Staveley et. al., 2010 estimated that nonproductive time (NPT) related costs due to drilling issues amounted to $15-37 billion per year globally and wellbore instability issues alone cost the industry around $8 billion per year (Dodson et al. 2004). One of the major challenges in analyzing historical drilling performance to optimize the drilling design is data management, which includes the difficulty in analyzing historical data, statistical analysis, lack of access to relevant data or unavailability of relevant information, and the inability to effectively correlate multiple wells in a single view. Statistical analysis of historical data can provide an understanding of the complex challenges. Historical analysis of geomechanics studies of offset wells, surface drilling parameter data, bottomhole assemblies (BHAs), bit records, mud data, log data, drilling events, lessons learned, and best practices of the wells previously drilled will help us understand the formations better and help predict drilling challenges in advance to proactively plan a mitigation strategy.
This paper talks about how the historical data analysis of wellbore stability issues, lost circulation events, stuck pipe, tight spots, and drilling fluid parameters on all the nearby offset wells helped us understand the challenging formations. We also discuss how analyzing historical data sets might be overwhelming. It is critically important to structure the data sets to focus on specific drilling events. Multiple sets of offset wells were analyzed prior to drilling a new well. These analytics helped us in planning the design for future wells by having in place an advanced mitigation strategy for stuck pipe due to wellbore instability issues while drilling across weak formations, mitigating the issues caused by clay swelling, and eliminating the NPT in the target well by changing the drilling direction to avoid drilling in a direction almost parallel to the weak shale bedding plane. When there is a lack of information on the logs, downhole stresses, and rock properties of the wells, we can utilize the lessons learned from these historical drilling events to plan and optimize the drilling.
The drilling results from formations across the Middle East and Asia demonstrated that the historical statistical geomechanics-based studies helped the operator optimize drilling by designing a proper mud system and effective mud weight window. These studies helped the operator in providing a roadmap to the optimized drilling of gas wells, clay formations, and highly laminar shaly formations.
This paper illustrates techniques for analysis of historical drilling data, increasing the drilling efficiency, and minimizing/eliminating the NPT and the data subsets that need to be created for structured data management. The holistic partnership between geomechanics studies and historical data analysis is discussed in detail. These studies demonstrate how the offset well data helped in effectively drilling challenging wells by planning in advance mitigation strategies for undesirable drilling events like stuck pipe, tight spots, and clay swelling.
