Abstract
Cementing the section/casing without inducing losses has always been challenging in narrow margins of allowable equivalent circulating density (ECD) from fracture gradient. The losses are caused by exceeding the ECD limit. Exceeding the limit results in annulus integrity issues and a leaking casing shoe that leads to sustained casing pressure. When this happens, it requires extensive remedial planning. The conventional and current loss cure tool is addition of loss control fibers, and we must manage the pump rates in pre-job planning. But there is no control or monitoring of the ECDs during the job. Historically, for similar cementing jobs, decisions for future improvement are made only after post-mortem analyses, i.e., remediation plans are formulated for future operations based on what previously went wrong. Significant time is spent on deliberating over several indirect factors that may or may not have affected job outcomes. With the recent emphasis on performance, digitalization, and sustainability, the operator must identify a workable solution based on real-time parameters.
A real-time measurement and simulation solution that addresses the previously listed challenges was deployed to monitor and control a challenging 13 3/8-in. casing cement job in a remote well with extreme health, safety, and environment (HSE) risk. In this well, the permitted ECD margin from mud weight was only 1.3 ppg. A formation integrity test was performed at 15.9 ppg using 12.5-ppg mud. However, because of wellbore stability issues, mud weight was increased to 15.6 ppg, leaving behind a narrow margin of permitted ECD from fracture limit (set at 16.9 ppg based upon offset well data). Accordingly, spacer and cementing fluids were designed to keep the ECD within the fracture limit to avoid losses.
The job was monitored in real time for pumping pressure and calculating downhole ECDs in comparison with planned values. While working remotely, it enabled the customer to make real-time decisions on pumping rate to keep the ECD in check. The job was successfully pumped without any losses and the final ECD was kept within the 16.9-ppg limit.
The monitor/simulation software application enables users to monitor, compare, and evaluate cement job acquisition data with dynamic simulations generated in real time. Customers and experts can monitor the job remotely, diagnose abnormal events, and propose solutions in a timely manner, providing interpretation and support throughout the job execution. The solution eliminates the need to travel to the rig for cement job monitoring, saving staff hours and contributing toward sustainability. It remotely monitors cement jobs, decreases travel time, and decreases the time needed to make decisions, while also assuring preestablished job objectives are met.
