International Pipeline Conference — Volume I A SM E 1998 IPC1998-2010 THE ALLIANCE PIPELINE - A DESIGN SHIFT IN LONG DISTANCE GAS TRANSMISSION Todd S. Janzen, P. Eng. W. Norval Homer, P. Eng. Alliance Pipeline Limited Alliance Pipeline Limited Calgary, Alberta Calgary, Alberta Downloaded from http://asmedigitalcollection.asme.org/IPC/proceedings-pdf/IPC1998/40221/83/2507289/83_1.pdf by guest on 26 September 2021 ABSTRACT Competition in the natural gas industry grows steadily. The demand for natural gas transportation has typically exceeded the capability of the existing natural gas pipelines within Canada for several years. Even though intense competition exists with producing and marketing natural gas, limited transportation options limits the business opportunities available for energy companies. This competitive spirit is driving the Alliance Pipeline Project. Once the pipeline is complete, producers will have an additional transportation option to move their products to Chicago, Illinois, which is emerging as an important business hub for natural gas marketing. Designing and constructing a natural gas pipeline in the late 1990's will allow Alliance Pipeline Limited the ability to implement the latest technology into all aspects of the design. THE HISTORY OF ALLIANCE PIPELINE LIMITED During August 1995, 22 producing/marketing companies agreed to fund the Northern Area Transportation Study (NATS). The purpose of the study was to evaluate the feasibility of constructing a producer owned, high pressure, directly routed, rich gas pipeline from Northeast British Columbia to the Midwest of the United States. Some conclusions of the study included: • A directly routed pipeline, operating at high pressure with significant Natural Gas Liquid (NGL) content is the most economic method for pipeline expansion. • There are sufficient gas reserves in the Western Canada Sedimentary Basin (WCSB) to support such a pipeline. • The Midwest United States can absorb additional Canadian gas without negative market impacts. The conclusions of the NATS study established the foundation of Alliance Pipeline Limited. Alliance Pipeline Figure 1. Pipeline Routes from Alberta to Chicago Limited is owned by eight partner companies who possess a significant amount of experience building and operating In Figure 1, the lightly dashed line from northwest Alberta pipelines throughout North America and the World. to Chicago represents the following pipelines (in order) from north to south, NOVA Gas Transmission Ltd. (NGTL), Foothills Construction of the Alliance Pipeline System is anticipated Pipe Lines (FPL) and Northern Border Pipeline (NB). The to commence in late 1998, the pipeline is expected to be in natural gas that is transported via this route travels a similar operation by the second half of the year 2000. distance to the proposed Alliance Pipeline. THE PIPELINE PROJECT The second dashed line that originates in Alberta and travels east to Manitoba and then diverts south to Chicago The Route represents the pipeline route of NGTL, TransCanada Pipelines As concluded from the NATS study, the most economic (TCPL) and the proposed Viking-Voyageur Pipeline (TCPL). approach to get gas from the proposed supply area to Chicago The gas that would be transported on this route would travel was a directly routed pipeline. Figure 1 illustrates the additional distance to arrive at the target market. proposed supply area for the Alliance Pipeline and two of the options to move gas to the Chicago market, which is emerging The solid line is the Alliance Pipeline. The pipeline starts as a major market hub in British Columbia and terminates near Chicago, Illinois. Copyright © 1998 by ASME The Alliance Pipeline Concent Applying the benefits of increased pressure have been The Alliance Pipeline Project was driven by the desire of limited by the technology available to the designer, in the several natural gas producers/marketers within Alberta to have 1870’s, 250 kPa was considered high pressure, in the 1950’s additional natural gas pipeline capability leaving Alberta. Once this rose to 6205 kPa and by the late 1970's, 9930 kPa was complete, the Alliance Pipeline will provide an additional 37.5 being routinely applied. 106 m3/d (1.325 bcf/d) of firm new pipeline capacity for the WCSB. There have been many new pipeline projects around the world that have used a high pressure design approach. Table Phase 1 of the Alliance Pipeline will consist of 1 shows some of these pipelines with their respective locations approximately 3000 km of 914 mm diameter pipeline with 14 and maximum allowable operating pressures (MAOP). equally spaced compressor stations (193 km) ranging from 23 MW to 28 MW. Table 1. High Pressure Gas Pipelines From design to eventual daily operation, the Alliance MAOP Downloaded from http://asmedigitalcollection.asme.org/IPC/proceedings-pdf/IPC1998/40221/83/2507289/83_1.pdf by guest on 26 September 2021 Pipeline will be different from the other large natural gas Name Country - yffcPal Product transmission pipelines in Canada. The two main differences lie Zeepipe Norwav/Belqium 15700 Natural Gas within the composition of the gas stream and the planned Sable Island Canada 15300 Natural Gas higher operating pressure made possible by new high Souris Valley USA/Canada 15000 CCb strength/high toughness steels. FLAGS Scotland 14007 Natural Gas Ruhrgas AP Germany 10335 Natural Gas Alliance Pipeline Limited plans to transport richer natural Iroquois Canada/USA 9922 Natural Gas gas to Chicago. This refers to a gas stream where the heavier hydrocarbons such as ethane, propane and butane (NGL) have not been completely removed in a deep cut plant Once The Benefits of Gas Composition on Pipeline Efficiency the gas gets to Chicago, the NGL's will be removed through a Increasing operating pressure improves pipeline processing plant and be redistributed for other uses. The efficiency, however, it is not the only way to increase efficiency. gross heating value (GHV) of the Alliance Pipeline gas stream An alternate method is to modify the gas composition. By is expected to be approximately 41.1 MJ/m3 (1100 BTU/ft3). leaving the heavier hydrocarbon gases in the gas stream there Traditional North American pipelines transport gas with GHVs are two beneficial effects. from 37 to 39 MJ/m3 (990 to 1050 BTU/ft3). 1. Increases the density and the supercompressibility of the Significant economic advantages accompany this concept gas stream however, these economic benefits are balanced with serious engineering challenges. As the gas stream increases in 2. Avoids expenditures on deep cut processing systems (to heating value, benefits are realized with respect to pipeline remove NGL's) at gas plants, and the costly transportation throughput however, due to the gas composition, the pipeline of the NGL’s to end users. will require a steel toughness value higher than traditional pipelines. Table 2 shows the expected Alliance Pipeline gas composition and a Typical Pipeline gas composition from a natural gas pipeline where the majority of the NGL’s have been THE EFFECT OF PRESSURE AND GAS COMPOSITION ON removed. PIPEUNE EFFICIENCY Table 2. Alliance Pipeline and Typical Pipeline Gas The Benefits of Higher Pressures on Pipeline Efficiency Compositions The operating pressures used in gas transportation have significantly increased over this century. The reason for this is Alliance Pipeline Typical Pipeline that increasing the operating pressure increases the density of - Componènte. im ole,% ) f (m o !e% ) the gas, this reduces the velocity and the pressure drop. 0 .50 1.27 Higher pressures also increase the efficiency of gas compressors because they are primarily devices that generate ~ CCfe 0.50 0.55 fluid head. The denser the fluid the more effectively a ... 0 .00 0.00 compressor can generate head with a given amount of power. ? h 2 ... 0.00 0.00 - - - cm - - 89 .8 7 95.40 Significant technology advances since the 1970’s in CaHa 6 .50 1.97 steelmaking and steel chemistry now provide pipeline : GaHa"-, 1.90 0.51 designers with line pipe that can be operated at very high IC 4 ÿ 0 .2 5 0.17 pressures, and have the required toughness to be used with NC4 •-: 0.35 0.08 richer gas. C 5+ 0.13 0.05 The Compressibility of Natural Gases The power As the operating pressure is increased, the throughput is required to compress a unit of gas can be directly translated increased for the same diameter of pipeline. As the gas gets into the rise in pressure (head) or temperature that gas has to higher in ethane composition the power requirements drop. undergo. The relationship between pressure, volume and This reduction in power becomes accentuated at higher temperature of a gas can be expressed by the Gas Law, which operating pressures. is stated as: (1) PV=znRT Where: P = pressure of gas (kPa) V = volume of gas (m3) z = compressibility factor I n = number of moles of gas Ï R = the universal gas constant Downloaded from http://asmedigitalcollection.asme.org/IPC/proceedings-pdf/IPC1998/40221/83/2507289/83_1.pdf by guest on 26 September 2021 T = temperature of gas (degR) When compressed, gas molecules exert intermolecular forces on each other making them easier to compress. To compensate for this phenomenon, the compressibility factor, z has been added to equation (1) to account for the compressibility of a particular gas. Table 3 demonstrates that as the percentages of ethane and propane in the gas stream increase, the compressibility factor of the gas decreases which makes the gas easier to Figure 2. Power Required vs. Ethane Composition compress. To demonstrate the effect of the total energy transported Table 3. Compressibility Factors for Natural Gases within a pipeline operating at high pressure and high heating value, the Alliance Pipeline will be used as an example. The P ressu re CH< C3H . CiH s O th e r Alliance Pipeline plans to operate at 12000 kPa MAOP and a frP a ) 1%) <%) <%> Z F acto r gas composition similar to the one listed in Table 2.