A Novel Approach to Delayed Survey for Stuck-Pipe Prevention Practices and Drilling Performance

Abstract

Abstract In onshore Oman, difficulties are encountered where required dogleg for horizontal wells exceeded 8 degrees and execution put it above 10 degrees due to the added geological factor. Optimized landing in thin targets needed real time adjustments, which increased the stress on the trajectory, and increased the risk of hole instability due to limitation on hole cleaning capabilities, while running high tech tools in a high Dog-Leg Severity (DLS) area, where fishing comes with a low success rate. A precise well trajectory is crucial and the way to ensure the integrity of the well path is by surveying the borehole at an acceptable frequency as per the well surveying program. Which in accordance with world wide industry practices. Such acquired data is utilized in the drilling campaign starting from the planning phase throughout execution all the way to post drilling activities. The 8.5in section is executed with a high dogleg severity (DLS) application. As such, a flexible-designed BHA (bottom hole assembly) is utilized to deliver the high deviation required to accurately land the well 0.5m true vertical depth (TVD) into the desired zone of interest. The current survey procedure of this BHA takes approximately 5-7 minutes of stationary time, not inclusive of connection time, leading to higher stuck-pipe risk such as solids-induced pack-off and differential sticking. Therefore, an optimized mud weight is planned to support the borehole with its Nahr Umr (shale) and Shuaiba (Limestone) formations exposed. With such high mud wight, differential sticking risk becomes high in the limestone, and drill string stationary time becomes crucial to stuck-pipe prevention measures. Delayed survey was trialed in the past to be an option to overcome low efficiency pumps on some rigs, and also for under-balanced or foam drilling. In this case study, it was decided to adopt such practices to eliminate any possible survey stationary time while drilling. The trial proved successful and reduced stationary time after connection, from 7 minutes per stand to 0 minutes per stand (100% survey time reduction). As an additional benefit, drilling performance improved and saved approximately 4.5% of well AFE time due to reduction of survey time. This experiment helped to redesign the stuck-pipe prevention practices, deploy it on all wells, and start implementation on the 12.25in hole also to save another 6% of AFE time. As a result of the trial, such practice is adopted in all rigs by the operator, and this contributed to the increased performance and reduction of stuck risk in this drilling campaign.