Reservoir rock typing and zonation in sequence stratigraphic framework of the Cretaceous Dariyan Formation, Persian Gulf (original) (raw)
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Marine and Petroleum Geology, 2015
The Aptian carbonate reservoirs of Persian Gulf, known as the Dariyan Formation (Shu'aiba equivalent), are among the most important oil reservoirs of Iran. Despite its significance, a little is known about the facies characteristics, diagenetic history, sequence stratigraphy, and reservoir quality of this formation. Using the new core data, this study presents an integrated geological reservoir characterization of this formation in four giant fields in the Persian Gulf. Using the results of the facies analysis it could be suggested that this unit formed in a shallow carbonate platform surrounding intra-shelf basins of Kazhdumi and Bab in the western and eastern Persian Gulf, respectively. A major relative sea-level fall in the Late Aptian resulted in exposure of this unit and subsequent clastic influx as well as meteoric diagenesis. This phase of meteoric diagenesis has resulted in some important diagenetic features, special geochemical trends, and considerable variations in reservoir quality of the Dariyan Formation. Sequence stratigraphic interpretation of this formation has resulted in the recognition of 2 nd and 3 rd order depositional sequences in the studied wells. They are closely correlated across the studied wells in the Persian Gulf, SW Iran, and other places in the Arabian Plate. Reservoir characterization has revealed that the high quality units are
Upper Cretaceous Petroleum System of Northwestern Persian Gulf
2015
Three well - known source rocks of the Zagros basin and the Persian Gulf are Mesozoic in age.The Jurassic Sargelu, Albian Kazhdumi and Neocomian-Coniacian Garau formations have charged the Cretaceous reservoirs of this area. The northwest part of the Persian Gulf is strongly influenced by two major N-S trending paleohighs (Hendijan- Bahregansar-Regesafid-Izeh and Kharge- Mish) and surrounding plaeotroughs that play the most important role in the reservoir and source rock development. The most important reservoirs are the Cenomanian- Turonian Sarvak and Santonian Ilam formations which locally separated by a thin shaly unit of the Coniacion Laffan Formation. The reservoir facies are dominated by benthic and rudist debris on the paleohighs which laterally grading down to the basinal Cenomanian Ahmadi and Santonian Gurpi pelagic marls. In order to study the petroleum system of the northwest Persian Gulf, several 2D seismic lines and six wells were interpreted. Based on the interpreted s...
Journal of Petroleum Science and Engineering, 2021
Dariyan Formation (Aptian) is one of the important hydrocarbon reservoirs in the Persian Gulf. In this reservoir, porosity is controlled by various depositional and diagenetic factors. This study integrates petrographic, geochemical, petrophysical and reservoir quality data to distinguish various pore types and their evolution in two fields selected from the SE and NW Persian Gulf. Primary (depositional) and secondary (diagenetic) pore types are differentiated using the results of macroscopic (core) and microscopic (thin section and SEM) petrographic studies. Pore size distribution and reservoir importance are evaluated by MICP and porosity-permeability measurements on core-plug samples. Macroscopic pores are formed within the grain-dominated and dissolved mud-dominated facies that are located in the RST of third-order sequences, especially within the lower carbonate unit. Micropores are recorded in mud-dominated facies of middle to outer ramp settings with minor effects of meteoric dissolution. Accordingly, evolution in an open diagenetic system with high water/rock ratio is proposed for grain-supported facies, and a closed diagenetic system for mud-dominated intervals. There are close relationships between micrite micro-textures (MTCs) and reservoir properties of mud-dominated facies. A dynamic pore evolution model is presented for the Dariyan Formation that integrates all 2 depositional and diagenetic features in sequence stratigraphic framework. This model can be used for ongoing reservoir studies of this formation in hydrocarbon fields of the Persian Gulf.
CARBONATE RESERVOIR ROCKS AT GIANT OIL AND GAS FIELDS IN SW IRAN AND THE ADJACENT OFFSHORE: A REVIEW OF STRATIGRAPHIC OCCURRENCE AND PORO-PERM CHARACTERISTICS, 2019
SW Iran and the adjacent offshore are prolific petroleum-producing areas with very large proven oil and gas reserves and the potential for significant new discoveries. Most of the oil and gas so far discovered is present in carbonate reservoir rocks in the Dehram, Khami and Bangestan Groups and the Asmari Formation, with smaller volumes in the Dashtak, Neyriz, Najmeh, Gurpi, Pabdeh, Jahrum, Shahbazan, Razak and Mishan (Guri Member) Formations. The Permo-Triassic Dehram Group carbonates produce non-associated gas and condensate in Fars Province and the nearby offshore. The Jurassic-Lower Cretaceous Khami Group carbonates are an important producing reservoir at a number of offshore fields and in the southern Dezful Embayment, and are prospective for future exploration. Much of Iran's crude oil is produced from the Oligo-Miocene Asmari Formation and the mid-Cretaceous Sarvak Formation of the Bangestan Group in the Dezful Embayment. This review paper is based on data from 115 reservoir units at 60 oil-and gasfields in SW Iran and the adjacent offshore. It demonstrates that the main carbonate reservoir units vary from one-another significantly, depending on the particular sedimentary and diagenetic history. Ooidal-grainstones and rudist-and Lithocodium-bearing carbonate facies form the most important reservoir facies, and producing units are commonly dolomitised, karstified and fractured. In general, reservoir rocks in the study area can be classified into six major types: grainstones; reefal carbonates; karstified, dolomitised and fractured carbonates; and sandstones. The stratigraphic distribution of these reservoir rocks was principally controlled by the palaeoclimatic conditions existing at the time of deposition. A comparative reservoir analysis based on core data shows that dolomitised and/or fractured, grain-dominated carbonates in the Dehram Group, Lower Khami Group and Asmari Formation typically have better reservoir qualities than the Cretaceous limestones in the Upper
Paleogeography and Sequence Stratigraphy in Dariyan Carboante Reservoir, NE Shiraz
Open Journal of Geology, 2016
Zagros Basin is a very important hydrocarbon region in the Iran and World. One of the major reservoirs in this basin is the Lower Cretaceous Dariyan Formation. Based on petrographic studies, 9 microfacies were determined and interpreted as related to lagoon, barrier island and open marine environments. Facies associations show deposition in a carbonate ramp. Sequence stratigraphy studies show two sequences, each one with a transgressive system tract, marked by open marine microfacies, and then a retrogradational highstand, marked by barrier and lagoonal facies. Paleogeography and sequence stratigraphy studies of this formation and correlation of it with other sections may provide useful information about reservoir characterizations.
Journal of Petroleum Geology, 1993
Detailed petrologic, sedimentologic and geohistory analyses have been carried out on the Neocomian (Lower Cretaceous) Shurijeh Formation in the eastern part of the Kopet-Dagh Basin, NE Iran. The results of these analyses show that the diagenetic history of Shurijeh sandstones was aflected by their depositional settings, and the subsequent subsidence of these units through meteoric and compactional hydrologic regimes in this part of the Kopet-Dagh Basin. These rocks consist mostly of sub-litharenitic redbeds deposited during a regressive phase of sedimentation dominated by rapid siliciclastic sediment supply. The lower and middle portions of the interval studied were deposited in low-sinuosity braided fluvial systems, and the upper portion was deposited in high-sinuosity meandering systems. The porous and permeable sand-rich units were partially filled by infiltrated clays, and early calcite, anhydrite and silica cements as they subsided through the meteoric regime. In the compactional regime, feldspars altered to clays, dolomite replaced calcite and penetrated authigenic silica, and a late-stage of calcite cementation and replacement took place. These diagenetic events were followed by partial dissolution of early and late-stage calcite cements that created secondary porosity in the sandstone units. During the late Mioceneearly Pliocene (approximately 10 million years), the Late Alpine Orogeny resulted in the formation of structural traps in the Shurijeh Formation of the Sarakhs area. This was followed by migration of gas into the porous units of this formation, accounting for the Khangiran and Gonbadli gasfields. Relationships revealed in this study can be used to develop diagenetic models that will help predict diagenetic styles in dominantly non-marine sandstones in other basins similar to the Kopet-Dagh of Iran.
Bulletin of Geosciences, 2015
The Lower Cretaceous (Aptian-Albian) Dariyan Formation (northeastern Arabian Plate, Iran) represents the youngest sediments of the Khami group in the Zagros fold belt. This study is based on six sections located in the Izeh Zone and Interior Fars Province documenting transition from platform to a basin margin facies. Three assemblage zones based on benthic foraminifers have been identified and provide an early Aptian-early Albian age. Petrographic and microfacies analyses characterize thirteen carbonate microfacies and two mud rock lithofacies-types. The vertical and lateral facies variations observed in this study for the Dariyan Formation are in agreement with a depositional environment going from a homoclinal carbonate ramp to margin of intra-shelf basin type. Based on the identification of three sequence boundaries (SB), the Dariyan Formation sediments has been divided into three 2 nd -order depositional sequences which encompasses six and five 3 rd -order sequences in the margin of intra-shelf basin and the shallow platform settings, respectively. The early Aptian sea-level rise led to the extension of the carbonate platform and deposition of pelagic facies as a maximum flooding surface on margin of intra-shelf basin. In the late Aptian highstand phase, the platform was exposed as a result of glacio-eustatic mechanisms, whereas sediments continued to accumulate in the margin of intra-shelf basin. This study supports the general paleogeography of the studied area documented by previous studies and provides better insight to the interpretation of the evolution in this area and other similar basins. •
Journal of …, 2012
Carbonate sediments within the Mid-Cretaceous Sarvak Formation form an important reservoir at the Abteymour oilfield in the western Dezful Embayment, SW Iran. The poroperm characteristics of this reservoir were controlled by factors including deposition under tropical climatic conditions and early diagenesis, repeated phases of subaerial exposure due to local, regional and global-scale tectonism, and diagenetic modification during burial. From microfacies analysis, the Sarvak Formation carbonates in the Abteymour field were interpreted in a previous study as having been deposited on a homoclinal ramp-type platform. Three third-order sequences were recognized in the middle Cenomanian to middle Turonian part of the formation. The reservoir quality of the carbonates was enhanced both by dissolution (comprising separate phases of eogenetic and telogenetic meteoric dissolution) and dolomitization (especially stylolite-related dolomitization). In this paper, a rock/pore type approach was used in order to integrate petrophysical data with facies and diagenetic models within a sequence stratigraphic framework. Two different rock-typing methods for the determination of flow units were considered. Hydraulic flow units (HFUs) were identified firstly using flow zone indicators and secondly using a stratigraphic modified Lorenz plot. The flow units resulting from these two methods are compared, and their close correspondence within the sequence stratigraphic framework is discussed. In addition, the previously-used large-scale reservoir zonation scheme for the Abteymour field is correlated with the defined flow units, and four new Integrated Reservoir Zones are introduced. By integrating geological information with petrophysical parameters (including porosity, permeability and saturation) within a sequence stratigraphic framework, field-scale variations and controls on reservoir quality are described.