Well Control Analyses on Extended Reach and Multilateral Trajectories
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For economic and technical reasons, the industry has utilized directional, extended reach, horizontal, and multilateral wells. For the planning of the well trajectory in a two dimensional plane, in the past we have used composite buildup charts or several directional equations depending on the trajectory type. We can develop a simple equation for the length and angle of the first hold section, by computing the hold length first using vertical depth, kick off point, horizontal departure, and buildup rates. Surface choke pressures are highly dependent on kick vertical height in the wel and well trajectory. As the final hold angle of the well increases from vertical, shutin casing pressure reduces to shutin drill pipe pressure and becomes the same as long as the kick stays in the horizontal section. For the equal vertical depths, the maximum choke pressure is not sensitive to hold angles or hold lengths as long as the initial pit volume gain is the same. However, for directional and extended reach wells, choke pressure can increase even without kick expansion due to the change of kick vertical height in the build section. This may mask choke pressure reduction when the kick passes the casing shoe, especially if the kick off point and casing shoe depth are close. In multilateral wells with more than one flowing wellbore, shut in drill pipe pressure is affected by the maximum value due to the kick influx volume and formation overpressure of each branch wellbore. Therefore, we should be careful in the interpretation of the shutin pressures. For safe circulation of the kick out of the hole, we must consider imposing additional pressure to compensate for hydrostatic pressure reduction resulting from kick migration and expansion from branch wellbores. Copyright 2004, Offshore Technology Conference.
author list (cited authors)
Choe, J., Schubert, J. J., & Juvkam-Wold, H. C.