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, , 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 .

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 (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 . 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. 95.4 1.97 0.51 2.12 0.83 12000 89.87 6.5 1.9 1.73 0.78 Figure 3 shows data for the Alliance pipeline operating at 85.0 11.5 1.8 1.7 0.73 maximum summer throughput of approximately 43.5 106rrr/d 95.4 1.97 0.51 2.12 0.85 (1.55 bcf/d) at varied ethane compositions. 9930 89.87 6.5 1.9 1.73 0.80 85.0 11.5 1.8 1.7 0.76 95.4 1.97 0.51 2.12 0.87 8275 89.87 6.5 1.9 1.73 0.62 85.0 11.5 1.8 1.7 0.79 (%) Gain Capability Eneroy 95.4 1.97 0.51 2 .12 0.69 6895 89.87 6.5 1.9 1.73 0.85 85.0 11.5 1.8 1.7 0.82

The benefits of high pressure pipeline operation have been recognized for several years. The phenomenon of combining high pressure operation with higher heating value gas composition is the design basis of the Alliance Pipeline.

The efficiency gains for a pipeline able to combine high pressure with high heating value gas are realized by a reduction in the power required to compress the gas along the pipeline, as well as an increase in the total energy transported within the pipeline. Figure 3. Volume and Energy Capability Gain vs. Ethane Composition for the Alliance Pipeline Figure 2 shows a 914 mm pipeline operating at three different pressures, 8275, 9930 and 12000 kPa. Each pipeline Figure 3 shows that with an ethane content of was modeled to its maximum throughput with three approximately 6.5%, the incremental volume transported is compressor stations (approximately 22.5 MW each). small. Significant benefits with respect to throughput are realized at higher ethane content levels. When the content of ethane in the gas stream reaches 11.5%, the volume Figure 4, below, illustrates the full range of expected transported in the pipeline increases by a factor of 1.0125 or operations for the Alliance Pipeline including outage conditions 550 1 03m3/d (20 mmcf/d). for any one segment of the 914 mm mainline between compressor stations. Figure 4 shows the expected pressure As the ethane content within the gas stream is increased, and temperature profiles for normal winter and summer the amount of energy that is transported rises significantly. In operations, outage conditions and a shut-in condition (mainline Figure 3, when the ethane content is 6.5% the increase in valve closure). Pressure and temperature profiles are also energy transported within the pipeline is approximately 10%. referenced at individual block valve sites, there will be 5 block valve sites between compressor stations equally spaced at THE EFFECT OF PRESSURE AND GAS COMPOSITION ON 32.4 km each. The area labeled 'Outage operations' TOUGHNESS REQUIREMENTS FOR NATURAL GAS represents expected pressures and temperatures during times PIPELINES when a compressor station is unavailable leaving this portion of the system to operate at lower pressures and temperatures. A concern with pipeline designers since the late 1970’s is to introduce a fracture prevention and control program into the Downloaded from http://asmedigitalcollection.asme.org/IPC/proceedings-pdf/IPC1998/40221/83/2507289/83_1.pdf by guest on 26 September 2021 design of a new pipeline. Pipeline fractures are normally caused by some kind of initiation event (such as an impact to a pipeline section), which can cause the induced fracture to continue for many metres along the pipeline unless property arrested.

Fracture control requires line pipe to have a minimum toughness so that the fracture speed of the pipeline is slower than the decompression-wave velocity of the gas contained within the pipeline. Decompression-wave velocities are dependent on gas pressure, temperature and composition. As a general rule, the higher the operating pressure and the higher the heating value of the natural gas, the slower the decompression-wave velocity of the natural gas.

In order to determine the minimum toughness specifications required for the Alliance Pipeline, the full range TEMPERATURE C” of operating conditions (gas composition, pressure and temperature) were developed. The future operation of the Alliance Pipeline has the possibility of higher heating value gas Figure 4. Alliance Pipeline Operating Conditions vs. being transported to Chicago by ways of ethane injection into Toughness for 914 mm Mainline the pipeline. For the fracture control program, this worst case gas composition was the basis for specifying the toughness For this section of the Alliance Pipeline, the worst case requirement of the pipeline. Table 4 shows the component condition which controls the fracture design occurs when the breakdown of this gas composition. The gas composition in pipeline operates at 12000 kPa and 24 degC, just downstream Table 4 has a heating value of approximately 44.33 MJ/m3 of each compressor station. (1188 BTU/ft3). In order to achieve this high composition of gas, approximately 14000 m3/d of NGL’s would have to be Due to the high operating pressure and the heating value injected into the gas stream. of the gas displayed in Table 4, it was quickly determined that the toughness required for the Alliance Pipeline was greater Table 4. Ultimate Rich Gas Composition than 95 Joules. Since the standard measurement of toughness using a Charpy V-notch (CVN) test is know to over­ Ultimate Rich Gas Composition predict the actual toughness at these levels, Alliance Pipeline Com ponent (m ole % ) Limited retained the assistance of the Batelle Memorial Ni„ 0.44 Institute. Batelle developed a relationship (correction factor) C O i 0 .44 between the toughness measured by the CVN test and the HaS 0 .00 actual useful toughness of pipe. Alliance Pipeline Limited used y. Ht \ 0 .00 the developed correction factor to increase the required cm 79.49 toughness specifications. c 2h 6 15.55 Figure 5 shows the calculated toughness required for the CaHa 3 .23 914 mm Alliance Pipeline using worst case condition of 12000 IC 4 ‘ 0 .27 kPa and 24 degC. The required toughness has been NC4 0 .4 7 calculated with both the PICARD and GASDECOM C 5+ 0.11 decompression models. Figure 5 demonstrates the sensitivity design combined with strategic placement of horsepower to try of the required steel toughness to the gas richness. and introduce a similar level of outage reliability as its predecessors. The Benefit of High Pressure and Gas Composition for zap------r------:------, ------; Outage Operations 270 - SfrtlPt)».*HAapeO6M = i80J(lui«...... One benefit of high pressure operation is that a pipeline 2 50 contains more linepack than lower pressure pipelines. Under 230 ...... i...... ; an outage condition (depending on location) more often than 210 not, a large percentage of deliveries can be made without restriction. Once the outage is complete, several days will normally be required to refill the pipeline with the appropriate amount of linepack. As stated earlier in the paper, higher pressure combined with higher heating value gas results in

lower pressure drop per unit distance that will assist in Downloaded from http://asmedigitalcollection.asme.org/IPC/proceedings-pdf/IPC1998/40221/83/2507289/83_1.pdf by guest on 26 September 2021 mitigating the impact of an outage on the Alliance Pipeline.

The Placement of Horsepower on the Alliance Pipeline As described in an earlier section, the Alliance Pipeline will have 14 compressor stations equally spaced along the pipeline. To account for outage reliability, two of these stations have been design to have standby compression. The first and Figure 5. Toughness Specified and Toughness Required last compressor stations will each have a standby compressor for Various Gas Compositions at Worst Case Fracture unit to handle any upset condition that may occur. Design Condition (12000 kPa and 24 degC) An innovative approach that Alliance Pipeline Limited will In Figure 5, using the worst case pressure and implement is the plans to install additional horsepower at each temperature, worst case gas composition and Vie worst case station to provide additional reliability under outage conditions. between the two decompression models the required pipe Under steady-state firm capacity, the compression requirement toughness for the Alliance Pipeline is 195 Joules based on the at Alliance Pipeline compressor stations is approximately ‘All Heat Average’ (AHA). For the 914 mm Canadian portion of 15MW. Installed horsepower at each site will be approximately the Alliance Pipeline, the pipe that will be installed will have an 23 MW. This leaves 8 MW per station to provide outage AHA toughness of 280 Joules. reliability. One exception is for Station 3A which is located near Whitecourt, Alberta and is designed to raise the operating One of the surprising conclusions of Alliance Pipeline’s pressure from the low pressure gathering system to the high various risk studies is that higher pressure pipelines are safer pressure mainline. than lower pressure. As the wall thickness increases, the risk of penetration from third party damage or corrosion both go The reasons for this approach is that adding incremental down dramatically, these are the two main risks to pipelines installed power to a single unit is much cheaper than providing today. duplicate units. Therefore, Alliance Pipeline used a design approach where additional power was built into each station. If OUTAGE OPERATIONS ON THE ALLIANCE PIPELINE one station is unavailable, the gas will travel 390 kilometers and reach the inlet of the next station unit at approximately Older, more established natural gas pipelines within North 6205 kPa (equal to traditional operating pressures). The next America were constructed at a time when high pressure few compressor stations use their additional installed power to operation was considered 6205 kPa. Over the lifetime of these recompress the gas. Within three to four stations the lost older pipelines, most have undergone a significant amount of pressure has been completely recovered. expansion. Many of these pipelines have looped existing lines several times in their history. Pipelines that have several loops Figure 6 depicts a typical compressor outage (Station 9A, Kerrobert) on the Alliance Pipeline and the resulting pressure have the ability to mitigate the effect of a compressor station being unavailable much easier than single line pipelines. In profile. In this example, the pressure across the ‘ga p ’ falls from 12000 kPa to approximately 6205 kPa at the inlet to the most cases, these pipeline systems have a tremendous next compressor station approximately 390 km away. The flow amount of horsepower installed in several units at each station, across the ‘ga p ’ falls significantly, however, the pipeline can (operating at low compression ratios) and many pipes running past the compressor station leaving the operators numerous still deliver its firm volume and can then draw upon the large reserve of linepack to sustain even higher deliveries. This operating configurations to deal with an outage to maximize transient mode of operation will last for several days, a few throughput days for the station to come back on-line and then the following few days to refill the line with the appropriate amount of Unlike traditional pipelines, a new ‘bullet-line’ has to introduce outage flexibility into the pipeline design. The linepack to return to steady-state conditions. Alliance Pipeline used two key components of the pipeline Figure 6 shows that will take four of the compressors ACKNOWLEDGEMENTS downstream to get the pipeline back to maximum operating pressure. This paper is a brief summary of some the hard work that employees and consultants who work for Alliance Pipeline Limited have performed over the previous few years.

The authors would like to thank the participants of the NATS study whose innovative ideas are the reason Alliance Pipeline Limited will become reality in the near future. We would also like to thank the team who worked on the fracture control program for the Alliance Pipeline. Your innovations will benefit the entire industry.

REFERENCES Downloaded from http://asmedigitalcollection.asme.org/IPC/proceedings-pdf/IPC1998/40221/83/2507289/83_1.pdf by guest on 26 September 2021

Alliance Pipeline Limited Partnership. 1997. 'Application to the National Energy Board for a Certificate of Public Convenience and Necessity”.

DEML Energy Management Inc. 1995. “Northern Area Transportation Study.

Figure 6. Outage Pressure Profile for Alliance Pipeline Carlson, Dr. L, Gilroy-Scott, A. and Homer, W. N. 1998. The Alliance Fracture Prevention and Control Program”

In Figure 6, the Station 9A (Kerrobert) is unavailable. In this example, it takes approximately 580 km to restore the pipeline back to its maximum operating pressure. After the station comes back on line a few days later, the process of refilling the pipeline with the appropriate amount of linepack begins.

A major advantage of designing a reserve into each station rather than lumping it all at one station is that under normal operations when all units are available and running, the additional horsepower can be used to deliver extra volume. This is the reason why the Alliance Pipeline can actually transport approximately 43.9 1 06 m3/d to 46.7 10s m3/d (1.55 to 1.65 bcf/d depending on the season) when all units are running. This is approximately 5600 to 8500 10s m3/d over the firm contracted volume. Given the history of capacity constraints, the expectation is that it will be fully utilized.

CONCLUSIONS

The Alliance Pipeline represents an innovative new project that answers the clearly expressed need for more gas transport capacity. It does so using the latest pipeline technology that will allow a combination of higher pressure and richer gas to provide a significant efficiency benefit to shippers.

Significant technology advances in steelmaking, computer simulation and information systems will result in the Alliance Pipeline being one of the most efficient and safest pipelines operating in the World.