Obtaining high resolution, quality formation evaluation data is still only possible with wireline logging. However, with the continued push into deeper and more complex drilling environments, many challenges have been placed in the way of wireline logging, including high tension, high deviation, and increased differential pressure. These factors contribute to an increased risk of tool sticking incidents and lost-in-hole scenarios. Several methods of mitigating these issues on surface (powered capstans, pipe conveyance, etc) have been implemented in the past, but none have been successful in reducing or eliminating the risk downhole without introducing further drawbacks.
This paper describes how a new wireline conveyance system has eliminated these issues. The conveyance system consists of wheeled carriages that carry the toolstring off-centre. The mass of the toolstring acts as a counterweight to ensure correct tool orientation in the wellbore. This orientation feature also enables a "guide" device to help navigate ledges and washouts. Such a system eliminates toolstring hold ups, allows access to highly deviated wells without pipe conveyance or tractors, and significantly mitigates differential sticking hazards, while also offering additional benefits in operational efficiency and data quality.
A case study from a particularly difficult well in New Zealand is presented. Data acquisition in this well was fraught with challenges: In addition to the 2000m tangent section at 67° deviation, well had severe borehole breakouts. Previous experience in similar scenarios with conventional data acquisition methods yeided poor results. The wheeled carriage system was deployed in multiple innovative configurations resulting in the acquisition of excellent quality data from five wireline descents in hole.
This wireline conveyance system has been routinely deployed on multiple deepwater operations in the Gulf of Mexico. One such operation is presented where large gains in logging efficiency have been realised, particularly with the elimination of differential sticking risk and time-consuming pipe conveyed logging.
The new technology takes a holistic approach to wireline tool conveyance: Prevent sticking issues using wheeled carriages and mitigate fishing risk using ultra-high strength wireline cables. Wheeled carriages greatly reduce the tool-borehole contact area, preventing the incidence of tool sticking. In addition, wheeled carriages reduce drag while ensuring optimum data quality by sensor position and orientation within the wellbore. Ultra-high strength cables provide ability to log at very high tensions and at the same time provide high overpull capability.
The result is a safe, efficient, cost effective and complete Wireline data acquisition.