Non-Intuitive Choke Control During Clean-Up Operations Allows Significant Reduction of Emissions

Abstract

Abstract Every well needs to be cleaned-up, at least once – after the end of the well construction phase but could be after stimulation operations or workovers over their full life. The clean-up / flowback operations are sometimes executed with a full or partial disposal of the fluids as either no production system is available (the case of most exploration and appraisal wells) or when the production system is intolerant to the fluids produced (low pH. High solid content, excess water, or for rheology incompatibilities). The disposed fluids are sent to a flare and their combustion induce a significant amount of emissions. These operations are typically executed according to the prior experience of similar wells. The paper presents a novel approach to significantly reduce emissions by optimizing the clean-up operation by varying the choke settings in rapid interval at surface. Field case confirm the ability to significantly reduce the duration and the quantity of fluids flared in these operations and accelerating the time to shift the flow to the production line – if available. The challenge is that every well configuration leads to a different choke schedule that minimizes emissions. This is due to the complex combination of near wellbore properties of the formation and the invaded fluids, the complexity of the well trajectory and the variability of fluids used to kick-start the well. It is intuitive that the acceleration of the choke change would lead to a reduction of the emissions. This leads to a reduction of 10 to 30% of the CO2 balance. To achieve superior savings, it is necessary to consider a reduction of the maximum rate – which can lead to 50% range of reduction in some wells. Further improvements are achieved with more complex choke sequences that the paper describes. This novel method consists in the detailed prediction of the dynamics of the flow during the clean-up operation is a key element to optimize the choke sequence. A rapid model allows to evaluate several scenarios and select the optimum settings that will achieve a significant reduction in emission while keeping the near well bore in a safe operating zone (geomechanical phenomena), protect the integrity of stimulated zones, and guarantee the safety of the completion (collapse). Finally, several contingency cases are considered to ensure that a robust operation can safely be delivered.