Managed Pressure Drilling Applications Index
Authors: Coker Ian C. 
Published: October 2008

Abstract
Managed Pressure Drilling (MPD?) uses existing underbalanced technology to transform a well operation into one where the pressure can be precisely managed, whatever it is, in relation to the pore pressure of the surrounding rock. MPD may apply to underbalanced, near balanced or overbalanced drilling operations. This makes it possible for operators to increase the range of fields considered economic, which could be very advantageous for the industry, considering that presently over 50% of prospective offshore hydrocarbon formations are economically undrillable using conventional overbalanced drilling methods.
This paper describes and explains the Applications Indexes, that align certain UBD equipment required to nullify or eliminate a number of conventional overbalanced drilling barriers or obstacles, i.e., loss circulation, slow Rate of Penetration (ROP), narrow fracture to pore pressure margins, excessive casing programs, shallow geo hazards, extended reach issues, etc.

Introduction
Though these applications of UBD methods to MPD are being recognized throughout the industry, they are not formalized into suitable reference documents. To address this shortfall a Managed Pressure Drilling Applications Index (MPDAI) has been developed which provides a cross-reference matrix format to indicate the specific tools and methods best applicable to each of the drilling obstacles that may be encountered in a marine drilling environment. Four Applications Indexes have been developed to guide users of MPD technology for offshore drilling applications in:Rigs with a surface BOP stacks.Rigs with a subsea BOP stacks.Riserless drilling of top holes in deep water.Emerging variations of MPD such as dual gradient deep water drilling and slim riser deep water drilling with a surface BOP stack.

Defining Managed Pressure Drilling
This accepted industry definition of MPD was addressed at the Managed Pressure Drilling Forum 2004: "Managed Pressure Drilling has been characterized as "Walking the Line." This adaptive drilling technique precisely controls the annular fluid pressure profile within a wellbore. The concept of containment practiced in MPD allows drilling of what might otherwise be economically unattainable prospects. MPD allows faster corrective action to deal with observed pressure variations. The purpose of MPD is to both ascertain the downhole pressure environment limits and manage the annular hydraulic pressure profile to fit within that window. MPD is a tool, which will, in comparison with conventional drilling, mitigate the risks and costs associated with drilling wells within narrow, downhole environmental limits by proactively managing the annular hydraulic pressure profile.
MPD may be accomplished by many means including combinations of backpressure, variable fluid density, fluid rheology, circulating friction, and hole geometry. Containment used in this context means that MPD is focused not on creating a pressure draw down across formations, which may produce hazardous flow products, but instead to contain any flow incidental to the operation."1

Importance of MPD offshore.
It is important, almost vital, that MPD become widely and comfortably used in the offshore market. This technology can, and will, lead to many current offshore resources becoming available. Some industry professionals would quote figures that as much as 70% of current offshore hydrocarbon resources are economically undrillable using conventional drilling methods.