Coiled Tubing Logging
General descriptions of the technology
Cable logging is mostly applied to vertical wells and wells with an inclination of less than 45°. When the well inclination is more than 45°, some special tools, such as a guider, knuckle joint, pulley and sink bar, are needed. If wells are inclined by more than 60°, it is hard to conduct logging by using traditional methods. With increasing well inclination, vertical stress component of these tools is decreasing. As the component is not strong enough to overcomefriction resistance, these tools cannot fall by themselves. In this view, cable logging is limited in greatly inclined wells and horizontal wells. Coiled tubing logging has just eliminated the defect of cable logging because coiled tubing is not only flexible but also rigid. The coiled tubing with logging instrument can push the downhole logging tool to greatly inclined well sections or horizontal well sections. Logging tool can be pushed forward by 900m in horizontal sections by coiled tubing.
Compared with traditional cable logging, coiled tubing logging has following features.
It suffers less abrasion and guarantees operational safety and reliability because cables are laid inside coiled tubing.
Special pressures can be utilized to control logging instruments because coiled tubing can transfer pressure.
Logging can be implemented in low-pressure wells by artificial nitrogen gas lift.
Downhole video technology
Cementing evaluation and neutron logging
Open hole logging
Liquid or nitrogen pumping