An Improved Dynamic Well Control Response to a Gas Influx in Managed Pressure Drilling Operations

Abstract Managed Pressure Drilling (MPD) offers the capability to control an influx dynamically, without conventionally shutting-in. Some current methods use applied-back-pressure (ABP) to force flow exiting the annulus to equal flow entering the drill-pipe, which is interpreted as influx cessation. However, solely ensuring flow continuity does not imply influx cessation, unless the annular fluids are incompressible. In this work, the impact of compressibility on dynamic well control is investigated. The transient response of compressible, multiphase flow in the annulus is examined using mass conservation over a control volume. Limitations of Qout = Qin indicating influx cessation are explored, and an improved ABP dynamic well control technique is proposed. The new technique is applicable in MPD operations where conditions warrant dynamic well control rather than conventionally shutting-in. It is shown that with some current methods, influx may not cease once flow out is constrained to equal flow in. It is also shown that in some situations, influx ceases before flow continuity is achieved, resulting in excessive bottomhole pressure. These outcomes are consequences of in-situ gas compressibility, making it invalid to solely rely on Qout = Qin to indicate influx cessation. The proposed technique is shown to offer accurate determination of influx cessation, even when compressibility is significant. New pressure and pressure derivative based parameters that carry the signature of influx cessation are defined. It is shown that consideration of these parameters appreciably increases the likelihood of successful well control. Several examples are shown to illustrate the new approach with the use of the new signature parameters. Numerous transient, multiphase flow simulations have supported the key analytical conclusions from this work. The results of this work are expected to improve the reliability of dynamic well control using ABP during Managed Pressure Drilling operations. Further, the new signature parameters are easy to monitor and interpret, and together with flow rate provide valuable additional information to assist dynamic well control.