe string and redirects the flow laterally through curl flow forming nozzles having their mouths arranged in a circular pattern, said nozzles arranged between ridges of a tool of an outer diameter of about 165 mm. At the lower end of the tool is a magnet in a cylindrical sleeve with a permanent magnet. The magnet has a maximum magnetic holding capacity of 1000 kg when in full areal contact with a piece of steel to be fished. Please notice that clay or mud may prevent full areal contact, thus potentially significantly reducing the holding capacity of this prior art tool. The so-called Tornar nozzles set up a curl flow only in an annular space starting above the magnet and extending upwards along the upper housing and the drill pipe string, a significant layer of clay or mud may cover the steel object below this curl forming tool of the prior art to a degree that one may not obtain a good or sufficient magnetic holding force. There is also a risk of magnetic particles to accumulate about the exterior surface of the lower housing holding the magnetic cylinder, with the accumulated particles restricting upwards flow past the tool. It is desirable to have a cleaner object to catch and hold, and desirable to have higher holding capacity on the lower surface of the magnet.
The invention is a petroleum well drill- or coiled tubing string (1, 1b) mounted fishing tool comprising
By using the tool of the invention comprising a curl flow forming unit flow and a Halbach magnet the above mentioned situations can be resolved and operations can continue as planned.
The device is provided with the strong magnetic elements such as Neodym magnets. The Halbach magnet has a lifting capacity of about 1400 kg with full contact, compared to about 1000 kg of the prior art. One significant advantage of the Halbach magnet used in the present invention is the fact that long metallic objects such as steel bolts of length 200 mm and φ 20 mm will be magnetized in their long direction, and held on one end by the magnetic field directed generally axially and orthogonally out of the magnet, thus the bolt will extend axially and parallel with the tool of the invention. This will also to some degree prevent magnetic objects from attaching to the side surface of the lower housing. The curl flow foring ports create a powerful upwards directed cyclone effect around objects and the surrounding wellbore, ensuring full object contact with the magnet and good debris cleaning and extraction.
The invention is a petroleum well drill- or coiled tubing string (1, 1b) mounted fishing tool. The tool, which is illustrated in
The main body (2) further comprises a generally cylindrical upper housing (2b) with a central, so-called vertical, preferably axial channel (4) with laterally directed so-called Tornar nozzles (6), i.e. curl flow forming nozzles (6), through the cylindrical wall of said upper housing (2b). The nozzles (6) are leading out into one or more helical grooves (7a) between helical ridges (7b).
The magnet (3) is advantageously comprising permanent magnets (31, 32, 33, 34, 35) arranged in a magnetization pattern which concentrates their combined magnetic flux through said downwards facing surface (3f). Preferably these permanent magnets constitute a so-called Halbach set of magnets.
The upper housing's (2b) vertical channel (4) extends near its lower end to peripherally directed channels (5a) extending to an outer wall of said lower housing (2a) about said set of magnets (3, 31, 32, 33, 34, 35) and leading to axially directed peripheral nose ports (5b) at a peripheral lower end of said lower housing (2a) and arranged for flushing fluid ahead of said set of magnets (3).
The central channel (4) is provided with a vertically displaceable cylindrical flow control sleeve (8) which is provided with a closing seat (81) near its lower end so as for receiving a ball (82) for shutting off the flow to said nose ports (5b) and redirecting said flow through apertures (84, 84a, 84b, 84c) in the wall of said sleeve (8) to said nozzles (6).
The apertures (84) are linked by a circumferential ring groove so as for allowing flow to said nozzles (6) independent of the exact orientation of the central sleeve (8), please see
Phrased in another way, the invention is a magnetic retrieval tool using curl flow forming angled flow ports, in a ported generally non-magnetic housing with the set of magnets and a ball drop operated flow control sleeve for flow diversion to remove accumulated debris from the borehole. This invention allows several related operations to be conducted with the same tool: debris cleaning, magnetic debris removal and wellbore cleaning operations, all generally in the same run.
In an embodiment the curl flow forming nozzles have a diameter of 14 mm and the diameter of the ridge (7b) portion is about 165 mm. The diameter of the set of magnets (3), preferably the Halbach set of magnets (3, 31, 32, 33, 34, 35) is 125 mm. A larger diameter unit may have proportionally larger dimensions, with φ=20 mm flow forming nozzles.
In an embodiment of the invention shown in
In an advantageous embodiment the curl flow forming nozzles (6) are arranged in a nozzle-bearing wall (7bw), please see
In an advantageous embodiment, please see
In an embodiment of the invention, please see
In the embodiment shown in
In a preferred embodiment of the invention said curl flow forming nozzles (6) have an upward direction component, please see
In an embodiment of the invention shown in
Each of said curl flow forming nozzles (6) are formed through a side face (7bw) of said external ridge (7b), said curl flow forming nozzle (6) leading into a radial channel (61) in said external ridge (7b), said radial channel (61) drilled radially through said external ridge (7b) to said central channel (4) and plugged outside said curl flow forming nozzle (6) by a plug (71), please see
Advantageously, said Halbach magnet (3, 31, 32, 33, 34, 35) is formed from a high flux alloy such as Neodymium steel. As shown in
The Halbach magnet is a multiple-domain magnetized cylinder composed of five pieces of ferromagnetic material producing an intense magnetic field mainly confined within the cylinder's lower face and with low magnetic field intensities at the lateral cylinder surface and possibly the upper surface facing inwards in the tool housing. The Halbach cylinder is contained by epoxy inside a nonmagnetic housing closed off with a lid and held in place by four bolts on the nonmagnetic housing. Said nonmagnetic housing 2a contains the flow ports 5b for fluid distribution.
Low magnetic field on the outer cylindrical housing surface. Low magnetic field on top of magnet cylinder. Intense magnetic field on bottom of magnet cylinder.
The present invention's combination of a Halbach magnet and a nonmagnetic housing with flow ports creates a more powerful magnetic field through one downward-facing surface 3b which is the lower surface of the tool. The intense magnetic field at the lower surface of the tool is utilized to attract magnetic fragments, steel debris and missing parts that are undesired to have in a wellbore (see illustration 1.).
The described set of magnets (3, 31, 32, 33, 34, 35) is utilized to obtain the following:
The fact that the tool housing including the curl flow forming body is generally non-magnetic (of low magnetic permeability) prevents the magnetic field from the Halbach magnet to propagate and thus spread and induce a magnetic field in the flow sleeve and curl flow forming body that could result in magnetic debris buildup inside the tool, and thus plug up the hole tool and cause circulation problems.
The curl flow forming body of the upper housing 2b receives fluid under pressure through the drilling string or coiled tubing. It has angled flow nozzles releasing and initiating a powerful cyclone of drilling fluid. As the fluid has only one way out, upwards, its flow creates an effective lift force on any debris.
The mandrel may in the shown embodiment be provided with a flow control sleeve 8 inside its central cylindrical cavity 4. The flow sleeve is for controlling the fluid distribution and is displaceably operated by a steel ball dropped into the flow. The flow sleeve has equal distribution ports for balanced fluid distribution before the steel ball releases the flow control sleeve.
In operation the wellbore fluid is equally distributed thru the nose ports of the flow ported non-magnetic housing and the curl flow forming ports by the lower flow control distribution ports of the sleeve 8. By dropping the ball and shifting the flow sleeve downwards the entry to the ported non-magnetic housing nose ports about the Halbach magnet are blocked and wellbore fluid is distributed through said curl flow forming ports for well bore cleaning combining curl flow well cleaning and removal of magnetic debris. When the nose ports are closed the downward flushing force on the magnetic object held on the Halbach magnet ceases. However, the Halbach magnet is so strong so the nose flow will have little negative effect when a single object is held on the magnet, but it will prevent a large amorphous magnetic mass from being gradually flushed off the magnet. The most important contribution of closing the nose flow is to redistribute the flow volume to the curl flow after having caught the magnetic object.
In the embodiment shown in
Filing Document | Filing Date | Country | Kind |
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PCT/NO2013/050009 | 1/14/2013 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2014/109643 | 7/17/2014 | WO | A |
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