Simply put, Managed Pressure Drilling offers the ability to adjust and control the Bottomhole Pressure (BHP) in the well.
The three main MPD methods today 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 usage areas are limited. SBP can provide Influx Management but has the worst pressure profiles and requires frequent displacements and slow (s)tripping speeds. CML eliminates the flat time associated with MPD and is straightforward to use for all 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 different MPD methods. In an attempt 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 without losses, gains or collapse while reducing fatigue cycling of the well. Today, this is still the primary application for MPD.
Managed Pressure Cementing (MPC) is also a common application for MPD. The BHP would remain the same, or be less increased, when the cement was displaced up the annulus by using MPD to avoid losses and ensure the desired Top of Cement was reached.
MPD when used for CBHP and MPC is an enabling technology where a conventional approach is insufficient due to the operating environment. The drawback is the extra time added through slow tripping and frequent displacements which to some extent have limited the use of MPD to only when it is a necessity.
Other enabling MPD applications are drilling in 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 with the 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.
Primarily through the CML method, MPD is more frequently used to optimize operations as well as enabling them. Side benefits with CML include using it to trip faster and safer while avoiding displacements. By increasing or lowering the riser level the pressure profile is shifted to mitigate the surge or swab effect giving a larger tripping margin. The improved tripping speed also leaves the open hole exposed for a shorter time. Conventional drilling can be optimized by adjusting the fluid level in the riser instead of changing fluid properties and/or drilling parameters.
MPD can also 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 for reaching and unlocking more of the reservoir.
A Dual Gradient Effect is generated when drilling with a reduced fluid level, which causes the pressure profiles to have a lower pressure at shallow depths (Shoe) and increasing pressure deeper down the well (Bit). By benefiting from this effect, especially deepwater wells are commonly drilling two sections as one section because this pressure profile follows the same trend as most operating windows.
Simplifying the Well Design makes it easier to drill and complete the well in addition to the time and cost saving of removing a section. In other environments, sections can be drilled longer without having to set casing or use contingency liners and MPD is more frequently 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 jobs are completed when a full screen out is achieved without taking losses. The results give a significant increase in production rate.
With MPD comes Early Kick and Loss Detection (EKLD). The CCS method use 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 use pressure sensors in the riser which monitors directly on the well subsea providing near instant feedback on gains or losses in the well.
With a riser closure device installed, either a 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 drillfloor is not only an added safety feature but also reduces rig time by avoiding conventional well control events which can be time consuming - particularly for 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, especially 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 gradually used for more drilling and completion operations. The list below contains the most common applications for MPD.
The main application for MPD is drilling wells which are considered undrillable with conventional methods. For some of the MPD methods there are also side benefits through optimized operations.
With increased familiarity MPD is more frequently used for optimizing 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.
The applications for the present and future of MPD are increasingly on the optimization side – often together with the enabling applications. Combining the applications improves the value offered by MPD.