Abstract
This paper outlines the planning and assessment of a multi-staged clean-up strategy in a horizontal well, post-drilling. The strategy strikes a balance between efficient well clean-up from drilling and stimulation fluids and the risk of coiled tubing stress cracking. The staged clean-up approach, conducted from the toe to the heel of the long lateral horizontal well, allowed us to perform uniform and gradual clean-up process along the entire horizontal length.
In the pursuit of optimizing horizontal well clean-ups, the implementation of a staged approach presents significant advantages over a single stage clean-up. The staged clean-up process is particularly beneficial in scenarios where flow dynamics favor the heel portion of the well. This could lead to future issues when the toe portion of the well starts contributing after downhole pressure/flow dynamics balance, potentially causing plant upsets due to the flowback of unrecovered drilling and stimulation fluids. This method involves the sequential opening and clean-up of sleeves, commencing from the toe to the heel, which ensures a thorough and efficient removal of drilling and acid stimulation fluids.
The introduction of the horizontal well clean-up technique, spanning a total length of 2 km with 23 sleeves, marked a first for the organization. It necessitated extensive planning and alignment meetings due to the lack of initial operational implementation experience, the high costs associated with Schlumberger's Management of Residuals Materials (MRM) unit deployment, and the challenges posed by shifting tools such as coiled tubing and tractors in a high H2S environment, where coiled tubing's corrosion resistance could be compromised.
The logic of the three-staged MRM clean-up proposal was driven by reservoir characteristics and the strategic grouping of sleeves to prioritize zones of lower quality. The procedure also incorporated well sweetening and inhibitors pumping to maintain the integrity of the coiled tubing. Continuous well-head samples were collected to monitor the recovery of drilling and stimulation fluids. The well clean-up operations were successful, achieving their objectives by effectively recovering most of the drilling and stimulation fluids. The coiled tubing was used efficiently without encountering any integrity issues.
The data gathered from each clean-up stage offered valuable insights into well productivity and played a crucial role in shaping the design of subsequent stimulation interventions. This demonstrates the effectiveness of the staged clean-up approach in not only ensuring a thorough clean-up but also in providing critical data for future operations.
