Patent Application
20150308205
The present disclosure relates to an apparatus and method for accommodating surge and swab experienced at the bottomhole assembly (BHA) of a drill string during tripping procedures from a marine platform. More particularly, the disclosure provides for a surge relief system carried by the drill string adjacent the drill bit to minimize damage to the formation that could be experienced as a result of movement of the platform during tripping procedures.
Drilling for oil and gas off-shore is completed from one of two general types of drilling platforms, namely, platforms that are supported by the sea floor, such as fixed drilling rigs and jack-up drilling rigs, or platforms that float near or on the surface of the water, such as drill ships, spar, semi-submersibles and the like. Although drilling operations conducted from these types of drilling platforms are similar, at least one major difference exists: floating platforms move with the waves of the sea and wind, while fixed or jack-up drilling rigs remain fixed to the sea floor.
The movement of drilling platforms caused by waves and wind presents a unique problem in drilling with these types of platforms. Most common among these problems is that of heave on the drill string during drilling, namely movement of the drill string up and down with the waves during drilling operations. In particular, as the floating rig moves up and down, the drill string extending below the rig will also move up and down and correspondingly, the drill bit at the end of the drill string will move as it is engaging the formation. For a drill bit to perform as efficiently as possible, the desired or optimum weight on the drill bit (“WOB”)—i.e., the downward force applied to the bit—must be kept as constant as possible. Heave, however, removes weight from the drill bit as the ship or rig rides to the crest of a wave, and puts weight back on the drill bit as the ship or rig rides down into the trough between waves.
This fluctuation in the force applied on the drill bit severely hinders an operator's ability to drill the well bore.
To account for this problem associated with heave, floating drilling platforms are equipped with heave compensation systems. The heave compensation systems are typically in the form of an active heave drawworks system or a system that is an integral part of the drilling derrick or mounted directly on an extension of the traveling block. Such systems are intended to protect against the effects of heave during drilling operations to ensure appropriate WOB is maintained.
Heretofore, little, if any, attention has been focused to the effects of heave on a drillstring as it is tripped into and out of a wellbore. The drill string, and in particular, the bottom hole assembly and drill bit will experience upward and downward motion as it moved tripped in and out. This will cause the bit and BHA to act as a piston on the fluid in the wellbore, driving the wellbore fluid to create surge and swab effects on the surrounding formation. These effects can severely damage the formation by alternatively applying excess pressure to the formation by forcing wellbore fluids into the formation as the drill string is driven down into the wellbore by wave motion, in which case, wellbore fluids surge out into the formation, and forcibly drawing formation fluids out of the formation into the wellbore as the drill string is pulled up in the wellbore due to reduced wellbore pressure as the drill string is drawn up. Swabbing is generally considered harmful in wellbore operations, because it can lead to kicks and wellbore stability problems.
Accordingly, what is needed is a system to minimize the effects of swab and surge caused by heave on a drillstring as it is tripped into and out of a wellbore.
The foregoing disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” “uphole,” “downhole” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the apparatus in use or operation in addition to the orientation depicted in the figures. For example, if the apparatus in the figures is turned over, elements described as being “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
With reference to
With reference to
Drill bit 28 has a proximal end 48 and a distal end 50. Drill bit 28 is also provided with an annulus 52 that extends at least partially through drill bit 28. It will be appreciated that annulus 52 may be open to the wellbore 16 in any of a variety of known configurations, such as via jets (not shown) disposed in the body of drill bit 28 or other openings, such as opening 54, so as to supply drilling mud to wellbore 16. The embodiments described herein are not limited to a particular type of BHA assembly or drill bit or configuration of the two; rather, the valves 34 and passages 32 may be accordingly disposed in many different types of BHAs and drill bits disposed on a drill string.
In any event, the surge relief system 30 includes a first flow passage 32a defined in drill bit 28. First flow passage 32a has a first port 54 at the distal end 50 of drill bit 28. In certain preferred embodiments, first port 54 is axially disposed so as to open towards the bottom of wellbore 16 when drill bit 28 is positioned therein. In certain preferred embodiments, first port 54 is the opening for annulus 52.
First flow passage 32a also has a second port 56. Second port 56 is preferably positioned between the distal end 50 of drill bit 28 and the second end 40 of BHA 36, although it should be understood that that first flow passage 32a may have any position or orientation so long as it permits pressure relief from flow through first port 54 in drill bit 28. In certain preferred embodiments, second port 56 is disposed at proximal end 48 of drill bit 28, while in other embodiments, second port 56 may be along the length of drill bit 28. In yet other embodiments, first flow passage 32a may extend into BHA 26, in which case, second port 56 may be positioned on the exterior 48 of tubular 36. A first relief valve 34a is disposed in first passage 32a between the first and second ports 54, 56, respectively. In certain preferred embodiments, valve 34a is adjacent second port 56.
While surge relief system 30 may simply utilize a single passage with a relief valve disposed therein, surge relief system 30 may further include a second flow passage 32b. Although it may be defined in drill bit 28 in certain embodiments, preferably second flow passage 32b is disposed in tubular 36 between the first end 38 and second end 40. Second flow passage 32b has a third port 58. Third port 58 is preferably positioned between the first and second ends 38, 40, respectively, of tubular 36. In preferred embodiments, third port 58 is uphole from second port 56 and defined in the exterior surface 48 of tubular 36. Preferably, second flow passage 32b is in fluid communication with first flow passage 32a so that flow through the system of passages 32 from first port 54 sequentially encounters second port 56 and then third port 58 for discharge of fluid into the wellbore 16 as will be described.
A second relief valve 34b is disposed in second passage 32b. In certain preferred embodiments, valve 34b is adjacent third port 58.
Finally, surge relieve system 30 includes a valve 60 to block back flow along the annulus of the drill string 24. In certain preferred embodiments, valve 60 is a non-return valve, such as a float valve, ball valve, flapper valve or the like, that is actuated by backflow through the drill string 24. In certain preferred embodiments, valve 60 is positioned in the annulus 42 of tubular member 36, preferably adjacent the first end 38 uphole of passage 32b and relief valve 34b.
With on-going reference to
A third relief valve 34c is disposed in third passage 32c. In certain preferred embodiments, valve 34c is adjacent forth port 62.
Moreover, the passages 32a, 32b and 32c, may be angled relative to the axis of the drill string 24 to control flow of the wellbore fluid therethrough. For example, as illustrated by passage 34a, a passage may be angled uphole so that uphole movement of the drill string will drive wellbore fluid through port 56 into the passage, down and out through the first port 54. Likewise, as shown in
As illustrated in
With on-going reference to
In certain preferred embodiments, surge relieve valves 34a, 34b and 34c may have adjustable activation pressures or otherwise may be selected to activate upon a certain pressure threshold.
Preferably, activation pressures for all of the valves 34 would be higher than the mud circulating pressure utilized during drilling. Moreover, the activation pressures for valves 34a, 34b, 34c may be set to sequentially higher activation pressures. For example, the activation pressure of valve 34a may be lower than the activation pressure of valve 34b, which may likewise be lower than the activation pressure of valve 34c. Thus, as flow induced by heave progresses axially along the passage 34 system from first port 54, the activation pressures for valves 34 becomes increasingly higher, thereby permitting the flow to be managed. In this regard, one or more transducers 70 may be disposed in the passages 34 and valves may be activated utilizing a control system 72 either positioned locally or at the surface. Additional valves 34 in additional flow passages may likewise be selected to activate based on a predetermined fluid pressure. Finally, surge relieve valves 34 may be one-way or two-way. As described below, in certain embodiments of the disclosure, flow through the valve in one direction is utilized to minimize the effects of surge on the formation, while flow through the valve in the opposite direction is utilized to minimize the effects of swab on the system.
Thus, to utilize a surge relief system 30 during the drilling of a wellbore from an offshore floating platform, a drill string 24 having a BHA 26 and drill bit 28 with the surge relief system 30 is positioned in a wellbore 16. The system is utilized during periods when drilling, i.e., engagement of a drill bit with the formation, has been suspended. In this regard, the system is most useful during dripping of the drill string into or out of the wellbore. During such a process, downward heave on the drill string resulting from wave action will force the drill bit down into the wellbore fluid. The wellbore fluid will be forced through the first port and driven into the first passage. Once the pressure of this fluid in the first passage reaches a predetermined threshold, the first relief valve is actuated, allowing the flow to pass through the second port and back out into the wellbore. Likewise, as wellbore fluid is driven into the second passage, and then the third passage, the second and then the third relieve valves will actuate, to allow the flow to pass through the corresponding ports back out into the wellbore.
To the extent this flow passes into the lower annulus, the backpressure valve can be activated to prevent the fluids from passing pack up the drill string.
Likewise, as upward heave on the drill string pulls the drill bit and BHA upward, wellbore fluid can pass through the second, third and fourth ports into the surge relief system where the fluid can be forced out of the first port in the drill bit, thereby minimizing the creation of low pressure in the wellbore by virtue of a sudden upward movement of the drill string.
Although the number, locations and orientations of the various flow passages and ports have been illustrated herein, certain embodiments of the disclosure are not limited to the illustrated numbers, positions and orientations so long the overall surge relieve system 30 is disposed to pass flow of wellbore fluids through the system of one or more passages and ports to minimize the effects of surge and swab in the wellbore. Thus, flow passages may take various shapes or routes through the BHA and drill bit. Likewise, ports for the flow passages may be positioned at a number of locations along the overall BHA/drill bit assembly without limiting the disclosure.
While the foregoing disclosure is directed to the specific embodiments of the disclosure, various modifications will be apparent to those skilled in the art. It is intended that all variations within the scope and spirit of the appended claims be embraced by the foregoing disclosure.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US12/72116 | 12/28/2012 | WO | 00 |
