Sampling in a highly deviated well involves additional risks that can compromise efficiency and costs. Operators and service companies have developed options to overcome the technical challenge of going from tubing-assisted logging to tractor-conveyed operations.

Tubing-assisted logging will mitigate the issues and stuck risks caused by wireline key seating, differential sticking, swelling formations, heavy muds, borehole breakout, doglegs, ledges, and cuttings but will require slower operations resulting in additional rig time and therefore costs. Tractor conveyance, on the contrary, can be efficient but will add costly operating rates and higher cost exposure if the tools are lost in hole.

An operator in offshore Southeast Asia had an objective to perform formation evaluation by means of pressure tests with pump out to obtain clean samples for CO2-level measurements in a slim well geometry (6 1/8-in. hole) with 73° deviation. Sampling wheels that configure with the wireline formation tester tool were introduced to the operator to reduce the contact area, keep the tool body off the low side of the borehole wall, and aid gravity descent.

The operation objective was successfully accomplished and reached the target depth (TD)/reservoirs by performing five pressure tests, setting up three fluid characterization stations, and retrieving six samples in approximately 12.5 operating hours, resulting in savings of more than USD 350,000 for the operator.

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