P & A
BOP & Wellhead Jetting
The DAV MX™ CircSub has been used many times for BOP and wellhead jetting applications, it is ideal for removing drilling debris from these important barriers when pulling out of hole. Efficiency is optimized by doing this in the normal course of exit eliminating the need for a special trip, especially useful in deep water.
Double benefit is provided as the installed DAV MX™ can also be deployed during the drilling phase, secure in the knowledge that it will open again on demand to jet later. It’s this ultra-high reliability that allows it to be cycled by the user with confidence for multiple applications.
2015 - GOM, 23,620ft, activated for hole cleaning, then dry tripped and finally jetting the wellhead. 2 x SDD (1 for Hole Cleaning, 1 for Jetting / Tripping). This demonstrates the diversity of the circsub, saving time during tripping and removing the need to run in with specialist wellhead jetting assemblies.
2015 - GOM, 27,770ft, activated for hole cleaning, dry tripping, and jetting the BOP. 2 x SDD (1 for Hole Cleaning, 1 for Jetting/ Tripping).
2010 - In one 58° well three separate bypass cycles were required to cure losses at around 14,755ft before the section drilling was completed. After each pill was spotted the valve was cycled shut, with a fourth cycle deployed on reaching the BOP’s on the way out.
With the DAV MX™, cement can be pumped safely into the annulus without the risk of contaminating the lower BHA. The tool is designed to be robust and simple, with minimal cavities that could be contaminated, Churchill use single use Smart Darts™ as opposed to J-slots. The latch and seal protection which is unique to the Smart Darts™ guarantees you won’t see LCM in your BHA. A cementing sequence can be performed using the tool, with the closing cycle naturally flushing any potential contamination to the BHA out of the ports, prior to the resumption of thru-bit circulation.
The resilience and reliability of the Smart Dart™, combined with it is unique latch and seal protection, provides a stable barrier against cement ingress into the BHA, which in turn delivers surety of closing after the cementing cycle. The tool also offers class-leading resilience when thru-bit cementing is unavoidable.
In 2011, whilst drilling on a deepwater exploration well an operator used the DAV MX™ to pump a significant amount of cement into the annulus to cure massive losses. The DAV MX™ was activated whilst RIH at 5,293ft with the ADD, activating the valve when pumping, and preventing any through flow of cement to the BHA. The tool was then deactivated as pumping was stopped, allowing the operator to RIH and drill ahead having safely stabilized the well.
Once taken, a valuable core sample can be protected from excessive circulation by opening a DAV MX™. This allows users to circulate above the core, and get a clean exit from hole, without compromising the sample taken.
In 2012 the DAV MX™ was used for a successful core barrel isolation. By using the 100% bypass Standard Diverter Dart with its lock-open capability, pulling out of hole could be done in the "open" position to deliver a safer and faster dry trip.
Due to the flexibility of the MX™ system, the DAV MX™ can be easily customized for users requiring a low shear closing. The number of shear pins used in the make-up of the Smart Darts can be reduced, allowing for a shear out at pressures as low as 600psi.
Churchill can offer two solutions to differential sticking, firstly a slightly unconventional one to release the pipe from the stuck formation and secondly recovery options when free-up attempts fail.
Reducing the mud-weight in the well can reduce or even remove the differential forcing the pipe onto the formation. If it is safe to do so, a quick way to reduce the mud-weight is to pump down a lighter mud into the string and then allow the heavier annulus mud to U-tube it back out of the string. This effectively lowers the head in the annulus and reduces down-hole pressure. Using one of our unique lock-open darts to hold the valve open will allow this U-tubing to occur, it can also be used to relieve pressure by pumping in the lighter fluid. This method has traditionally been achieved by perforating the drill-pipe to facilitate the displacement.
If free-up attempts fail, stuck pipe can be released from hole above the sticking point using a HyPR™ dart to sever the string. (See product page).
Circulating a mud displacement through the bit can be inefficient. It is often much faster to use bypass and with improved hydraulics achieve a much quicker result.
Prior to August 2015 the DAV MX™ CircSub had completed 23 accelerated displacement operations. Having displaced the lower BHA through the bit, operators then open the DAV MX™ to displace directly into the upper annulus, bypassing the bit more and circulating with much better hydraulic efficiency.
In an MPD off-shore displacement in 2014, the DAV was cycled 4 times at depths of around 13,500ft to make various displacements ranging between 11.7 to 15.9ppg. When complete a fifth cycle was used for boosted hole-cleaning prior to pulling out of hole.
The DAV MX™ is unique in its class because Smart Darts™ are highly resilient to heavy muds. Field proven up to 18.6ppg there is no practical limit to the weight of mud that can be securely bypassed.
Dry Tripping has many safety and performance benefits and again the lock-open feature of the DAV MX™ system provides a unique cost-saving solution. In fact this application is probably the most commonly exploited benefit that operators get from the system, with the valve having being “tripped-out” open on no less than 92 occasions prior to September 2015.
The valve is commonly deployed at the end of the run for boosted hole cleaning, activated with either the Split-Flow or Standard Diverter Dart. Simply skipping the closing cycle will deliver a faster and safer dry trip. This confirms the DAV MX™ as the best value in class with two application savings for the cost of a single tool in the string.
GoM, 2015, 29,896ft. a Standard Diverter Dart was left holding the tool in the open position after hole cleaning to POOH and allowing fluid to drain from the drill-string.
Hole cleaning is a common challenge in angled or extended reach sections, where annular velocity (AV) is insufficient to flush the cuttings from the hole efficiently. With AV hampered either by BHA restrictions or by ECD or pressure window considerations a bypassing CircSub is often the go-to solution.
Hole cleaning is the number one application for the DAV MX™ and accounts for around a third of all dart activations. By using the unique lock-open darts (Standard or Split Flow), users also have the opportunity of tripping out dry by leaving the valve open after the bypass cleaning interval.
Additionally, by using the Split Flow Dart to lubricate and cool the BHA, further efficiency can be gained by spinning the pipe to increase agitation of the cuttings. Measured flow rates from these applications indicate that the SFD delivers around 15% of flow to the bit, providing sufficient flow to maintain temperature control whilst sustaining continuous rotation. The multiple dart configuration options give the operator maximum flexibility in selecting an optimized hole-exit strategy.
2015 - 29,896ft., Gulf of Mexico, hole-cleaning for 4 hours, SDD
2015 – 12,538ft., Norway, hole-cleaning 22% flow to bit, SFD
2015 – 27,770ft., Gulf of Mexico, hole-cleaning followed by BOP jetting whilst POOH, 2 x SDD
2014 – 11,715ft North Sea, Hole Cleaning whilst reducing ECD, SFD
2014 – 13,415ft, North Sea Hole Cleaning and displacements (5 Activations, HPHT), SDD
2013 – 26,012ft., Gulf of Mexico, hole-cleaning and reamer bypass (bypass interval 64 hours), SDD
2011 – 14,500ft, North Sea, Hole Cleaning, SFD
2010 – 13,878ft., Ghana, hole-cleaning and anti-swab POOH, SFD
Liners & Screens (In-hole Drifting)
As the well nears completion, the sunk costs rise and the cost of failure escalates. Before installing the liner or screen it is required that the drill pipe be drifted to ensure that it is clear for setting balls and or cement plugs. This is because it may have become compromised during the drilling operations.
Virtually since drilling began, operators have been drifting their pipe, however depending on the method normally deployed the Drift Catcher method can save a lot of time, increase process visibility and significantly reduce operational risk.
Note pipe obstructions are not common, but their cost is so high that they need to be checked for. Further note that it has been known for ad-hoc drifting methods to cost a well by actually introducing obstructions to pipe that would have otherwise been clear.
Used since 2003 with over 1500 runs by over 60 different operators, the system has become the preferred method for many rigs. A recent GoM operator based study concluded that a saving of over a minute per stand can be achieved by not having to drift manually while tripping the pipe in or out of hole. This means that with the DC downhole drifting method, over one and a half hours can be saved per 10,000ft of drillpipe tripped out of hole.
After hole-cleaning and tripping from hole, curing losses is the next most common dart application for the DAV MX™ CircSub. That being said the impact of severe losses on Well Control are such that the tool is very often run as a contingency for insurance for loss situations which are successfully avoided. Including these “non-activated” contingency applications in the figures would, in all probability, make it the number one application for the tool. This application applies equally to both use of LCM or cement.
Low Cost: As contingency insurance, the tool is the most economical solution because it is simple, doesn’t require a service hand, has the largest straight thru-bore in class and the highest level of dormancy integrity available. So when not activated it has the least impact on the program of any tool on the market.
Speed: Not only can they be pumped down quickly but the steel darts will have dropped several thousand feet towards the tool by the time the top-drive is made back up. When losses occur, there is no tool that can deliver bypass faster, saving the operator both time and mud. Firstly with a single shot high speed activation the time to activate is extremely rapid. Secondly there is a very precise and clear opening stroke so spotting can start immediately; and thirdly anti-blow-thru means there is very little danger of secondary cycling attempts being required and causing NPT.
Isolation Integrity: Keeping contamination out is the main purpose of application. Unique latch and seal geometry means that the jewelry is fully protected from any LCM ingress by the darts (all darts except SFD). The darts are resilient to U-tubing, which is quite common with heavy LCM, and can’t be unseated as a barrier. Furthermore the high shearing safety factor in the darts means that even the heaviest muds will not be able prematurely shear them out of the way.
Multiple Loss Intervals: On some sections, multiple curing cycles are often required, this where simplicity and reliability comes to the fore. With these single use high integrity darts in a simple and rugged tool design, the sub is maintained in optimum condition for secondary operations.
Soft Shear: Where there are concerns that shear-out may re-fracture the formation after curing, the Smart Darts can be easily customized to shear out at lower pressures. The number of shear pins in the MX™ mechanism can be reduced to allow a shear out at a much lower pressure (~600 psi), yet is still protected from premature blow-thru. This soft-shear option is available on request and is also well suited to coring applications.
2015 – 5064ft, North Sea, Dynamic losses of 121bbls/hr cured, LCM, 43bbls,10.9ppb, SDD x 1
2015 – 11,509ft, Ivory Coast, Spotting LCM, 121bbls,
100ppb, SDD x 1
2014 - 4,765ft, Saudi Arabia, Dynamic Losses of 253bbl/hr cured, LCM, 700bbls, 200ppb, SDD x 3
2014 – 15,644ft, GOM, Spotting LCM, 170bbls, 200ppb, SDD x 3
2014 – 9,507ft, English Channel, Static/ Dynamic losses of 40/200bbl/h cured, LCM, 90bbls, at 98°, SDD x 2
2013 – Southern Italy, Static/ Dynamic losses of 500/1000bbl/h cured, LCM, 10 course pills spotted, SDD x 2
2010 – 14,735ft, North Sea, Static/ Dynamic losses of 30/180bbl/h cured, LCM, 217bbls, 224ppb, ADD x 3
Milling & Mud Shearing
There are a couple of useful applications of our tools that make the milling process more efficient. The first issue is that having flow through the mill is not always convenient when tripping or hole-cleaning. The second is that milling fluid has to be conditioned because of its viscosity properties which carry the swarf out of hole.
Tripping bypass is easily obtained by using one of the lock-open darts, usually the SFD, and if required a tool can be supplied with a lock-open dart pre-installed. At TD, a closing dart can be deployed quickly to activate the mill before a second cycle is used to bypass and accelerate hole-cleaning. As is often desirable the valve can be left locked open for a fully relieved dry trip from hole with the bit bypassed.
Swarf is obviously a highly destructive form of debris, one which is able to contaminate and damage both top-side and down-hole equipment very quickly. Our experience with this application and some unique features on the darts and tools will minimize the operator’s risk of being affected by swarf contamination. Please contact us for more details on this application.
In 2013 an operator successfully bypass the milling assembly using the SDD, before thinning the mud from 15.4 to 14.2ppg by circulating it for 25 hours. Region - North Sea. Activation depth - 15,675ft. Opening time - approx. 15 minutes.
The Mud Shear Sub™ has been run 16 times by 4 different operators and cuts shearing times by around a half. This sub is extremely compact, convenient and quick to install just below the rotary table. When combined with bypass it delivers extremely rapid and efficient shearing with massive time savings. Mud is brought into condition far more quickly than with conventional methods and so milling can commence much earlier.
In a 2013 case study across 7 wells during a P&A operation, the sub delivered approximately 28 hours of time saved on the platform. Region - North Sea.
Motors, Mills, Reamers & Turbines
Cutting assemblies which consume a lot of flow power or which are activated by flow, can impede some of the phases of a section’s operation. Typically this can be either running into or out of the hole or during a hole-cleaning session. It can therefore be extremely useful to have bypass valve in the string to take control over the flow path and the hydraulics. This will produce both a quicker operation and or reduce some of the risks associated with running the cutting tool.
Dart lock-open is a very useful option for running some of these devices into or out of the hole in the de-activated state. The SFD, most commonly, will fully de-risk and accelerate the trip with pressure fully relieved as the string moves through the hole.
Reamer Bypass - 2013 - 26,012ft, Gulf of Mexico, angles up to 44°, SDD
Motor Bypass – 2014 – Central North Sea, SFD
Mill Bypass (used in conjunction with Mud Shear Sub) – 2013 – 15,675ft, Central North Sea, SFD
Recovering circulation will regain primary well control and with a DAV MX™ CircSub above the pack-off point (and below 60° degrees in angle) it is possible to do so quickly. We have a 100% success rate when attempts were made to regain circulation in these rare scenarios. We also have a strong track record in helping users regain circulation after the string becomes plugged, this is however highly dependent upon pressure and mud volume.
Pack-off: In most cases the pack-off point is on the stabilizers, so positioning the valve above them will mean that when the valve opens circulation has been regained. Once regained further attempts can be made to free the pipe until such time as a severing decision is required.
Plugged string: As with pack-off, sufficient compression in the fluid between the valve and the plugged point must be available to allow the piston to travel so the ports can open. Whilst this is possible in a plugged string this is more restricted as fluid volumes are smaller and there is no access to any elasticity in the formation. However once opened, recovery prospects are good if the wellbore has remained in condition.
Drop the ball: Each tool is supplied with an Emergency Opening Ball (EOB), a steel ball is proven to have the best chance of reaching and seating in the tool under gravity alone. For lower angles (below 50°) there is an optional retrievable diverter dart for special applications.
The DAV MX™ CircSub has been used 6 times where the string has been packed off or plugged. Pack off occurs when insufficient hole cleaning leads to cuttings building up and plugging the wellbore around the BHA. It can also be caused by troublesome formation collapsing or swelling whilst drilling as per the case history below. Plugging has been seen due to tool failures in the BHA, heavy materials plugging the string, cementing or pumping LCM into loss zones through the BHA and not the DAV MX™, which can be activated to regain circulation as per the case histories below.
Pack-off – 2015, North Sea, 1 x EOB operated at 42°, the tool worked well and circulation was regained.
Plugged String – 2015, GOM at 28,414ft , 1 x EOB operated at 25°, successfully regained circulation.
Plugged String – 2013, North Sea at 10,742ft, 1 x EOB operated at 18°, successfully regained circulation.
Once circulation has been regained around the pack-off a HyPR dart can be deployed into its sub to sever the string quickly for sidetrack or fishing.
Pipe Filling & Surge Relief
In certain applications the inconvenience of running into hole (RIH) with floats can be costly, either in terms of top-fill time or slow RIH for surge mitigation. Three products in our range can be used to greatly relieve the situation with slightly different approaches.
One conventional mitigation method is to run ported floats, however for many applications this may not be compliant, for example in HPHT situations. Ported floats tend to fill much slower effecting RIH speeds, meaning that top-filling is still required. A second method is a type of float, in which the float is held open by a temporary fixing latch until pumping unlatches and closes the float. This technique doesn’t support shallow hole testing of the MWD on RIH, which will prematurely activate the float.
Up until summer 2015, this tool had been deployed 39 times for self-filling the string when running into hole. Again using the unique lock open dart mode, a useful filling path around the bit allows the string to be filled from the annulus as it runs into the mud.
In a North Sea operation in 2013 the DAV MX™ was estimated to have saved 5 hours of rig time running into hole locked open down to 15,675ft.
A more recent development is the Self-Filling Float which has been used by 4 different operators up to 2015. This can be used either partially on tripping in (cased hole only) or fully (open hole too) depending on the application. In super critical (MPD) and deepwater applications where tripping to replace failed floats is very expensive, the system can also be run as a back-up to conventional floats to save trips. The SFF can also be applied in other than drilling operations such as Completions and P&A where using standard drilling floats can be operationally inconvenient. In those specialist runs the ‘dart activation’ aspect of the SFF proves very useful.
2015 - during a North Sea Completions setting operations, the SFF successfully safeguarded the string and the rig from uncontrolled influx of CO2
2012 - during a case study across two different runs during a 8-1/2” section drill-out, the tool helped save over 7 hours of rig time by allowing the pipe to self-fill while running into hole locked open. Region - North Sea. De-activation depth - 11,900ft.
When top-filling simply can't be avoided there is no faster or easier way to couple and fill than with the TopJet™. Used on over 300 occasions on 32 different rigs for 28 operators/companies, the tool has proven to be a very useful piece of rig floor equipment. Saving up to 50% of filling time, it can be used either stand-alone or in conjunction with down-hole tool options.
One caveat is that new users will need to take a little time to optimize usage intervals, couple loading and pumping rates to get the full benefit. A couple of rigs have been unsuccessful in making it work for them. However over 90% do succeed quickly and we have a simple process for ensuring the tool works even if your top-drive is not fully aligned.
Pressure testing an upper part of the drill string is easily done with the use of Churchill’s Pressure Test Sub™. The PTS™ system is a simple yet accurate way to pressure test to a specific pre-set pressure and be able to regain circulation after the test.
The PTS™ Sub is operated by placing it below the section that is to be tested. Pumping the pre-configured PTS™ dart to the landing seat will deliver the testing pressure. Users have found the shearing pressure to be extremely configurable and accurate when regaining circulation, thanks to the consistency of the MX™ design. A catcher sub below stores the used darts for multiple test cycles.
On the special occasions when fluids are to be circulated in the reverse direction, Churchill’s DAV MX™ can help manage hydraulics more efficiently.
Opening up a generous TFA between the annulus and the string, using the unique DAV MX™ lock-open mode is an extremely robust solution. The Split Flow lock-open mode gives a fully vented option allowing ingress through the bit. The preferred method, however, is to use it in conjunction with a float below the CircSub in order to prevent ingress through the bit while reverse circulating. With a differential pressure rating of 10,000psi, the tool is also highly specified for maintaining reverse pressure integrity when shut.
Running Lower Completion (Packer Setting)
Setting the packer on the lower completion is often made easier with greater control of the hydraulic flow paths. Churchill have a number of tool options that have assisted operators to control flow rates, pressures and barriers during these operations.
The DAV MX™ has been used many times as a means of bypassing a lower completion packer. Typically the valve will be run in hole locked open above the setting assembly to permit full circulation and pressure relief. Once at depth the valve is closed, to activate the liner/packer.
In 2012, in one HPHT well, it was locked-open at surface using a SFD before being RIH to 13,630ft. After allowing the lower completions packer to be hydraulically bypassed (as to not activate prematurely), the DAV MX™ was closed before setting the packer using 9000psi.
The DAV MX™ CircSub has a class leading 10,000psi differential pressure envelope (both inside-to-out and outside-to-in) to provide operators with widest possible operating and safety margins.
The flapper version of the Self-Filling Float has a through-bore prior to activation, allowing setting balls to pass through as well as bi-directional flow. After the setting of the lower completion, the float is activated by a dart to release its flappers and prevent any returns up the string.
In 2015, the Self-Filling Float protected a drill string from CO2 influx after allowing the setting of a lower completion at 10,194ft.
Our tools offer multiple solutions to a wide range of drilling, completions and P&A applications. Browse through our applications library to see how we are helping operators improve performance.
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