Underbalanced Drilling: Real Time Data Interpretation and Decision Support

Abstract

The accurate prediction of the downhole pressures and the returning flow rates in low-head drilling (LHD) and underbalanced drilling operations (UBD) is a major concern in the oil industry. The present work shows an original formulation of a dynamic two-phase flow model based on the classic drift-flux set of conservation equations. However, different from the traditional approach, the closure of the system is obtained by using measured data acquired during the execution of the operation. The innovative concept consists of formulating simple closure relations that are dependent on unknown parameters, which are calculated and updated from time to time to minimize the differences between model predictions and measured data.The potential of this new approach is discussed by presenting some transient examples of application. The current study represents a first step on the development of a methodology for the introduction of a learning while drilling process in the hydraulic design and follow-up of LHD and UBD operations.