Abstract
Reaching bottom with logging tools is difficult when the well is highly deviated and has significant pressure overbalance. This often leads to mechanical and differential sticking risk on cable operations and the desired depth not being reached. The normal practice is to deploy formation testers on drill pipe (pipe conveyed logging – PCL). This paper aims to provide guidance to operators for performing safe and efficient wireline formation pressure testing jobs in challenging conditions, saving considerable rig time.
It is critical to understand the factors which cause tool obstruction and cable sticking. This helps to optimize the conditions needed for successful wireline operations and prevents high-impact events, such as tools getting stuck, fishing operations, wiper trips, cancelled logging and PCL jobs. The main contributing factors were analyzed and divided into different categories: well design and trajectory, borehole conditions and geomechanics considerations, drilling fluid properties and wireline equipment selection. A tailored operational workflow with detailed risk assessment with prevention and mitigation measures were combined into a practical guide and then it was implemented to perform a series of jobs.
Following the new systematic approach, wireline logging jobs could be safely conducted in several wells across 8-3/8" and 5-7/8" sections in a challenging drilling environment. The maximum inclination was 60° and maximum overbalance of 3,920 psi. The vast majority of planned pressure points were collected and there weren't held ups or overpulls observed during the operations. For the tester tool to reach the bottom, it was essential to have a proper well design and trajectory construction, good borehole quality with minimum disturbance and exposure, right mud weight selection together with fit-for-purpose drilling fluid and bridging plan.
All best practices and lessons learnt, were put together to a guide and made available to the project team for future operations. This technique was adopted as the new standard for logging through carbonates formations in deviated sections in the field, with high depletion. As operational costs are a concern in long deviated logging, optimization done using alternative methods offer benefits in terms of rig time and efficiency. If the main risks aren't assessed properly, then it incurs significant costs and inefficiencies.
This innovative multidisciplinary approach integrates different domains to perform wireline formation testing operations in a cost effective and time efficient manner when compared to running logs on drill pipe. This method will serve as a reference for operators and service providers to achieve step changes in similar operations. The key elements of this initiative will be described in detail in the paper.
