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The U.S. natural gas pipeline industry is facing the twin challenges of increased flexibility and capacity expansion. To meet these challenges, the industry requires improved choices in gas compression to address new construction and enhancement of the currently installed infrastructure. The current fleet of installed reciprocating compression is primarily slow-speed integral machines. Most new reciprocating compression is and will be large, highspeed separable units.The major challenges with the fleet of slow-speed integral machines are: limited flexibility and a large range in performance. In an attempt to increase flexibility, many operators are choosing to single-act cylinders, which are causing reduced reliability and integrity. While the best performing units in the fleet exhibit thermal efficiencies between 90% and 92%, the low performers are running down to 50% with the mean at about 80%. The major cause for this large disparity is due to installation losses in the pulsation control system. In the better performers, the losses are about evenly split between installation losses and valve losses.The major challenges for high-speed machines are: cylinder nozzle pulsations, mechanical vibrations due to cylinder stretch, short valve life, and low thermal performance. To shift nozzle pulsation to higher orders, nozzles are shortened, and to dampen the amplitudes, orifices are added. The shortened nozzles result in mechanical coupling with the cylinder, thereby, causing increased vibration due to the cylinder stretch mode. Valve life is even shorter than for slow speeds and can be on the order of a few months. The thermal efficiency is 10% to 15% lower than slow-speed equipment with the best performance in the 75% to 80% range.The goal of this advanced reciprocating compression program is to develop the technology for both high speed and low speed compression that will expand unit flexibility, increase thermal efficiency, and increase reliability and integrity.Retrofit technologies that address the challenges of slow-speed integral compression are: (1) optimum turndown using a combination of speed and clearance with single-acting operation as a last resort; (2) if single-acting is required, implement infinite length nozzles to address nozzle pulsation and tunable side branch absorbers for 1x lateral pulsations; and (3) advanced valves, either the semi-active plate valve or the passive rotary valve, to extend valve life to three years with half the pressure drop. This next generation of slow-speed compression should attain 95% efficiency, a three-year valve life, and expanded turndown.New equipment technologies that address the challenges of large-horsepower, high-speed compression are: (1) optimum turndown with unit speed; (2) tapered nozzles to effectively reduce nozzle pulsation with half the pressure drop and minimization of mechanical cylinder stretch induced vibrations; (3) tunable side branch absorber or higher-order filter bottle to address lateral piping pulsations over the entire extended speed range w...

Natural gas leakage from unmanned facilities, such as compressor stations, gathering sites, and block valve locations, can pose significant economic and safety impacts. Additionally, methane, the primary constituent of natural gas, is a powerful greenhouse gas with 84 times the global warming potential of carbon dioxide on a mass basis over a 20-year period (IPCC 2013). Due to the remote location of many of these facilities, fluid leaks can persist for extended periods of time. Continuous leak detection systems would facilitate rapid identification and repair of leaks. However, existing technologies, such as infrared cameras, are cost-prohibitive to be installed at a high number of sites and are instead used in periodic monitoring as part of leak detection and repair programs. Such periodic monitoring does not provide for quick detection of “fat tail” leaks that dominate the emissions from gathering and transportation systems (Mitchell et al. 2015, Subramanian et al. 2015). A unique and innovative arrangement of various stakeholders was utilized to initiate a technology development and testing program aimed at expedited deployment of low-cost technologies at high numbers of sites. The technologies targeted for this work were low enough in cost to economically justify the installation of such sensors at every gas gathering and transportation site. This work was driven by an environmental advocacy organization under a partnership with eight different oil and gas companies and technical oversight from various universities, non-profits, and government agencies to give a wide perspective on the needs of such technology. Four different technologies were developed and tested in realistic release environments. The technologies ranged from sensors modified from automobile-based technology to laser-based systems used for monitoring gases in coal mines. The systems were treated as “end-to-end” units whereby all components (e.g., sensor, data acquisition, enclosures, etc.) needed to perform according to the provided specifications. The testing involved controlled releases under numerous environmental conditions and with different gas compositions. The largest focus of the testing was on outdoor releases where the systems had to detect the transient nature of gas plumes. The primary objectives of the testing were to determine the readiness of the technologies for pilot testing in the field and identify continuous improvement opportunities. The project demonstrated that there are newly-developed technologies that could be deployed as low-cost continuous monitoring solutions for the gas industry.

The operation of remote offshore pipelines, particularly those under seasonal ice cover, may need a means of detecting potential leaks at any point along the pipeline and at any time. Potential leak cases of interest are pinhole leaks out of the bottom of the pipe due to corrosion, weld or seam cracks, or damage due to third-party contact. Technologies are desired to provide leak detection coverage around the clock over long lengths of pipeline. One potential technology is distributed temperature sensing.A key element of evaluating the applicability of leak detection systems is to characterize the behavior of leaks. It is important to understand how leaks behave when employing a technology that has only been previously used for other conditions. A joint-industry program was initiated to evaluate the thermal behavior of hypothetical underwater leaks. The environments studied range from shallow, Arctic applications to deep offshore installations. Analytical models were assessed to predict the jetting behavior of simulated leaks and their near-field thermal responses. These models were validated by means of laboratory experiments.This information can be leveraged by a number of technologies, as the data are independent of the measurement mechanism. While the intention of this work is to evaluate distributed fiber-optic systems, the data on leak characteristics may also provide indications of applicability of other techniques for detecting potential underwater leaks. The data from this project will allow the industry to improve the understanding of potential leaks from underwater pipelines and, hence, lay the foundation for determining appropriate detection systems.

The pipeline industry is improving its ability to detect and locate leaks through emerging technologies. There has been a variety of research in recent years aimed at further development of sensor-based technologies for leak detection. A key obstacle to retrofitting existing pipelines with leak detection technologies is the cost and risk of installing hardware, particularly those sensors that require excavation near the pipe. There are many advantages to employing leak detection systems that can leverage existing instrumentation access locations. One such technology may be negative-wave leak detection systems. Negative-wave technologies work by measuring dynamic pressure changes in the pipe. It should be noted that some negative-wave systems require line modifications to accommodate multiple transmitters. While such systems have been on the market for many years, there is insufficient data available about their performance under various pipeline operating conditions for widespread adoption. In an effort to close many information gaps on the performance envelope of negative-wave technologies, a PRCI-funded field test was performed on a 41-kilometer segment of a 30-inch diameter heavy crude oil pipeline. Products from three suppliers were installed at either end of the test segment. Actual commodity withdrawals were conducted at a remote valve site approximately 21 kilometers into the segment during various operations to test the systems’ abilities to detect the withdrawals without direct user interaction. These test points included withdrawals during steady-state flowing, pump startup, and shutdown conditions. Data were collected from each system to determine their abilities to detect leaks under various conditions, abilities to locate the leak, false alarm rates, and response times. This test provided significant insight into the performance of such systems over the range of conditions tested. The key focus of this paper is the approach for conducting such multi-vendor commodity withdrawals. This project required some unique considerations for its execution. Such considerations are also documented to provide input to others who are considering such a test.