Meeting emission control through improved actuation

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Courtesy of Rotork

Introduction
Reducing fugitive emissions, particularly methane, is a major priority in the fight against climate change. Although valves and actuators have been the focus for reduction efforts because valve leakage accounts for more than half of total fugitive emissions, the problem is mainly old valves that weren't designed using the latest materials and technologies. New technologies can also help to detect system leaks such as a stuck open valve.

Emission control technology in oil & gas production
Oil and gas wells, pipelines and processing facilities are receiving heightened attention from regulators and environmentalists.
Pressure is mounting on the global oil and gas industry to reduce its environmental footprint while, at the same time, the industry is under significant pressure to reduce costs.

In the USA, the Environmental Protection Agency (EPA) recently adopted three new rules that will curb emissions of methane and VOC for the first time. These rules require owners and operators to find and repair leaks, mandate fixed inspection schedules and urge the use of special equipment such as cameras and analyzers to find leaks.

In October this year, the EPA also agreed to review the accuracy of its decades-old estimates of air pollution from flaring near oil and gas drilling sites and refineries.

The control of gas and fluids is undertaken by large numbers of valves at the wellhead. Traditionally spring diaphragm actuators, powered by the produced gas, were used to actuate these valves. Because they released gas at each operation into the environment, the EPA mandates now limit this process in order to reduce greenhouse gas emissions to the atmosphere.

The EPA suggests that as many as 80% of high-bleed valve and control devices can be replaced or retrofitted. With the use of electric actuation the cost of the implementation is usually recovered within a year.

Fig 1 - Many shole wells and flow lines ore unmanned and located in remote areas that are difficult and expensive to monitor. Skilled technicians must check data and perform manual shutdowns, increasing costs for the time to travel to site, identifying the problem and stopping the flow, which is not cost-effective or practical. Actuators provide an ideal solution to automate valves at the remote wells.

Traditionally, spring diaphragm actuators powered by the produced gas have been used, but EPA mandates now limit this process to lower fugitive emissions. A key objective is therefore to provide an efficient and reliable process control actuator which can be retrofitted on installed valves to improve the level of control without venting gas and with the low power demand required for renewable energy sources.

Electric actuator replacement for natural gas powered pneumatic devices on control valves can help eliminate methane and VOC emissions, updating equipment to maintain technology can improve the operator's return on investment and profits. From the producer's point of view, eliminating emissions allows more gas to be sold, regaining the lost vented gas revenue and decreasing the need for emission monitoring.

Remote oil and gas wells often use the produced gas to power valves and equipment and these generate emissions to atmosphere. Smaller, continuously modulating electric actuators are now a possible alternative and do not emit fugitive emissions. Efficient electric motor design and robust control improve reliability.

New USA government regulations require all pneumatic controllers at the wellhead to have a maximum consumption of 6 SCFH (Standard Cubic Feet per Hour). In Canada and other countries, carbon credits can provide economic incentives to utilize low emission products, so the challenge is to provide controllers which reduce or eliminate these fugitive emissions.

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