Your account already exists. Please login first to continue managing your settings.
Tight holes, lost circulation, and well control problems are being solved by turning control over to automated managed-pressure drilling systems.
The automation of managed-pressure drilling (MPD) is providing the speed and precision necessary for managing some of the most complex and troublesome downhole pressure environments.
By enabling the identification and control of downhole pressure fluctuations (with pumps off or while circuiting), automated MPD methodologies are providing a greatly enhanced ability to prevent or mitigate many costly drilling problems such as wellbore stability and kick/loss cycles.
In offshore drilling, and especially in deepwater operations, automated MPD is often the only solution to drilling wells within extremely narrow margins of pore pressure and fracture gradient. These wells typically exhibit high pore pressures at shallow depths due to fast sedimentation and lack of compaction and low fracture pressures due to the lower overburden of water compared to denser sediments. Automation is critical to staying within these narrowly defined drilling windows where influx and loss fluctuations require a rapid, precise response.
In the North Sea, highly accurate real-time monitoring and control using Weatherford’s automated Microflux system cut about 50 days per well in an HP/HT drilling program. Key to this reduction was the ability to bleed off high-pressure, low-volume gas pockets and allow drilling to continue without changing mud weight.
The system provided very sensitive, accurate identification of wellbore pressure variations. While drilling one of the wells, the system detected five small bottomhole influxes while drilling the 12 1/ 4 -in. section. The minor gas influxes were safely controlled and circulated out of the well in much less time than conventional mud and BOP methods. Precise adjustments of equivalent circulating density (ECD) in real time also reduced the risk of fluid losses caused by exceeding the fracture gradient.
The speed and precision of automated MPD also is central to preventing and mitigating sensitive wellbore instability conditions. Managing these conditions is critical to drilling long lateral sections and complex wellbore geometries.
For example, automated MPD operations eliminated historic shale instability and hole collapse problems in the reservoir section of an extended-reach horizontal well. The North Sea drilling operations avoided wellbore destabilization by using the MPD system to greatly reduce pressure cycles during connections, and limit pressure surges that lead to pack-offs. The improved wellbore quality allowed trouble-free running of the completion screens to target depth. The performance cut 13 days rig time vs. offsets, and the shale section was the longest ever drilled in the field.
Automation involves control systems and information technologies that reduce human work in the production of goods and services. While mechanization uses machinery to reduce the muscular requirements of work, automation reduces the need for human sensory and mental efforts.
An automated MPD system provides downhole pressure management by monitoring and controlling the wellbore environment with hydraulics modeling software, an automated drilling choke, and sensors for pressure and flow data. Mass flowmeters measure volume and density pumped into and out of the well to identify downhole events. A rotating control device contains and redirects annular flow to create the closed-loop circulating system on which MPD systems are based.
This MPD system is made up primarily of conventional rig equipment and is easily added to existing drilling and pressure control equipment. Once the system is in place, operations can easily transition between MPD (closed-loop) and conventional drilling (open-to-atmosphere) based on drilling conditions and requirements.
Control is achieved by applying the automated drilling choke. In the closed-loop system, choke variations at the surface are transmitted downhole to effect an immediate change in ECD. The result is the same as the conventional response of changing mud weight but achieved with much greater speed and precision.
The system automatically executes various control processes according to predefined parameters, including kick and loss detection, kick control and circulation, and kill-weight mud circulation. It also has the ability to execute pump ramps during pipe connections.
Influxes and losses are detected based on comparisons of actual and predicted flows and pressures and trend recognition. Once a change is detected, the system executes a driller’s method response. Conventionally this involves the application of constant bottomhole pressure and two circulations – one to remove the influx and the second to kill the well. The automated MPD response circulates the influx out of the well bore but does not require the time-consuming changes in mud weight.
The system also is able to “fingerprint” pressure behavior during connections and pipe movements to determine whether a kick is being swabbed or if the well is statically underbalanced. Surge and swab pressures are easily tracked and their consequences, usually swabbing a kick or inducing a fracture, are very quickly identified and confirmed . This not only provides a more effective response but also avoids the sometimes-significant repercussions of misdiagnosing a pressure flux and exacerbating rather than mitigating the situation.
Automated MPD puts in place the elements required for remote operation monitoring. The real-time data acquisition and control system incorporates a database server and various human machine interfaces (HMI), including the main system operator’s panel, driller’s panel, MPD screen panel, and remote panels as required.
The HMI is linked to the intelligent control unit (ICU), which is located on the MPD manifold and is the brain of the system. All data is acquired and directed to the ICU, and operations are monitored and controlled from this unit. All the critical controls, algorithms, and data acquisition are installed at the manifold to avoid any potential problems with communication and to increase the reliability of the system.
The system acquires all the data from other service providers on the rig, such as mud logging, directional, and PWD/MWD/LWD, via standard wellsite information transfer specification protocol. All the data is stored at the system database on the rig and transmitted to a service company central server using a standard Internet connection.
From this central server, data can be retrieved anywhere an Internet connection is available. This provides full interaction between service company technical support, the operator‘s technical team, and the rig. This interaction has proven extremely useful in interpretation of rig events and evaluating the response options.
If automated MPD systems can be controlled from the operator’s panel on the rig, theoretically they also can be controlled from hundreds or even thousands of miles away.
It is apparent from the success of automated MPD in improving efficiency and safety while solving challenging drilling problems that this technology and its application will continue to grow.