Advantages to CTD
1. Underbalanced drilling
The ability to work with surface pressure while flowing produced fluids and continuously pumping when tripping into and out of the hole clearly represent the most important advantage to CTD. This unique ability allows for maintaining underbalanced conditions on the formation to minimize the potential for formation damage and increase drilling penetration rate. Maintaining underbalanced conditions on the reservoir at all times is critical in reducing the potential for formation damage in sensitive reservoirs. The majority of CTD operations performed in Canada are primarily for this reason.
2. Managed pressure drilling
Again, the ability to work with surface pressure gives a unique advantage to the CTD process. Experienced coiled tubing unit (CTU) crews are well…show more content… This high viscosity often exceeds a low shear-rate viscosity (LSRV) of 40,000 or more and tasks the ability of solids-control equipment to efficiently remove solids. Finally, the high friction losses and associated turbulence degrade many common biopolymers used in CTD applications. All these factors result in higher costs to maintain a drilling-fluid system.
4. Limited equipment and limited experience manpower base
As previously discussed, the limited equipment base and lack of widespread application of CTD technology limit the availability of equipment and experienced manpower. These factors often result in higher-cost operations, and because the experience base is not nearly as high as that for rotary technology, the potential also exists for reduced chance factor of success in some instances.
5. Logistics of getting equipment to the work