Analyzing Critical Flow Measurements
In November, we discussed the special needs of making custody transfer measurements in large-scale applications where product characteristics are complex and dynamic. In this installment, two applications are highlighted where end users have addressed requirements to monitor multiple product variables simultaneously, with reliability and precision.
|EnCana has to monitor flows at strategic points throughout its enormous network. In some cases it may be at a collection point from a cluster of satellite wells, or farther down stream at a major distribution point. The dynamic nature of its product mix requires agility and precision from instrumentation and control equipment. Source: Prosoft|
Field application: EnCana
DPH Focus Engineering of Calgary, Alberta, provides turnkey oil and gas plant automation and process control engineering. In the early 1990s, EnCana (Canada’s largest oil and gas company) approached DPH about improving production monitoring to improve management of its energy resources.
EnCana produces approximately 4.4 billion cubic feet of natural gas equivalent per day. More than 80% is natural gas and the balance is from in-situ recovery of bitumen through steam-assisted gravity drainage. EnCana has been a leader in development of this tar sands recovery technique, with much of that product sent to the U.S. for processing in its refineries there. EnCana produces oil from five Canadian sites and gas from nine major sites primarily in Canada but also in the U.S. Growing demand has pressed the company to increase production by 14% in 2007 over 2006 levels. The large geographical areas involved combined with a mix of products requires sophisticated control of operations and distribution.
EnCana and DPH started out by assessing the flow measurement techniques that were in use. EnCana was using mostly manual collection methods such as chart recorders for recording flow information and then compiling flow totals. As DPH investigated more sophisticated methods, it discovered that EnCana had a number of Rockwell Automation Allen-Bradley PLCs installed at key monitoring and control points. Intrigued with leveraging this installed base, DPH located ProSoft Technology, an early developer of PLC-based flow computing technology. The initial products were limited in functionality, but offered much promise.
Over the years, DPH worked closely with ProSoft to expand features and tailor the in-rack flow computer to solve EnCana’s flow measurement challenges. DPH was not only an early adopter of this technology, but promoted development and commercial success of embedded flow computer technology.
Today DPH and EnCana have incorporated PLC-based flow computer technology in many different applications at hundreds of locations throughout Alberta. The technology is in use in pipelines, well heads, satellite (clustered) wells, compressor stations, and processing plants.
EnCana’s gathering system and its various SCADA hosts are spread across many business units. Because the embedded flow computer module has Modbus connectivity, flow information is easily distributed over EnCana’s extensive SCADA network. Using a combination of licensed and license-free wireless with telecommunications, reliable flow information is consistently available for operation and management staff.
Calculated flows and volumes provide the basis for volume balancing, plant control, well testing, leak detection, and market-driven production control. EnCana is now able to have up-to-the-minute knowledge of energy inventories and make real-time decisions on production and transmission based on energy demand. The integrated flow computer’s flexibility, proven reliability and accuracy are keys to maintaining a strong link for all levels.
|Getting the natural gas and liquids to consumers and export terminals from the Camisea regions was a major challenge.|
Field application: Camisea
A large natural gas deposit was discovered in the Camisea region of Peru in late 1980s. The San Martin and Cashiriari natural gas fields are one of the most important non-associated natural gas reserves in Latin America. The proven volume of gas in the ground is 8.7 TCF (trillion cubic feet), with an estimated recoverable volume of 6.8 TCF of natural gas, and 411 million barrels of associated natural gas liquids (propane, butane and condensate). The pipelines will make both the gas and liquids available for domestic consumption and export. Natural gas is delivered to the main consumption center in Lima, where it will be used for residential, industrial, and electric utility purposes. The liquids will supply the domestic propane market and provide a critical source of export earnings. However, while the fields promised to be a tremendous energy resource and boon for the local economy, they are hundreds of miles away from the nearest port and deep in the thick jungles of the Malivinas rain forest. Exploiting the resource presented major engineering and construction challenges.
Given that the producing field and pipelines are in areas of high environmental sensitivity, launching the project was not without its controversy. The biological diversity of the rainforest in both flora and fauna demanded a high level of caution during the construction and ongoing operation. Moreover, there are many isolated pockets of residents in that part of the country and the activity had to impact them as little as possible. Consequently, issues related to safety and operational control have been paramount, with a high level of dependence on the reliability of equipment, instrumentation, and control strategies.
The goal was to build two pipelines to carry natural gas and liquid gas to processing plants located at major ports. Years of planning and development gave birth to the Camisea natural gas and natural gas liquid transportation systems, which depend on remote control and monitoring of the pipelines for success.
ISI-Solutions, an experienced system integration and engineering firm, was hired to design the controls and communication systems for the pipelines. After studying various approaches, its designers settled on the Allen-Bradley ControlLogix platform. The ControlLogix programmable automation controller (PAC) proved to be suited for automated controls along the remote pipelines and for flexible communications.
One of the key features of the ControlLogix platform was its direct interface with ProSoft’s flow computer module. In-rack mounting reduced commissioning time and ensured compatibility within Allen-Bradley architecture. The module also provided easy integration into the SCADA system.
Today, the Camisea pipeline system consists of dual pipelines carrying liquid and natural gas from the natural gas field deep inland to processing stations and shipping ports along the coastline. The liquid and gas pipelines transverse 330 miles side by side, and then the natural gas pipeline extends another 120 miles up the coastline. The system includes four pumping stations, 40 block valve stations, three regulation stations and two control centers. The critical pipeline controls are dependent on mass flow calculations from four in-rack flow computer modules. After many years of operation, the system has proven to be very reliable.
|Jim Ralston and Scott Monton are sales engineers for ProSoft Technology Inc. Reach them at firstname.lastname@example.org , and email@example.com , respectively.|