The Pros and Cons of Today’s and Tomorrow’s Control Technologies
This blog is the first in a series that will address the five main technologies for manifold operation and control. Read below for a brief write-up on manually-operated high-pressure manifolds.
For decades the oil and gas industry has relied on a key piece of equipment to manage flow, monitor wellbore pressure, and isolate equipment for repair: high-pressure flow iron manifolds. While manifolds are used for a variety of applications such as flowback, drill-outs, choke and kill, debris catching, and cementing, the manifolds themselves share the same key components regardless of the application in which they are being used. These components include plug valves, choke valves, and the conductors, also known as “flow iron” (tees, crosses, pipe, hammer unions). The plug valves (on/off) exist to isolate flow through the left side of the manifold from the right side (or vice versa). The choke valves (positioning) are used to regulate flow through the manifold which is usually adjusted in accordance with another unit of measurement in the application, typically wellbore pressure or downstream flow. Both types of valves (plugs and chokes) require a means of opening or closing to achieve the desired application outcomes. Currently, five main technologies exist for operating and positioning these valves: manual, hydraulic, pneumatic, electric, and wireless.
Despite the hazardous conditions present in some oilfield applications and the high-pressures associated with oilfield production, manual operation of high-pressure iron manifolds is the most popular method of operating plug and choke valves today. Requiring little technology, these manifolds are cost-effective and simple to use. However, there are two key factors that must be considered: safety and human error. The most important of the two is technician/operator safety. The only way to open/close the plug and chokes valves is for a technician to manually rotate gear operators at the plug or choke valve. These adjustments are often performed during high pressure, high flow operations. If a pipe connection is not perfectly sealed or there is a failure in the flow iron, serious injury to life or property can occur. While rotating gear operators and handwheels is a simple means of opening/closing valves, there usually exists little to no electronic feedback for monitoring manifold conditions. Therefore, control and monitoring must be performed at the skid. Secondly, human error is a potential risk for operations as the wrong valve could be opened/closed or the flow adjustments could be over/under the desired amount. Choke valve adjustments for flow are often performed using a handwheel which requires a technician to visually monitors the stem’s travel. These adjustments are very short from one position to the next and it is easy for a technician to accidentally overshoot the intended position. Therefore, manually-operated manifolds leave room for human error at the valves which could produce unintended consequences for the application in question. Read below to find a small summary of a manifold’s advantages and disadvantages.
Advantages
- Cost-effective, little to no technology and a minimal amount of equipment.
- Simple operation: gearbox with a handwheel or a pipe bar for valve operation.
- Environmentally-considerate: zero opportunity for unwanted leaks of hydraulic oil or any other fluid that can be harmful to the surrounding environment.
- Meets most applicable hazardous area certifications or requirements.
Disadvantages
- Safety: operator must be at the manifold near high-pressure and high-flow applications.
- Control: no feedback sensors, automation, or external monitoring or status (health) of system or position of valves.
- Mobility: requires operator to approach the manifold each time a choke adjustment is needed, or a plug valve(s) needs to be opened/closed.
- Rig-up and rig-down time not optimal.
Manually-operated manifolds are a time-tested technology for oilfield applications and will continue to exist due to their low-cost user friendly design. However, the simplicity does not come without consequence. Operator safety has driven a need for automation and enhancement related to process control and system monitoring.
The following blogs in this series will cover other operating technologies (pneumatic, hydraulic, electric, wireless) that will address how the industry has worked to improve upon the manually operated high-pressure flow iron manifolds.
