Managing Pressure Drilling with Continous Circulation, A Summary of Eni Experience

Abstract

Abstract Drilling exploration wells may be challenging due to uncertainties related to several factors like well downhole pressure, pore and fracture pressures, etc. As a result, a well may fail to reach its target depth. Managed Pressure Drilling (MPD) is a useful technique in challenging conditions. It allows pore and fracture pressures to be accurately calculated while drilling, and the mud weight adjusted accordingly. Besides, it reduces the chance of human errors as it is an automatic device managed by specific software. Eni's distinctive MPD system is the e-nbd™ (Eni Near Balance Drilling). This system consists of an innovative drilling process that maintains constant bottom hole annular pressure at all times. The system does not require that mud circulation be stopped and compensated with a back up pressure. The e-nbd™ is assisted by a proprietary system for continuous circulation that is called e-cd™ (Eni Circulating Device). The e-cd™ system is composed of special subs that are positioned on top of each drilling stand. The number of required subs is defined by the length of the open hole section that is to be drilled with continuous circulation. The system is completed by a dedicated manifold that is positioned on the rig floor that automatically diverts mud flow from the Stand Pipe Manifold to the subs. e-nbd™ through the e-cd™ System ensures a continuous MPD process, without any "transient" time. This paper presents this innovative system and the achieved results. It reports a summary of the applications performed to date, including some offshore applications from floaters, as well as the major benefits of the system.