Patent Grant
7281592
The present invention relates to a method and system for introducing a fluid into a borehole formed in an underground earth formation. The term fluid is used in the specification and in the claims to refer to any material that can be pumped through a tubular drill string, for example cement, lost circulation material, or cleaning fluid. The fluid can also include solid particles.
Lost circulation material is any material, which can be used to block fractures in underground formations and is generally of a coarser nature.
The invention relates in particular to introducing such a fluid into the borehole ahead of the drill bit at the lower end of the drill string.
In the course of a drilling operation, in particular when drilling an oil or gas well, it is on occasion desirable to pump a fluid into the borehole. For example, when drilling into a fractured or porous zone, it is desired to cure losses and to maintain formation strength by using cement and/or lost circulation material. Another example is setting a cement plug for abandonment of a well or well section, possibly followed by drilling of a branched well section.
It is considered highly undesirable to attempt pumping of a fluid of high density or viscosity and/or comprising coarse material through the drill string with a drill bit attached. Conventional drill bits such as polycrystalline diamond cutter (PDC) bits or roller cone bits are provided with bit nozzles. However, the fluid would need to be forced through the bit nozzles, and there is a high risk for the nozzles to plug up due to the high shear, rapid pressure drop, and small orifice. Nozzles normally comprise a nozzle channel with a nozzle insert, and the orifice could in principle be increased by removing the nozzle inserts from the bit. This option is however not seriously contemplated in practice since it would significantly impair the performance of the bit for progressing into the formation.
Therefore, in practice the drill bit is removed from the drill string and is replaced by a tool with a sufficiently large orifice in order that fluid can be introduced. To this end the drill string needs to be pulled out of the borehole. In order that the drill string can be pulled, it is often required to first temporarily stabilize the borehole by introducing lost circulation material. This can be done through ports in the lower part if the drill string above the drill bit that can be opened and closed again, for example arranged in a so-called circulating sub. Introducing lost circulation material via this route above the bit can plug the annulus between borehole wall and the lower part of the drill string including the drill bit, thereby requiring removal of the drill string and further complicating operations. The pumping of cement through the same ports is not a practical option, since there is a significant risk that the lower part of the drill string including the drill bit will be cemented in place.
When the drill string then has been fully pulled up, the drill bit is for example replaced by a cementing stinger, and the drill string is lowered again in the borehole to the desired depth, whereupon fluid can be introduced into the borehole. If it is then desired to resume drilling, the drill string needs to be pulled out of the borehole hole a second time, so that the drill bit can be mounted again.
This procedure is time-consuming and therefore uneconomic. Moreover, introducing a fluid such as cement is often needed in a situation where the borehole is unstable, and in such situation it can be undesirable to pull the drill string out of the borehole.
It is an object of the present invention to provide a method for introducing a fluid into a borehole, wherein fluid can be safely introduced through the drill string with a drill bit attached at its lower end.
It is a further object to provide a system for introducing a fluid into a borehole which system allows to drill and to introduce fluid into the borehole without the need to replace the drill bit.
To this end there is provided a method for introducing a fluid into a borehole formed in an underground earth formation, in which borehole there is arranged a tubular drill string including a drill bit at its lower end, wherein the drill bit is provided with a passageway between the interior of the drill string above the drill bit and the borehole exterior of the drill bit, and with a removable closure element for selectively closing the passageway in a closing position, and wherein there is further provided a fluid injection tool comprising a tool inlet, and a tool outlet in fluid communication with the tool inlet, which method comprises the steps of:
The invention is based on the insight, that a drill bit having a sufficiently large passageway can, except for drilling, also be used for lowering a fluid injection tool into the borehole ahead of the drilling bit, in order to introduce a fluid into the borehole. In order that the drill bit can be efficiently used for both operations, the passageway is provided with a closure element that can be selectively removed from the closing position by using the fluid injection tool from the inside of the drill string.
During normal drilling operation, drilling fluid is normally ejected from inside the drill string via nozzles provided in the drill bit. With the passageway open it would not be possible to create the high-speed jets of drilling fluid through the nozzles, that are needed to carry the drill cuttings away from the drill bit and aid in formation penetration. Therefore, the closure element is in the closing position for normal drilling operation, and preferably the closure element is provided with cutting elements that form a joint bit face with the cutting elements on the drill bit during drilling operation.
For introducing fluid into the borehole, the fluid injection tool is lowered through the drill string into the drill bit to the closure element, in order to remove the closure element from the closing position. This is preferably done by connecting the fluid injection tool to the closure element. The outlet of the fluid injection tool can then be passed through the passageway into the borehole ahead of the drill bit, whereas the tool inlet remains in and in fluid communication with the interior of the drill string. In this position, which is referred to as landing position, fluid communication is provided between the interior of the drill string and the borehole exterior of the drill bit via the passageway. The length of the fluid injection tool and the shape of the tool outlet can be designed according to the specific application, such as introducing a cement, lost circulation material, or a cleaning fluid.
It will be clear that a drill bit nozzle is not considered a passageway. Preferably, the smallest cross-sectional area along the passageway is at least 5 cm2, more preferably the passageway is arranged so as to allow a conduit, e.g. a fluid injection tool, of about 2.5 cm (1 inch) diameter to pass through the passageway.
U.S. patent publication No. 2,169,223 discloses a reamer bit of the fish-tail type, provided with a central longitudinal passageway. During normal operation the reamer bit is used to increase the diameter of an existing borehole, the so-called rat hole. For the reaming operation the passageway is closed from inside the drill string by means of a plug, which can be retrieved to surface by wireline. Thereafter a flushing apparatus may be lowered for flushing out the rat hole.
German patent application publication No. DE 198 13 087 A1 discloses a system for rotary and hammer drilling and for injection drilling. The known system comprises concentrical and decoupled outer and inner drill strings, which form a drill bit at the end. The inner drill string is provided with injection nozzles along its length, and can be slid out of the outer drill string for high-pressure injection drilling, eventually followed by cementing.
A drill bit having a passageway and a removable closure element is disclosed in the International Patent Application with publication number WO 00/17488.
There is further provided a system for drilling and for introducing a fluid into a borehole in an underground earth formation, which system comprises:
The means for removing the closure element from the closing position suitably comprises a connection means for selectively connecting the fluid injection tool from inside the drill string to the closure element in the closing position.
The fluid injection tool serves to guide the fluid from the passageway to the position in the borehole where the fluid is to be introduced. Depending on the type of fluid to be introduced, the fluid injection tool and particularly the tool outlet can appropriately be designed.
If the fluid is cement or lost circulation material, the fluid injection tool suitably has the form of a cementing stinger, which can be for example up to 100 m long, or more. If the fluid is lost circulation material, the tool can be much shorter, for example 10-20 m. Examples of lost circulation material include cellophane flakes, walnut hulls, ground calcium carbonate. When a salt saturated drilling mud is present in the borehole, even salt can be used.
The fluid injection tool can in particular have telescopic form, allowing to increase the length during operation. The telescopic form can be less robust than a conventional stinger, however this form is possible since the tool is designed to be deployed within the drill string, wherein it is better protected than a conventional stinger when lowered into a borehole.
The fluid can also be a cleaning fluid. The cleaning fluid can for example be water or brine, but can also comprise acid (e.g. 5% hydrochloric acid or acetic acid), finely suspended particles (e.g. calcium carbonate, hematite), polymers or other chemical agents, mixed with water and/or oil. A cleaning fluid can for example be used to remove mudcake from the borehole wall, or to clean the face of the drill bit. In that event the tool outlet has the form of jetting nozzles which are oriented in the desired direction, or possibly rotatably arranged.
Suitably, the fluid injection tool is further provided with a landing member, which is arranged so as to close the passage through the bit nozzles when the fluid injection tool is in the landing position. The landing member therefore prevents that the bit nozzles become plugged when the fluid is introduced from the drill string via the passageway and the fluid injection tool into the borehole.
The invention will now be described in more detail and with reference to the drawings, wherein
With reference to
The drill bit 1 is further provided with a removable closure element 10, which is shown in
The latching section 14, which is fixedly attached to the rear end of the insert section 12, has substantially cylindrical shape and extends into a central longitudinal bore 20 in the bit body 6 with narrow clearance. The bore 20 forms part of the passageway 8, it also provides fluid communication to nozzles in the insert section 12.
Via the latching section 14 the closure element 10 is removably attached to the bit body 6. The latching section 14 of the closure element 10 comprises a substantially cylindrical outer sleeve 23 which extends with narrow clearance along the bore 20. A sealing ring 24 is arranged in a groove around the circumference of the outer sleeve 23, to prevent fluid communication along the outer surface of the latching section 14. Connected to the lower end of the sleeve 23 is the insert section 12. The latching section 14 further comprises an inner sleeve 25 which slidingly fits into the outer sleeve 23. The inner sleeve 25 is biased with its upper end 26 against an inward shoulder 28 formed by an inward rim 29 near the upper end of the sleeve 23. The biasing force is exerted by a partly compressed helical spring 30, which pushes the inner sleeve 25 away from the insert section 12. At its lower end the inner sleeve 25 is provided with an annular recess 32 which is arranged to embrace the upper part of spring 30.
The outer sleeve 23 is provided with recesses 34 wherein locking balls 35 are arranged. A locking ball 35 has a larger diameter than the thickness of the wall of the sleeve 23, and each recess 34 is arranged to hold the respective ball 35 loosely so that it can move a limited distance radially in and out of the sleeve 23. Two locking balls 35 are shown in the drawing, however it will be clear that more locking balls can be arranged.
In the closing position as shown in
The inward rim 29 is arranged to cooperate with a connection means 39 at the lower end of a fluid injection tool 40, which connection means 39 serves as a means for removing the closure element from the closing position. Only the lower part of the fluid injection tool 40 is shown. The connection means 39 is provided with a number of legs 50 extending longitudinally downwardly from the circumference of the fluid injection tool 40. For the sake of clarity only two legs 50 are shown, but it will be clear that more legs can be arranged. Each leg 50 at its lower end is provided with a dog 51, such that the outer diameter defined by the dogs 51 at position 52 exceeds the outer diameter defined by the legs 50 at position 54, and also exceeds the inner diameter of the rim 29. Further, the inner diameter of the rim 29 is preferably larger or about equal to the outer diameter defined by the legs 50 at position 54, and the inner diameter of the outer sleeve 23 is smaller or approximately equal to the outer diameter defined by the dogs 51 at position 52. Further, the legs 50 are arranged so that they are inwardly elastically deformable as indicated by the arrows. The outer, lower edges 56 of the dogs 51 and the upper inner circumference 57 of the rim 29 are bevelled. It shall be clear that the lower end of the fluid injection tool 40 including the connection means 39 can form a separate auxiliary tool for removing the closure element. The auxiliary tool can be so arranged that it can be releasably mounted on the fluid injection tool.
The drill bit 1 with the closure element 10 in the closing position as shown in
When it is desired to introduce fluid into the borehole 2 below the drill bit 1, the drill bit is first positioned a distance above the bottom of the borehole. Then, the closure element 10 can be outwardly removed from the closing position in the drill bit 1.
To this end, the fluid injection tool 40 is lowered from a position inside the drill string 3 along the passageway 8 in the bit body 6, until the connection means 39 engages the upper end of upper end of the latching section 14 of the closure element 10. The dogs 51 slide into the upper rim 29 of the outer sleeve 23. The legs 50 are deformed inwardly so that the dogs can slide fully into the upper rim 29 until they engage the upper end 26 of the inner sleeve 25. By further pushing down, the inner sleeve 25 will be forced to slide down inside the outer sleeve 23, further compressing the spring 30. When the space between the upper end 26 of the inner sleeve 25 and the shoulder 28 has become large enough to let in the dogs 51, the legs 50 snap outwardly, thereby latching the fluid injection tool to the closure element.
At approximately the same relative position between inner and outer sleeves, where the legs snap outwardly, the recesses 37 register with the balls 35, thereby unlatching the closure element 10 from the bit body 6. At further pushing down of the fluid injection tool the closure element is integrally pushed out of the bore 20.
When the closure element has been fully pushed out of the bore 20, the diameter of the fluid injection tool 40 determines if fluid communication through an annular orifice between the outer diameter of the auxiliary tool 40 and the bore 20 is possible. Suitably, the fluid injection tool is so arranged that no such orifice is present or that fluid communication through the orifice is blocked.
The injection of fluid into the borehole through the fluid injection tool will be described in more detail with reference to
Reference is now made to
The drill bit 1 connected to the lower end of the drill string 3 is shown in the borehole 2. As shown in
The cementing tool 60 further includes a cementing stinger 62. The stinger 62 comprises a substantially cylindrical conduit 63 of about 50 m length, wherein tool inlets 65 and tool outlets 66 are arranged near the upper and lower ends, respectively. The tool outlets have the form of slits arranged around the circumference of the conduit 63. One tool inlet is arranged at the top of the fluid injection tool so that it can receive a ball or plug from the drill string, other inlets can also be arranged as slits.
The cementing tool 60 further comprises a landing member 69 which is annularly fitted around the conduit 63, between the tool inlet 65 and the tool outlet 66. The landing member has a landing surface 70, which cooperates with a landing seat 72 of the drill bit, so that the passage of fluid along the channel 9a to the nozzle 9 is blocked when the landing member 69 rests on the landing seat 72.
In the landing position as shown in
A number of swab cups 74 are fitted around the circumference of the conduit 63, and prevent fluid flow in the annulus between the conduit 63 and the wall of the passageway past the position of the tool inlet 65. Further, the fluid injection tool 60 is provided with a rupture disc or shear disc 75 which closes off the conduit 63 as long as it is not destroyed, with a fishing neck 76 to which a wireline to the surface can be attached, and with a catcher or landing seat 77 which is arranged so as to catch balls or plugs that are received in the conduit 63, without blocking fluid communication between tool inlet 65 and tool outlet 66.
The drill bit 1 can for example have an outer diameter of 21.6 cm (8.5 inch), with a passageway of 6.4 cm (2.5 inch). The conduit 63 of the fluid injection tool in this case can have an outer diameter of 5.1 cm (2 inch).
During normal operation, the drill bit 1 with the closure element 10 in the closing position can be used for drilling in the borehole 2. During drilling, drilling fluid is circulated down the drill string, through the bit nozzles 9 into the borehole 2, and up to the surface, carrying drill cuttings to the surface. It is assumed that the fluid injection tool is located at the surface in the course of drilling, but it will be clear that the tool can also be stored in the drill string above the drill bit.
We will now consider the situation that a significant loss of drilling fluid is noticed, which loss is caused by drilling into a fractured/porous formation layer. It is desired to cure the losses by blocking fluid flow into the fractured formation by means of cement.
Then, rotation of the drill bit is stopped, and if necessary a short section of the drill string is retrieved, to allow sufficient space in the borehole ahead of the bit. The cementing tool 60 is deployed by pumping down or lowered through the drill string 3 by wireline attached to the fishing neck 76. The connection means at the lower end 61 connects to the latching section 14 of the closure element 10 and unlatches the closure element from the bit body 6. The closure element 10 is fully removed from the closing position by further pushing or pumping the fluid injection tool down, until the landing member 69 lands on the landing seat 72, where it blanks off the openings to the channels 9a.
Then the rupture disc 75 is destroyed for example by applying overpressure, and cement is circulated down in the interior of the drill string, preceded by a ball or plug if desired. The bottom of the cement reaches the drill bit 1, flows in the passageway 8, where it is received by the tool inlets 65, and then passes through the bit and further in the conduit 63, until it reaches the tool outlets 66. There it is introduced into the borehole. The ball or plug is caught in the catcher 77. The blow-out-preventer of the well may be shut to enable the cement to be squeezed into the formation. When the top of the cement in the annulus between the conduit 63 and the borehole wall about reaches the level of the face of the bit body 6, or earlier, pumping of the cement is stopped. The drill string 3 including drill bit 1 and cementing tool 60 are raised sufficiently to ensure that the insert section is above the cement. The drill string and fluid injection tool are cleaned by circulating drilling fluid, while the cement is setting. The hardening of the cement can be tested by setting down the fluid injection tool on the cement plug.
When the cement has hardened sufficiently, the fluid injection tool can be retracted to re-latch the closure element 10 into the closing position. Then, the cement can be drilled out. If fluid losses are cured, the fluid injection tool can be retracted to surface, and drilling can be continued. It shall be clear that the drill bit for use in such a cementing application should preferably be provided with a closure element that has a significantly smaller diameter than the borehole. In that case the cementing tool can also easily be retracted without disturbing the cement setting. In comparison with conventional cementing, the drill string does not have to be pulled out of the borehole for the entire operation of curing losses, and it is also not necessary to first stabilize the borehole by lost circulation material.
The fluid injection tool can further be provided with a means for treating the cement before introducing it into the borehole, so as to influence the hardening process. It is known in the art that additives to the cement can be used to trigger a reaction under downhole well conditions which initiates the hardening. The fluid injection tool can include a storage tank for additives, which is arranged so that additives are mixed to the cement received from the drill string before the mixture is introduced into the borehole. It is also possible that additives are already contained in encapsulated form in the cement received through the drill pipe. In this case, the fluid injection tool can include a shearing device which breaks up the encapsulated additives so that they can react with the cement.
It will be clear, that instead of drilling the cement plug out, the borehole section below the plug can also be abandoned. In the latter case, drilling can be continued in a deviating direction, or the entire drill string can be retrieved to surface.
An embodiment suitable for introducing lost circulation material ahead of the drill bit looks basically similar to the embodiment schematically shown in
In another application of an embodiment as shown in
In yet another application a cement plug is set in the borehole by contacting two cement-forming fluid components only in the borehole outside of the drill string, wherein the first fluid component is introduced into the borehole through the fluid injection tool as described hereinbefore, and wherein the second component is pumped down the annulus between borehole and drill string. This is particularly advantageous in a situation of acute losses of drilling fluid downhole. On the one hand there may be no time or too high a risk for pulling the drill string up; on the other hand the losses allow to pump fluid down both inside and outside the drill string without taking additional measures to prevent excessive pressure build-up. A further advantage is that one can achieve almost instantaneous setting of the cement after contacting of the two cement-forming components, without running the risk of solidifying prematurely in the drill string. In this way the operational risk and time needed for cementing is further reduced.
Two-component cement systems are well known in the art, see for example the book “Well Cementing” by B. E. Nelson, Elsevier Science, 1990, Schlumberger Educational Services, TSL-4135/ICN-015572000, section 6-11.3 (page 6.13) or the U.S. Pat. Nos. 5,447,197 and 5,547,506.
Suitably, a cement slurry is introduced as the first cement-forming component through the fluid injection tool, and contacted with an aqueous or oil-based second cement-forming component which triggers the slurry to set. An aqueous Portland cement slurry as first component and a diesel oil mixed with Bentonite as second component form upon contact a very viscous cementitious mass. It shall be clear that as two-component cement systems in this context are also regarded organic and inorganic two-component systems which have the ability to almost instantaneously form a solid mass when the two components come into contact, such as two component (epoxy) resins, polyesters, silicone rubbers, and calcium carbonate/sodium silicate.
Reference is made to
The jet cleaning tool can for example be used in conjunction with a drilling operation, in order to remove mudcake from the borehole wall, or to clean a section of a casing above a drilled open hole section where a liner hanger, packer or other isolating device is to be installed. Drilling is stopped, the jet cleaning tool is deployed through the drill string and pumped out, thereby unlatching and removing the closure element from the closing position similar to the unlatching of the closure element discussed with reference to
In a different embodiment of a jet cleaning tool (not shown) the nozzles can be arranged to eject fluid jets in other directions. This can for example be useful in a situation where the bit face has become clogged up (balled) with drill cuttings, so that normal drilling performance is seriously impaired.
A shorter version of the jet-cleaning tool, wherein the nozzles in the landing position point towards the bit face can be used to clean the bit face.
In the embodiments discussed with reference to
While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be readily apparent to, and can be easily made by one skilled in the art without departing from the spirit of the invention. Accordingly, it is not intended that the scope of the following claims be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all features which would be treated as equivalents thereof by those skilled in the art to which this invention pertains.
| Number | Date | Country | Kind |
|---|---|---|---|
| 01306310 | Jul 2001 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP02/08206 | 7/23/2002 | WO | 00 | 7/8/2004 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO03/010410 | 2/6/2003 | WO | A |
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| Number | Date | Country | |
|---|---|---|---|
| 20040238218 A1 | Dec 2004 | US |
