The Interception of a Lost Leg in Brazilian Deep Waters

Abstract

Drilling from a tension leg wellhead platform (TLWP) to targets away from the slot creates several challenges and brings many operational risks that are not always easy to predict. The decision to reduce costs with dry completions, wellheads, and deep-water rig day-rates considerably increases drilling complexity. In this scenario, an involuntary sidetrack incident happened while circulating for hole cleaning below the casing shoe. This left a reservoir exposed in the mother well. This paper shows the decision-making process, the premises, and the directional work up to the interception of the original well. The BHAs used, drilling parameters, planned and actual well path will be discussed. The rotary steerable performance and settings while drilling to intercept the original well and the survey strategy receive special attention. Discussion about the BHA selection after the identification of the incidental sidetrack is also covered. Having an exposed reservoir made the required trajectory critical. It should be precise but also feasible, including the casing run thereafter. An additional reaming run smoothed the high local doglegs. The conclusion summarizes the complexity of this type of directional drilling operations and the estimated savings in one of the most challenging well drilled in Brazilian deep waters. There were multiple lessons learned from the operation that can help prevent the situation in future, and sharing this knowledge provides guidelines when facing a similar challenge.