Enhance ECD Management Using Sub-Based Uninterrupted Circulating System Application

Abstract

Bottomhole pressure management is essential to address challenging issues in hostile drilling environmentsbecause of wellbore pressure disparity during pump cycles while in circulating or noncirculating modes. This disparity can cause substantial instability on equivalent circulating density (ECD). While drilling in deepwater, HPHT, or any other hostile environment, these conditions may result in costly nonproductive time, may jeopardize operational safety, or may disrupt the well drillability.

One of the most advanced methods to enhance ECD management during drilling and connection is use of a sub-based uninterrupted circulating system. This technology has been proven to improve drilling performance by maintaining continuous circulation during drilling and connection to retain wellbore pressure stability without significant changes to the rig operation system. This system enables operators to improve drilling performance in wells with a slim pressure window, challenging geomechanical instability, extreme temperature (geothermal), high and long tangent section where hole cleaning is very essential, as well as in extended reach. This system also can be easily integrated with managed pressure drilling technology that exists in the present market.

This system uses a small-footprint, sub-based system with an automated flow switching mechanism to eliminate personnel exposure to the high-pressure system. By maintaining steady state circulation throughout the drilling process, the CFS remedies wellbore pressure disparity to retain continuous circulation and ECD management along the entire wellbore. This condition can effectively assist the operator to reduce nonproductive time, to enhance operational safety, and to enable drilling the well to target depth in a timely and safe manner. This paper will describe the equipment design of this uninterrupted circulating system as well as the best practice and constraints during operation. Generic factory testing will also be discussed to provide comprehensive understanding the reliability of the system.