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Copyright 2007, Society of Petroleum Engineers

This paper was prepared for presentation at the 2007 SPE Latin American and CaribbeanPetroleum Engineering Conference held in Buenos Aires, Argentina, 1518 April 2007.

This paper was selected for presentation by an SPE Program Committee following review ofinformation contained in an abstract submitted by the author(s). Contents of the paper, aspresented, have not been reviewed by the Society of Petroleum Engineers and are subject tocorrection by the author(s). The material, as presented, does not necessarily reflect anyposition of the Society of Petroleum Engineers, its officers, or members. Papers presented atSPE meetings are subject to publication review by Editorial Committees of the Society ofPetroleum Engineers. Electronic reproduction, distribution, or storage of any part of this paperfor commercial purposes without the written consent of the Society of Petroleum Engineers isprohibited. Permission to reproduce in print is restricted to an abstract of not more than300 words; illustrations may not be copied. The abstract must contain conspicuous

acknowledgment of where and by whom the paper was presented. Write Librarian, SPE, P.O.Box 833836, Richardson, Texas 75083-3836 U.S.A., fax 01-972-952-9435.

Abstract

This work shows the main considerations adopted and proved

successful for oilfield reactivation and production increase

through the handling of very high gross production flow rate

with high water/oil ratio. The execution strategy is focused onmaximizing the production anticipation in the short-term by

taking maximum advantage of the existing facilities and, in the

mid- term, by developing facilities with new systems sizedwith flexibility and supplying them timely. All of these

allowing to take advantage of the most suitable technologiesexisting in the market for handling, separation, treatment anddisposition of high produced water flow rates, during the

lifetime contract for each oilfield.

Examples of this approach are the study cases presented

related to water injection for secondary recovery and disposal

purposes. The knowledge obtained during the development

and operation of a given mature field, has been adapted for itsapplication in another field, and so on, considering particular

features and different contractual terms, allowing PESA tosuccess in very mature oilfields with apparently very restricted

development opportunities.

Introduction

The development and operation of mature oilfields in many

cases demand handling high volumes of gross production,

obsolete and under rated facilities that require hugeinvestments, and tight returns making mandatory the

optimization of operating expenses.

In order to plan and develop the surface facilities required toreach the objectives for reactivation and production increase in

specific mature oilfields, main adopted considerations have

been focused on three basic aspects:

- Increasing both oil production, and recovery factor, as wel

as advancing oil production when possible (Fig. 1).- Optimization of capital expenses (Capex) in new

equipment and facilities, considering the convenience ofkeeping existing equipment and the duration of operative

contracts.

- Reduction of the operating expenses (Opex) during thecycle of life of each projected facility.

The advantage of the obtained knowledge during thedevelopment and operation of mature fields, and the

adaptation for extending its application to a different field

considering its particularities, including different contractuaterms, allowed us to develop a high capacity in making fine

adjustments to find opportunities in oilfields with high level of

maturity.

Facilities Design. Criteria

The key factors applied in designing facilities in matureoilfields under revitalization are:

-Handling very high flow rates of gross production, withhigh water / oil ratios (WOR of 50 to 90, or higher).

- Applying a multidisciplinary approach (Reservoirs, Wells

Construction, Production Engineering, and Surface

Facilities) from the feasibility phase of each development

In this way, its possible to reach production objectiveswhile optimizing Capex, making the most of the existing

and proposed surface facilities.

- Permanently valuating the impact of the facilities design

on the operating expenses for each oilfield.

All of these factors are considered within the terms and

duration of the specific operative contract for each oilfield

which is a real constraint in the planning of each developmentand a very important element for the project development

analysis.

A significant common factor in these projects has been the

decision to centralize the oil treatment in one facility, havingsatellites facilities for oil partial dehydration, from where the

separated produced water is sent to water treatment plants

These plants are located in order to handle and pump the

treated produced water into injection wells for secondaryrecovery or disposal purpose. (Fig. 2).

This approach allows reducing energy requirement for the

movement of fluids in the field, to take advantage of thedimensions and size of the equipment, and to have more

SPE 107740

Surface Facilities Development for Mature FieldsRafael Morales and Jorge Navarro, Petrobras Energa S.A.

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reliable systems reducing maintenance requirements. Thus,

avoiding distributing operations in different zones, and

simplifying operations, with the consequent reduction of both

capital investments and operating expenses.

During the phase of opportunity identification, Capex andOpex evaluations are made for each scenario, in order to

identify the best option for the oilfield development, alwaysfocusing the bottom line. Sometimes the higher value ofreserves or oil rate or advancing peak production, may not be

the most convenient or economical option, when gross

production, Capex and Opex for the lifetime of the oilfield are

taken into account. So that, it appears an interesting gamebetween different factors: reserves, oil rate, gross rate, and size

of facilities impacting on both, capital expenses and operating

costs. These factors show the importance of selecting the right

dimension of the operation during the remaining time of theoperative contract for the oilfield.

Facilities Design. Considerations

The execution strategy to be applied is based on several

aspects, such as:- Considering existing equipment. Maximizing short-term

production by getting the most of the existing facilities,meaning the use and cap of the existing capacity, while

gross production is increased. Sometimes, there is not

need to incorporate new equipment for earlydevelopments but to change the service of existing ones

(like converting an existing storage tank into wash tank to

make initial partial oil dehydration, in scenarios of high

water / oil ratio).

-High capacity new equipment. By the mid-term,

production increase is handled by developing new

facilities including new high capacity equipment and

systems sized with flexibility for the development (as

relocation in the field, etc.).- Quality, in due time and form. New equipment and

facilities must be supplied and built with required qualityand timely.

- Modular expansion design, with final tie-ins. Theplanning and design of the facilities should consider

modular expansions with final dimensions of piping and

tie-ins defined from the beginning of the development.Additionally, the design must be flexible to manage

reservoir uncertainties and a better use of remainingcapacities, to deal with eventual changes in production

and injection criteria, as exploitation of the reservoiroccurs.

- New technologies, adopted if proved successful from

previous experiences. This is, taking advantage of the

most suitable technologies in the market and previously

experienced by other operators, specially to avoid highlevel of exposure when defining new high capacity

equipment for handling, separation, treatment and

disposition of high gross production and produced waterflow rates. Usually we do not have enough time in our

projects to test or develop new technologies considering

our oilfield contracts, and the cost of opportunity if

production increase would be delayed waiting for

technology testing. That is the reason for looking a

proved technologies in the market, which has shown goodresults.

- Regional and national laws. In each case it is necessary toreview existing and previously experienced designs to

adapt them to the specific conditions and regulations, at

both regional and national levels, for fields developmenin different areas or countries. Sometimes, this involve

high impact decisions about the feasibility of project

development: approval of commingled production, roads

vs. heli, etc.- Environmental impact. Given PESAs strong commitmen

with the environment (PESAs operations are ISO-14001and OHSAS- 18001 certified), it is paramount to take into

account the environmental impact of the proposed

facilities because sometime good equipment experiencesfor a specific oilfield may not be suitable for another one

with different environmental conditions.

Common factors in the development strategy for oilfields withhigh produced water flow rate have been the following ones:

- Partial oil dehydration in satellite facilities. Grossproduction is received in facilities, like flow stations

adapted to make an initial separation of the high flow rateof produced water.

- Centralize crude oil treatment. The crude oil partiallydehydrated (up to 50% BS&W) at several satellite

facilities is sent to a central production facility, for crude

oil treatment where delivery specifications are me(typically 0.5% BS&W).

- Centralize water treatment and injection. The producedwater separated from satellite flow stations and centra

production facilities, is sent to treatment plants, in order tomet injection specifications prior to be pumped to the

injection wells. These specifications usually vary between10 and 50 ppm for both TSS (total suspended solids) and

OIW (oil in water), depending on reservoir properties

These water plants are specifically located depending on

the oilfield geometry for secondary recovery goals or

disposal purposes, and the equipment has beenstandardized in order to have easy exchange or stand by.

This development strategy allows us to:- Reduce the energy requirements for the movement of

fluids in the field.- Take advantage of scale economy by the dimensions and

size of the equipment and piping.

- Make the systems more reliable, reducing maintenance

requirements and operational crew needs, avoiding works

in distributed zones, and simplifying operations, with the

consequent reduction of both capital investments andoperating expenses.

Field Examples

As examples of the all previously mentioned, three (3) study

cases will be presented:

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Example 1 (Fig. 3):

The first one is an oilfield where we have massive water

injection for secondary recovery requirements.During the last 15 years the water injection flow rate raised

significantly, from 68,000 bpd (11,000 m3/d) to 597,000 bpd

(95,000 m3/d) as well as the gross production, from 72,000

bpd (12,000 m3/d) to 510,000 bpd (81,000 m3/d). In this case,

we have one centralized oil treatment plant and twoindependent produced water treatment and injection plants, the

first one located close to the oil treatment plant, and thesecond one placed to the north of the oilfield. This oilfield has

another water plant since the beginning of the operations that

treats and pumps fresh water in order to meet water injection

requirements. The decision of using a three-phase separator or

wash tank is made according to an economical analysis, takingmaximum advantage of existing equipment. Additionally,

sometimes the size of equipment needs to be reviewed for

constructability and transportation limits criteria for different

locations.The development of the field was designed to have partial

production dehydration in existing flow stations and in a newsatellite station, located close to the second water plant, inorder to separate the produced free water from the stream.

Combinations of two-phase separators and wash tanks or

three-phase separators have been installed in the existing flow

stations, while a battery of Free Water Knock Out wereinstalled in the satellite station. The size of each FWKO was

defined and standardized in order to meet the production

requirements that satisfy the development plan of the field.

In this way it has been possible to handle the incrementalgross production with minimum increase of the capacity in

surface facilities, taking the incremental produced water out of

the circuit before arriving to the existing facilities.

Additionally, it was a very simple way of increasing capacityin this field without affecting the normal operation of thefacility. The produced water separated is sent to the water

injection plants for treatment, and the oil partially dehydrated

is sent to the main oil treatment plant.

In the oil treatment plant (Central Production Facility) thisapproach allowed us to handle the incremental production with

no needs to replace or increase the size of the main wash tank.

Besides, we could postpone investments optimizing Capex(and development cost) and reduce future operating costs of

the facility.

The main wash tank with 69,000 bls (11,000 m3) of capacity,

was designed to handle up to 90,000 bpd (15,000 m3/d) of oil

to delivery specifications of 0.5% BS&W.The water treatment plants were designed to use new high

capacity equipment of about 77,000 bpd (12,264 m3/d) each

one, and were installed between 1996 and 1998. The selectedwater injection pumps were multistage centrifugal, delivering

30,000 bpd (5,000 m3/d) @ 1700 psig (115 Kg/cm2), with

electrical driver (1550 HP). For both systems, it was also themost appropriate technology at the moment of the design.

Example 2 (Fig 4):

The second example shows the experience of handling very

high gross production flow rate with a water cut of around90%, and disposal of produced water. In this case the

challenge was not only the very high gross production and

water flow rate, but the crude oil, heavy and extra heavy of 20

to 12 API.

At the starting of the contract, the fields oil production was8,000 bpd (1,300 m3/d), after several decades of operation

being the average gross production during the last 10 years o

about 10,000 bpd (1,600 m3/d). In this case, the oil production

was increased to a level of 50,000 bpd (8,000 m3/d), handling

a gross production higher than 500,000 bpd (80,000 m3/d)which means more than 450,000 bpd (72,000 m3/d) of

produced water.The oilfield was developed to have one centralized oi

treatment plant and three independent produced water

treatment and injection plants, the first one located close to the

oil treatment plant, and the others located north and south of

the oilfield.

The development of the field was designed to allow a partiaseparation of the free produced water in one new facility and

two existing and renovated flow stations. In these flow station

three-phase separators have been installed with heating

(heater-treaters) to handle the extra heavy crude. Existing flowstations had to be renewed, including high capacity three-

phase separators (heater-treaters). For this application, jus

one 50,000 bpd three-phase separator (heater-treater) was ableto substitute six two-phase separators, two heaters, two wash

tanks, and two transfer pumps. Nevertheless, the existing

equipment has been left as stand by during maintenance

activities for each of the three-phase separators (heater

treaters).An additional advantage is the smaller footprint of the

equipment, requiring a reduced area and less piping for thetreatment process. Each of the 50,000 bpd three-phase

separators is 14 feet in diameter and 70 feet in length, the

operating pressure is 100 psig, and the heating capacity is 14

MMBTU/hr to increase the entering oil temperature from 90to 140 F.A modular expansion criteria was applied to this developmen

and final piping, tie ins, and future equipment foundations

were completed from the beginning, giving additiona

advantages during future equipment installationcommissioning, and start up.

In the Central Production Facility the oil treatment process is

carried out by four washing tanks of 20,000 bbls. each. Thetotal design capacity of the plant is 60,000 bpd of 16 API oil

treated to 0.5% BS&W for export specifications. This plan

was commissioned by the year 1997.

The original water treatment plants process was built using

existing skimming tanks, but since 2001, two high capacityInduced Gas Flotation (IGF) cells were commissioned, about

75,000 bpd each, for water treatment process. The water

injection pumps were selected to be the same multistagecentrifugal delivering 30,000 bpd (5,000 m3/d) as in the firs

example, but operating at 1700 psig (115 Kg/cm2), with a

driver of about 2700 HP. For both systems it was also thebest-proved technology at the moment of the design and

standardization.

Example 3:

The experiences of the two previous field cases and newtechnologies are being used in a current development of a

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mature oilfield that has been in production since the beginning

of the 20th century, having, as expected, very low productivity

per well. The oilfield is currently producing 14,000 bpd (2250

m3/d), of 35 API oil and the projected re-development isexpected to increase the oil production up to 28,000 bpd

(4,500 m3/d). Water injection for secondary recovery of about

200,000 bpd (32,000 m3/d) is an important part of the project,

and other enhanced oil recovery methods, as natural gas or

nitrogen injection depending on further evaluations, are alsounder consideration. For the entire project, high efficiency in

the Opex is required, specially taking into account the increasein costs associated to the new secondary recovery projects, as

well as the high flow rates and operational problems usually

related to water handling (corrosion, scale, bacteria, oxygen

removal, etc.).

The general conditions of this project forces us to go deeplywith the concepts applied in previous examples to permit

making this project a reality.

Conclusions

The advantage of the obtained knowledge (know-how) during

the development and operation of mature fields, and the

adaptation for its application in future developmentsconsidering its particular characteristics and different

contractual terms, has allowed PESA to develop:

- High sensitivity and capacity in making fine adjustments

to find opportunities in oilfields with apparently very

restricted development opportunities due to its high level

of maturity.- Improvements in existing oilfields in order to reduce

operative expenses.

- Adjustments for specific strategies.

- Business improving through an active game between

facilities and other disciplines.

Also, it is important to mention the interaction between

Facilities and other disciplines (for example, ReservoirsProduction) plays an active game, evaluating several scenarios

to find the best one to improve the business.

Acknowledgements

The authors acknowledge PESA for permission to publish this

paper.

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