First Trial of Constant Bottom Hole Pressure Drilling Application in Kazakhstan

Abstract

An increase in differential sticking events, due to depletion of the reservoir and high angle wells being actively drilled in recent years, was a primary driver to utilize Managed Pressure Drilling technology in the Tengiz field. MPD offers a more dynamic and rapid wellbore pressure control by being able to adjust the surface back pressure applied at the annulus for a given mud weight, decreasing the risk of differential sticking while maintaining constant bottom hole pressure conditions. The paper describes the results of the first Managed Pressure Drilling application in the Tengiz field and experience gained during execution where drilling multiple formations together enabled the target depth to be reached without NPT. It further highlights the operational complexity and the challenges faced during the implementation of this technology while drilling formations with varying pore pressures. The reservoir hole section had different pressure intervals, which required higher mud weight and thus high potential of differentially stuck-pipe conditions. The successful field trial shows that the Constant Bottom Hole Pressure (CBHP) application provides flexibility to be able to manage annular pressures when applying surface back pressure using an MPD choke manifold. The paper elaborates on the lessons learned and how CBHP was implemented continuously with regards to health, safety, and environment (HSE) during drilling operations. The short-term goals were to evaluate whether the application of MPD could avoid the risk of differential sticking and reduce pumps-off gas, enhance drilling performance by using lower ECD, reducing well control time by working as early kick detection tool and provide a potential for mud cost savings, along with a long-term goal of providing the option to optimize the casing design by reducing one liner section and combining drilling of two reservoir sections in one run.