scholarly journals Integrated Porosity Classification and Quantification Scheme for Enhanced Carbonate Reservoir Quality: Implications from the Miocene Malaysian Carbonates

2021 ◽  
Vol 9 (12) ◽  
pp. 1410
Author(s):  
Hammad Tariq Janjuhah ◽  
George Kontakiotis ◽  
Abdul Wahid ◽  
Dost Muhammad Khan ◽  
Stergios D. Zarkogiannis ◽  
...  
Keyword(s):  
Total Porosity ◽  
Depositional Environments ◽  
Carbonate Reservoir ◽  
Pore System ◽  
Secondary Porosity ◽  
Rock Classification ◽  
Thin Sections ◽  
Diagenetic Processes ◽  
Wide Range ◽  
Pore Types

The pore system in carbonates is complicated because of the associated biological and chemical activity. Secondary porosity, on the other hand, is the result of chemical reactions that occur during diagenetic processes. A thorough understanding of the carbonate pore system is essential to hydrocarbon prospecting. Porosity classification schemes are currently limited to accurately forecast the petrophysical parameters of different reservoirs with various origins and depositional environments. Although rock classification offers a way to describe lithofacies, it has no impact on the application of the poro-perm correlation. An outstanding example of pore complexity (both in terms of type and origin) may be found in the Central Luconia carbonate system (Malaysia), which has been altered by diagenetic processes. Using transmitted light microscopy, 32 high-resolution pictures were collected of each thin segment for quantitative examination. An FESEM picture and a petrographic study of thin sections were used to quantify the grains, matrix, cement, and macroporosity (pore types). Microporosity was determined by subtracting macroporosity from total porosity using a point-counting technique. Moldic porosity (macroporosity) was shown to be the predominant type of porosity in thin sections, whereas microporosity seems to account for 40 to 50% of the overall porosity. Carbonates from the Miocene have been shown to possess a substantial quantity of microporosity, making hydrocarbon estimate and production much more difficult. It might lead to a higher level of uncertainty in the estimation of hydrocarbon reserves if ignored. Existing porosity classifications cannot be used to better understand the poro-perm correlation because of the wide range of geological characteristics. However, by considering pore types and pore structures, which may be separated into macro- and microporosity, the classification can be enhanced. Microporosity identification and classification investigations have become a key problem in limestone reservoirs across the globe.

scholarly journals Linking Depositional Environments and Diagenetic Processes to Porosity Evolution and destruction in the Arab Formation reservoirs, Offshore oilfields of Qatar

2020 ◽  
Author(s):  
Fadhil N. Sadooni ◽  
Hamad Al-Saad Al-Kuwari ◽  
Ahmad Sakhaee-Pour ◽  
Wael S. Matter
Keyword(s):  
Depositional Environments ◽  
Oil Reservoir ◽  
Secondary Porosity ◽  
Future Directions ◽  
Thin Sections ◽  
Intergranular Porosity ◽  
Porosity Evolution ◽  
Diagenetic Processes ◽  
Exploration And Production ◽  
The Impact

Introduction: The Jurassic Arab Formation is the main oil reservoir in Qatar. The Formation consists of a succession of limestone, dolomite, and anhydrite. Materials and methods: A multi-proxy approach has been used to study the Formation. This approach is based on core analysis, thin sections, and log data in selected wells in Qatar. Results: The reservoir has been divided into a set of distinctive petrophysical units. The Arab Formation consists of cyclic sediments of oolitic grainstone/packstone, foraminifera-bearing packstone-wackestone, lagoonal mudstone and dolomite, alternating with anhydrite. The sediments underwent a series of diagenetic processes such as leaching, micritization, cementation, dolomitization and fracturing. The impact of these diagenetic processes on the different depositional fabrics created a complex porosity system. So, in some cases there is preserved depositional porosity such as the intergranular porosity in the oolitic grainstone, but in other cases, diagenetic cementation blocked the same pores and eventually destroyed them. In other cases, diagenesis improved the texture of non-porous depositional texture such as mudstone through incipient dolomitization creating inter-crystalline porosity. Dissolution created vugs and void secondary porosity in otherwise non-porous foraminiferal wackestone and packstone. Therefore, creating a matrix of depositional fabrics versus diagenetic processes enabled the identification of different situations in which porosity was either created or destroyed. Future Directions: By correlating the collected petrographic data with logs, it will become possible to identify certain “facio-diagenetic” signatures on logs which will be very useful in both exploration and production. Studying the micro and nano-porosity will provide a better understanding of the evolution and destruction of its porosity system.

Depositional Environment and Diagenesis processes impact on the carbonate rock quality: a case study, southeastern of Iraq

2019 ◽  
Vol 60 (5) ◽  
pp. 1104-1114
Author(s):  
Afrah Hassan Saleh
Keyword(s):  
High Energy ◽  
Negative Influence ◽  
Depositional Environments ◽  
Carbonate Reservoir ◽  
Reservoir Properties ◽  
Thin Sections ◽  
Diagenetic Processes ◽  
Marine Lagoon ◽  
Lagoon Environment ◽  
Low Porosity

Deposition environment and diagenesis processes are very important factors which affect and control the reservoir properties.  The carbonate Mishrif Formation has been selected as a carbonate reservoir in selected wells from southeastern Iraq to understand the influence of the Deposition environment and diagenesis processes on the carbonate reservoir. A core examination of thin sections, shows that Mishrif Formation comprises of six depositional environments, these are: deep marine, lagoon, rudist biostrome, back shoal, and shallow open marine.  These environments have effect by many diagenetic processes, including dolomitization, dissolution, micritization, cementation, recrystallization and Stylolite, some of these processes have improved the reservoir properties of the Mishrif reservoir, these are: dissolution, dolomitization and the stylolization.  The others diagenetic processes have negative influence on the Petrophysical properties, such as cementation, compaction, and recrystallization processes, which damage the porosity and decrease the pore size. The reservoir properties are controlled by deposition environment, where lagoon environment is mostly compact with low porosity, shoal environment reflects a high energy and grain-supported environment and has good reservoir potential, deep-marine environments consist of mudstone to wackestone, which represents low energy level with low porosity and represents the non-reservoir environment.

scholarly journals QUANTITATIVE PARAMETERS OF PORE TYPES IN CARBONATE ROCKS

2013 ◽  
Vol 31 (1) ◽  
pp. 125 ◽  
Author(s):  
Dayse Daltro de Castro ◽  
Paula Lucia Ferrucio da Rocha
Keyword(s):  
Carbonate Rocks ◽  
Total Porosity ◽  
P Wave ◽  
Geometrical Parameters ◽  
Pore Shape ◽  
Thin Sections ◽  
Wide Range ◽  
Siliciclastic Rocks ◽  
Shape Characteristics ◽  
Pore Types

Carbonate rocks are controlled by variable depositional systems and diagenetic process and have a wide variety of pore and grain shapes/sizes. Those characteristics imprint different petrophysical properties in carbonates, which are more difficult to predict than in siliciclastic rocks. Measurements on carbonates reveal that pore/rock type parameters are function of total porosity and play an important role in the relationship between porosity and P-wave velocity. In this research, thedatabase consists of carbonate rock samples with a wide range of bulk porosities, pore types and rock textures, from different Brazilian areas in Southeast Continental Margin. We investigated the hypothesis that scatter values observed in velocity at a given porosity can be explained by pore types and pore shape characteristics. The quantification of pore shape/size distribution in each sample was based on four geometrical parameters from thin sections measurements – pore size, aspect-ratio,tortuosity and pore complexity. By multivariate analysis, those parameters were applied in the correlation between porosity and P-wave velocities in order to reducescatter values normally observed. RESUMO: As rochas carbonáticas são compostas por calcários e dolomitos de diversos tipos. Além da deposição, os processos de cimentação, dissolução e recristalização transformam essas rochas, produzindo uma grande variedade de tamanhos de grãos, formas e estruturas de poros, criando ou reduzindo porosidade e permeabilidade. Estas características dos carbonatos imprimem grande peculiaridade às propriedades físicas tornando-as mais difíceis de predizer do que em rochas siliciclásticas. As formas dos poros também afetam as propriedades físicas das rochas carbonáticas, produzindo um efeito específico nas propriedades acústicas devido às relações geométricas com a fase sólida das rochas. Por tudo que foi exposto, a compreensão do sistema de poros leva ao melhor entendimento e quantificação das propriedades petrofísicas das rochas carbonáticas. Nesta pesquisa foram utilizadas rochas carbonáticas com diferentes texturas, porosidades e tipos de poros de diferentes áreas da Margem Continental Sudeste Brasileira e o principal objetivo foi melhorar a correlação entre a porosidade e a velocidade das ondas P obtidas de plugues de rochas secas e úmidas. Para tal, foi realizada a avaliação e a quantificação do sistema poroso utilizando a análise multivariada de parâmetros geométricos (tamanho, forma, tortuosidade e complexidade do poro) obtidos de fotografias digitais de lâminas delgadas, para auxiliar na redução da dispersão normalmente observada nas relações entre velocidade e porosidade.Palavras-chave: propriedades petrofísicas, lâminas delgadas; porosidade; velocidade das ondas P

scholarly journals Petrofacies investigations of the Cretaceous Pab Formation Rakhi Gorge Eastern Sulaiman Range Pakistan - Implication for reservoir potential

2021 ◽  
Vol 72 ◽  
pp. 37-46
Author(s):  
Mubashir Mehmood ◽  
◽  
Shahid Ghazi ◽  
Abbas Ali Naseem ◽  
Muhammad Yaseen ◽  
...  
Keyword(s):  
Total Porosity ◽  
Secondary Porosity ◽  
Thin Sections ◽  
Diagenetic Processes ◽  
Medium Reservoir ◽  
Primary Composition ◽  
Diagenetic Minerals ◽  
Reservoir Potential ◽  
Petrographic Study ◽  
Good Medium

Petrologic investigations of the sixty representative thin sections from the Pab Formation within Rakhi Gorge section Eastern Sulaiman Range Pakistan have been used to characterize different diagenetic patterns, identification of primary composition and reservoir characters. Sublithic, lithic and quartzose sandstones have been the principal constituents of the formation. The processes responsible for the late-stage alteration and diagenetic processes identified during the petrographic study include compaction of lithic fragments and mud clasts, formation of quartz overgrowth structures, feldspar replacement and alteration, cementation, and replacement of grains by clay minerals other ferrous elements and diagenetic minerals. The study shows that the initial porosity has been primary intergranular, but the secondary porosity has been originated in the rocks as a result of the alteration of the primary and secondary constituents, as well as fracturing. These facies characters replicate the reservoir quality including, good, medium, low-quality, and non-reservoir. Samples displaying average total porosity greater than 10 % have been declared as good quality. While rocks samples having 7 % or greater porosity are grouped as a medium reservoir. Those samples consisting of porosity values between 1 and 4% are considered as a low quality reservoir while those samples having porosity ranges low than 1% have been called non-reservoir. Based on the investigated parameters the studied samples from the Pab Formation displayed the characters of a medium reservoir that may hold significant hydrocarbon. This different quality including good and low quality zonation can be attributed to the facies and diagenetic change in the formation.

Redefining Reservoir Architecture of Hydrocarbon-Bearing Ngrayong Formation in Banyu Urip Area:New Insights to Unravel Hidden Potential in East Java Basin

2021 ◽  
Author(s):  
L. O Ahdyar
Keyword(s):  
Deep Water ◽  
Energy Demand ◽  
Carbonate Reservoir ◽  
Reservoir Quality ◽  
New Paradigm ◽  
Thin Sections ◽  
Carbonate Cement ◽  
Reservoir Architecture ◽  
Wide Range ◽  
Clastic Reservoir

Results of Banyu Urip (BU) carbonate exploration, appraisal and development drillings revealed the existence of hydrocarbon-contained in Serravallian deep-water clastic reservoir on top of the primary BU carbonate reservoir. This clastic reservoir is equivalent to the Ngrayong Formation in East Java Basin which is widely known as a mature exploration target and consists of a wide range of depositional environment from fluvio-deltaic (northern part of the Basin) to basin floor (southern part of the basin) with various reservoir quality. However, after a century of exploration activities in East Java Basin, commercial discoveries in the Ngrayong Formation are still considered insignificant (approximately 330 MMboe) (Mazied et al. 2016). This probably due to complex reservoir architecture posted high uncertainty of its reservoir presence, distribution, and quality as well challenging on their dynamic aspects such as un-known hydrocarbon connectivity, un-even contacts and low-deliverability. This paper will present new insights and the potential of Ngrayong clastic opportunity in BU area based on static and dynamic data including BU wells, newly reprocessed 3D seismic data, conventional core and thin sections, as well as integrated geologic and geophysical analyses. Integration of the available dataset suggest the presence of stacked deep water channels and deep water lobes systems. The distribution of stacked channels and lobes seem to be more predictive and widespread, hence providing a better understanding of its reservoir distribution. Furthermore, well data indicates approximately total of 100m net stacked clastic reservoirs consist of mixed carbonate-clastic materials, and have good reservoir pressure connectivity with the carbonate reservoir underneath. This mixed clastic-carbonate system in Ngrayong Formation is diagenetically-altered, and this diagenesis process plays as an important roles in modifying reservoir quality. Although carbonate cement and diagenetic overprint impose challenging reservoir quality prediction, a dissolution creates better reservoir quality, generates excess permeability and produces high flow reservoir. Detail study of reservoir architecture and diagenesis process are critical to better assess volumetric and development opportunity. These key components will open up new paradigm and essential for successful of Ngrayong Formation exploration in East Java Basin in order to contribute to the country’s energy demand.

DETRITAL AND AUTHIGENIC MINERALOGY OF THE PRETTY HILL FORMATION IN THE PENOLA TROUGH, OTWAY BASIN: IMPLICATIONS FOR FUTURE EXPLORATION AND PRODUCTION

1995 ◽  
Vol 35 (1) ◽  
pp. 538 ◽  
Author(s):  
B. M. Little ◽  
S. E. Phillips
Keyword(s):  
Reservoir Quality ◽  
Secondary Porosity ◽  
Water Contact ◽  
Thin Sections ◽  
Authigenic Minerals ◽  
Wide Range ◽  
Resistivity Logs ◽  
Exploration And Production ◽  
Reservoir Sandstones ◽  
The Impact

The Pretty Hill Formation in the Penola Trough is a productive gas reservoir in the Katnook, Ladbroke Grove and Haselgrove fields. Thin sections, X-ray diffraction, scanning electron micros­copy and electron microprobe analyses have been used to characterise the mineralogy of core samples from eight wells. The reservoir sandstones are typically fine to medium grained, moderately sorted feldspathic litharenites. Framework grains comprise detrital quartz, feldspars (albite, microcline and anorthite), lithics (dominantly volcanic), mica and accessory minerals. Authigenic minerals of chlorite, laumontite, carbonate, quartz, feldspar, sphene, anatase, glaucony and illite are present in all wells. Kaolinite is restricted to Ladbroke Grove-1. Chlorite, laumontite and carbonate are volumetrically the most important authigenic minerals.There is a wide range in core plug porosity (one to 23 per cent) and permeability (10"3to 103 md) in the reservoir sandstones. In samples with high per­centages of authigenic clays microporosity is im­portant. Regional trends indicate reservoir quality decreases with increasing depth but superimposed on this trend is the influence of the detrital and authigenic mineralogy. Cleaner, coarser sublitharenites and subarkoses have good reservoir char­acteristics but where lithics concentrate in the finer feldspathic litharenites and litharenites deformation of these ductile grains has limited porosity and permeability. Authigenic minerals have both reduced and enhanced reservoir quality. Chlo­rite rims with associated microporosity have decreased the impact of mechanical compaction and inhibited silicification. Pore filling cements of laumontite and carbonate have occluded intergranular pores and replaced grains. Secondary porosity produced by the dissolution of these cements in the gas zones has significantly improved reservoir quality.Other information gained from the mineralogical study could influence future exploration and production. Lack of contrast on resistivity logs between gas and water zones is not due to the mineralogy of the Pretty Hill Formation. However, the restriction of early diagenetic laumontite to the water zones of gas producing wells does indicate the location of the gas-water contact. Laumontite was dissolved from the gas zone by an increase in C02 prior to hydrocarbon migration. Use of acids to enhance permeability in the Pretty Hill Formation should take into account the probable formation damage caused by reactions with the clays. Kaolin- ite could dissolve to produce a silica gel and the high Fe3+ content of the chlorite will result in a gel unless iron chelators are used in the mud acid. The depositional environment of the Pretty Hill Forma­tion has historically been interpreted as braided fluvial stream deposits interfingering with finer grained lacustrine shales and siltstone. However, this model can not explain the presence of glaucony grains, unless the glaucony has been reworked, but there is no unequivocal evidence to support this hypothesis.

scholarly journals Diagenetic Processes Overprint and Pore Types of Mauddud Formation, Badra Oil Field, Central Iraq

2020 ◽  
pp. 1353-1361
Author(s):  
Mena Jamal Faisal ◽  
Thamer A. Mahdi
Keyword(s):  
Effective Porosity ◽  
Oil Field ◽  
Reservoir Properties ◽  
Thin Sections ◽  
Diagenetic Processes ◽  
Different Types ◽  
Interparticle Porosity ◽  
Calcite Cement ◽  
Primary Porosity ◽  
Pore Types

Diagenetic processes and types of pores that control the reservoir properties are studied for Mauddud Formation in selected wells of Badra oil field, central Iraq. The microscopic study of the thin sections shows the effects of micritization, cementation, neomorphism, dissolution, dolomitization, compaction, and fracturing on Mauddud Formation carbonate microfacies. The decrease of porosity is resulted from cementation, compaction, and neomorphism. Different types of calcite cement occlude pore spaces such as drusy cement, syntaxial rim cement, and granular (blocky) cement. The neomorphism of micritic matrix and skeletal grains reduces porosity as indicated by development of microspar or pseudospar. Evidence of decreasing porosity by compaction includes closer packing of grains, which reduces interparticle porosity. Dissolution process has prominent effect in creating and increasing the effective porosity in different depositional textures of Mauddud Formation. Reservoir properties are increased in grain-supported microfacies, which have vuggy porosity or primary porosity, whose pore size differs depending on the size of the grains. The reservoir properties in the mud-supported microfacies are reduced due to the low occurrence of pores and their lack of connectivity if they exist.

Analysis of Uncertainty Introduced by Scaleup of Reservoir Attributes and Flow Response in Heterogeneous Reservoirs

SPE Journal ◽  
2011 ◽  
Vol 16 (03) ◽  
pp. 713-724 ◽  
Author(s):  
Juliana Y. Leung ◽  
Sanjay Srinivasan
Keyword(s):  
Spatial Models ◽  
Total Porosity ◽  
Volume Averaging ◽  
Transport Processes ◽  
Carbonate Reservoir ◽  
Transport Mechanisms ◽  
Length Scales ◽  
Reservoir Models ◽  
Wide Range ◽  
Conditioning Data

Summary Reservoir heterogeneities occur over a wide range of length scales, and their interaction with various transport mechanisms controls the performance of subsurface flow and transport processes. Modeling these processes at large scales requires proper scaleup of petrophysical properties that are autocorrelated or heterogeneously distributed in space, and analyzing their interaction with underlying transport mechanisms. A method is proposed to investigate and quantify the uncertainty in reservoir models introduced by scaleup. It is demonstrated that when the volume support of the measurement is smaller than the representative elementary volume (REV) scale of the attribute to be modeled, there is uncertainty in the conditioning data because of scaleup and that uncertainty has to be propagated to spatial models for the attribute. This important consideration is demonstrated for mapping total porosity for a carbonate reservoir in the Gulf of Mexico. The results demonstrate that in most cases, the uncertainty distributions obtained by accounting for the scaleup procedure successfully characterize the variability in the actual core and log data observed along new wells. Conventional reservoir models considering the well data as "hard" conditioning data fail to predict the "true" values. Following this discussion on scaling of reservoir attributes, a conceptual understanding of the scaling characteristics of flow responses such as recovery factor (RF) is provided, in terms of the mean and variance of RF at different length scales. Finally, a new technique is presented to systematically quantify the scaling characteristics of transport processes by accounting for subscale heterogeneities and their interaction with various transport mechanisms based on the volume averaging approach. The objective is to provide a tool for understanding the scaling relationships for RF using detailed fine-scale compositional reservoir simulations over a subdomain of the reservoir.

Geological Heterogeneities Important to Future Enhanced Recovery in Carbonate Reservoirs of Upper Ordovician Red River Formation at Cabin Creek Field, Montana

1982 ◽  
Vol 22 (03) ◽  
pp. 429-444 ◽  
Author(s):  
Kenneth Ruzyla ◽  
Gerald M. Friedman
Keyword(s):  
Enhanced Recovery ◽  
Depositional Environments ◽  
Carbonate Reservoir ◽  
Red River ◽  
Reservoir Rock ◽  
Pore Geometry ◽  
Upper Ordovician ◽  
Thin Sections ◽  
Size And Shape ◽  
Porosity Percentage

Abstract Several different pore systems are present in dolomite reservoir rocks of the Red River formation (Upper Ordovician) at Cabin Creek field, MT. Each system is associated with particular depositional environments and diagenetic regimes. Pore geometry is mostly a function of the size and shape of the dolomite crystals composing the rock matrix. Mean pore-throat size, a statistical measure of pore geometry, increases as porosity percent increases, depending on the type of dolomite. This relationship permits prediction of reservoir pore geometry and a better assessment of recovery efficiency once lithofacies distribution, porosity origin, and diagenetic history have been determined for the reservoir by study of cores and rock thin-sections. Introduction The reservoir characteristics of any rock type depend on the arrangement of the pore space and how the pores are interconnected. The pore-system geometry of a reservoir rock must be understood to determine fully its response to primary or enhanced recovery. To predict pore geometry trends, it is necessary to establish relationships between measures of pore geometry and petrophysical parameters. which are measurable by electric-log surveys of boreholes. This is because cores, which are necessary for pore geometry determination, are usually available for select wells of any given field. Pore geometry is mostly a function of depositional environment and diagenetic processes such as cementation, recrystallization, mineralogical alterations, and selective leaching of rock components. This study presents an approach for determining heterogeneities of carbonate-reservoir pore geometry and for delineating pore geometry throughout the reservoir. The application to future enhanced recovery also is discussed. The formation under study is the Red River formation (Upper Ordovician) of Cabin Creek field, a producing oil field located in southeast Montana (Fig. 1). The Red River formation is a major producing reservoir in the area, and Cabin Creek is a potential candidate for tertiary recovery. Structurally, Cabin Creek is on the Cedar Creek anticline, a long asymmetrical feature on the southwest margin of the Williston basin (Fig. 1). Fig. 2 is a structure contour map of Cabin Creek field. The Red River formation averages about 500 ft (153 m) in thickness and consists of a sequence of alternating limestones and dolostones (Fig. 3). Production is from the U2, U4, and U6 dolostone units in the upper 150 ft (46 m) of the formation. The interstratified U1, U3, and US limestone units are nonproductive and nonporous (Fig. 4). Lateral and vertical variations in degree of dolomitization are mostly responsible for variations of reservoir properties. Commingled Ordovician and Silurian oil production was 61,570,000 bbl as of Sept. 1979, with reserves of 13,425,000 bbl (2 134 405 m ). The field has been on waterflood since April 1964. Approximately 1,450 ft (444 m) of core from 12 different wells was studied to delineate field stratigraphy, distribution of lithofacies, and depositional environments. Core slabs were ground with abrasive grit, then etched in diluted hydrochloric acid to enhance sedimentary structures and aid in identification of carbonate grains and matrix material. Staining methods were used to aid mineralogical identification. Diagenesis, porosity types, and origin of porosity were determined by petrographic analysis of thin-sections. Values of porosity percentage, permeability, and saturations are from core-plug analyses. Size and shape of pore throats were determined from mercury capillary-pressure data and from scanning-electron micrographs of resin pore casts, respectively. Plots were made of porosity percentage vs. parameters of pore geometry for producing zones within the Red River formation. SPEJ P. 429^

Carbonate Pore System Characterization, a Study Case from Drowning Cap Sequence in VITA Field, ExxonMobil Block Cepu Limited (EMCL)

2021 ◽  
Author(s):  
V.T Dewi
Keyword(s):  
Reservoir Simulation ◽  
Carbonate Reservoir ◽  
Reservoir Rock ◽  
Reservoir Quality ◽  
High Porosity ◽  
Pore System ◽  
Diagenetic Processes ◽  
Porosity And Permeability ◽  
Study Case ◽  
Low Porosity

Carbonate rocks are known as one of the principal reservoir rocks in the world due to their good porosity and permeability. However, the heterogeneity of carbonate reservoir quality is difficult to predict. Variability of diagenetic processes overprinting carbonate depositional texture has resulted in a complex carbonate pore system. As a consequence, this complexity results in a harder reservoir characterization and also a discrepancy between actual and model properties, that leads to a harder history match in reservoir simulation. By presenting a study case from the Drowning Cap Sequence in the VITA Reservoir Block Cepu, this paper will present a comprehensive approach which focusing on characterization of a carbonate pore system for optimum geomodel, simulation and surveillance. This approach utilized static data of 100 ft total of cores, ±500 thin sections, well, and image logs. The study has resulted in definition of four Carbonate Reservoir Rock Types (RRT) which were clustered using the analysis of carbonate dominant pore types and the porosity-permeability relationship. Results revealed that there are 4 RRTs observed as follows: (1) RRT 1 – Touching Vugs-dominated, with high porosity and permeability, (2) RRT 2 – Interparticle- and Moldic-dominated, with moderate to high porosity value and lower permeability than RRT 1, (3) RRT 3 – Microfracture-dominated, with very low porosity value and low to moderate permeability, and (4) RRT 4 – Minimum Dissolution, with very low porosity and permeability value, lower than RRT 3. Each RRT was integrated with well and image logs to understand its characteristics and behavior. Ultimately, all data were integrated, analyzed and successfully captured carbonate reservoir quality variation, distribution and depositional evolution along with overprinted diagenetic processes vertically and laterally. This approach successfully captured carbonate heterogeneity which ultimately will be useful to develop better geological and reservoir simulation models after being integrated with dynamic data and observations.

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