Among the main objectives of Pemex Exploracion and Produccion Region Sur is found the analysis of the operation, the optimizacion and the modernization of the systems of produccion, transportation and distribution of hydrocarbons, in order to provide better security conditions, efficiency and opportunity, without forgetting the proteccion to the environment and the society. For the foregoing, it results from great importance to count on a methodology for planning the behavior and development of the infrastructure of produccion and transportation to face current and future needs, bearing in mind the operational requirements and quality that demand best engineering practices. The utilization of Process and Transport Simulators to analyze the facilities in the current operation conditions, and to predict their behavior under different stages is a valuable tool that applied combined with the best practices of engineering allows to predict, with meaningful time savings, the necessary modifications to be adjusted to the new operative philosophy, without putting on risk the facilities. As added value, the results obtained from the application of this methodology also contributes to the construction of a data base, of the facilities of produccion as well of transportation, of great usefulness for activities related to the maintenance programs.
Trang 1Copyright 2000, Society of Petroleum Engineers Inc.
This paper was prepared for presentation at the 2000 SPE International Petroleum Conference
and Exhibition in Mexico held in Villahermosa, Mexico, 1–3 February 2000.
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Summary
Among the main objectives of Pemex Exploracion and
Produccion Region Sur is found the analysis of the operation,
the optimizacion and the modernization of the systems of
produccion, transportation and distribution of hydrocarbons, in
order to provide better security conditions, efficiency and
opportunity, without forgetting the proteccion to the
environment and the society
For the foregoing, it results from great importance to count on
a methodology for planning the behavior and development of
the infrastructure of produccion and transportation to face
current and future needs, bearing in mind the operational
requirements and quality that demand best engineering
practices
The utilization of Process and Transport Simulators to analyze
the facilities in the current operation conditions, and to predict
their behavior under different stages is a valuable tool that
applied combined with the best practices of engineering
allows to predict, with meaningful time savings, the necessary
modifications to be adjusted to the new operative philosophy,
without putting on risk the facilities
As added value, the results obtained from the application of
this methodology also contributes to the construction of a data
base, of the facilities of produccion as well of transportation,
of great usefulness for activities related to the maintenance
programs
The results of modeling are completed with an economical
analysis in order to find the best alternative to solve a
particular situation The obtained information is documented
and ordered to justify the new projects and the required investments
Introduction
The Region Sur has an importance of first order in the context
of the economics and the national politics From the fiftys the states of Tabasco, North of Chiapas and Veracruz began to receive strong investments that sponsored the takeoff of this zone as international trade pole in base to three factors:
• Their geographic location that connects them with large three ports (Dos Bocas, Pajaritos and Salina Cruz)
• The great industrial development achieved in the other subsidiaries of Pemex (Pemex Refinacion, Pemex Gas y Petroquimica Basica and Pemex Petroquimica)
• The quality of the hydrocarbons, what permits to improve the crude mixtures for exportation as well as for the processing at domestic level
In general terms the Region Sur is characterized by generating
20 percent of national produccion of oil, 46 percent of the produccion of the gas, and 16.6 percent of gas liquids
Currently the produccion of gas in the region is of 2 190 mmpcd in average Of this volume 86 percent originates of the Mesozoic and 14 percent of the Tertiary Concerning to gas liquids the produccion is of 14 725 bpd of which 96 percent corresponds to the mesozoico and 4 percent to the Tertiary
The gas and condensate produced have as final destination the processing gas centers of Cactus, Nuevo Pemex, Cd Pemex and La Venta It is convenient to indicate that the Region Sur receives part from the gas from the Marine Region by Atasta for its processing in Cd Pemex, Cactus and Nuevo Pemex
In general terms the gas and the condensate that are transported in the Region Sur are sour and saturated with water, what implies a greater duct and equipment deterioration due to corrosion On the other hand, part of the infrastructure could be in the limit of its operative life, therefore to prevent any further risk is necessary the substitution of some components
Design and Development of Hydrocarbon Surface Production Facilities and Pipelines Based on Process And Transport Simulators.
M.P Castillo, SPE, Instituto Mexicano del Petroleo; M Murillo, Pemex Exploracion and Produccion Region Sur,and C Cabrales, Instituto Mexicano del Petroleo
Trang 2Additionally, the produccion of gas and of condensate tends to
reduce, therefore in some instances it must be considered the
sustitution, relocation or modification of the infrastructure, or
even to propose different alternatives of operation
Based on all of the above a team of engineers carried out the
modelation of the systems, particularly concerning the
managing of the gas and the condensates in the Region Sur
This modelation has the purpouse of detecting bottle necks in
the current infrastructure, and to optimize transportation
systems to face future demands
Description of Process and Transport Simulators
In the market exists a great variety of simulators that have
proven their usefulness in oil industry, particularly with
respect to optimize nets of ducts and facilities for
hydrocarbon processing
In figure 1 are shown the computer programs that were used
an their capacity to reproduce and predict the necessary
operation conditions for the design of produccion and
transportation systems
These simulators were selected in base to the obtained
experiences from their application, that is to say the accuracy
to reproduce the operation conditions as obtained from the
field
Concerning what is referred to the quality and type of
informacion fed to the models we can say that this is of three
types: the obtained from the instruments installed in field
(Pressure, Temperature and Flow); the mechanical
characteristics of the system (Diameter, Length, Thickness,
Material of Contruction, Right of Way and Topographic
Profile); and the Compositional Analysis of the Hydrocarbons
(C1 to C6+, CO2, N2, H2S and water content)
On the other hand, it is also mandatory to know the
produccion forecasts required to evaluate the systems under
different operative stages, and the information obtained from
calibrating pigs which provides data on the current situacion
of the thickness of the pipeline, crucial information to
establish the maximum operating pressure of the pipe, that is
pressure for transport
Characterization of fluids
This factor is a key factor for the design and development of
Production and Transportation facilities, since the results that
are obtained as product from modeling are found intimamente
related to the composition of the fluids processed
For the case of the hydrocarbons processed in production
facilities the information of the - PVT Analysis- obtained from
reservoir samples is used With respect to gas transportation,
cromatographic analysis is been used
Modeling Procedure
In figures 2 and 3 are shown the Produccion and Transportation Systems, from which we began construction of the models These figures indicate the way the produccion of gas and condensated, originated from the different facilities is gathered, and the physical characteristics of the available pipelines Finally these volumes of hydrocarbons are delivered to the processing gas centers of Cactus, Nuevo Pemex and Cd Pemex
In agreement with the authorities of Pemex Exploracion and Produccion, the Instituto Mexicano del Petroleo began the process of modeling with the following objectives:
• To reproduce the behavior of the transportation systems, particularly with respect to the cases of two phase flow in which "Retrograde Condensation” phenomena takes place
• To analyze in transportation nets the effect by incorporating greater volumes of hydrocarbons, or decline
of the produccion
• To detect possible bottle necks
• To accomplish overall sensibility studies (Technical and Economical) of the operation of the system
Hydrocarbons Characterization
In spite of the fact that the characteristics of the products obtained in a production unit depend on the compositional analisis of each one on the wells that flow to this, by the difficulty that represents the availability of recent samples, a discrimination of the existing informacion is adopted and, as
of the Analisis - PVT - available, through the use of simulators was obtained the necessary characterization for the modeling However, in some instances before the absence of exact information “Black oil” option has ben taken
In figure 4 is presented an example of the data treatment that
is effected to a Sample - PVT - of a well to obtain the corresponding compositional analisis
With respect to the transported gas, the chromatographic analisis is preferred the one that routinely is performed in production facilities The experience has demonstrated the usefulness that represents the power to determine with the greater possible accuracy the heavy ends, since they influence accuracy in prediction of condensacion during transportation,
as well as the identification of undesirable flow patherns In the table 1 is shown a typical example of gas composicion obtained in the region
Due to the difficulty to determine the concentration of water in the gas streams produced in production facilities, it is been adopted, with good results, to determine this concentracion as
of the operation conditions and the composition of the hydrocarbons, applying equations of state (Peng-Robinson and Soave-Redlich-Kwong) The accuracy of this
Trang 3consideration has been corroborated comparing the obtained
results from the modeling against information of field in those
points where water could be measured in liquid form
Required Information and Design Criteria
The simulators are capable of modeling production and
gathering systems, including within these parallel pipelines or
"Loops"
These simulators report composition of phases, pressure drop,
liquid formation or "Hold Up", flow patterns , transportation
velocity, and thermophysical properties of the fluids involved
in the design of the equipment
To get this data the following informacion is fed:
molecular weight streams this is obtained from data
treatment from the - PVT Analisis - to obtain the
concentration of identificable components asi well as
pseudocomponents In the case of the gas streams, light
molecular weight, chromatographic analysis is used
directly
obtained from operating logs In those cases when is
intended to operate at different conditions of the current,
is agreed with the operator the range in which these
variables can be modified so that, during the stage of
modelacion of stages, are analyzed only those feasible
cases to be carried in practice
throughout several years devoted to the modelation of
production facilities has carried us to use, for the
calculation of gas-liquid equilibria, thermophisical
properties,Peng Robinson, Soave-Redlich-Kwong,
Lee-Kessler, Grayson Streed In regard to the viscosity, it has
been proven that the utilization of experimental
viscosities for heavy fractions is highly advisable
In what concerns to the multiphase transport, horizontal or
vertical , it has been used Taitel-Dukler-Barnea, Beggs and
Brill, Dukler-Edton-Flanigan
provided the informacion related to the size of the
equipment, the internal diameter, length and topographic
profile of the pipeline
• On the other hand, taking into account the characteristics
of the right of way, our experience recommends to use
overall heat transfer coefficients “U” of 1.20 and 0.66
BTU HR FT² ºF/FT for gas and liquid transportation
respectively
recommend velocities to design pipelines In most of the cases this recommendations seek to avoid, through the control of the velocity, erosion, stratificaction of water or solids, and undesirable flow patherns
However, in our case, in the one which the systems are existing; that they began their operation in different conditions from the current; and that in the future is possible that they have to comply with different operation conditions, these recommendations have been considered
as a reference, and the projects accomplished in the Region Sur have developed their own criteria
As a reference we could mention for gas 20-60 FPS and for liquids 4-10 FPS
undesirable flow patterns such as "Slug" and "Plug" However you dont’n have to forget that in the case of the transportation of the associated gas the phenomena of
"retrograde condensation" which leads to multifhase flow, the alternative to control the volume transported to avoid these patterns could be identified in the field by the fluctuacion of the operation conditions in the delivery points at the end of pipe
information to the model, a series of runs in the computer are performed which main objective is to reproduce, as close as possible, from the operation conditions of the system in the origin, the conditions in the extreme of the duct
These final conditions commonly are: volumes of liquid and gas, pressure and temperature, volumes of liquids displaced by pigs, etc
Forecasts.-Such as we mention before, in order to establish if a system has the necessary operative flexibility, it is important to count on with the production forecasts
This document contains the yearly produccion of hydrocarbons during a period of at least 15 years, and upon using it we will be able to know to identify bottle necks in the system and then to find out the operative or constructive alternatives to avoid them
Modeling of Gas Gathering System “Catedral-Muspac-Chiapas-Giraldas-Cactus”.
Catedral-Muspac.Chiapas-Giraldas-Cactus System is a high pressure pipeline network which gathers associated gas obtained in four production units The total amount of gas is
Trang 4delivered at high pressure to be processed in a Gas Processing
Plant located in Cactus
Figure 5 shows the results obtained when we apply the
methodology for a high pressure sour gas gathering system
This figure presents a comparison between operating
conditions and those values obtained by simulation As we can
see deviation in the majority of cases remains in aceptable
level, therefore the model is validated
Figure 6 shows the proposed infraestructure required to
operate the same system but at lower pressure including some
other separation units
Conclusions
1 The use of processing and transportation simulators has
been of great help to analyze, eliminate bottle necks and
to optimize the current and future facilities for the
managing of gas and condensate in the Region Sur
2 The decisionmaking to change the philosophy of
operation of the facilities, or to justify the construccion of
new infrastructure, preserving the security margins
recommended to protect the environment and population,
avoiding the deferred produccion, is facilitated with the
employment of the simulators without putting on risk the
infrastructure
3 It is been proved the usefulness that represents countting
on recent compotional analysis However it is advisable to
detect as much as possible high molecular fractions in the
chromatograph
The resource of using a - PVT anlysis - or the option
"Black Oil" leads to greater deviations and alone are
recommended as the last resource, or for very general
studies to explore alternatives of operation
4 The aplicacion of simulators to plan the development of
the processing infrastructure, with sufficient flexibility to
fulfil future requirements, requires of reliable information
the one which is obtained from an adequate and calibrated
instrumentation in the field
5 The routine use of simulators for the design of processing
and transportation facilities of hydrocarbons allows the
optimization of the infrastructure making it efficient and
adjusted to the requirements of Pemex Exploracion and
Produccion Region Sur
6 Nowadays IMP is working in an integral model which
considers the total network of gas an liquids pipelines in
Region Sur This tool when completed could facilitate
estimation of produccion delivered to gas processing
plants, predict operating conditions required to cope with
the missoperation of a pipeline or failure, and detect best
alternatives to handle hydrocarbons within the gathering network
Nomenclature
MMSCPD=Million standard cubic feet per day
BPD= Barrels per day FPS=Feet per second P=Pressure, kg/cm² T=Temperature, ºC CPG= Gas Processing Plant
References.
1 John Campbell: Gas Conditioning and Processing Vol I
2 J McHugh:On Target with Rough Gas Engineering and Management
3 Gas Processors Suppliers Asociation:Engineering Data Book, 1972
4 Word Rosen: Gas Processing,1996
5 O W Boyd: Petroleum Fluid Flow Systems, 1983
6 A Minkkenen: Make Best use of Associated Gas,1981
7 Norma No 07.3.13, PEP 171,Requisitos Minimos de Seguridad para el Diseño, Construccion, Operación, Mantenimiento e Inspeccion de Tuberias de Transporte, 6ª Revision, Septiembre 1994
8 PEMEX FA-2716: Evaluacion de los Sistemas de Recoleccion, Transporte y Distribucion de Hidrocarburos
en la Region Sur 1997
9 PEMEX P-1008: Analisis Tecnico Economico de Opciones de Proceso, Transporte y Entrega de Gas y Condensado en la Coordinacion Tecnica Operativa.1999
Trang 51.151 2.528 4.656 73.683 10.276 4.375 0.696 1.343 0.421 0.431 0.441
50 °C
TABLE 1 TYPICAL GAS COMPOSITION
MOL %
PRESSURE TEMPERATURE
COMPONENT
PIPEPHASE PIPESIM-NET PIPEFLOW LINEAS II
TRANSPORT PROCESS
HYSYS PRO II ASPEN PLUS SIMPROC
FLOW
COMPOSITION
TEMPERATURE
PRESSURE
HEAT TRANSFER “U”
DESIRED FLOW PATTERN
TOPOGRAPHIC PROFILE
RIGHT OF WAY
GAS-LIQUID EQUILIBRIUM
THERMOPHYSICAL PROPERTIES
PRESSURE DROP
OPERATING CONDITIONS ALONG THE PIPELINE
RETROGRADE CONDENSATION FLOW PATTERN
FIGURE 1 COMMERCIAL SIMULATORS
Trang 612"Ø x 6 KM
36" x 16 KM
36" x 7 KM
36" x 34 KM
36" x 9.9 KM
36" x 15.7 KM
36" x 21 KM
24"Ø x 13 KM
24" x 7.1 KM
16" x 10 KM
24" x 10 KM
16"Ø x 6 KM
24" x 9.9 KM
24"Ø x 34 KM
36" x 70 KM
16" x 10 KM
EXISTING PIPELINES PIPELINES IN CONSTRUCCION PIPELINES IN PLANNING
20" x 9.4 KM
24" x 0.5 KM
L-2 36" x 92 KM L-3 36" x 92 KM
36" x 14.7 KM SLUG-CATCHER
36" x 9 KM
24" x 11 KM
36" x 14.7 KM
36" x 65.7 KM
12" x 8.5 KM
16" x 14.4 KM
30" x 37 KM
16" x 21 KM
Trang 7BAT Y COMP CUNDUACAN
C.P.G. CACTUS
24" X 10 KM
8" X 7.1 KM
8" X 4.9 KM 24" X 79 KM
16" X 91.5 KM
8" x 15 KM
8"O X 14 KM
8" X 20.9 KM
8" X 32.8 KM (1)
8"X8 KM
8" X 7 KM
8" X 30 KM
8" X 11 KM
10"X21.8 KM
8" X 15 KM
8" X 10 KM
8" X 28 KM
16" X 91.5 KM
IT WORKS AS AN OIL PIPELINE
4" X 15 KM
EXISTING PIPE LINE PIPELINES IN CONSTRUCCION PIPELINES IN PLANNING
8" X 14.7 KM
AREA NUEVO PEMEX
8" X 21 KM
Trang 8RESERVOIR PVT ANALYSIS
OPERATING CONDITIONS
CHECK PROPERTIES AGAINST EXISTING DATA ON
FIELD
MAKE ADJUSTENTS
IN COMPOSITION.
COMPOSITION OK FOR FUTURE SIMULATIONS
NO
YES
END
MODELING OF PRODUCTION FACILITIES
RESULTS MATCH EXISTING INFORMATION IN THE FIELD ? (MOL %, GOR, ETC)
FIGURE 4 PVT ANALYSYS DATA TREATMENT
Trang 9FIGURE 5 HIGH PRESURE SOUR GAS GATHERING SYSTEM: CATEDRAL-MUSPAC-CHIAPAS-GIRALDAS-CPG CACTUS,
2 )
16"Ø X 6
36"ø X 9.9
36"ø X 15.7
36"ø X 13
24"ø X 13
SLUG - CATCHER
Trang 10C.P.G CACTUS
16"Ø X 6
Km
36"ø X 9.9
Km
36"ø X 15.7
Km
36"ø X 13
24"ø X 13 SLUG - CATCHER
16"ø X 10 Km
2 ).
EXISTING PIPELINE PROPOSED PIPELINE