Gathering Pipeline Measurements

Transcription

1 Gathering Pipeline Measurements Authors: Daniel Zimmerle, Cody Pickering, Colorado State University STATUS: Final 1.0 Description of the Study Area This annex provides an overview of the field measurement campaign for gathering pipelines. During the field campaign, the study team, in cooperation with study partners, had access to complete GIS information for gathering pipelines in the study area. Figure 1-1 shows representative pipeline routings for a portion of the study area using data from MapSearch and partner data. The figure illustrates the density and complexity of the gathering pipeline system. While infrequent in the study area, pipelines from multiple operators may occupy ROWs which are nearly coincident (e.g. opposite sides of one road), and in rare cases, may share a ROWs. However, no shared ROWs were measured in this study. Figure 1-1: Representative gathering line routings. The gathering systems shown are representative of the gathering system topology for a portion of the study area, and are not complete. Display uses information available to the study team for publication a combination of partner data and MapSearch data from 2010 or earlier. Lines are colored to identify interconnected pipeline subsystems, differentiated by both connection and operator. Pipelines typically leading from wells to a transmission system sales point. The figure illustrates that pipelines from multiple operators may occupy ROWs which are nearly coincident. 1 P a g e

2 2.0 Sampling Plan To develop a sampling plan, gathering pipelines were treated as random segments of pipeline, from a starting location where the team could enter the ROW to an ending location where the measurement team could again exit the ROW onto public roads. During the field campaign segments of gathering line were randomly chosen for measurement. The resulting survey included the lines identified in Figure 2-1. Production wells are more densely populated in the western half of the Fayetteville shale play and drive more density in gathering pipelines. One partner company mows ROWs once every two years; in 2015 the company had only mowed rights-of-way (ROWs) in the western half of the basin. For that more measurements were completed in western half of the study area for that partner. Qualitatively, pipeline in the eastern and the western halves of the study area are configured similarly, and there is no evidence that emissions behavior would be statistically different. Figure 2-1 Sections of gathering pipeline surveyed during field campaign. Measurements were biased toward the western half of the study area because one partner had mowed only ROWs in that area. Highlighted pipeline segments are driven ROWs. Purple dots are individual well pads, orange line is flight boundary for the October 1 st mass balance flight. Image provided by Google Earth. Determining which ROW to measure was guided by both experimental guidelines and physical limitations. Experimental guidelines were implemented to achieve an adequate characterization of the basin. Pipelines had to be randomly sampled in different regions of the basin, and include ROWs that were both near towns and rural. However, random sampling was conditioned by the accessibility of the ROWs, including the following physical limitations: Grade of ROW was too steep to traverse safely and effectively ROW was covered with un-harvested crops Landowner restricted access. Vegetation covering the ROW was too dense to traverse Access to the ROW was had water or mud that made it impossible to traverse safely Figure 2-2 & Figure 2-3 illustrate the range of vegetation on typical ROWs in the study area. In consultation with study partners, the study team selected sections of ROW to traverse each morning to best implement 2 P a g e

3 the study plan while accommodating local conditions. To maximize ROW traversed, areas were selected with 2-3 segments of traversable ROW each day. Operators would provide options for drivable ROWs and measurement contractor randomly selected which ROWs to traverse to reduce sampling bias. Figure 2-2 ROW with a steep slope, but mowed and relatively accessible. 3 P a g e

4 Figure 2-3 ROW with dense vegetation and reduced accessibility?. In addition to pipelines, two types of auxiliary equipment are also installed on study partners pipeline systems pig launchers or receivers and block valves. A pig is a cleaning plug pushed through the pipeline by the gas flow in the pipeline. Pig launchers and pig receivers are nearly identical components, but installed in different orientations to launch or receive a cleaning pig. Pigs are inserted into the pipeline by configuring and depressurizing a launcher. The pig travels through the line, pushing any debris or water from the line toward a pig receiver, where operators depressurize the receiver, remove water and debris, and recover the pig. When a pig does not travel the intended route, operators may need to check several receivers to locate the pig after cleaning operations. Depressurizing launchers and receivers releases some gas to the atmosphere. Each launcher is also equipped with multiple valves, flanges, and taps for pressure gauges, a pressurized door, and other equipment which may leak gas if seals fail. Hereafter, both launchers and receivers called pig launchers for simplicity. Block valves are used to stop the flow of gas in a pipeline or change direction of flow. In general, block valves are simpler than pig launchers, with fewer gauges, flanges, and valves, reducing potential sources for fugitive emissions. 3.0 Measurement Methods All measurements were performed by Gutteridge Haskins and Davey (GHD) using measurement devices owned by GHD and calibrated by GHD employees. The complete list of equipment provided by GHD can be found in Table 1Table 1: Measurement equipment list.. 4 P a g e

5 Table 1: Measurement equipment list. Manufacturer Instrument Model Number Use Serial Number Heath Consultants RMLD-IS RMLD-IS Underground pipeline leak delineation/detection Heath Consultants DP-IR DP-IR Underground Leak Delineation Bascom-Turner Gas Sentry CGI-211 TSL VelociCheck 8340 High Flow Gas Concentrations Aboveground / Underground leak measurements High Flow Gas Flow Rate Aboveground / Underground leak measurements BT-GCI-211 INDACO High-Flow Underground pipeline leaks w/ enclosure - TSL Ultra-Portable Gathering pipeline leak screening Los Gatos Instruments GHG Analyzer (mobile ambient measurements) CH4/CO2/H2O Geneq Inc. GPS Sx Blue Ambient Monitor Position - GHD s vehicle measurement system (VMS) was designed to detect methane enhancements low to the ground using vehicle bumper-mounted air intakes with four inlets (see Figure 3-1). The four inlets were joined together and routed to the Los Gatos analyzer. Figure 3-1 Front bumper of vehicle measurement system The analyzer was paired with the Geneq GPS to track location, as shown in Figure 2-1. Equipment was calibrated on a regular basis. The VMS could not be validated at a facility with controlled emission releases. Therefore, the efficacy of the system was qualitatively evaluated by confirming that the VMS observed elevated methane concentrations in proximity to known sources. Since all above-ground emission points at pipeline auxiliary equipment were detected and measured independently of the VMS, these locations provided a natural experiment to qualitatively evaluate the VMS. 5 P a g e

6 Figure 3-2 shows CH 4 concentrations detected near the single underground pipeline leak (4.0 kg/h) as a reference case. Figure 3-3 and Figure 3-4 illustrate elevated concentrations near much smaller emissions typical of auxiliary equipment. Emission rates cannot be recovered directly from measured concentrations, but VMS measurements near each facility show clearly CH 4 concentrations clearly elevated above the background CH 4 concentration. Since these concentrations correspond to far smaller leaks than seen in the detected pipeline leaks, there is strong evidence that the VM would have detected pipeline leaks much smaller than that in Figure 3-2. Qualitatively, the study team estimates that the VMS would likely detect all underground pipeline leaks in excess of 0.2 kg/h. Figure 3-2: Methane concentration near the underground pipeline leak 6 P a g e

7 Figure 3-3: VMS data near a pig launcher emitting 88 g CH 4/hr. Figure 3-4 VMS data near a pig launcher emitting 38 g CH 4/h. 4.0 Facility Measurements Gathering Sampling Information Comments Screen Value (ppm) Leak Location Leak Rate (scfm) Leak Rate (g CH 4/hr) Facility Total Leak Rate (g CH4/hr) 500 F Block Valve Block Valve V V D V V V F P a g e

8 500 F V D V V Block Valve V V Block Valve 0 V Block Valve V V V D Block Valve 1000 V Block Valve 7500 V Underground Pipeline Leak V V D F V V G Block Valve 30 V V V F F F V V Block Valve 5000 V V V V P a g e

9 1800 V V V Block Valve 370 V Block Valve V V D V V V D V D V V V V V Block Valve 120 V V V Block Valve 5000 F ,000+ D D V D V Block Valve 20 F V V V V D P a g e

10 40000 D Block Valve 4600 V V Block Valve 7500 F V V V F V V V Block Valve 5000 V V Block Valve 1200 V Block Valve 300 V Block Valve G V F V V V V V D P a g e