Wireline cable sticking is most frequently experienced during formation fluid sampling. In this situation, if the cable cannot be freed, strip-over fishing is the only remedy; this is a cost and risk-intensive activity which may extend the logging job by several days and result in further inefficiencies such as wiper trips or pipe-conveyed logging to fully satisfy the formation evaluation objectives. In this paper, the authors outline a proven engineering approach that permits the systematic identification of high-risk wells for cable sticking, where the deployment of wireline standoffs (WLSOs) may facilitate safe and efficient sampling on wireline. The precursor of all cable sticking is slot cutting into mud-cake or formation. The slot is generated by sustained lateral pressure from the moving (tensioned) logging cable, referred to hereafter as "cable thrusts". A sophisticated 3D cable force model evaluates the cable contact zones and thrusts along the open hole section under analysis. For differential sticking, a cable contact and sticking limit in mud-cake is computed, having adjusted the pore pressures to offset data. For keyseating, the well is benchmarked against wells with similar trajectories, gained from a global study on cable sticking. Sticking-linkage is also assessed, whereby overpulls from tool sticking may induce cable sticking, via amplified cable thrusts against mud-cake or formation. To reduce cable sticking risks to an acceptably low level an array of WLSOs may be deployed, combined with optimised logging procedures and winch techniques. Operators are now employing this approach on a regular basis as an important risk management tool, from the well planning stage through to completion. WLSOs have been successfully deployed for 40 sampling runs on 25 wells, in fields with a history of severe cable sticking or fishing. Prior signs of sticking have largely been eliminated, resulting in significantly reduced well costs, whilst avoiding pipe-conveyed logging or LWD, and without consideration to the value of lost data or samples. Well Engineering may now use this approach to design and optimize ambitious well trajectories, potentially saving a hole section, in the full knowledge that future wireline fluid sampling can be performed within the bounds of acceptable risk. Real-time risk assessments have proven invaluable, to track the risk trend as the well is drilled, leading to a final decision on the requirement for WLSOs, with additional optimisation of the sampling procedures if needed. Operational best practices and lessons learned are summarized, as well as an outline for future R&D to understand and reduce wireline conveyance risks even further.

During open-hole wireline operations, at least 95% of cable sticking events are known to be predictable and avoidable. Approximately 40% of these cable sticking events escalate to fishing operations, adding substantial costs to the AFE. Sub-optimal well design, from a wireline acquisition perspective, is known to contribute to such sticking. This paper offers practical guidance for drilling engineers on how their well designs may impact wireline conveyance and sticking risks and what measures they can take at both the design and execution stages to ensure a safe and efficient wireline logging job.

In a tool stuck situation, wireline conveyance systems incorporate a downhole mechanical weakpoint to safely release and retrieve the logging cable during or prior to pipe conveyed fishing operations. In wells with high tension profile and long open hole sections, the weakpoint strength should be carefully selected to ensure high pulling capabilities in shallower sections of the well while not exceeding the cable safe working load (SWL) in deeper sections of the well. To overcome this limitation, electrically controlled release devices (ECRD) were introduced in the past. Release is only possible with a surface command. As such full pulling capability is maintained at all times and depths. The swap however, introduced new sets of challenges such as full tension drop requirement for mechanical release and a labor intensive tool preparation procedure. As a result nonrelease incident rate increased leading to high risk and costly recovery operations. To minimize this risk, clients often have to reduce or cancel wireline logging programs leading to missed critical well data. To address the limitations of ECRD type weakpoints, Chevron Thailand E&P, LTD commissioned Schlumberger to address such challenges. The project was completed in Dec 2011 with the introduction of SureLOC 12000. Improvements include release with 1000 lbf of cable tension, 12,000 lbf (up from 8,000 lbf) of safe operating pull and substantial reduction in maintenance and redress procedures. Reliability has since improved by 75% allowing Chevron to acquire full data in wells where logging operations would have been otherwise cancelled. The improved reliability and increased operational range of the new device have allowed Chevron to safely carry out Wireline logging operations and achieving well data acquisition targets with substantial financial benefits.

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