Real Time Demand for a Gas Pipeline Design – Dealing with Modern Challenges – Part 2

Sidney P. Santos
- 2017

Figure 1 – Mobile applications for Gas Pipeline Design
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Real Time Demand for a Gas Pipeline Design – Dealing with Modern Challenges – Part 2

By Sidney P. Santos, At Work Rio Solutions (AtWorkRio.com), Rio de Janeiro, Brazil.

Introduction

In line with the previous article, “Real Time Demand for a Gas Pipeline Design – Dealing with Modern Challenges” published in December 2015 issue of Pipeline International magazine, this article presents new functionalities of the GasPipelineExpansion mobile application as part of the innovative mobile technology to support gas pipeline design through the web.

The availability study of the compression system and the optimum capacity ramp up of the transmission system are the new functionalities of GasPipelineExpansion and are of key importance in the process of designing a feasible gas pipeline project.

ABOVE: GasPipelineExpansion thermohydraulic simulation graph result; Availability analysis without standby compressor units; Capacity ramp up study with 1 compressor station (year 1), 3 compressor stations (year 2) and 7 compressor station (year 3 to 30).

Innovative Technology

Following the same approach presented in the referred previous article At Work Rio implemented new features in the application GasPipelineExpansion and presents detailed information – through a case study – to highlight its capabilities.

GasPipelineExpansion performs cost estimate for a new gas pipeline project or capacity expansion of an existing one, add compressor stations to an existing project, does capacity ramp-up and availability studies and works with GIS information (latitude, longitude and elevation profile) of the pipeline route. It covers:

GasPipelineExpansion – Visualization in Google earth
  • New Project or Capacity expansion: for gas pipeline duplication, duplication of an existing section of a gas pipeline or a pipeline interconnection, where transmission or distribution companies see an opportunity to increase system capacity GasPipelineDesign and GasPipelineExpansion can be used together to provide the best feasible solution for the expansion be it an installation of a loop line or compressor station(s).
  • Capacity ramp up: New gas pipeline projects normally do not start operation with full capacity. It is necessary to determine the best configuration for compressor stations and compressor unit installation to cope with the capacity ramp up through the first years of operation and the schedule of the installation of compressor stations and compressor units. This approach optimizes CAPEX cash flow and makes the project more competitive
  • Availability study: GasPipelineExpansion® incorporates a powerful and flexible module for availability study that performs Monte Carlo Simulation. Compressor units’ failure, their frequency and scenarios are identified and each scenario is thermohydraulically simulated and its capacity under failure is quantified. The frequency of failures versus capacity under failure will allow the evaluation of the compressor system availability and also support the definition of the adequate level of redundancy (standby units) for the gas pipeline. The simulation process can be as follows:
    • Simulate the compression system without any standby units and get the availability
    • Select target compressor stations to have standby units and run again and get improved availability for the system
    • Continue testing other arrangements of standby units until the availability satisfy the Project needs
    • Or simulate with a standby unit for all the compressor stations.
    Electric Power Research Institute – EPRI (1) has surveyed many compressor stations with different arrangements of compressor (centrifugal or reciprocating) and driver (electric motor, gas turbine and gas motor) and identified their reliability and availability values as follows:
    	
        Reliability, %	Availability, %
        Electric motor + Centrifugal:		99.4		98.9
        Gas turbine + Centrifugal:		98.2		97.1
        Gas motor + Reciprocating:		97.1		94.3
    

    The simulation runs 100000 iterations and compiles groups of failure results with their respective gas transmission capacity and frequency. The application can handle different sizes and types of compressor units at any compressor station each unit with their own availability figures.

    Availability study with Monte Carlo simulation is of key importance for a feasible gas pipeline project. Transmission company must mitigate its operation risk to comply with Transportation Agreements with Local Distribution Companies or End Users with regard to firm capacity clause and related penalties for non-compliance. On the event of compressor units’ failures impacting pipeline capacity transmission company would face penalties and loss of revenues impacting dramatically its economic result (2,3,4,5).

These innovative mobile technology applications have been developed by Sidney P. Santos who retired from Petrobras in 2012, after working for more than 25 years as a Senior Consultant and a gas pipeline design engineer. Using his extensive knowledge of the technology of pipeline design, as well as programming on spreadsheets, Visual Basic and C#, Mr. Santos lately has worked with qualified software developers to perfect his applications. His most recent projects at Petrobras prior to retiring was the design of the Bolivia-Brazil Gas Pipeline - GASBOL and the expansion project of the gas pipeline network in Brazil. He had a key participation in many prospective projects such as the Venezuela-Brazil Gas Pipeline – GASVEN and the Integration Gas Pipeline – GASIN. He also provided consulting assistance to KazTransGas and Intergas Central Asia for the Kazakhstan section of the Trans Asia Gas Pipeline.

Case Study

The case study used to illustrate this article is based on the Bolivia-Brasil Gas Pipeline Project should we have to design it by now. Based on prevailing market condition and technical and economic assumptions by the time it was designed – around the year 1995 –the main section of the project has a nominal diameter of 32”and 14 compressor stations. The transmission capacity is 1059 MMSCFD (30 MMSCMD).

With the same technical requirements and today’s economic assumptions and by using At Work Rio innovative technology the best alternative for the project is as follows:

Technical assumptions:
Capacity: 1059 MMSCFD
Length: 1068 miles (straight route) 
Length: 1118 miles (geographic route)
MAOP: 1420 psi
Pipe material: API5L X80
Gas specific gravity: 0.6000
Inlet pressure: 1410 psig
Delivery pressure: 1000 psig 
Compression ratio: 1.4000 
Gas Deliveries, MMSCFD:
D1, at milepost 363.4 miles	: 	1.7657 
D2, at milepost 589.3 miles	: 	47.6748 
D3, at milepost 781.6 miles	: 	68.8636 
D4, at milepost 877.1 miles	: 	2.8252 
D5, at milepost 1025.1 miles	: 	14.1259 
D6, at milepost 1092.5 miles	: 	40.2587 
D7, at milepost 1104.3 miles	: 	5.6503

Economic assumptions:
Pipe material cost: 2500 US$/ton
Fuel gas cost: 5 US$/MMBTU
Pipeline O&M: 1.5 % of Pipeline CAPEX per year
Compressor Station O&M: 5% of Compressor Station CAPEX per year
Project economic life: 30 years
Discount rate: 12 % per year
Construction time: 4 years
Pipeline CAPEX schedule: 15% year 1, 30% year 2, 30% year 3, 25% year 4 
Compressor station CAPEX schedule: 0 % year 1, 10% year 2, 40% year 3, 50% year 4 

Results for the Selected gas pipeline configuration:
Technical
•	Nominal diameter	: 36”
•	Total length	: 1118 miles
•	Transmission capacity	: 1,100.76 MMSCFD
•	Compr. station quantity	: 7
•	Compr. station operating units	: 2
•	Compr. station standby units	: 1 per compressor station
•	Total required power	: 125,144 hp
•	Total installed power	: 298,812 hp
•	Total required fuel gas per year	: 9,517.08 MMSCF
•	Compressor system availability	: 
o	Without stanby units	: 0.9811
o	With 1 standby at CS# 4	: 0.9836
o	With 1 standby at CS# 2, 4, 6	: 0.9925
o	With 1 standby at each CS.	: 0.9997
•	Capacity ramp up	:
o	1 compressor station (CS# 4)	: 565.21 MMSCFD
o	3 compressor stations (CS# 2,4,6)	: 775.83
o	7 compressor stations (CS# 1,2,3,4,5,6,7)	: 1100.76
Economic, MMUS$ 
•	Pipeline total cost	: 	3,528.48
•	Pipeline total cost PV	: 	2,630.48
•	Compressor station total cost	: 	800.55
•	Compressor station total cost PV	: 	546.13
•	Pipeline O&M present value	: 	270.95
•	Compressor station O&M PV	: 	204.91
•	Total fuel gas PV	: 	237.26
•	Inventory (Line pack) gas PV	: 	11.01
•	Total CAPEX	: 	3,176.61
•	Total OPEX	: 	724.13
•	Total Project PV	: 	3,900.73

Conclusion

In conclusion, At Work Rio’s innovative technology covers all important aspects related to the design process of a gas pipeline process such as thermohydraulics, failure analysis with Monte Carlo simulation, capacity ramp up, cost assessment and economics.

This state-of-the-art, innovative mobile technology improves productivity on gas pipeline conceptual design with simple, practical, accurate, reliable and speedy solutions.

Reference

  1. ELECTRIC POWER RESEARCH INSTITUTE, EPRI. Report No. RP 4CH2983, 1999
  2. SANTOS, S. P., Monte Carlo Simulation – A Key for a Feasible Gas Pipeline Design. Pipeline Simulation Interest Group – PSIG, Galveston, Texas, USA, 2009.
  3. SANTOS, S. P., Availability and Risk Analysis Effects on Gas Pipeline Tariff Making. In: INTERNATIONAL PIPELINE CONFERENCE, 2008, Calgary, CA.
  4. SANTOS, S. P.; Bittencourt, M. A. S.; Vasconcellos, L. D., Compressor Station Availability – Managing its Effects on Gas Pipeline Operation. International Pipeline Conference, Calgary, Canada, 2006.
  5. SANTOS, S. P.; SALIBY, E., Compression Service Contracts – When Is It Worth It? Pipeline Simulation Interest Group – PSIG, Bern, Switzerland, 2003.
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