Frequently Asked Questions

Downhole flow diversion technology

Is CE-BOND a replacement for casing centralizers?

How can we be sure that CE-BOND will self-orientate?

Can casing be rotated and reciprocated if CE-BOND is being used?

How many CE-BOND’s are installed on each casing joint? Are they used all the way to surface?

Does CE-BOND increase pack-off risk?

Does CE-BOND increase Equivalent Circulating Density (ECD)?

Does CE-BOND increase drag while running casing?

Will CE-BOND increase the risk of casing becoming stuck?

Is there a risk that CE-BOND tools become damaged whilst RIH?

Can the composite material that CE-BOND is manufactured from be damaged by H2S, CO2, OBM, or other wellbore fluids or gases?

Does CE-BOND work in Wash-outs?

How can we verify the effectiveness of CE-BOND?

Why wouldn’t you run CE-BOND as a casing accessory in highly deviated or horizontal wells?

Is CE-BOND a replacement for casing centralizers?

No, not at all. CE-Bond is designed to be run in conjunction with casing centralisers. The Operator can choose to run bow spring or solid body centralizers of their choice as normal. CE-BOND will be installed using the same "slip-on" method and retained between two stop collars. But CE-BOND does not centralise a casing string - it optimises circumferential fluid displacement by altering the velocity profile in the casing to wellbore annulus.

How can we be sure that CE-BOND will self-orientate?

CE-BOND has been designed with a strong upwards buoyancy force (around 10kg equivalent). To put this into perspective, picture a 10 kg weight hanging from a casing joint - the force required to rotate this weight is significant. It should be noted that this buoyancy force comes into play as soon as the wellbore builds angle, so CE-BOND will self-orientate onto the high side as soon as wellbore angle exceeds around 5°. This self-orientation will therefore normally take place during cased-hole. Once CE-BOND is orientated onto the high-side, the tendency of the casing to lay on the low-side (due to gravity) and the elliptical geometry of CE-BOND mean that it is almost impossible for CE-BOND to be forced onto the low-side.
 
It should also be noted that as long as multiple CE-BOND tools are run on a casing string, it is not essential for them all to be perfectly orientated onto the high-side. A step-change in hole cleaning and cement displacement will still be observed if only 80% of the CE-BOND tools on the casing string are correctly orientated for example.

 

Can Casing be rotated and reciprocated if CE-BOND is being used?

Casing can be freely reciprocated with CE-BOND installed. In fact, reciprocation while circulating prior to cementing operations increases the wellbore cleaning efficiency of CE-BOND so is a recommend step in the operational procedures. Casing can also be rotated with CE-BOND installed. 

How many CE-BOND’s are used per joint? Are they used all the way to surface?

Each well is different and multiple factors come in to play such as: calliper data, hole angle, geology, etc. This information is used to provide space out requirements on a well by well basis.

On average, CE-BOND will be spaced one per joint with the shoe track possibly having two per joint.

CE-BOND is only suggested for use in areas of critical cement requirements such as the shoe, isolating formations, future abandonment zones and structural areas.

Does CE-BOND increase pack-off risk?

No. Pack-off risk is defined by the size of discrete flow areas in the casing to wellbore annulus, and the fluid velocity within these flow areas. If CE-BOND is compared to a conventional solid-body casing centralizer, CE-BOND represents a lower pack-off risk. This is because the flow area on CE-BOND is larger than the discrete flow areas between blades on a solid-body centralizer, and for identical flow rates the fluid velocity within the CE-BOND flow area is significantly higher.
 
To summarise, CFD modelling conclusively proves that a conventional solid-body casing centralizer represents a greater risk of pack-off than CE-BOND.

Does CE-BOND increase Equivalent Circulating Density (ECD)?

CE-BOND has a short length and this is the major factor that dictates pressure drop across the tool. The pressure drop across CE-BOND while pumping at normal cement displacement rates is in the range of 0.6 -1.0 psi/tool (0.041 – 0.069 bar).
 
Installing 20x CE-BOND tools on a casing string would therefore introduce a maximum annular pressure drop of 20 psi (1.38 bar). However, if a deviated or horizontal wellbore suffers from a residual cuttings bed when casing is installed (as is common), the CE-BOND tools can clear this cuttings bed and therefore deliver a net decrease in wellbore ECD.

The effectiveness of CE-BOND clearing a cuttings bed can be viewed here

Does CE-BOND increase drag while running casing?

Typically no; in gauge hole, CE-BOND will only come into contact with the wellbore if the casing is 100% centralized. Since no centralizer programme can achieve 100% standoff, this scenario will only occur through areas with high dogleg severity. The composite material that CE-BOND is manufactured from has a very low coefficient of friction, so if CE-BOND does contact the wellbore, drag is not significantly impacted. The length of each CE-BOND is short, so even a scenario where multiple CE-BOND tools are contracting the wellbore will not significantly affect the friction factor seen by the casing string. 

Will CE-BOND increase the risk of casing becoming stuck?

In comparison to a solid-body centraliser, the maximum OD on CE-Bond is only 1/8" (3mm) larger than the centralizer blade height. In gauge hole, CE-BOND is intended to lightly contact the high side of the wellbore only if the casing is 100% centralized. Regardless of the centralizer programme in use, achieving more than 80% casing stand-off is effectively impossible to achieve in deviated hole.
 
CE-BOND also has the freedom to rotate. It can therefore rotate itself clear of a high-side (below gauge) restriction using it's plough-shaped nose and then flip back to the high-side under buoyancy force to be correctly orientated.
 
CE-BOND is extremely robust, and will be physically tested to withstand 100,000 lbs (45 T) overpull force without damage (in case stuck casing is being worked or jarred free).  

Is there a risk that CE-BOND tools become damaged whilst RIH?

CE-BOND uses state of the art composite materials (the space industries’ material of choice). With a combination of Carbon Fibre and Kevlar, CE-BOND is stronger than steel and has a high resistance to impact and abrasion.
 
CE-BOND was designed using advanced composite Finite Element Analysis (FEA) techniques to ensure the capability to withstand all possible downhole forces and service loads that occur while installing casing. A physical testing programme is also used to categorically demonstrate the ability of CE-BOND to withstand all possible downhole load conditions.  
 
CE-BOND will also be tested for impact resistance which simulates the casing string travelling at running speed while coming into contact with a solid restriction.

Can the composite material that CE-BOND is manufactured from be damaged by H2S, CO2, OBM, or other wellbore fluids or gases?

Composite materials are extremely inert and are highly resistant to H2S, CO2 and oil-based chemicals. Ironically, since water molecules are so small, designing a composite material to be fully water resistant under high pressure is the big challenge!
 
An extensive physical testing programme has been developed to categorically demonstrate the compatibility of CE-BOND with all fluids and gasses that may be encountered downhole.

Does CE-BOND work in Wash-outs?

CE-BOND functions also in wash-outs, as it has a choking effect on the high-side flow, leading to better flow distribution.

CFD modelling shows that the CE-BOND is effective in improving cement displacement for up to a 1” wash-out.

How can we verify the effectiveness of CE-BOND?

Ultrasonic cement bond logs provide a high resolution 'image' of cement bond quality around the casing circumference, and the ability to identify channels and assess overall cement bond quality. If an ultrasonic cement bond log is performed after installing casing with CE-BOND, the log data will normally have sufficient resolution to identify the depth and orientation of the CE-BOND tools, as well as qualifying the circumferential cement bond that has been achieved. If relevant offset well data is available from the same field, a direct comparison can be made between ultrasonic cement bond logs from similar wells, with and without CE-BOND.

If an ultrasonic cement bond log is not planned, the effectiveness of CE-BOND can be physically confirmed by the increase in hole cleaning efficiency that is observed while circulating before the cement job (increased cuttings returns at surface).

The improvement in well integrity that is associated with full circumferential cement bond will also be observed and recorded throughout the well lifecycle as part of routine well integrity management.

Why wouldn’t you run CE-BOND as a casing accessory in highly deviated or horizontal wells?

If you have identified potential risks or challenges associated with CE-BOND that are not addressed in the FAQ section, please let us know by mailing us at: info@centraflow.com.

We appreciate expert critique and would love to hear from you!
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