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Frequently Asked Questions

1. What is EC-Drill®?

EC-Drill® is a Controlled Mud Level (CML) technology that allows manipulation of bottom hole pressure (BHP) while drilling a well. The system controls the BHP by adjusting the fluid level in the marine drilling riser, and thereby the hydrostatic pressure applied. This is achieved by installation of a Subsea Pump Module (SPM) on the riser which pumps all mud and cuttings returns up a separate Mud Return Line (MRL). The system can be used to adjust bottom hole pressure at any point during well construction regardless of whether or not the drill string is currently in the well. It can be used for many applications, including the traditional MPD application of holding BHP constant when pumps are started and stopped during a connection.

By the IADC (International Association of Drilling Contractors) categorization System, EC-Drill® is a Controlled Mud Level (CML) system, it controls the mud level in the marine drilling riser. As a marine drilling riser is installed, the system is only applicable to offshore wells.

2. Do you need RCD with EC-Drill®?

No, EC-Drill® manipulates the fluid level in the marine riser and does not require a Rotary Control Device (RCD) or an additional choke manifold at surface contrary to Surface Back Pressure MPD.

3. What are some applications of EC-Drill®?

Some applications for EC-Drill® include

-        Drilling depleted zones

-        Drilling narrow windows

-        Running casing and cementing in depleted zones and narrow windows

-        Running completions in depleted zones and narrow windows

-        Drilling into unknown pressure regimes

-        Extending shallow casing strings via the dual gradient effect

-        Freeing differentially stuck wireline tools, stuck completion assemblies or drillstring

-        Drilling zones with risk of high or total losses

-        Well Testing operations: reduce level to increase production flow temperatures

4. When can EC-Drill® be used?

EC-Drill® use is limited to offshore wells. It is normally used on wells drilled from floating rigs (semi-submersible or drillship) using a subsea BOP. EC-Drill® has also been used on jack up rigs during the initial hole sections taking suction from the conductor. There is also application for use on specific platform applications with a surface BOP when a subsea casing hanger system and separate drilling riser is used.

5. Where has EC-Drill® been used?

EC-Drill® to date has been used offshore Brazil, offshore Mediterranean, in the North Sea, in the Barents Sea and in the Gulf of Mexico. It is applicable from shallow to ultra deep water application, with jack-up, semi-submersible or drillship.

6. Can I perform cementing operations with EC-Drill®?

Yes, EC-Drill® is well suited to manage pressure during cementing operations. The EC-Drill® system can easily perform Managed Pressure Cementing (MPC) in an operationally convenient manner. The combination can allow for use of more conventional cementing techniques in some cases.

7. What are some of the additional benefits of EC-Drill®?

Once the EC-Drill® system has been installed on the rig, our clients typically see additional applications for EC-Drill® to improve drilling efficiency, including:

-        Changing BHP without changing mud weights saving circulation time

-        Ability to apply a trip margin without changing mud weight

-        Improved and simpler cementing operations via MPC

-        Improved ability to convey completion strings to TD

-        Longer Horizontal Sections drilled

-        Reduced overbalance during logging runs improving logging results

-        Reduced differential sticking condition

8. Do you need a MPD ready rig?

EC-Drill® does not require a MPD ready rig as it can install on any offshore mobile drilling unit. The surface pipework that is required by EC-Drill® is minimal. If the rig is “MPD ready” for Surface Back Pressure (SBP) MPD, some of this pipe work can likely be used, but the amount EC-Drill® surface pipework is small, and this would not be a major factor in installation of EC-Drill® on a rig.

9. What is an EC-Drill® ready rig?

An EC-Drill® ready rig is in a rig where the supporting equipment is available to allow operation to commence within a short lead time. The only equipment to be mobilized is a Subsea Pump Module and Control system.

10. Do I need to change EC-Drill® between sections?
No, the EC-Drill® equipment is run with the drilling riser. It remains subsea and available for use during the entire period of the well drilling operation. It is then recovered with the BOP at the conclusion of the well.

11. What modifications/addition equipment is required to integrate EC-Drill® onto a rig?

The main items required to integrate EC-Drill® onto the rig are

  • Modified Riser Joint (MRJ) – this is a riser joint with port to allow EC-Drill® to take suction from the riser, the modified riser joint also includes the Riser Isolation Valves (RIV) and the mounting for the EC-Drill® Subsea Pump Module (SPM)
  • Mud Return Line (MRL) – the conduit to convey Mud and Cuttings to surface from the SPM
  • Surface lines – the surface line installation is minimal, consisting mainly of a mud return line with flow meter to the low pressure mud system
  • Top fill pump – this is a small pump taking suction from active system and pumping into the top of the riser to provide a flow of mud to ensure the mud above the EC-Drill® SPM is fresh and at the same density

12. What are the mud return line (MRL) option?

The MRL can be a fixed line installed as an auxiliary line on the riser above the SPM, a flexible hose, or a string of pipe run separately in the water.

13. What is the top fill pump and what are the requirements of the top fill pump?

EC-Drill® takes suction from below the level of the fluid in the riser. This leaves a column of mud above the pump suction that would be static without the use of the top fill pump. The topfill pump takes suction from the active system and puts fluid at a controlled rate into the top of the riser, normally at the diverter housing. The SPM then returns both the fluid being pumped down the drillstring and the flow from the topfill pump. This causes a downward flow of fresh mud from active above the subsea SPM.

The required pump is normally placed such that it can take gravity feed from the active system and is controllable to a rate of 200-1200 lpm (50 – 320 gpm). It is commonly connected with the rig’s drilling control system and controlled by the driller.

15. What are the main equipment elements of EC-Drill®?

The main equipment elements of EC-Drill® are

  • Subsea Pump Module (SPM) – instrumented pump system used to pump all mud and cuttings to surface.
  • Control System – the computerized control system that controls and monitors the SPM and associated equipment allowing for precise control of fluid level in the riser and thereby well pressure

EC-Drill® is a modular system that typically requires a 14ft Office Container, a 14ft Control Container, a Subsea Pump Module docked on the riser and an Umbilical reel.

16. What is the maximum flowrate the SPM can deliver?

The EC-Drill® system can deliver sufficient flowrate for drilling in hole sections up to 26” or larger, the EC-Drill® pump module is typically limited by shaker capacity ( 6000 lpm or 1580 gpm)

16. How deep in the water column is the EC-Drill® pump installed?

The EC-Drill® is typically docked on riser up to 500 m (1600 ft) below RKB irrespective of the water depth when greater than 500m. If the water is shallower than 500 m, it would be docked near the subsea BOP.

17. How fast can EC-Drill® be mobilized?

With the popularity of EC-Drill®, the equipment is subject to availability. With available EC-Drill® equipment, the limiting factor will be rig integration time. The 3rd party modified riser joint is typically a longest lead item, with a usual lead time of 6 months, although 3 months lead time has been achieved on previous projects.

18. What impact does EC-Drill® have on well planning? How late in the planning process can I include EC-Drill®?

EC-Drill® is easy to include in well planning. The application of the system is simple and straightforward, with the desired riser level specified in the drilling program. The EC-Drill® software includes the ability also to compensate for EC-Drill® by automatically adjusting the riser level based on the pump rate. EC-Drill® impact on the mud system is limited to optional increase in mud weight over that used conventionally.

Enhanced Drilling has a complete set of operating and contingency procedures available and can assist with required risk analysis.

When EC-Drill® is included early enough in planning, there is a potential to alter casing settings depths, and to increase length of productive sections. The required well planning modifications can normally fit into the equipment lead time easily.

19. Can I use EC-Drill® with any mud type?

Yes, EC-Drill® is engineered for Non Aqueous Fluid (NAF) or Water Based Mud (WBM)

20. Does EC-Drill® interfere with MWD/LWD or BHA equipment?

No, EC-Drill® does not interfere with any drilling BHA equipment. EC-Drill® has been used with the major MWD/LWD/RSS system in operation without any issues.

21. What redundancy features do you have in the SPM?

The EC-Drill® system includes redundancy on critical equipment including riser pressure sensors (for monitoring riser level) and subsea electronics modules.

22. How is the riser level monitored?

The riser level is monitored by two dual sensors, providing 4 independent riser pressure readings. The sensors riser level sensors have an accuracy of +/- 0.145 psi.

23. In case of power outage, will we still be able to monitor the level in the riser?

Yes, the EC-Drill® control system, including the riser sensors are on UPS (Uninterruptable Power Supply) battery backup. The riser level reading remains available in event of power failure. The main power for the EC-Drill® pump module would be lost with the remaining power on the rig and is placed in the rig power shedding philosophy at a similar level to the rig mud pumps.

24. How accurately can the EC-Drill® system control the riser pressure?

The EC-Drill® system can control the riser pressure quite accurately, routinely the riser pressure can be controlled to +/- 1 bar (14 psi) through pump starts, stops and rate changes. More precise control is possible with controlled ramping of the mud pumps.

25. How do you connect umbilical and mud returnline to theSPM?

Both the umbilical and the mud return line are dry connected to the SPM in the moonpool.

26. Does Enhanced Drilling have the experience with Certification and Regulatory approval?

The EC-Drill® system has been qualified to DNV-RP-A203 -Qualification of New Technology
EC-Drill® is certified to DNV-OS-E101 and can also be ABS certified.

The EC-Drill® system has been approved for use by both PTIL in Norway and BSEE in the US.

27. Does the EC-Drill® system affect Barriers and Well Control?

The EC-Drill® system does not make a major change to barriers and well control. The primary barrier to well flow remains the mud with density monitored. We add to this monitoring of the riser level with the redundant riser level sensors.

The secondary barrier remains the BOP, wellhead, casing and cement, and conventional well control procedures are used.

28. How do you fill the riser if required?
The desired riser level is set on the control system to fill up the riser with the EC-Drill® system. The EC-Drill® SPM reduces flowrate to allow the riser to fill with the mud flow from the drill string, top fill pump, and/or boost pump. This will depend on the most convenient method for the operation being performed.

29. Can you combine EC-Drill®, RMR , MPC and CTS?

In addition to EC-Drill®, Enhanced Drilling also offers RMR (Riserless Mud Recovery), a system to return top hole mud and cuttings to surface to allow re-use of the mud and volume monitoring of the top hole. Managed Pressure Cementing (MPC) can also be performed on top holes. In addition, our Cuttings Transport Service (CTS) allows for cutting and cement returns from top hole drilling to be directed to another subsea location if they cause an issue near the wellhead. These services can be combined with EC-Drill® service with some common use of much of the same type of equipment.

30. What is CMCD?

CMCD is Controlled Mud Cap Drilling. This is a method of addressing total losses on a well using a sacrificial fluid to drill the reservoir and a heavy mud monitored in the annulus. With EC-Drill®, it is straight forward to use this method to address total losses on a well and has an easy transition to and from “conventional” MPD with EC-Drill®.

31. What is the power requirement?

The power requirement for the main motors on the EC-Drill® Subsea Pump system is 1200 amps of 3 phase 690 VAC. It is possible to accommodate other voltages including high voltage from the rig power supply.


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