Managed Pressure Drilling

MPD 101

What is Managed Pressure Drilling?

The International Association of Drilling Contractors (IADC) defines Managed Pressure Drilling (MPD) as an “adaptive drilling process used to precisely control 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 a much better and more efficient way to control the pressure profile in the well. It is possible because an MPD system creates a closed circulating system instead of the open one used in conventional operations.

In conventional operations, the system is open to the atmosphere on the top. There is no way to control the pressure by means of applying pressure on surface.

In MPD, a Rotating Control Device seals the annulus against the drill pipe, allowing pressure to be applied on surface without any fluid spill. This allows for the use of gas as a fluid as well.

Drilling choke valves precisely control the pressure on surface, allowing for the necessary changes in the pressure profile along the wellbore.

Conventional vs. Managed Pressure Drilling

Conventional Drilling requires a change in mud weight for the entire well to change the bottomhole pressure conditions, while Managed Pressure Drilling (MPD) utilizes additional surface equipment that allows closed-loop drilling and application of desired Surface Back Pressure (SBP) in the annulus to rapidly change downhole pressure conditions.  

MPD offers a more controlled and adaptive approach, allowing operators to manage downhole pressure more precisely, enhance drilling efficiency, and mitigate risks, making it a valuable tool in optimizing drilling operations in challenging geological environments.

Both profiles need to be zero at surface in Conventional Drilling

Conventional Drilling:

​​In conventional drilling, the well drilling system is open to the atmosphere at the top.

  • This creates two profiles:
    • The static one which is due to the drilling fluid hydrostatic pressure (solid line)
    • The dynamic or circulating one due to the hydrostatic pressure plus the pump pressure necessary to circulate the fluid into the wellbore (dotted line). This one is called Equivalent Circulating Pressure or ECD.
  • One of the limitations of an open system is that the pressure profile always starts at zero at surface.
  • There is also a difference in the pressure at the bottom caused by the added pressure when pumps are on.

Both profiles can have similar bottom hole pressures

Managed Pressure Drilling: 

  • MPD enables the driller to adjust the surface pressure in order to fit the drilling annulus pressure profile within the drilling window.
  • This allows the drilling of wells that would otherwise be undrillable.
  • The conventional hydrostatic pressure is no longer a constraint as some pressure can be applied on surface to add to the bottom hole pressure, creating a different profile when pumps are off called Equivalent Static Density (ESD).

Downhole pressures

Downhole pressure is the measurement of the pressure at certain TVD (true vertical depth) of the well whereas (bottomhole pressure) BHP is typically the measurement of the pressure at the bottom (TVD) of the well. Fundamentally in MPD, there are three components of bottomhole pressures which include hydrostatic pressure, annular friction losses (AFL) and surface back pressure (SBP).

Formation or pore pressure

Pressure of hydrocarbons within the pores of a hydrocarbon reservoir. Pore pressure is at times the hydrostatic pressure which is exerted by the water column from the depth of a hydrocarbon formation up to the sea level.

Breakout pressure

Pressure at which stress-induced enlargements of the wellbore cross-section occur. When a wellbore is drilled, the material removed from the subsurface is no longer supporting the surrounding rock. As a result, the stresses become concentrated in the surrounding rock and the borehole walls can collapse into the hole.

Breakdown or fracture pressure

Pressure at which the formation rock will break and allow fluids to flow inside.

Hydrostatic pressure

Pressure of fluids present in a hydrocarbon reservoir. This pressure is usually exerted by a column of water on sea level from the depth of a hydrocarbon reservoir inside the earth’s surface.

The Drilling Window

The Drilling Window defines the operating range for the well to be drilled to the target depth and completed safely. It’s crucial because drilling is a complex process, and operating outside of the drilling window can lead to problems like wellbore instability, fluid losses, or even a blowout.

  • Oil and gas wells are drilled through several formations that have different pressure trends.
  • Drilling must be performed in a way that does not cause any of the following:
    • Well flowing oil, water or gas in an uncontrolled fashion (formation or pore pressure)
    • The formation collapsing, closing into the hole that was just drilled (breakout pressure)
    • Breaking (fracturing) the downhole rock, causing all fluids used to drill to be lost in the hole (breakout or fracture pressure)
  • These three pressures define the window in which the pressure created by the drilling fluid can exist within without causing problems.
  • Wells are designed in a way that every time the drilling window is narrowed down to almost zero, a new casing string is set.
  • This allows drilling to target a particular group of formations at the time, where determined hydrostatic and circulating pressure profiles can be maintained as to not exceed the defined drilling window boundaries.

MPD Drivers

Managed Pressure Drilling (MPD) drivers refer to the key factors or motivations that lead to adopting and implementing managed pressure drilling techniques in oil and gas operations.

These drivers are often influenced by the need to address challenges encountered during conventional drilling, such as wellbore instability, narrow mud weight window, influx, or lost circulation. In some more complex scenarios, MPD is also an enabler for the wells to be drilled and completed safely and successfully.

  • MPD helps maintain wellbore stability by controlling the annular pressure profile. This is crucial in preventing issues such as wellbore collapse, kicks, and lost circulation, which can occur in unconventional or challenging formations.

  • MPD allows for real-time monitoring and control of wellbore pressure, reducing the risk of kicks (uncontrolled influx of formation fluids) during drilling operations. By adjusting the backpressure, operators can mitigate the risk of formation fluid entering the wellbore.

  • In some drilling scenarios, the pressure window between pore pressure and fracture pressure is narrow. MPD enables precise control of downhole pressure, allowing drilling within these challenging pressure windows without compromising safety.

  • MPD can improve the overall efficiency of drilling operations by optimizing the drilling parameters. Maintaining constant bottom-hole pressure makes it possible to drill faster and more accurately, reducing non-productive time and improving wellbore quality.

  • Managed Pressure Drilling can be used for underbalanced drilling, where the wellbore pressure is intentionally kept lower than the formation pressure. This helps reduce formation damage and improve reservoir productivity.

  • MPD is beneficial in geothermal drilling and high-pressure/high-temperature (HPHT) wells where the downhole conditions are extreme. The ability to precisely control pressure in such environments enhances safety and drilling performance.

  • MPD systems can be configured to minimize fluid losses to the formation, reducing the environmental impact and preserving drilling fluids. This is especially important in environmentally sensitive areas.

  • MPD is beneficial in extended-reach drilling, where maintaining stable wellbore conditions becomes challenging due to the long horizontal sections. It helps mitigate issues such as wellbore collapse and differential sticking.

  • MPD systems provide real-time data on downhole conditions, allowing for quick decision-making and adjustments to drilling parameters. This contributes to safer and more efficient drilling operations.

  • MPD enhances well-control capabilities, making it an important safety tool. Managing and controlling wellbore pressure reduces the risk of blowouts and other well-controlled incidents.