Contingency Management During Clean-Up Operations in Deep Water Environments

Abstract

Clean-up and well start-up operations are often considered as routine operations. This paper provides insights on the proper planning processes to manage several potential contingencies during the initial flow of new wells in deep water environments. Examples of ill-planned operations quantify the downtime, reservoir damage and permanent productivity impairments. A review of the last 25 years of operations in deep water in various regions from the Gulf of Mexico, Brazil, Angola, East African, India, and Black Sea has led to a significant enhancement of the planning processes and execution techniques of initiating and displacing completion fluids out of the well bores. A weighed ranking of the individual causes of operational unconformities provides a prioritization of the necessary contingency plans that need to be addressed. They rank from MetOcean challenges (wind, heave, rain) to human induced activities or to well, reservoir or fluids "surprises". The key to the success of these operations lies mainly in the early determination of the mitigation's procedures. Unplanned shut-in during the early part of the clean-up (less than three hours) can lead to significant back flow of unwanted fluids to the formation and potential damage to the near well bore zone. The initial step of the process involves the ranking of the potential disruption that could occur in the specific operating area/fluid/geology settings. Next, the proposed methodology involves the systematic utilization of transient well bore models coupled with a near well bore model to simulate the various scenarios that may affect the flow. Sensitivities on parameters uncertainties or operational flexibility enable the determination of the worst-likely case scenario and for each of these (or combinations of), a workaround / contingency solution is virtually tested and verified. The cost/benefits of each contingency plan are evaluated and mapped in a traditional risk/frequency matrix. As a support to the well clean-up/start-up, an expected pressure / temperature / rate history is provided with dynamically set high and low alarm levels to enhance the governance of any operational unconformities. Real time monitoring of downhole and surface information allows the confirmation of the status of the clean-up/flowback at all time, and reduces the number of potential contingencies as the well is getting more and more cleaned-up. The paper provides a novel approach to define the global efficiency of clean-up and allows a computation of the environmental footprint of the operation and its contribution in terms of carbon intensity. Wells have been cleaned-up since the beginning of the petroleum industry.