The need for a safe and cost effective conveyance method in horizontal well logging increased with the increase in the number of horizontal wells and their horizontal section length. Coiled tubing was initially used for conveyance, however it has a limited reach and the operations are complicated with some operational risks, demanding logistics and higher cost.
The inchworm tractor was tested and evaluated in various horizontal well completions such as cased hole, slotted liner, gravel packed, ESP, open hole, and multilateral wells; with long horizontal sections. The tractor was also tested in open hole completions where the formation unconfined compressive strength (UCS) varies from 150 to 23,000 psi.
Logging wells with soft formations was the most challenging task. The tractor design was modified to be able to initiate and maintain tractor movement in the soft formation.
This paper will cover the test results of the inchworm type tractor such as effectiveness of conveyance, quality of logged data, maximum logged horizontal section and cost saving. It will also discuss the limitations of this technology. The screening process of suitable candidates as well as pre-job planning will be summarized.
As indicated above, the number of horizontal wells and the complexity are increasing as fields are developed and mature. Despite the immediate need of conveyance for number of reasons, a majority of horizontal wells can not be logged and can not be intervened effectively today. Although the number of tractor vendors is increasing, the tractor conveyance is still limited and can not fully overcome challenging conditions associated with horizontal and multilateral wells.
In this paper, the extensive field experience of inchworm tractor conveyance is presented with integrated production logging results in a variety of completions.
This inchworm tractor is designed to convey wire line production tools into wells where a gravity descent is not possible due to high deviation or friction. In addition to the objective of extended reach, it offers an economical alternative to drill pipe conveyed logging and Coiled Tubing Logging. The tool is designed to tractor down into a horizontal well and to be retrieved by a wire line cable.