Angelo Calderoni

ENBD, the proprietary Eni Managed Pressure Drilling with Uninterrupted Mud Circulation: Technical Update after the First Year's Activity

“MPD means an adaptive drilling process used to control precisely the annular pressure profile throughout the wellbore. The objectives are to ascertain the downhole pressure environment limits and to manage the annular hydraulic pressure profile accordingly. MPD is intended to avoid continuous influx of formation fluids to the surface” (IADC). Eni owns its own MPD, called “ENBD Eni Near Balance Drilling”. ENBD is an innovative drilling process used to maintain constant bottom hole annular pressure at all times while circulating, and to manage the annular dynamic hydraulic pressure profile accordingly. ENBD is assisted by a proprietary system for continuous circulation, called “E-CD” and composed of special subs which are positioned on top of the stands. Only the stands which will be drilled through the section of the well requiring continuous circulation need to have the subs installed. A dedicated Manifold positioned on the rig floor will divert the mud flow from the Stand Pipe Manifold to the subs. ENBD through E-CD System assures the continuity of the MPD process, without “transitory” times. The conventional MPD instead, always needs to stop the mud circulation and requires to back-up the momentum lack of friction losses in the wellbore by means of some “surrogate” systems. Having conceptualized the ENBD back in 2005, several independent test applications were requested before bringing the “whole tool” at work; the E-CD tool independently accumulated more than 1800 working days over 10 challenging wells, including two extended horizontal sections (one in an Extended Reach Well), three HP/HT’s, and one complicated deep sidetrack. The first ENBD application selected to prove the concept and benefits, was conducted within the most challenging available environment: mud weight has ranged up to 2.23 sg (18.6 ppg), with fracture gradient of equivalent 2.26 sg and with operational pressures of 5000 psi. This paper will update the Industry about the achieved results, including some offshore applications from floaters.