A vital part of any natural gas gathering and transportation system is the compressor. Compressors allow for the continuous flow of natural gas from the well to the ultimate delivery point. The inefficient operation or failure of the compressor results in deferred production, and increased expense. With customers expecting pipelines to provide a continuous supply of natural gas, the challenge of monitoring and attending to unexpected issues with compressors driving that flow of gas becomes extremely important.
Companies transporting natural gas cannot afford to have their flow of supply interrupted, and compressor stations that drive and sustain that cash flow are paramount to a business’ success. In this regard, keeping compressors maintained and online while also keeping costs low directly affects a company’s profitability.
Ideally, engineering teams would continuously monitor operating conditions, perform daily inspections, run comprehensive compressor models, and compare results to actuals for each piece of equipment. Unfortunately, the time required to continuously perform surveillance to this level of detail is too high for most operations. It may be perceived easier to adopt a run-to-failure—“if it isn’t broken, don’t fix it”—approach to compressor maintenance as the data analysis burden required for a compressor fleet can be daunting, but such a methodology is not without risks. For example, signs of potential equipment failure may go overlooked, resulting in expensive unscheduled repairs. Or in a worst case scenario, entire compressor packages may need to be replaced. This would halt the flow of gas and result in more lost revenue and increased costs.
The sub-optimal operation of a compressor fleet can also affect the ultimate production from the entire system. Flow from gas wells into gathering systems, and from gathering systems onto the main lines varies. Wells come online, undergo work-overs, or experience production decline, leading to an increase or decrease in gas supply within a particular system. In response, a production network’s line pressure would fluctuate, resulting in production deferment, altering operating efficiencies, and even potentially damaging compressor equipment. Establishing a link between compressor surveillance and well surveillance could allow operators and gatherers access to the compression fleet’s operating conditions in order to maximize throughput and cash flow, while also potentially extending the life of equipment.
OVS Group built the Compressor Surveillance Workflow to address the specific needs of energy companies operating compressor fleets. Compressor Surveillance connects to real-time data sources from the field along with compressor models, historical performance data, and recommended compressor operating parameters. The workflow automatically takes real time field data and compares it to the most recent iteration of the compressor model, alerting to deviations from nominal operating conditions. Both centrifugal and reciprocating compressor types are supported, with the process running in either an on-demand or unattended mode, as required.
The workflow begins by gathering the required inputs from the field’s SCADA system, which usually consists of suction and discharge temperature and pressure, the prime mover’s RPM, compressor throughput, and any other operational parameter that needs to be monitored through preset alarm ranges. Once the compressor model of your choice is updated with the most recent field inputs, Compressor Surveillance will run the model and displays the compressor’s current operating conditions on a performance curve. Should the model yield any signs of concern—such as a compressor operating above the surge line, at an unexpectedly-low efficiency, or the operating conditions fall outside of other predefined tolerances—the workflow will automatically notify all need-to-know personnel immediately of a potential problem. Otherwise, Compressor Surveillance will automatically validate sufficiently-performing compression equipment and save the results to any desired storage database. This “Surveillance by Exception” (SBE) allows for facility and process engineers to proactively focus on compressors not performing adequately, so that they can take action in a timely manner. With Compressor Surveillance automatically performing the majority of low-level tasks for you, engineers are made available to perform more important tasks.
In addition to highlighting under-performing compressor equipment, the workflow includes additional functions for Compressor Opportunity Identification. This workflow links with well production data from other One Virtual Source workflows—such as Well Review Tool and Virtual Metering—to allow facility and process engineers the ability to optimize compression equipment across the network. With access to forecasted changes in gas supply, Compressor Opportunity Identification can predict expected changes in throughput, that require changes in suction pressure to maximize system efficiency and maintain operations. Engineers have the ability to keep compressors running optimally by responding in-time with changes to operational parameters further upstream.
Integration with 3rd Party Models
The Compressor Surveillance workflow integrates with a number of third-party modeling applications, including Ariel and HYSYS . Similar to other third-party integrations supported by One Virtual Source, this enables companies to standardize surveillance processes, bring best practices to a common environment, and maximize their investment in modeling tools.
Workflows in Action
A large, international energy company implemented Compressor Surveillance to manage a large fleet of both reciprocating and centrifugal natural gas compressors. One goal was to improve the efficiency of their compressor surveillance activities. Immediately upon deployment, the automation provided by this workflow resulted in significant time savings and virtually eliminated the need for the engineers and technicians to perform this work manually. Another goal was to detect potential operational issues before they could result in downtime. With Compressor Surveillance, the client’s engineers were able to identify undesirable operating conditions early-on using the workflow’s trend analysis and automated alerts. The system began demonstrating value on its first day in operation when a previously missed step-change in discharge pressure was detected and resolved, and a lengthy shut down or remediation effort avoided.
- Real-time information for compressor, e.g.:
• Suction pressure
• Suction temperature
• Current prime mover RPM
• Discharge pressure
• Cooler temperature
- Compressor model
- Compressor specifications
- Performance tolerances & alarm presets
- Compressor performance curves
- Automatic model validation
- Historical trends compared with predefined tolerances/limits
- Automatic Alarms
• Sub-optimal compressor performance
• Surge warnings
• Pressure & temperature alerts
- Configurable to both centrifugal and reciprocating compressor types
- Consolidates important compressor data, making it easier to see important information allowing personnel to make informed decisions in a timely manner
- Massive reduction in the time spent updating and calibrating models
- Decreased downtime for compressor maintenance
- Improved average run-life for compressors
Many of the OVS workflows apply to any production operation of an oil and gas company. OVS Compressor Surveillance utilizes much of the expertise gained from these production operations, such as surveillance by exception, and applies them to compressor operations. This surveillance workflow adds significantly to the OVS Workflow Library and can be combined with other workflows in the library to create a powerful and complete surveillance system.