The applications of Managed Pressure Drilling (MPD) proceed to expand. With increased familiarity, and improvements in MPD technologies and methods, the range of operations where MPD can be applied continues to grow together with the value it can provide.
In its early years, MPD was primarily associated with maintaining a near Constant Bottom Hole Pressure (CBHP) while drilling. Now, there are several MPD methods to choose from, each with different capabilities and application areas. As a result, MPD is used not only to enable drilling operations, but also to support cementing, optimize tripping operations, influence well design, and improve completion performance.
In this article, we explain MPD and the three main methods, and how their capabilities influence their application areas. By the end, you will hopefully have a clear understanding of its benefits and if this is the preferred method for your operations.
Simply put, Managed Pressure Drilling offers the ability to adjust and control the Bottom Hole Pressure (BHP) in the well.
The three main MPD methods discussed in this article are Continuous Circulation System (CCS), Surface Back Pressure (SBP), and Controlled Mud Level (CML).
It is vital to understand the differences between these MPD methods and their respective advantages. CCS will, for example, offer improved hole cleaning and ideal pressure profiles, but its application areas are limited. SBP can provide Influx Management but requires frequent displacements and creates an undesirable pressure profile . CML eliminates the flat time associated with MPD and is straightforward to use across a wide range of operations but cannot be used on rigs with a surface BOP stack. To get a better understanding of these methods, and their differences, please refer to a separate article “CCS, SBP, CML - A Comparison Guide” which details this matter.
Check out: How Does CML MPD work?
The application areas of MPD are increasing, and they also differ between the various MPD methods. To provide a better overview, this section is divided into applications where MPD is used as a necessity, applications where MPD is used to enhance operations, and applications where MPD is used to improve operational safety.
The initial application for MPD was enabling drilling in narrow operating windows deemed undrillable with conventional methods. By operating with a CBHP at a given setpoint in the well, the BHP remained near constant at that point enabling drilling.Today, this remains one of the primary applications for MPD.
Managed Pressure Cementing (MPC) is also a common application for MPD. By using MPD, the increase in BHP during cement displacement can be reduced or managed, to avoid losses and achieve the desired Top of Cement.
When used for CBHP and MPC applications, MPD is an enabling technology where a conventional approach is insufficient due to the operating environment. Historically, additional time associated with slow tripping and frequent displacements has limited the use of some MPD methods to situations where they were considered necessary.
Other enabling MPD applications include drilling through pressure ramps with a high degree of uncertainty regarding actual pore pressure, and drilling in depleted fields where conventional approaches are unable to continue drilling. For pressure ramps, a SBP system is well suited due to its ability to rapidly increase the BHP as needed according to actual downhole conditions. When drilling in mature fields CML is ideal for lowering the BHP according to the actual degree of depletion.
Figure: Generic pressure profiles for CML and SBP during static and dynamic conditions.
CML and SBP use different approaches to pressure management, resulting in different pressure profiles throughout the well. These differences influence where the methods are typically applied and the operational benefits they can provide.
Primarily through the CML method, MPD is increasingly used to optimize operations as well as enable them. Side benefits with CML include faster and safer tripping while avoiding the need for fluid displacements. By increasing or lowering the riser level, the pressure profile can be adjusted to mitigate the surge or swab effect, providing a larger tripping margin. The improved tripping speed also leaves the open hole exposed for a shorter period of time. Conventional drilling operations can also be optimized by adjusting the fluid level in the riser instead of changing fluid properties and/or drilling parameters.
Systems such as EC-Drill® utilize this approach to provide pressure management through riser level adjustments during drilling operations.
MPD can also help address unforeseen events such as stuck pipe. With CML, the fluid level is reduced until the pipe is free before resuming operations.
In mature fields, CML works both as an enabler to continue drilling and as an optimizer by supporting access to more of the reservoir.
A Dual Gradient Effect is generated when drilling with a reduced fluid level, resulting in a pressure profile with lower pressure at shallow depths (Shoe) and increasing pressure deeper down the well (Bit). By benefiting from this effect, particularly deepwater wells, it is possible to extend sections and simplify casing design because the pressure profile aligns more closely with the trend of most operating windows.
Simplifying the well design makes it easier to drill and complete the well, while also reducing the time and cost associated with an additional casing section. In other environments, sections may be drilled longer without having to set casing or use contingency liners, and MPD is increasingly used to improve well planning.
Managed Pressure Completion, and particularly Managed Pressure Gravel Pack, is possibly the greatest value driver for MPD. By using the CML method, the completion assembly can be run in faster, and the gravel pack operations can be completed after a full screen-out is achieved without taking losses. In the right applications, this can contribute to improved completion quality and increased production performance.
With MPD comes Early Kick and Loss Detection (EKLD). The CCS method uses a mass-flow meter, and the continuous circulation means there is always flow through the meter while drilling. The SBP method also use a mass-flow meter to provide EKLD when circulating. The CML method uses pressure sensors in the riser, monitoring directly on the well subsea providing near-instant feedback on gains or losses in the well.
With a riser closure device installed, either the Rotating Control Device for SBP or a Dual Annular or Active Control Device for CML, Riser Gas Handling can be addressed. The ability to conduct Influx Management and divert returns away from the drill floor is not only an added safety feature but also reduces rig time by avoiding conventional well control handling which can be time consuming, particularly in deepwater wells.
MPD can also address unforeseen events instantly and allow operations to resume without risk of downtime or more serious permanent issues. One example being free stuck pipe, or even wireline, particularly with CML MPD where the BHP can be reduced in steps until the pipe is free.
Read more: MPD methods: Pros and Cons of CML vs SBP
MPD is increasingly used across a wider range of drilling and completion operations. The list below contains the most common applications for MPD.
The main application for MPD remains enabling wells which are considered undrillable with conventional methods. For some MPD methods, additional value can also be generated through optimized operations.
With increased familiarity, MPD is more frequently used for optimizing well planning and well design and improving production. Simplifying the well design in deepwater wells is now a standard approach with CML MPD and Managed Pressure Gravel Pack has documented a significant increase in production rate and lifespan.
The present and future applications of MPD increasingly combine enabling and optimization objectives. As experience with the different methods grows, so does the range of applications and the value they can provide.