MPD, Continuous Circulation Systems Increase Safety Levels, Performance

High safety standards on the drilling rig floor combined with the reliability of the system’s components are in line with Drillmec’s philosophy in all drilling operations. The future of the industry is to move to fully automated remotely controlled drilling rigs, increasing safety standards and profitability, said Angelo Calderoni, vice president, R&D and marketing, Drillmec.

“Consider that in offshore activities 25% of the kicks happen during drilling and circulating, 25% are related to making connections and the last 50% are related to tripping the drillpipe in and out of the well. Through the integration of the Heart of Drilling (HoD) system in conventional rigs, it is possible to avoid 75% of the kicks, those related to making connections and tripping phases. The 25% remaining kicks that can happen during drilling can be immediately detected and mitigated,” he explained.

E&P interviewed Calderoni on continuous circulation and managed-pressure drilling (MPD) systems and how those systems will become standard equipment on all new rigs.

E&P: Why does the drilling industry need continuous-circulation MPD techniques? How will this contribute to a more fully automated drilling system?

Calderoni: In situations with a narrow drilling margin between pore-pressure fracture gradients, it is not unusual that a well is abandoned before reaching the target, thus failing technical and commercial objectives.

In the last decade, technologies such as MPD and continuous-circulation systems have been developed to manage bottomhole pressure and its related problems. In my long experience in drilling wells all around the world, I have utilized both systems. But for different reasons I believe that interruption of mud circulation for a connection is one of the main causes of typical drilling problems.

The mud acts as the first safety barrier in the well. Most frequent drilling accidents happen when the mud pumps are off due to bottom fluctuations in ECD [equivalent circulating density] and downhole pressure spikes like connection kicks or stuck pipes can happen. In conventional drilling this 'stop/start' cycle of mud circulation occurs very frequently, every 9 m, 18 m, 27 m or 36 m [30 ft, 60 ft, 90 ft or 120 ft] of hole being drilled.

With continuous circulation, the formations do not suffer from pressure oscillations, hole-cleaning improves and the ability to pump out of the hole for extended intervals usually means the string can be moved until it is inside the previous casing, reducing the chance of problems in open hole. I have drilled more than 150 wells onshore and offshore with continuous circulation, always reaching the target. Sometimes continuous circulation made the difference that ensured achieving the target.

This process requires the continuity of drilling operations, where the first objective is the continuity of the first safety barrier, the hydraulic barrier. Important data can be collected from circulating mud, while every time we stop the mud circulation we lose the link with the bottom.

E&P: How does the Heart of Drilling system work and what are the advantages?

Calderoni: The HoD was designed by Drillmec to prevent drilling accidents and improve drilling efficiency. It combines the advantages of continuous circulation (HoD^CC), a high-resolution flow-rate monitoring (HoD^FM) system and an anti-friction device (HoD^AF).

In line with Drillmec’s philosophy, everything in the HoD’s continuous circulation system is designed to guarantee high safety standards on the drill floor, system components’ reliability, and easy and fast rigup-down in all rigs in operations.

The HoD^CC is composed of a set of valves, integrated in special subs mounted on top of each drill stand used to drill well phases with continuous circulation. Subs are compatible with all sizes of drillpipes, from 4½ in. to 6 5⁄ 8 in., and their inside diameter allows wireline intervention.

The clamp provides the valve to open and close in a fully automated way, avoiding all kinds of hand-based operations on pressurized equipment. The HoD manifold, connected to the rig mud circuit, acts to divert flow from the standpipe line to the clamp and consequently to the valve, ensuring uninterrupted mud circulation when the top drive is disconnected from the drillstring.

The HoD^CC introduces changes to the conventional mud flow circuit only during drillpipe connection/disconnections. Before starting the connection/disconnection of the drillpipes, the mud flow is diverted to the manifold, and in a few seconds the system is able to start the flow switching sequence. Two operators set the clamp on the sub and move away to a safe position
where a human-machine interface [HMI] is located.

The HoD’s valve configuration consists of a double mechanical barrier between the mud pressure inside the pipes and the outside (both with a working pressure of 7,500 psi), ensuring high safety standards on the drill floor and in the well.

One operator can manage and monitor all phases of the flow’s switching sequence by means of a dedicated XHoD control system and its HMI, from the driller control cabin or a safe position. After the pipe connection/disconnection, the mud flow is restored to the conventional standpipe line, the HoD manifold is disconnected and the clamp is removed from the sub.

E&P: What is the value of the high-resolution flow-rate monitoring system, and how does it work?

Calderoni: Drillmec provides high-resolution flow-rate monitoring, where two measuring skids perform data acquisition from the circulating mud, allowing an accurate monitoring of mud parameters over a large range of flow rates, mud weights and types and providing a real-time alarm if influx of formation fluids or mud losses arise.

The combination of continuous circulation and flowrate monitoring is an open-loop MPD, where continuous circulation acts as prevention of accidents, ensuring continuity of the hydraulic safety barrier, and the flow-rate monitoring helps operators to quickly make the right decision in case of kicks or mud losses.

E&P: Why is the anti-friction device important?

Calderoni: The Drillmec patent-pending anti-friction device provides a wear-resistant and low-friction coating layer that reduces friction between the drillstring and the internal casing surface, particularly during extended-reach drilling. The device can be mounted on each HoD sub, ensuring maximum protection of casing surface and a reduction of stresses coming from the drillstring to the top drive.

Combining the continuous cuttings’ transport ensured by continuous circulation with a friction reduction in the well makes it possible to increase the length of horizontal wells.

E&P: What are the safety implications of the HoD system?

Calderoni: The HoD package has been designed in compliance with the main industry standards for a working pressure of 7,500 psi and a maximum flow rate of 1,200 gal/min. The double safety barrier configuration of the HoD valve and the full remote control of any operation guarantee very high safety standards, in line with Drillmec’s hands-off philosophy.

With the XHoD’s HMI, the operator can manage and monitor continuous circulation components and high-resolution flow-rate monitoring data. It provides a full and clear overview of the status of any system components, focusing on the status of any HoD manifold valve, pressure line and main function of the HoD clamp.

During operations the software provides help to operators with help text messages and warnings.

E&P: What will be the next generation of MPD systems?

Calderoni: Drilling ‘continuously’ is the present for some operators and will be the future for the entire industry. Preventing accidents and cost savings are the crucial aspects.

Continuous circulation increases both safety levels and performance with a very simple economically feasible configuration that can be easily integrated in all rigs in operation.

Similar to what happened for the top drive, the continuous circulation technology will be fully integrated into all new drilling rigs after a period where continuous circulation is provided as a service.

The next generation of fully automated drilling rigs will be designed considering continuous circulation as an integral part of the mud system. Drillmec, following its focus on innovation, has developed a new generation of fully automated hydraulic rigs for deep wells, named AHEAD, where the technology is already integrated.