Papers

A collection of papers published by AtWorkRio in international Conferences are made available for customers and are an example of the expertise acquired by AtWorkRio along more than 25 years of professional activities in the gas business chain.



2013
Sidney P. Santos
Matt Lubomirsky
Rainer Kurz
IBP1162_13

Abstract

Infrastructure projects are characterized as being capital intensive, with long economic life and high level of economic risk due to many players involved in the natural gas business chain. Project sponsors of a gas pipeline project need to carefully manage its most important variables in order to optimize its implementation. This paper highlights some of these variables – such as economic life, internal rate of return, market gas demand growth, design pressure, strength of steel, pipeline internal coating, compression station design, compression system redundancy level and compression ratio – that impacts transportation tariff that in turn, associated with gas commodity price, composes the final gas price for end users. Natural gas final price must be competitive when compared to other energy supplies and this alone underline the need of a well performed feasibility analysis for a gas pipeline project. A case study with a methodology is presented in this paper along with sensitivity curves for each variable studied to help gas pipeline designers to understand and manage their impact on the project.


2013
Sidney P. Santos
Matt Lubomirsky
Rainer Kurz
PSIG_1310

Abstract

While the transmission compressor stations in pipelines normally operate at relatively low pressure ratios in the order of 1.2 to 1, there are applications that require significantly higher pressure ratios. This paper presents the results of a study conducted for a compressor station design where multiple pipelines feed into one new pipeline. One of the feeder pipelines is designed for significantly lower pressures than the other feeder and the transmission line. As a result, some operating conditions require a very high compression ratio, in some instances as high as 2.8 to 1. The purpose of the study is to select the best feasible turbocompressor unit for the project between two technical available options with different technologies: single compartment and dual compartment compressors. The methodology adopted is designing a (i) compressor station configuration for single compartment compressor technology with aftercooler and for (ii) dual compartment compressor technology with intercooler and aftercooler, pre-selecting the compressor units to address all operating conditions, perform thermohydraulic simulations, evaluate the gas fuel demand for each year of operation and then evaluate the economics for each alternative. The paper can serve as a guide line for compressor station designers to make decisions not only based on technical aspects – that could lead to higher project life cycle cost – but rather on overall technical and economic aspects that produces lower project life cycle cost.


2011
Sidney P. Santos
Matt Lubomirsky
Rainer Kurz
IBP1076_11

Abstract

Feasibility studies for Gas pipeline projects need to take into consideration some key uncertainties that have a direct and significant impact on the economics of a project. Such uncertainties if not properly addressed will expose project sponsors to economic risk and may destroy value. Such uncertainties includes, but are not limited to, gas reserve appraisal, gas market demand, CAPEX, OPEX and Construction Schedule. This paper will focus on Market risk and how gas demand uncertainty may be addressed and how pipeline designers and project sponsors may act to mitigate such risk while selecting a flexible strategy based on gas compressor station design, compressor units stand buy philosophy, pipeline sizing, MAOP definition and some other aspects to be considered in the gas transportation agreement.


2011
Sidney P. Santos
Matt Lubomirsky
Rainer Kurz
Zhan Kulzhanov
PSIG_1118

Abstract

Internal pipe coating technology is available for natural gas pipelines, and can be primarily used to reduce surface roughness, and thus internal friction. This will reduce the pressure drop between compressor stations, and thus allows installing less power and consume less fuel. The potential to lower CAPEX (due to lower compression power requirement) and OPEX (due to lower fuel consumption) are counteracted by the extra cost of the internal coating...


2009
Sidney P. Santos
PSIG_0906

Abstract

Gas pipeline projects are capital intensive and are exposed to many risks related to uncertainties of their main components such as capital investment (material and services) – Capex, operation and maintenance costs – Opex, construction and assembly – C&A schedule, C&A Costs and others. Such items need to be properly addressed to mitigate project risk otherwise they may impact negatively the project sustainability normally measured by the project net present value – NPV...


2008
Sidney P. Santos
IPC08-64083

Abstract

On a competitive market gas transportation rates must be as low as possible while recovering capital expenses - Capex and operating and maintenance expenses - Opex at a return rate expected by the project sponsors to recover their investment. To guarantee project feasibility, designers must be concerned not only with technical and direct economic aspects but should also incorporate availability and economic risk analysis to make sure that under operating conditions along the economic life of a project the cash flow will be kept inside predicted values and therefore will not expose project sponsors to undesirable negative Net Present Values - NPV. This paper will present a methodology to address these important aspects with focus on pipeline economics. Pipeline availability study associated with compressor stations failure analysis will be evaluated under Monte Carlo simulation and consequently their impacts on gas pipeline capacity will be economically evaluated. Quantitative economic risk analysis using Monte Carlo simulation is part of the methodology. The adoption of this methodology allows committing more pipeline transmission capacity to a level close to maximum without exposing the Transporter to losses of revenue and contractual penalties. Also prevents designing an oversized and less competitive system with unused spare capacity and consequently higher transportation rates.


2008
Sidney P. Santos
Antonio Orestes de Salvo Castro
José Eugênio Leal
IBP1544_08

Abstract

An efficient management of the natural gas business chain, based on pipeline transmission network and taking into consideration the interaction between the main players such as Shippers, Suppliers, Transmission Companies and Local Distribution Companies, requires the use of decision-making support systems to maximize resources and mitigate contingencies due to gas supply shortfalls, operational contingencies from scheduled and non-scheduled equipment outages as well as market demand shortfalls. This work presents a practical utilization of technologies such as thermohydraulic simulation of gas flow through pipelines, Monte Carlo simulation for compressor station availability studies and economic risk evaluation related to potential revenue losses and contractual penalties and linear programming for maximization and minimization objective function. The proposed system allows the definition of the optimum availability level to be maintained by the Transporter, by means of installing redundancy, to mitigate losses related to revenue and contractual penalties. Identifies, quantifies and justifies economically the installation of stand-by compressor units, mitigating Transporter exposure to losses due to capacity shortfalls as consequence of scheduled and non-scheduled outages.


2006
Sidney P. Santos
Matt Lubomirsky
PSIG_06A1

Abstract

Thermo-hydraulic simulations of centrifugal compressors are usually based on a set of information derived from manufacturer design tools that are used for compressor modeling. When operating gas pipelines transportation companies use the simulation tool to predict and anticipate the behavior of the gas pipeline under different scenarios. The operation with different gas compositions from differentsupplies is not uncommon as well as the exposure to gas quality changes whenever contingencies happen to the gas processing plants. This paper address this important subject, presents a methodology of evaluation, a sensitivity study using different gas qualities and shows the impact on compression overall performance. A compressor is selected based on a set of conditions and then is checked for performance changes when working with different gas quality. The results are presented for comparison purposes and some suggestions are also presented on how to handle this situation to guarantee that the thermo-hydraulic simulation tools will always provide good resultswhen dealing with natural gas quality changes.


2006
Sidney P. Santos
Maria Angélica S. Bittencourt
Luiz Diogo Vasconcellos
IPC06-10560

Abstract

An optimized Gas pipeline design requires not only a qualified management of good engineering and planning, but also accurate estimates of capital investment and O&M. Compressor stations play a very important role on the success of a gas pipeline design and a careful selection of centrifugal compressors and drivers are key aspects for the success of the project. The state of the art design available nowadays for these kind of equipment provides overall high thermodynamic performance and consequently minimizes installed power requirements and energy usage with expressive savings on operating expenses along the economic life of the project. This paper will present a guideline for proper station design and selection of its turbo-compressors giving emphasis on the impact of fuel consumption on the economics of a gas pipeline project.


2005
Sidney P. Santos
Rainer Kurz
Matt Lubomirsky
IBP1044_05

Abstract

Feasibility studies for Gas pipeline projects need to take into consideration some key uncertainties that have a direct and significant impact on the economics of a project. Such uncertainties if not properly addressed will expose project sponsors to economic risk and may destroy value. Such uncertainties includes, but are not limited to, gas reserve appraisal, gas market demand, CAPEX, OPEX and Construction Schedule. This paper will focus on Market risk and how gas demand uncertainty may be addressed and how pipeline designers and project sponsors may act to mitigate such risk while selecting a flexible strategy based on gas compressor station design, compressor units stand buy philosophy, pipeline sizing, MAOP definition and some other aspects to be considered in the gas transportation agreement.


2004
Sidney P. Santos
IPC04-0183

Abstract

Gas pipeline projects are capital intensive and normally are developed under scenarios of uncertainty. Such uncertainties vary from closing take-or-pay, ship-or-pay or delivery-or-pay agreements to those uncertainties related to the acquisition of equipments, material and construction and assembling contracts. Natural gas compression service contracts with compressor station using gas motors and reciprocating compressors have been widely adopted at PETROBRAS as economically feasible against holding the stations as part of the pipeline asset as well as providing an effective approach to mitigate risks inherent to the gas business and associated to the compressor stations. Although compression service contracts with turbo compressors (gas turbine drivers and centrifugal compressors) have not yet been accomplished at PETROBRAS for gas pipeline projects, studies and preliminaries discussions shows that, taken into consideration certain relevant aspects, they will also present great opportunity to be adopted and will generate the same advantages already perceived for the compression service contracts with stations that uses gas motor drivers and reciprocation compressors. This paper has the objective of presenting an economic approach and a business model addressing the main points that must be considered while doing feasibility analysis between the alternatives of holding property of the compression station asset against the opportunity of having a compression service contract as operating cost for the project. Questions such as how to address depreciation, overhaul costs and tailor made equipment, such as centrifugal compressors, are raised and answered.


2004
Sidney P. Santos
PSIG_0405

Abstract

Feasibility studies for Gas pipeline projects need to take into consideration some key uncertainties that have a direct and significant impact on the economics of a project. Such uncertainties if not properly addressed will expose project sponsors to economic risk and may destroy value. Such uncertainties includes, but are not limited to, gas reserve appraisal, gas market demand, CAPEX, OPEX and Construction Schedule. This paper will focus on Market risk and how gas demand uncertainty may be addressed and how pipeline designers and project sponsors may act to mitigate such risk while selecting a flexible strategy based on gas compressor station design, compressor units stand buy philosophy, pipeline sizing, MAOP definition and some other aspects to be considered in the gas transportation agreement.


2003
Sidney P. Santos
Eduardo Saliby
PSIG_03A4

Abstract

It is not uncommon to face a situation when we need to make capital investment decisions to increase transportation capacity of a pipeline under uncertainties such as market development, project costs, schedule and so forth. This was the situation we faced related to the energy shortage in Brazil that prompted for the need of alternative and reliable energy sources that could be put into operation in a short period of time based on many prospective Gas Fired Power Plant projects but without having the necessary agreements signed. The Ministry of Mines and Energy of Brazil set a program addressing initially 55 thermo power plants totaling about 20,402 MW. From this total 18,263 MW of installed power was from 49 gas fired power plants demanding gas volumes in the range of 88 MMm3/d, most of this power were to be available from 2001 to 2003. With this challenge, Petrobras has started to design a gas pipeline network expansion plan with investments of more than 1 billion US$ for its system alone, including new gas pipelines, new compressor and custody transfer stations and loop lines, in addition to expansion projects for the Bolivia-Brazil Gas Pipeline in Bolivia (0.2 billion US$) and in Brazil (0.35 billion US$), and the new gas pipeline from Argentina to Brazil (0.25 billion US$). Under this scenario we considered the option of contracting compression service for some pipelines in our networks as an alternative for conventional and permanent compressor stations while discussing the gas and transportation contracts and others investments. We did a feasibility analysis for two alternatives of compression service contract and permanent compressor station both using Monte Carlo Simulation Method. The results and methodology are presented in this paper.


2003
Sidney P. Santos
IBP424_03

Abstract

The worldwide competition and the availability of new business opportunities have paved the way for service contracts as an attractive option when performing feasibility analysis for gas and energy projects. This paper addresses this subject and incorporates the experience gotten at Petrobras focusing on Compression Service Contract for Gas Pipeline Transmission System and also on Gas Processing Contract for gas dew point adjustment for natural gas production so as to specify the gas for industrial and automotive use. The methodology presented, that incorporates Monte Carlo Simulation for Risk Analysis, can be applied for any project with similar characteristics. This paper also underlines the importance of the use of Risk Analysis for feasibilitystudies.


2000
Sidney P. Santos
SPS_02

Abstract

This subject is always present when designing a gas pipeline that requires compressor stations to optimize the transportation and also capital and operation costs. On the Bolivia-Brazil gas pipeline project original design the technical economic analysis, thermo-hydraulic studies and failure analysis determined a selection of a parallel arrangement for the fourteen (14) compressor stations with four (4) 7000 hp ISO gas turbines per station. The project schedule considered the installation of three (3) initial compressor stations that were necessary for three (3) years of operation. With more accurate information from market development, transportation contract ramp up changes and the experience acquired from the original design a new set of studies were done. The results obtained allowed a better understanding of compressor station operation and also allowed the selection of the size and arrangement of units to be adopted for the expansion. The new studies considered bigger turbocompressors with series and parallel arrangement and electric driven compressors as an alternative for the project since there is an electric transmission line parallel to the gas pipeline in Brazilian side. The optimization study proved series arrangement to be a better solution for the configuration with electric driven compressor taken benefit of the driver sizing and speed. Economics aspects including capital cost, although considered in detail for the Bolivia-Brazil gas pipeline project, will not be addressed in this paper because of their particularities in terms of logistics, market competition and labor costs that will vary differently depending on the location of the project. The purpose of this paper is to underline the need to simulate different sizes and arrangements for compressor station units and not selecting a off-the-shelf solution that might not be the best one in terms of capital investment, fuel usage and optimal energy management. The simulation tool used to perform all the simulation analysis for the Bolivia-Brazil expansion project was PipeLine Studio 1.2 from LicEnergy.This paper adds more information over the previous one presented on the PSIG Annual Meeting of 1997 entitled “Transient Analysis – A Must in Gas Pipeline Design”.


1997
Sidney P. Santos
PSIG_1997

Abstract

Traditionally, a new project for a gas pipeline system starts in a technical economical evalua-tion phase which considers a steady state flow analysis with a lot of guesswork and assumptions, such as market delivery build up, minimum and maximum flow and estimated number of compres-sor stations. For a reasonable evaluation of the system a load factor is normally adopted for the gas pipeline, which means that the pipeline will be calculated with a constant flow which will be higher than the nominal flow considered to be supplied to the foreseen market. The main difficulty is to de-fine a duty load that would represent the system under analysis since different flow profiles, operat-ing pressures, diameter and length of the pipeline will affect the behavior of the complete system. As soon as the technical economic evaluation shows an attractive return rate for the project and the companies involved decide on a go ahead position, the design phase takes place. It is in this phase that a transient analysis for the system has proved to be a must as we have experienced in the design of the Bolivia-Brazil Gas Pipeline. It is a 32" diameter and 1127 miles (1813 km) long pipeline from Rio Grande (Santa Cruz de La Sierra - Bolivia) to Campinas (São Paulo - Brazil) with 14 compression stations. It is designed for 1.043 Bcf/d (30 MM m3/d) of natural gas. Why do a transient analysis in the design phase? The first reason is related to the large investment that is required for such a system which in-cludes pipeline and compression stations. The system designed must be able to operate in the pre-dicted different scenarios, otherwise the transportation company would face penalties for not deliv-ering the contractual volumes of gas or make additional capital investment on the system, dramati-cally affecting the cash flow of the project. A second reason is that in this phase normally we face the inclusion of new deliveries with dif-ferent profiles such as thermal generation that may interrupt the gas consumption to zero for a cer-tain time on a weekly basis, as will normally happen in Brazil. These scenarios must be taken into account since they directly affect the schedule of placing compression stations and units into opera-tion depending on the gas build up delivery. Additionally we may use the transient analysis to make a pre-definition of the turbo compres-sors that best fit our system and also define the best arrangement for the units in the station, whether in a series (few units and bigger machines) or parallel arrangement (more units and smaller machines). In line with this we may do a failure analysis for a single unit or for a complete station and foresee how the system would cope with that, determine its remaining capacity, and also define a much better maintenance procedure, or even detect a necessity of a standby unit in the worst cases. The transient analysis will also be very useful during the negotiations of ship or pay contracts that starts even before the design phase. This paper will focus on a single line gas pipeline without storage facilities and with a flow de-mand that varies with respect to time in an hourly basis so as to show a behavior that could not be considered as a steady state flow. The software used was TGNET 5.3E from SSI.