Ph D Thesis Summary In English

Summary of the Thesis and work structure: English version. Full download available at
http://www.lume.ufrgs.br/handle/10183/17391

UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL
INSTITUTO DE GEOCIÊNCIAS
PROGRAMA DE PÓS-GRADUAÇÃO EM GEOCIÊNCIAS

GENETIC FLOW UNIT DEFINITION IN CLASTIC RESERVOIR
BASED ON DEPOSITIONAL AND DIAGENETIC
HETEROGENEITIES: A CASE STUDY IN ECHINOCYAMUS
FORMATION, LOWER EOCENE, TALARA BASIN, PERU

JOSÉ ALFREDO BORGES DAUDT

ADVISOR: Prof. Dr. Claiton Marlon dos Santos Scherer

CO-ADVISOR: Prof. Dr. Luiz Fernando De Ros

Examined by:
Dr. Mauro Roberto Becker – Petrobras
Dr. Guilherme Raja Gabaglia - Petrobras
Dr. Ubiratan Feruccio Faccini – Unisinos

Thesis submitted in partial fulfillment of
the requirement for the PhD in Science,
field of Stratigraphy.

Porto Alegre - 2 0 0 9


Daudt, José Alfredo Borges
Definição de unidades de fluxo genéticas em reservatórios clásticos com base em
heterogeneidades deposicionais e diagenéticas: o caso da formação
Echinocyamus, Eoceno inferior, Bacia de Talara, Peru
/ José Alfredo Borges Daudt. - Porto Alegre : IGEO/UFRGS, 2009.
218 f.: il.

Tese (doutorado). - Universidade Federal do Rio Grande do Sul. Instituto de
Geociências. Programa de Pós-Graduação em Geociências. Porto Alegre, RS -
BR, 2009.
Orientação: Prof. Dr. Claiton Marlon dos Santos Scherer
Co-orientação: Prof. Dr. Luiz Fernando De Ros

1. Unidades de fluxo. 2. Heterogeneidades. 3. Caracterização de reservatórios. 4.
Diagênese. I. Título.

_____________________________
Catalogação na Publicação
Biblioteca Geociências - UFRGS
Luciane Scoto da Silva CRB 10/1833

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Abstract

An integrated characterization of depositional and diagenetic heterogeneities for
the Echinocyamus Formation, Eocene, Talara Basin, Peru, has been developed. The
objective of this work is to define a significant and geologically based flow unit model
for these reservoirs. Sedimentological studies were done in cores and allowed the
establishment of a high-resolution stratigraphic framework of this unit. Deltaic and
fluvial successions are found as productive intervals, each of them compounded by sub-
domains or genetic units that may be recognized by typical log patterns. Due to a
complex tectonic setting (forearc basin close to a subduction zone with intense
transcurrent movements and associated vulcanism), the reservoir quality is strongly
affected by diagenetic processes that were constrained by the lithic composition of
these sandstones.

The concept of genetic flow unit, as proposed in this work, represents intervals
that may or may not have stratigraphic meaning and are defined to the level of
architectural elements association (sub-environments of deposition). The genetic flow
units present particular petrophysical properties that determine their storage and
productive capacity. They define volumes that are bounded by surfaces generated by
depositional or post-depositional changes that are reflected in structures, textures and
architecture of the unit, and/or in the distribution of their main diagenetic processes and
products. These processes may cause intense modification in porosity and permeability
relationships and, as a consequence, may substantially control the quality distribution of
the productive intervals. The diagenetic impact on the quality and heterogeneity is
appropriate approached by using the reservoir petrofacies concept. These petrofacies
are defined by the superposition of structural, textural and compositional aspects and
the types, habits, volumes and diagenetic phases. In the Echinocyamus example, the
diagenesis is influenced by the depositional framework and its impact on the quality
and heterogeneity can be understood and predictable considering the sequence
stratigraphy.

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Detailed petrologic analysis determined the main controls on diagenesis and
allowed the characterization of twelve reservoir petrofacies. These petrofacies are
found associated in different proportions in each sub-environment of deposition, what
made possible the statistic characterization of representative values of quality indicators
for each unit. This methodology has created a predictable model for diagenetic patterns
and reservoir quality for Echinocyamus Formation.

This study also presents a proposal for re-definition of heterogeneity hierarchy
in siliciclastic reservoirs considering the perspective of a secondary recovery project.
The depositional heterogeneities were hierarchized accordingly to their probable
influence in fluid movement within reservoir.

Presentation of this Thesis

The objective of this research was to analyze the integration of depositional and
diagenetic heterogeneities in order to build a geologically consistent flow unit model for
siliciclastic reservoirs. These flow units are discrete elements that represent the
transition between the static model created by the geologist and the dynamic approach
performed by the engineer. The definition of these models, however, is always subject
to discussion in the petroleum industry. Lack of clarity when defining the geologic
criteria to consider and the oversimplification of the models due time and software
constraints are among the main reasons for these disagreements.

Diagenesis, an important element that impacts the quality of many reservoirs, is
generally underconsidered and not propertly incorporated in the static models. Thus,
this research tried to find an innovative methodology to include diagenetic aspects in a
flow unit model, considering the depositional framework and the high resolution
stratigraphy as the base of the analysis.

The Echinocyamus Formation (Lower Eocene) in Talara Basin was the studied
object. Considering that tectonic is the main agent in compartmentalizing the productive
areas in that basin, the research focused on the elements responsible for heterogeneities
within the main structural blocks. In this unit, several water injection projects are being

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implementing or in the process of being implemented (Groba et al., 2005). In average,
the expectation of additional oil recovery due to these projects is around 5%. Two
examples of such projects are block B1-Somatito (stratigraphic section “A”, Document
4) and Ballena B9 (stratigraphic section “B”, Document 4).

The methodology proposed here is applicable in other geological settings with
similar injection projects. The test of this methodology in these new situations may
result in improvements or adjustments in it. This approach follows Popper (1989) where
a particular hypothesis (initial condition) is tested to verify the consistency of the
univeral model. This cycle will result in a stronger model and in the increment of the
predictive capacity of particular elements.
Regarding the organization, the Thesis is based on three scientific articles
written about the main topic. The organization includes the following parts:
a) Introduction, description of objectives and methodology used in this research.
It is presented an integrated discussion about the main results presented in the articles
and the implications of these results in the process of static reservoir characterization.
The work is organized to allow the construction of a general model from particular
observations made in the studied unit. This process is based on conceptual paradigms as
sequence stratigraphy, as well as new concepts, incorporating advanced reservoir
characterization. The approach starts with the definition of a depositional and
stratigraphic model, goes through the analysis of the diagenetic influence on reservoir
quality, and end up with the integration of all these elements in a geological flow unit
concept.
b) Reprint of the three papers that were submitted to publication in scientific
periods with permanent editorial board. All three articles had the author as the senior
author and were written during the development of this Thesis. These articles are
referred in the body of the Thesis by roman numbers:
Article I : Arquitectura de facies e evolução estratigráfica dos reservatórios flúvio-
deltaicos da Formação Echinocyamus (Eoceno Inferior) na área do Lote X (Bacia de
Talara, Peru). Authors: José Daudt and Claiton Scherer. This paper was published in
Boletim de Geociências da Petrobras, volume 14, nº 1, 2006, and it was written in
Portugues. It contains the depositional model and stratigraphic interpretation of the

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studied unit. It is also discussed aspects related with the use of this model in the future
phases of dynamic simulation. It is available at
http://www2.petrobras.com.br/portal/frame.asp?pagina=/tecnologia2/port/publicacoes_b
geociencia.asp. Expanded abstract in English is also available in the same web page.
Article 2: Stratigraphy, Petrology, and Reservoir Petrofacies of the Echinocyamus
Formation (Eocene, Talara basin, NW Peru): Use of high-resolution characterization for
improving reservoir development in a mature basin.
Authors: José Daudt, Karin Goldberg, Luiz Fernando De Ros and Claiton Scherer,
submitted to AAPG Bulletin. As of 2010, the article has not been published yet. This
article presents the results of the integration of facies architecture model, high-
resolution stratigraphic framework and the analysis of the impact of diagenesis on
reservoir quality. Petrologic analysis allowed the definition of the main controls on
diagenetic processes as well as their depositional and stratigraphical constraints.
Reservoir petrofacies was a concept used to characterize the petrologic parameters to
control reservoir quality and their distribution within stratigraphic intervals. The
association of petrofacies present in each stratigraphic interval was statistically treated.
It were also discussed the different aspects related to the impact of this integrated
methodology on the field management.
Article 3: Genetic flow unit: a concept for reservoir characterization based on
depositional and diagenetic heterogeneities. Authors: José Daudt, Luiz Fernando De
Ros, Karin Goldberg and Claiton Scherer, submitted to Marine and Petroleum Geology.
As of 2010, the article has not been published yet. In this article, it is discussed the
genesis of reservoir heterogeneity and its hierarchy. It is also approached the
incorporation of diagenesis in flow unit models. Flow unit concepts were critically
reviewed in order to recommend a new definition (genetic flow unit) where geologic
aspects are fundamental.
c) Additional documents:
Document 1: Revisión conceptual sobre el patron diagenético y potencial de las
areniscas volcanoclásticas como reservorios de petróleo. Author: José Daudt. The article
was published in the Boletin de la Sociedad Geologica del Peru, nº 100, volume 2, 2005.
It is written in Spanish and an English abstract is also included. The article is a
conceptual revision of diagenetic patterns in reservoirs with high content of volcanic
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fragments. The objective or this publication is to have a referential paper written in
Spanish in order to supply Peruvian geologists involved in reservoir characterization
studies.
Document 2: Reservoir petrofacies of the Echinocyamus Formation (Talara Basin,
Peru): an Approach for high resolution reservoir characterization. Authors: Karin
Goldberg, Mara Abel, Luiz Fernando De Ros, José Daudt and Claiton Scherer. It was
published as an abstract in AAPG Annual Convention, San Antonio, 2008. This poster
presents the criteria for definition of reservoir petrofacies in Echinocyamus unit. It also
presents statistic analysis of petrofacies proportions in each depositional domain (fluvial
and deltaic).
Document 3: Table containing the petrophysical and petrographic data/information of
analyzed samples.
Document 4: Illustrative stratigraphic cross-sections in productive areas:
Cross Section A: Block B1, Somatito Field.
Cross Section B: Block Ballena B9.

Brief Summary of the main conclusions:

1. Static Model of the Echinocyamus Formation:
1.1. Reservoir quality in the studied unit was partially controlled by the depositional
framework. Fluvial and deltaic domains present subtle differences in detritic
composition and diagenetic evolution that justify the reservoir quality
variability between them. The higher proportion of unstable fragments
(volcanic rocks and feldspar grains) found in the lower fluvial interval allowed
intense generation of early intergranular smectite. This intergranular smectite,
associated with a high concentration of plutonic fragments in this interval, was
crucial to preserve a great part of the initial depositional porosity during the
phase of most intense mechanical compaction. On the other hand, in the upper
fluvial interval, the plutonic fragments are in smaller proportions what favored
the mechanical compaction. Clay-rich flood plains intervals are more common

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in the upper fluvial interval, what also had a negative impact on reservoir
quality in this section.
1.2. Mechanical compaction was slightly more intense in the deltaic interval due to
the high proportion of soft fragments (sedimentary, meta-sedimentary and shale
fragments), resulting in a lower quality reservoirs. Intense bioturbation in the
delta front sub-environment, higher calcitic cementation and finer grain size are
other factors that also contributed to decrease reservoir quality in the deltaic
facies.
1.3. The stratigraphic model of the Echinocyamus Formation must be considered as
a fundamental element in the management of productive fields, especially
during secondary recovery projects. Small differences in the petrophysical
parameters in marginal projects may result in considerable differences in the
volume of original oil in situ or total or final recoverable volume, as
demonstrated by Smosna & Bruner (1997). Daudt et al. (2006) also showed
that, although the fluvial interval in block B9 Ballena (located within Block X
in Talara Basin) represents only 15% of the productive interval, its original oil
in situ reaches 30% of the total.

2. Hierarchy of heterogeneities and flow units:
2.1. The hierarchical model proposed in this Thesis is designed to support mature
asset field management where productive levels had already reached their
maximum historical pick. These projects have budget limitations due to the low
productivity per well. This factor, although being an extra-geology element,
was also implicitly considered in the definition of the more suitable scale for
flow units as too detailed models will lose the practical sense expected by the
industry. Also, the upscalling of highly detailed models is always a difficult
task due to processing limitations and time constraints. Thus, it is necessary to
identify the main heterogeneities by filtering those which caused a minor
impact in the fluid flow within the reservoir. It is a simplification of the
geological complexity within an acceptable variation that captures and keeps
“alive” these most important elements in the static model.

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2.2. The genetic flow unit concept was presented as a new methodological approach
that shows important differences when compared to previous models. The first
difference relies on the necessity to have a defined hierarchy or scale.
Depositional heterogeneities generate flow unit boundaries and are elements
scale-dependent and, by consequence, flow units are also scale-dependent. The
recommendation is to characterize flow units at the scale of sub-environment of
deposition (architectural element association) when dealing with mature assets.
The second difference is based on the inclusion of diagenetic impact in the flow
unit analysis and in the predictive models derived from them. This methodology
includes the reservoir petrofacies characterization and the statistic treatment of
these petrofacies within each sub-environment of deposition or flow unit.
2.3. It was highlighted the importance of geological characterization in the
definition of a flow unit framework. This geological characterization should
include a depositional model integrated within a high resolution sequence
stratigraphic approach, at the scale of sub-environment of deposition.

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CONTENTS
Abstract
Presentation of this Thesis ............................................................................................. 12
1. Introduction......................................................................................................... 15
2. Regional geology of Talara Basin ...................................................................... 16
3. Reservoir heterogeneity ..................................................................................... 17
4. Methodology ...................................................................................................... 20
4.1. Phase 1: Core description ....................................................................... 20
4.2. Phase 2: Basic petrophysics and petrography ........................................ 20
4.3. Phase 3: Integration, generation of a reservoir quality model ............... 21
5. Results ............................................................................................................... 22
5.1. Depositional and stratigraphic models ................................................... 22
5.2. Textural and diagenetic aspects ............................................................. 25
5.2.1. Composition and provenence ........................................................... 25
5.2.2. Diagenetic processes and products ................................................... 25
5.2.3. Reservoir petrofacies ........................................................................ 27
5.2.4. Controls on reservoir quality ............................................................ 31
5.2.4.1. Reservoir quality evolution ....................................................... 33
5.3. Integration and generation of a flow unit model .................................... 38
5.3.1. Reservoir geometry .......................................................................... 38
5.3.2. Hierarchy of heterogeneities ............................................................ 45
5.3.3. Genetic flow units ............................................................................ 47
5.3.4. Impact of diagenesis in the flow unit model .................................... 50
6. Final remarks ..................................................................................................... 53

6.1. Static model of Echinocyamus Formation …….......................................... 53

6.2. Hierarchy of heterogeneities and flow units ............................................... 54

References ...................................................................................................................... 56

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Articles

Article I – Arquitetura de Fácies e Evolução Estratigráfica dos Reservatórios Flúvio-
deltaicos da Formação Echinocyamus (Eoceno Inferior) na Área do Lote 10 (Bacia de
Talara, Noroeste do Peru) ..............................................................................................67

Article II – Stratigraphy, Petrology, and Reservoir Petrofacies of the Echinocyamus
Formation (Eocene, Talara basin, NW Peru): Use of High- resolution Characterization
for Improving Reservoir Development in a Mature Basin….…………………………96

Article III – Genetic Flow Units: a Concept for Reservoir Characterization based on
Depositional and Diagenetic Heterogeneities ………………………….…..…………152

Additional documents

I – Complete Article: Revisión Conceptual sobre el Patrón Diagenético y Potencial de
las Areniscas Volcanoclásticas como Reservorios de petróleo…............................... 190

II – Reservoir Petrofacies of the Echinocyamus Formation (Talara Basin, Peru): an
Approach for High-Resolution Reservoir Characterization………………………..…213

III – Table with petrophysical and petrographic information of the samples analysed
.......................................................................................................................................216

IV – Stratigraphic cross sections in productive areas:

Section A, NW-SE in Block B1-Somatito ......................................................219

Section B, N-S in Block Ballena B9 ...............................................................220

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