Technologies converge to improve sensor networks in the oil and gas industry
In a time of depressed oil prices, producers and large oil companies are working hard to increase production and reduce costs. However, adding sensors to oil and gas infrastructures allow engineers to better actuate extraction process efficiency and maximize production potential.
Oil companies continually strive to improve operations by trying new technologies and workflows to increase efficiency, enhance safety, and reduce costs. They are challenged to manage increasingly complex production hardware in an ever-more stringent regulatory environment. Many pieces of machinery and processes require monitoring, but manual observations are slow, sporadic, and prone to inadvertent inaccuracies.
The approach has been to incorporate mechanical monitors to reduce mistakes, increase speed and, in some cases, provide near-continuous data streams. One key to this solution is wireless sensor networks (WSN), used in refineries, petrochemical plants, onshore well sites and gathering stations, subsea developments, and offshore oil and gas platforms.
The successful expansion of sensor and instrumentation networks in the oil and gas industry is the result of a convergence of technologies. Wired sensor systems have expanded as costs decrease, and new technologies have spurred the installation of wireless sensor networks, led by micromachining techniques that create ever-smaller sensors with low power demand. Computing power is also being miniaturized and embedded in a variety of objects. Different network topologies optimize the way these tiny computers share information and resources and facilitate more efficient collaboration. Sensors are linked using wireless technologies that employ ubiquitous sensor networks at low data rates, such as RFID, ZigBee, and Bluetooth; and Wi-Fi networks, cellular, and satellite communications at higher data rates.
Sensor networks feed data into the "digital oilfield," which focuses information technology on the objectives of the petroleum business. The purpose is to maximize oilfield recovery, eliminate non-productive time, and increase profitability through data-sharing and integrated workflows, which often involve automation and cloud-connected solutions.
Connectivity is key, whether wired or wireless. In the downstream sector, the data acquired through sensor networks are integral to closed-loop control of operating facilities.
The challenge is to meet all regulatory requirements to monitor machinery and systems in remote, perhaps hostile environments, while safeguarding personnel and the environment. Engineers want reliable sensor systems that are simple to install and configure, and can provide useful data at a low cost. Better data lead to more accurate planning and scheduling for people, parts, and processes.
Sensor networks in the oilfield can provide early leak detection with automated warnings, and monitor pipeline integrity and hydrocarbon flow.
Rotating equipment is common throughout the oil and gas industry. Condition monitoring is the process of determining the condition of machinery while in operation, allowing the repair or replacement of problem components prior to failure. Sensors can be incorporated into condition monitoring to detect, analyze, and diagnose machinery faults.
Turbines, compressors, and large motors are now normally equipped with wired, online condition monitoring and protection sensor systems. But the dynamic data arrays captured in vibration monitoring places unique demands on wireless sensors, networks, and associated components, requiring high bandwidth, wide dynamic range, low noise, and high-level processing capabilities.
Sensors, nodes, networks
Most sensors are microelectromechanical systems (MEMS). A sensor node in a wireless network is capable of gathering, processing, and communicating information with other nodes. A sensor node, also known as a "mote," includes a microcontroller (consumes less power than a microprocessor), a transceiver (transmitter and receiver), external memory (flash), power source (battery or renewable), and one or more sensors. Note that a mote is a node, but a node is not always a mote.
Network topologies are primarily linear arrays, star (hub and spoke), or hybrid mesh designs (using patterns of high-powered and low-powered nodes). All nodes are routers and do not need to be continually active. They can be programmed to "wake up" and form a mesh, for instance, at regular intervals, collect and transmit information, then shut down again to save power. Linear arrays can be quite long, with multiple (25-50) data relay hops to a base station.
Ubiquitous sensor networks (USN) refers to a network of intelligent sensors that can be made available anywhere. A USN includes small-scale sensor nodes and limited power requirements, mobile and able to withstand harsh environmental conditions. It has a dynamic network topology, with node heterogeneity, and can be deployed on a large scale.
A USN comprises a sensor network (sensors plus power source to transmit data); a USN access network (intermediary or "sink" nodes that collect info from a group of sensors); network infrastructure; USN middleware (software to collect and process data); and a USN applications platform.
Wireless sensor networks (WSN)
David Culler, a computer science professor at University of California-Berkeley, told CNN in 2010 that developing wireless sensor networks is analogous to the creation of the World Wide Web: trendy, but with practical implications.
Companies deploy wireless sensors because they are far less expensive than traditional sensors, require less time to install, and can be networked. So the first step toward implementing a wireless solution is to run a cost-benefit analysis.
SKF’s Marty Herzog points out that the cost to install online, wired sensors at an onshore facility can be as high as 15 times the cost of an accelerometer. For offshore installations, installing a wired system can be more than 20 to 30 times the cost of an accelerometer. The use of wireless sensors could therefore equate to an approximate savings of some $1,500 per measurement point.
"Wireless sensors have become instrumental for oil and gas producers by speeding up the time it takes to automate a well and providing continuous monitoring solutions," said ON World research director Mareca Hatler.
Wireless sensing and control systems are increasingly deployed in exploration, production, pipeline, and tanker operations. They are successfully used for predictive maintenance and to detect and prevent health and safety issues. WSNs gather information that can lead to innovative solutions and optimize facility operations.
Mohammad Reza Akhnondi and colleagues at Curtin University of Technology in Perth, Western Australia suggest that WSN applications offer great opportunities to optimize production where the use of wired networks is prohibitive. Wireless networks can be used to remotely monitor pipelines, natural gas leaks, corrosion, H2S content, equipment condition, and real-time reservoir status.
Successful applications of sensors
The following are some real world examples of how the installation of sensors facilitated operations.
Using sensors at the wellhead provides continuous monitoring and increases the availability of information. It also removes the need for operator rounds to manually read pressure gauges. Super-major BP installed a smart wireless network with 40 wireless Rosemount pressure transmitters at one of its well sites at Wytch Farm, UK, to continuously monitor wellhead pressure. It took fewer than eight hours to remove old gauges, and install and calibrate the wireless sensors.
BP manager Chris Geen said, "Wytch Farm has been a critical pilot project for BP to see if self-organizing wireless mesh technology would be suitable for other similar projects. Following the success of this installation, BP is planning to install Emerson smart wireless transmitters in similar applications on offshore platforms."
Mexican state-owned PEMEX was using teams of people to teams to monitor temperature and pressure at thousands of scattered oil wellheads in different onshore field areas. The company wanted a solution to connect 1,420 WirelessHART field devices from remote wellheads to their control system. Cooper Bussmann’s ELPRO provided a high-speed wireless solution, and deployed a 900 MHz long-range Ethernet network, using 945 U-E industrial Ethernet modems to solve the problem.
A major coal seam gas supplier in Queensland, Australia was expanding production to 12 million metric tonnes per year of LNG from several thousand wells. The company wanted timely production data, the capability to shut down wells, reduce personnel on site, and expand safety. The solution was to add a wireless control mesh network among several hundred wells, incorporating Cooper Bussmann’s ELPRO radios into RDC500 standardized wellheads. The radio design uses a network of wireless access point repeater sites. Each site collects data on gas flow, water flow, pressure, and temperature, and can shut down valves or pumps.
Leak detection at large sites can be difficult when done manually with portable leak detectors. At a production center in Geel, Belgium, BP recently replaced twice-daily walking inspections with hydrocarbon sensors and smart wireless technology from St. Louis-based Emerson Process Management. The leak detection system includes Emerson’s Rosemount 702 wireless discrete transmitters combined with Pentair -formerly Tyco- Fast Fuel sensors and TraceTek sensor cables. If a sensor detects xylene or benzene, the associated transmitter sends an alarm signal to a gateway and from there to the control room where operators can decide on a course of action. The wireless system was installed by BP’s maintenance team, and using this solution saved an estimated 50% of the cost and 90% of the time that would have been required to install a conventional wired sensor system.
BP Bitumen tackled an incident in which the regular fuel system at its refinery near Brisbane, Australia, was shut down. Temporary LPG tanks were rushed into service, and BP used smart wireless technology from Emerson Process Management to monitor the integrity of transfer lines. Rosemount wireless pressure transmitters were quickly deployed to manage fuel delivery along with temperature transmitters to monitor the flow of hot bitumen. The sensors were designed to immediately report exceptional conditions to control room operators, and the wireless monitoring kept the bitumen plant running, saving BP $15,600 per day in lost production.
Sensor networks can also be employed for vibration monitoring, which is more complex than measuring scalar process attributes, such as temperature or pressure. BP selected Crossbow Technology to install MEMS-based inertial sensors on its oil tankers to monitor engine vibration. A wireless sensor network replaced manual sensor reading and provided more consistent measurements with fewer errors, and ultimately resulted in lower machine maintenance costs. This proved the reliability of a WSN in a harsh environment, and was recognized with the BP Helios Award.
Wireless systems can be used for condition monitoring of rotating equipment, such as motors, pumps, and fans that are normally monitored manually with portable data collectors. Last year, SKF, launched a wireless machine condition sensor that combines a sensor, data collector, and radio into a compact, battery-operated device. It can be used to expand condition-based maintenance into areas where the cost to install wired systems is prohibitive, while making data available to existing process control and information systems. To overcome wireless communication obstacles, sensors can be configured to operate as router nodes, allowing them to relay data from other sensors (mesh). The sensors use the WirelessHART communication protocol.
The SKF wireless machine condition sensor collects data on three key machine conditions: temperature (indicative of lubrication issues, increased friction, rubbing, etc.); overall machine condition (vibrations caused by misalignment, imbalance, mechanical looseness, etc.); and rolling element bearing condition (allows damage detection and diagnosis of source as ball/roller, cage, and inner or outer raceway).
Subsea developments use networked sensors and actuators to monitor petroleum production, to either prevent or detect oil and gas leakage or to enhance the production flow and yield of the wells, despite the fact that traditional sensors are large and expensive to deploy subsea.
Eight universities in Scotland were engaged in a five-year collaborative project: the Scottish Sensor Systems Centre (S3C), from 2009 to 2014. Scientists at the University of Aberdeen and Robert Gordon University studied different types of sensor systems required for remote subsea developments. Dr. Richard Neilson, Reader at the University of Aberdeen, said the university was focused on developing "innovative subsea technologies, which will help deliver new, or enhance the existing, sensor-based products being employed by industry."
Neilson presented the S3C’s work as "Smart Subsea Fields" at the Institution of Mechanical Engineers’ Subsea Engineering conference in Aberdeen, in May 2014. He said future subsea sensor system networks will need to provide operations data flow rates, pressure, temperature, condition data, corrosion, and actuator condition.
The follow-up to SC3 is a new university collaboration project, the Centre for Sensors and Imaging Systems (CENSIS), based in Glasgow.
Technological advances in electronic control systems, miniaturization (small nodes: UC Berkeley’s "smart dust"), improved communication capabilities, and decreasing costs will drive growth in sensor development and the sensor market for the foreseeable future. Eventually, we may see fully integrated, embedded sensors and standard industrial protocols. However, the expansion of wireless sensor networks means much more data will be collected, and it will be an ongoing challenge to properly analyze and manage these big data.
Wireless sensor network considerations
Best uses for oil & gas operations:
- Wellsite automation
- Downhole sensors
- Seismic surveys
- Pipeline operations
- Corrosion monitoring
- Structural integrity monitoring
- Equipment vibration analysis
- Tank farm monitoring
Most important factors to consider:
- Plug-and-play connectivity
- Installation plan that will cause minimal disruption
- Easily expandable network
- Reliability — overlap and error tolerance
- Power management — long-life battery systems, energy-scavenging modules
"Smart dust" is a rapidly developing technology comprised of a system of tiny sensors that communicate wirelessly. In 1998, researchers at the University of California-Berkeley were funded by the U.S. Defense Advanced Research Projects Agency (DARPA) to develop and build wireless sensor nodes with a volume of one cubic millimeter (smaller than a grain of rice). The smart dust project has led to many other research avenues.
Hewlett Packard has been working on a new inertial sensing technology that it considers a "breakthrough in nano sensing research," using the fluidic MEMS technology the company has developed over the past 25 years. In 2010, HP announced a project to put a trillion sensors all over the globe, dubbed the "Central Nervous System for the Earth" (CeNSE).
In the first commercial application of the CeNSE technology, HP is collaborating with super-major Shell to develop a next-generation, land-based, wireless seismic acquisition system. By vastly improving the quality of seismic imaging, HP says the new system will allow Shell to more easily and cost-effectively explore difficult hydrocarbon reservoirs. They initially planned to install 1 million matchbook-size sensor nodes containing ultra-sensitive, low-power MEMS accelerometers to measure rock vibrations and movement over a 15.5-square-kilometer area.
Following successful tests of the tiny new sensors at seismic testing vault in the U.S. Geological Survey’s (USGS) Albuquerque Seismological Laboratory facility in New Mexico in 2013, Shell’s Dirk Smit reiterated the need for "the cost-efficient, flexible deployment of seismic sensor networks, and said "The collaboration with HP demonstrates Shell’s strategic approach to driving innovative technology solutions through active partnering."
– Nina Rach has been working in the oil and gas industry since 1983. She’s a graduate of Cornell University: College of Engineering, Duke University Graduate School, and the University of Houston Law Center.
Original content can be found at Control Engineering.