Coiled Tubing Drilling Services

Nortech has contributed a step towards change in coiled tubing drilling services based on new technology development which is a big change. When coil tubing is in compression in the vertical section of a well caused by sliding friction or bit weight, it immediately forms a helical shape and reach is impaired as a result. When the well is deviated, the coil tubing first forms a helical shape. As the compressive forces increase caused by sliding friction or bit weight , it forms a helical shape. As the compressive forces on the helical coil tubing increase, the wall-contact forces associated with the helix increase. This increases friction, helical “Lockup” occurs when the friction forces increase to a point that the coil tubing helically “Locks itself” in the well. Slacking off more weight on surface does not increase the weight at bottom. Therefore, friction is what stops the coiled tubing in extending its reach in horizontal well bore.

The new unit (CTRD) concept would allow for slow rotation of the coil at speeds in the range of 5 to 25 RPM. This range of speed will be adequate to substantially break the axial friction which currently acts to resist transmission of weight to bit and also acts to buckle and “lock-up” the coil.

Rotating the coil at 5 to 25 RPM will reduce drag by a minimum of 60% and under a wide range of conditions by 80%. Reduction of drag by these levels will greatly enhance the reach of coiled tubing and increase operational efficiency.

Rotational capability will improve weight transfer and will increase reach by approximately 70% and enable Coiled Tubing to be an efficient drilling unit.

   
Coiled Tubing Drilling Services

The Coiled Tubing Rotary Unit (CTRU) rig is a rig design that shortens the gap between a conventional jointed drilling rigs and/or Snubbing units and Coiled Tubing Units.

The CTRU rig places the entire reel on the rig floor with a direct feed of tubing into the injector eliminating the gooseneck and in addition has the ability to rotate the Coiled Tubing reel and Injector head at a maximum of 25 rpm while the coiled tubing string is in the wellbore.

The CTRU design eliminates 80% of the cycle fatigue due to reduced goose neck cycles and permits the use of larger diameter coiled tubing in intervention applications making it more cost effective, reduces friction drag in the well bore and thereby increases horizontal reach, improves weight transfer to the BHA for improved milling and drilling efficiencies.

As an example of the main areas of major improvements to the coiled tubing drilling string versus jointed pipe applications the following can be mentioned:

Extensive Experience in developing and implementing new and specialized technology in the coiled tubing market.

Specialized module based hydraulic long stroke rig developed in co-operation with MENA clients Nortech Management has extensive experience developing and introducing specialized coiled tubing technology to the market. We see several opportunities for new Coiled tubing technology arising in the MENA and Caspian market due to: Increased number of horizontal wells New Coiled Tubing technology to match a $ 70/barrel market. Focus on technology to reduce well maintenance cost Rotating coiled tubing will remove sliding friction issues with coiled tubing drilling services and dramatically increase its efficiency and reduce cost for the Oil Companies. Eliminating the gooseneck will extent the fatigue life of coiled tubing by 370% and drastically reduce the operating cost of coiled tubing

“CTRD will enable increased accessibility in most wells and extend the efficiency of coiled tubing operations. It will be the number one remedy for optimal well interventions in horizontal wells”

   
The Rotary Unit Explained

The Nortech revolutionary Coiled Tubing design will prolong the operational use of coiled tubing by 370% compared to conventional coiled tubing design due to the bending cycles segments being reduced from 6 bending cycles to 2 bending cycles. This reduction in bending cycles will create major OPEX saving per year, per Coiled Tubing unit.

   
Patented Technology

   
The effect of slow rotation on the sliding friction factor

RUNNING-IN-HOLE (RIH) FRAG COEFFICIENT – NON ROTATING

HOLE TYPE	Dry Air/Gas/N2	Water. WBM	Produced Oil	OBM	Gel	COMMENTS
Open Hole	0.5600	0.4600	0.3600	0.4600	0.4000
Tubing/Casing/Liner	0.4600	0.3600	0.2600	0.2600	0.2000
Slotted Liner, Rough	0.4900	0.3900	0.2900	0.2900	0.2300	Rough holes/slots
Slotted Liner, Smooth	0.4600	0.3600	0.2600	0.2600	0.2000	Deburred

PULLING-OUT-OF-HOLE (POOH) DRAG COEFFICIENT – NON ROTATING

HOLE TYPE	Dry Air/Gas/N2	Water. WBM	Produced Oil	OBM	Gel	COMMENTS
Open Hole	0.4800	0.3800	0.2800	0.3800	0.3200
Tubing/Casing/Liner	0.3800	0.2800	0.1800	0.1800	0.1200
Slotted Liner, Rough	0.4100	0.3100	0.2100	0.2100	0.1500	Rough holes/slots
Slotted Liner, Smooth	0.3800	0.2800	0.1800	0.1800	0.1200	Deburred

RUNNING-IN-HOLE (RIH) DRAG COEFFICIENT – ROTATING @ 25RPM

HOLE TYPE	Dry Air/Gas/N2	Water. WBM	Produced Oil	OBM	Gel	COMMENTS
Open Hole	0.1400	0.1150	0.0900	0.1150	0.1000
Tubing/Casing/Liner	0.1150	0.0900	0.0650	0.0650	0.0500
Slotted Liner, Rough	0.1225	0.0975	0.0725	0.0725	0.0575	Rough holes/slots
Slotted Liner, Smooth	0.1150	0.0900	0.0650	0.0650	0.0500	Deburred

PULLING-OUT-OF-HOLE (POOH) DRAG COEFFICIENT – ROTATING @ 25 RPM

• 1. The amount of oil required to generate oil whetted conditions is not known.
• 2. SPE 16663: Casing run in open hole, water based mud POOH: .21 to .30, RIH: .38 to .43 (.15 variation between RIH/POOH)
• 3. Published literature, mostly drilling related shows quite a spread in friction factors for nearly equivalent situations.
• 4. Residual bend is dependent on tubing size, guide arch radius, grade, and maybe other factors.
• 5. Not all variation between RIH and POOH is explained by residual bend since the effect has been observed in running casing.