Realtime Well Engineering: Estimating Casing Runnability Risk While Drilling

Abstract There is an urgent requirement in the drilling industry to discern the plausible causes associated with a casing stuck event and short landing of a casing. Traditional methods involve analyzing widely used legacy models such as the Torque and Drag/Swab Surge models and requires the interpretation of several plots at once, making it not comprehensive enough to account for many factors that may cause the casing stuck; in particular, the geometrical aspect of the wellbore is often overlooked while determining the risk. Furthermore, the available methods rely heavily on the experience of the drilling engineer, which is exacerbated by the fact that the casing stuck event is usually detected close to the casing stuck event, leaving very little time to perform any corrective measures that might alleviate the situation. Any last-minute intervention is generally not enough or is expensive and not ideal. Thus, there is a need in the drilling industry to have solutions that work in real-time that asses the risk of the casing stuck event which is comprehensive enough to take most factors into account that might affect the probability of casing stuck. The solution provided should also be simple and must not involve reading several plots at once; this removes the operational fatigue of the drilling engineer while monitoring the drilling operation. Moreover, the casing stuck event ideally must be predicted way ahead of time so that appropriate intervention is possible without having to resort to extreme measures. This paper proposes one such solution which is validated across several wells. The solution encapsulates the risk of the casing stuck considering several factors that might affect the probability of getting stuck into a single number(index) between 0 to 100, higher the value indicates higher risk. The solution offers to predict the casing stuck during the drilling operation itself leaving sufficient time for any intervention that may be needed. The geometrical aspect of the wellbore is also included in the construction of this index along with several other factors making the solution comprehensive. Finally, a single plot of the index value versus the depth is presented to drilling engineer for easy interpretation. This paper presents the methodology adopted in the construction of the real-time solution and discusses a few validation points using real cases.