Analytical model to control off-bottom blowouts utilizing the concept of simultaneous dynamic seal and bullheading

The current methods for off-bottom control of blowouts involve pumping kill fluid into the well through an injection string. These are the dynamic kill and the momentum kill.;The dynamic kill, which is based on the steady state system analysis approach, and the momentum kill, that is loosely based on the Newton's Second Law of Motion, have been used extensively in off-bottom control of actual blowouts. A comprehensive study of these two concepts was performed. The review included an analytical analysis of the published design techniques for both of these methods. The application of these techniques to several different field and hypothetical cases were compared. The study drew conclusions about the conceptual validity, applications, advantages, substantial shortcomings, and design problems for each method.;In this work, an alternative method for controlling an off-bottom blowout was also developed. The method is based on the dynamic kill and bullheading concepts and is called "dynamic seal-bullheading". Conceptually, the method involves two important stages in the control process. First, a dynamic seal is established at the injection string depth. Second, this forces a portion of the kill fluid to flow downward displacing, equivalent to bullheading, the remaining formation fluid in the wellbore back into an open formation. The models for each stage of this method were implemented in a computer program to give a design method for estimating the kill parameters such as kill flow rate, kill fluid density, kill fluid volume, pumping time and effect of control depth. The program also calculates the formation fluid influx, surface pressure, bottomhole pressure, and pressure at critical points in the well as a function of time during the control.;The proposed method and the conventional dynamic control method were compared for two different off-bottom blowout scenarios using the new computer program. The first scenario is an actual field case and the second is a hypothetical blowout with input data from a real well configuration and reservoir. In both cases, dynamic seal-bullheading would provide a more reliable and conclusive kill in a minimum period of time.