Tackling Well Drifting Issues When Drilling Deep Gas Wells

Abstract When drilling a deep vertical well, there is always a small inclination build-up that occurs naturally due to dip angles of formations, stiffness of Bottom Hole Assemblies (BHAs), and applied drilling parameters. Sometimes dip angles can be extreme, which can lead to unwanted inclination build-up or drifting, due to which, the well-bore lands significantly away from the intended target location. When planning a well, it is necessary to know beforehand whether drifting will be an issue or not. A thorough study of wells drilled in various fields was conducted using available digital technologies, which assisted in compilation, synthesis, and interactive graphical evaluation to aid in the identification of drift-prone areas. In addition to the available data on formation dip angles, this approach presented an effective alternative to avoid costly correction runs later. During this analysis, the types of BHAs used in a particular interval of the wellbore were also studied, and the most effective BHA type was identified. Appropriate drilling strategies were outlined to develop a road-map for drilling in drifting-prone areas. Based on the results of this study, it was identified that in surface holes, a short-packed BHA would prevent any inclination build-up, although a semi-packed BHA is prone to inclination build-up due to less rigidity. In intermediate and deeper sections, it was observed that pendulum BHAs are the best choice to maintain verticality as they tend to counter any drifting tendency. In many instances when packed BHAs were deployed to maintain angle, it was observed that inadvertent drifting still occurred even with controlled drilling parameters, which is counter-intuitive to traditional drilling practices. This approach was then applied to drilling a deep gas well with good success. It helped reduce the costs associated with wellbore deviation surveying tools, which were previously typically run in shallow sections to monitor deviation. In this well, BHAs were run as per the heat map recommendations, and the well remained vertical all the way to final Total Depth (TD) as confirmed by gyro and Measurement-while-Drilling (MWD) measurements later in the drilling phase. This established the validity of the heat map model, which can be used in future wells with confidence and will lead to time and cost savings. The use of digital technologies enables efficient data analysis, from which key insights into drilling operations can be obtained. These help drilling engineers in the design phase to plan drilling BHAs in the planning phase and avoid having to deal with inadvertent drifting issues during well construction operations. In this way, such technologies are enablers for operational efficiency, bringing significant time and cost benefits.