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1、<p> 本科畢業(yè)論文(翻譯)</p><p> 英文標(biāo)題Continuous circulation </p><p> drillingsystem</p><p> Continuous Circulation Drill String Sub</p><p><b> Abstract</b>&l
2、t;/p><p> There is an increasing need to drill difficult reservoirs in a cost effective way. Over the past few years Managed Pressure Drilling (MPD) has made it possible to drill reservoirs which have a narrow
3、 window between pore and fracture pressure gradients. </p><p> Before the introduction of MPD techniques, safely drilling and completing these formations was very costly and not always successful. Cycling t
4、he mud pumps off and on for connections affects the pressure and is a major problem for MPD.Techniques and equipment have been developed to make a connection while continuing to circulate the drilling mud to maintain con
5、stant pressure. </p><p> Since 2005, the Continuous Circulation System (CCS) has allowed continuous circulation during connections with traditional jointed drill pipe, by using a chamber around the connecti
6、on. Several companies have developed continuous circulation subs which are threaded between tool joints to achieve continuous circulation without a pressure chamber.</p><p> These have had varying degrees o
7、f success from both an operational and safety standpoint. This paper describes the current MPD market and describes the philosophy adopted for a new side-entry sub.</p><p> Introduction</p><p>
8、 History was made in July of 2003, when the first continuous circulation chamber was tested in prototype form on a land rig. Jointed drill pipe was separated inside a sealed chamber, which was filled with drilling fluid
9、s provided by the mud pumps. The drill string was separated, another joint added, and drilling continued without ever shutting down the mud pumps. After its introduction in 2005, many operators have begun using the conti
10、nuous circulation chamber as a way to drill un-drillable wells</p><p> This means that the bottom-hole pressure must be very closely controlled at all times (even during connections) to avoid either fractur
11、ing the formation, or allowing an influx. The system has worked reliably for the last six years.However, many operators cannot easily accommodate the dedicated crew required to operate the continuous circulation chamber.
12、As operators weighed the benefits against the increase in drill crew, the obvious solution was to provide the same continuous circulation functio</p><p> When looking at continuous circulation chambers, the
13、 barrier to prevent fluid from erupting out of the separated connection is typically a gate valve, with replaceable rubber seals. This barrier is replaceable and inspectable before exposing the crew to a potential leak.
14、The recently introduced continuous circulation subs have all introduced a non-replaceable, non-inspected barrier. The rig crew is also responsible for attaching high pressure connections to the sub during operation.With
15、all thes</p><p> This ensures reliability of the barrier, regardless of how long the sub has been in operation. The entire system is designed with the idea that the driller and existing crew will operate th
16、e equipment just as easily as existing floor equipment (ie, iron roughnecks, pipe rackers, etc). The solution aims to become a standard part of the drilling process; some key contributing features will be described. With
17、 the initial testing phase completed, the results will also be presented and discussed.</p><p> The Concept</p><p> The new continuous circulation sub has been designed with the same attention
18、 to detail as the original continuous circulation chamber. It has hands-free connection of the mud bypass, a replaceable barrier, automated connection integrity checks, and integration into the drilling process with the
19、rig crew.</p><p> Hands free connection – When using the continuous circulation chamber, the drill pipe was fed through several ram type Blow Out Preventer (BOP) style seals. This provided a sealed chamber
20、around the connection. These seals were positioned at well center and were always in position, simply retracted when not in use. This posed a problem during operation, the floor was not clear for access. It is desired to
21、 improve the access to the well center when drilling ahead or otherwise not continually circ</p><p> potentially explosive environments. Others have used threaded plugs, or clamp-on housings. All of these a
22、re potentially exposing the rig crew to increased danger. The new continuous circulation sub is a totally hands-free unit for this reason. The mud is transported from the standpipe using industry accepted swivel joints a
23、nd piping, to allow movement. The sub is converted from drilling mode to side entry mode using very simple, easy to visually inspect, movements. The exact layout of the moveme</p><p> Replaceable barrier -
24、The novelty of the sub design is based on the barrier, which is a round ball, with sealing characteristics (ie, “soft” compared to the seat). This presents a perfect sealing surface, which can be re-used multiple times.
25、The ball is inserted through the side of the sub and shifted “up”, much like a shuttle valve, using differential pressure. Minimal amounts of pressure differential will be sufficient to shift the ball (a small test fixtu
26、re was used to prove this theory). Wit</p><p> Testing of the barrier - All continuous circulation processes utilizing a chamber have the advantage of being able to test the barrier for leakage prior to bre
27、aking the connection. The new circulation sub has a similar ability by utilizing two mud lines; one provides pressure and flow from the mud pumps,and the other is primarily a vent line. By having two high pressure access
28、 points to the connection, it is possible to have a “safe” pressure differential. If a leak is detected, the process can </p><p> Rig crew operation – The first continuous circulation chamber was an all-inc
29、lusive tool; having a pipe handling system, spinning wrench and torque wrench, pipe slips, and even functioning as a mud bucket. The rig has provisions for all of these operations, either manual or automated. It was foun
30、d in operation that the rig crew had difficulty in changing their work flow to use the newly combined functionality. In the new continuous circulation sub,and existing circulation subs, the crew uses all </p><
31、p> Initial Testing</p><p> Certain elements of the design have been developed based on the results of testing. The replaceable barrier has been tested using a flow fixture with various arrangments of va
32、lves to simulate the rig’s stand pipe manifold. The flow fixture was transparent where the ball enters the sub and seals. Water is flowed through the setup to simulate very thin drilling mud. The timing of the valves ope
33、ning and closing plays a role in how efficiently the ball is shifted into the circulation sub. It was a c</p><p> During testing it was found that the ball can be shifted with very little pressure different
34、ial and that velocity appears to be the largest influence on the operation. Once seated the pressure differential required to generate a seal is also negligible. Another development was the position and shape of the inte
35、rnal geometry, such that the ball is encouraged to travel “up” into the sub, even at very low transition speeds. A pressure gage on the downstream side of the sub registered almost no pres</p><p> The Marke
36、t</p><p> Managed Pressure Drilling has gained a lot of momentum in the last six years since the commercial introduction of a continuous circulation chamber in 2005. The demand for these chambers is growing
37、, from its initial applications in the North Sea and the Mediterranean Sea, to offshore Gulf of Mexico and Brazil. A 2011 survey published in the Journal of Petroleum Technology reached an industry consensus that 40% of
38、offshore wells would be using MPD within five years.There is a large demand onshore </p><p> The Continuous Circulation System: An Advance in Constant Pressure Drilling</p><p><b> Abstra
39、ct</b></p><p> In late July 2003, for the first time since rotary drilling was introduced, a section of hole was drilled without interrupting circulation while new joints of drill pipe were added to t
40、he drill string. This was made possible by the use of the Continuous Circulation System (CCS), developed over the previous three years by a Joint Industry Project (JIP) managed by Maris International, funded by six major
41、 oil companies (Shell UK, BP, Statoil, BG, Total and ENI), Coupler Development Ltd (CDL) and Va</p><p> ?Elimination of negative and positive pressure urges when stopping and starting circulation to make a
42、connection</p><p> ?No rig downtime to circulate out cuttings to clear the bottom hole assembly before making a connection</p><p> ?Improved drilling fluid management</p><p> ?El
43、imination of kicks on connections</p><p> ?Improved control of Equivilent Circulation Density (ECD)</p><p> ?Reduced Total Connection Time (TCT)</p><p> ?Reduced chance of stuck
44、pipe during a connection</p><p> ?No downtime in HPHT wells to circulate out connection gas</p><p> ?Reduced wellbore “breathing” or “ballooning”</p><p> ?Overall improvement in
45、hole condition</p><p> ?Improved safety around the rig floor Potential applications of the system are in drilling:-</p><p> ?Extended reach (ERD) and horizontal wells</p><p> ?Hi
46、gh Pressure/High Temperature (HPHT)wells</p><p> ?Near or underbalance (UBD) wells</p><p> ?Deepwater wells</p><p> The CCS is also a potential contributor in achieving the “One
47、Trip Well”, Journal of Petroleum Technology (JPT) May 2004. The concept was presented in the paper “Continuous Circulation Drilling” by L. Ayling at the Offshore Technology Conference in May 2002. Introduction The CCS re
48、lies on advancements made over recent decades in Top Drives, drill pipe handling equipment, BOP ram seals, Iron Roughnecks and computerized drilling control systems.The heart of the CCS is the Continuous Circulation Co&l
49、t;/p><p> The Concept</p><p> The Coupler (Fig 1) is effectively a pressure chamber located on the rig floor over the rotary table, through which the drill string passes and which seals around th
50、e drill pipe pin and box during the connection process.To make a connection, drilling fluid at circulating pressure is introduced into the pressure chamber, (Fig 2) equalizing the pressure inside and outside the drill st
51、ring, the connection is broken and the tool joint pin backed out and raised clear of the box. The pressure chamber </p><p> The pressure in the chamber is bled off, the seals opened and drilling is re-start
52、ed.</p><p> The Project</p><p> The project to develop the CCS was set up in four phases: Phase 1 - Preliminary Engineering - to develop the concept into a basic design, identifying any challe
53、nges to be investigated during the next phase of detailed engineering and to eliminate any “showstoppers”.Phase 2 – Detailed Engineering - to prepare the engineering design for construction of the prototype Coupler and a
54、ssociated equipment that form the CCS. This included testing of components.Phase 3 – Prototype Construction – to manufac</p><p> During a connection the drill string would be landed in slips in the rotary t
55、able and a snubbing device would be needed to grip and control the movement of the disconnected joint into or out of the upper chamber against the</p><p> upthrust of the circulating pressure. The “Snubber”
56、 would be connected to the top of the upper BOP body with hydraulic cylinders and would also contain the mechanical means to apply the torque to make/break and rotate the connection. The upper and lower BOP bodies would
57、be fitted with side connections and valves to allow drilling fluid circulation and pressure bleed off during the connection cycle. For protection and transportation, a protective framework would be fitted</p><
58、p> around the Coupler.The original Coupler concept considered designs for use with both Top Drive and Kelly drill string rotation systems. From the start of the project it was obvious that the Top Drive was the most
59、beneficial and practical application and work on a Kelly drive system was stopped.To complete the system and make the Coupler a useable tool,additional components were identified (Fig 3): -</p><p> ?Mud Div
60、erter Manifold - connecteded into the discharge line between the mud pumps and the standpipe manifold. Switches mud flow between the Top Drive and the Coupler during the connection process.</p><p> ?Extensi
61、on/Wear Sub - attached below the Top Drive. Connects to the top of each new stand/joint to correctly position the tool joint within the Coupler to make/break the connection.</p><p> ?Top Drive Connection To
62、ol. Allows the Extension/Wear sub to be made up to and broken out from the top of a stand in the derrick.</p><p> An independent Hydraulic Power Unit(HPU) and electro-hydraulic controls operated by the Dril
63、ler using a touch screen system.On completion of the preliminary design, a Hazard Identification and Risk Assessment (HAZID) meeting was convened by an independent assessor. Some safety considerations and operational con
64、cerns were identified to becarried forward into the etailed Engineering phase.</p><p> Challenges</p><p> During the Preliminary Engineering Phase a number of technical challenges to be addre
65、ssed in Phase 2 - Detailed Engineering were identified. These included: -</p><p> ?Accurately positioning the tool joint within the Coupler</p><p> ?Accurate control of tool joint make up/brea
66、k out to minimize the potential for</p><p> thread damage</p><p> ?Assessment of ram seal wear with both axial and rotary drill pipe movement and</p><p><b> pressure</b&
67、gt;</p><p> ?Minimising potential damage from gripping of drill pipe body by Snubber</p><p> ?Development of suitable thread lubricant to work in flowing mud environment</p><p>
68、?Assessment of erosional effects of circulation through open tool joint box</p><p> ?Control of rotary table slips Applications of the CCS</p><p> Since the inception of the development projec
69、t, potential applications have been investigated to determine where the most benefit will occur when drilling with continuous</p><p> circulation. Reducing Total Connection Time (TCT) – the time from stoppi
70、ng drilling to recommencing drilling – is the most basic benefit, particularly on rigs with a high daily operating cost. At the other end of the scale is the ability to drill a pressure sensitive section without imposing
71、 the pressure surges associated with stopping and starting circulation that</p><p> apply under current drilling conditions (Fig 4). The development of the CCS also comes at a time when more ambitious and t
72、echnically challenging wells are being attempted where continuous circulation, with steady downhole pressure and improved ECD control, is integral in their</p><p> success.Potential applications where the u
73、se of the CCS would be beneficial were identified as: -</p><p> Extended Reach (ERD) – Horizontal Wells.Uninterrupted circulation while drilling long sections of highly deviated hole will allow continuous m
74、ovement of drilled cuttings and minimise their build up in the annulus. Preventing the development of “weirs” will improve hole conditions and considerably reduce the possibility of stuck pipe occurring on connections. T
75、he cleaner annulus will also reduce rotary torque and allow improved directional control of the drill</p><p> string. The requirement for wiper trips to clean out the open hole can be minimised or even elim
76、inated.</p><p> Deepwater Wells. The ability of rigs to drill the unstable formations immediately below the sea bed where water flows occur, will be greatly improved by maintaining continuous circulation. T
77、he occurance of hole collapse and stuck pipe conditions can be minimised. Stuck pipe incidents</p><p> above and below salt intrusion “rubble” zones could be reduced</p><p> Underbalanced Dril
78、ling. Stopping circulation to make a connection when drilling underbalanced, is the source of considerable lost time. Bleeding down and re-pressuring the drill string consumes rig time as does re-balancing the system onc
79、e circulation is re-established (Fig 5) There is also the strong possibility of “killing“ the well and damaging the reservoir when circulating out fluids and cuttings that have accumulated in the annulus while circulatio
80、n has been</p><p> interrupted. Underbalanced drilling utilising the CCS will not only speed up connection time but will allow a steady circulating pressure regime to be established, eliminating the annulus
81、 pressure spikes generated by stopping/starting circulation and minimising the risk of damaging the exposed</p><p> reservoir. To maintain underbalanced conditions a trip valve must be included in the last
82、casing string. To protect the reservoir, the drill string can be tripped out as far as the trip valve maintaining continuous circulation, before setting aside</p><p> the CCS to pull the BHA.</p><
83、;p> NarrowPorePressure/FracturePressure Gradient Wells. Utilisation of the CCS allows continuous circulation to be maintained throughout a hole section and for the ECD to be controlled by adjusting circulation rate a
84、nd drilling fluid density. This will enable the more efficient drilling of hole sections where the pore pressure and formation fracture gradients are close (narrow pore pressure/fracture pressure window).Without continuo
85、us circulation the pressure surge each time the pumps are started af</p><p> “breathing” is discussed in SPE 71368 “Drilling Fluid Losses and Gains: Case Histories and Practical Solutions” by Tare etal and
86、in “Anatomy of a Ballooning Borehole using PWD” by</p><p> Ward and Clark.</p><p> Pressure Sensitive Wells. The loss of ECD when stopping circulation to make a connection can cause problems i
87、n formations sensitive to pressure change, such as shale and salt. Removing the ECD while a connection is being made allows these formations to relax and slough or squeeze into the well bore and can result in stuck pipe
88、and/or loss of the hole. Drilling with the CCS in place and eliminating the stop/start pressure surges will reduce well bore stress and help to</p><p> maintain formation stability.</p><p> Ci
89、rculate/Drill-in Liners. Where hole conditions liner lap will also be continuously swept eliminating the build up of cuttings/debris which can restrict or block the efficient of cement. Continuous circulation with the CC
90、S can also reduce the incidences of stuck pipe, which occur with drill-in liners with tight annular clearance.</p><p><b> Safety. </b></p><p> Drilling with the CCS offers an impro
91、vementin safety by the elimination of kicks while making a connection and the accompanying possibility of stuck pipe occurring while killing the well. Automation of the system removes personnel from the connection proces
92、s, improving the level of safety around the rig floor.Phase 2 – Detailed Engineering and Testing The objective of this phase was to design a CCS that is:-</p><p> ?stand alone and can be installed with mini
93、mal interference with the rig</p><p> ?of minimum height and weight</p><p> ?simple to mobilize and rig up/down</p><p> ?controlled by the driller through an automated control sy
94、stem</p><p> ?safe to operate</p><p> To achieve these objectives the CCS was designed with five main components: the Coupler, the Mud Diverter Manifold, the Top Drive Connection Tool (TDCT),
95、the control system and the Hydraulic Power Unit (HPU).The Coupler This is the heart of the CCS. The Coupler is a pressure</p><p> chamber comprising three 9” x 5000psi wp blowout preventer(BOP) bodies with
96、pipe rams in the upper and lower bodies and blind rams in the middle. (Fig 6) The lower pipe rams are inverted. For quick and easy access to change rams or ram seals, quick opening Shaffer NXT doors are fitted to each BO
97、P body. The Snubber is mounted above the chamber and connected to it by four hydraulic rams, which provide the vertical restraining force to control the movement of drill pipe</p><p> into and out of the pr
98、essurized chamber. Within the Snubber are the grips which contact the drill pipe body and transmit vertical and rotational forces to the pipe. The Snubber contains hydraulic motors to spin the pipe into or out of the con
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