The Influence of Lithofacies Features of a Deposit on the Efficiency of Reserves Recovery

The main task in petroleum engineering is to achieve the maximum possible production of hydrocarbon reserves with low expenditures. Many reasons influence the economics of the project. And one of them is related to choosing the right location for drilling a well in order to produce unrecovered hydrocarbons. The choice of this place has a direct correlation with the geological aspects of an oil field. This paper showed that different facies have a great influence on reserves recovery on the example of the South-Vyintoyskoye field. The classification of facies involved the study of production data. This study was presented by analysis of core sample, application of models by Muromtsev, reading of well logs, and build-up of geological models. The construction of geological models involved work in IRAP RMS TEMPEST, CorelDRAW, Geoglobe, Roxar Program package. The subject of study was the reservoir rock BV7/3-4that is a part of the Barremian age formation. It was concluded that this reservoir rock is composed of mainly argillaceous sandstones, interbedded with siltstones and shales. Authors identified that this formation belongs to three different depositional facies. The facies classification showed that the A1 zone is associated with well-graded fine to the fine-grained size of sediments. The reservoir rock of this zone is composed of sediments that belong to the distribution channel of deltas. And as a result, it is characterized by its high flow rate of production wells. The reservoir rock of the A2 facies zone is composed of sediments that are related to the collapse of mouth bars and branches of deltas. This zone has difficulties in fluid migration due to the presence of heterogeneities and clay material as well as the drilling of new wells close to the given zone lead to the medium flow rate of production wells. The reservoir rock of the A3 facies zone is composed of sediments that belong to turbidity flows. In this zone, organic matter has been recognized as a group of ichnofacies such as "Cruziana". This zone is characterized by the low flow rates of the production wells.

CORRELATION OF THE SILURIAN SEQUENCE OF THE 25-KOTYUZHINY STRUCTURAL WELL WITH THE DNIESTER REFERENCE SECTION OF THE SILURIAN IN THE VOLYN-PODILLYA PLATE

The paper is devoted to lithostratigraphic and biostratigraphic subdivision of the Silurian deposits of 358 m total thickness in the 25-Kotyuzhiny structural well and its comparison with the stratotypic Dniester section of the Silurian system in accordance with Legend to the geological map of Ukraine, the Volyn-Podolsky series of 1: 200 000 scale, consistent with the latest modernization of Silurian stratigraphic charts. The described section is a parastratotype for Silurian litho-stratons of the Kovel-Khotyn structural and facies zone and a reference one for Silurian deposits in the central part of this zone. The Silurian in the 25-Kotyuzhiny well is represented by the lower (Llandoverian and Wenlockian stages) and upper (Ludlovian and Przhidolian stages) series. According to the lithological-facies composition and sedimetantaion conditions during Silurian times, there are 3 major completed stages of sedimentation as transgressive-regressive cycles, corresponding to the the Yarugian, Malinovetsian and Rukshinian series, which are quite clearly subdivided into 10 suites and 12 sub-suites. In correlation with the Dniester reference section, litho-stratons of the Silurian are characterized mainly by carbonate and clay-carbonate composition, relative stable thickness and facies pattren, diversity of fauna with a predominance of shallow benthic forms. The well is characterized by bituninous manifestations indicating hydrocarbon potential of the area and its prospectivity for shale gas accumualtions in the formations of the upper Silurian in particular.

EVENT STRATIGRAPHY AND CORRELATION PROBLEMS OF THE ORDOVICIAN STRATA OF GORNY ALTAI AND SALAIR

Study of the Ordovician sedimentary sequences of Gorny Altai and Salair has revealed lithological and paleontological features correlating with global sedimentary events:(1) The Acerocare Regressive Event (an initial event in the Early Tremadocian);(2) Black Mountain Transgressive Event (Early Tremadocian);(3) Peltocare Regressive Event (Tremadocian);(4) Kelly Creek Regressive Event (Late Tremadocian);(5) Ceratopyge Regressive Event (Late Tremadocian);(6) Billingen Transgressive Event (Early Floian);(7) Stein Lowstand Event (Middle Darriwilian);(8) Vollen Lowstand Event (Sandbian);(9) Arestad Drowning Event (Middle Sandbian);(10) Frognerkilen Lowstand Event (Early Katian);(11) Linearis Drowning Events 1 and 2 (Middle Katian);(12) Terminal Husbergoya Lowstand Event (Hirnantian); and(13) Hirnantian Lowstand Event (HICE) (Late Ordovician).The chronostratigraphic levels with traces of the global sedimentary events in the Uymen-Lebed structural-facies zone (SFZ) (Gorny Altai) differ from those in the Charysh-Inya and Anui-Chuya SFZ (Altai). In the Ordovician, the Altai basin located in the Charysh-Inya and Anui-Chuya SFZ was a marine area separated from both the Uymen-Lebed basin and the coeval Salair basin. The traces of the global sedimentary and/or biotic events in the Altai and Salair sections can be used as a precise basis for direct correlation of the local stratigraphic units with the units of the International Stratigraphic Chart.

MICROFACIES AND DEPOSITIONAL ENVIRONMENT OF TERTIARY LIMESTONE, GORONTALO PROVINCE, INDONESIA

The research area is located in northern Limboto Lake in Gorontalo Province, which has complex geological characteristics. The geological complexities include stratigraphy and tectonics which influence the formation of the Limboto Basin. Limestone research in the Late Tertiary Limboto Basin is very intriguing to be done because of the lack of research in limestone. Gorontalo limestone outcrops, which become the focus of the research, have a total thickness of 30 meters. The research objective is to analyze facies, microfacies, and depositional environment of tertiary limestone. These two research objectives are attained by using two research methods, namely measurd section and petrography analysis. The research result exhibits that there are four Gorontalo limestones facies, including coralline rudstone intercalated with thin mudstone facies, sandy micrite intercession facies, coralline rudstone intercession facies and sandy allochem limestone intercession facies. According to the limestone micro- facies standard, the depositional environment of Gorontalo limestone is platform interior restricted (facies zone 8).

Groundwater Recharge Area Based on Hydrochemical and Environmental Isotopes Analysis in the South Bandung Volcanic Area

The determination of recharge areas needs to support the groundwater conservation in the southern volcanic Bandung area. This study aims to determine the recharge area based on environmental isotopes and hydrochemical. A sampling of 26 groundwater was carried out at springs, dug wells, and drilling wells. The variation in groundwater chemistry principally is controlled by a combination of ion exchange, silicate weathering, calcite, and dolomite dissolution of minerals. The hydrochemical facies were CaCl, CaMgCl, CaMgHCO3, CaHCO3, and NaKHCO3. The CaHCO3 facies describe moderate groundwater flows. The NaKHCO3 facies shows the mixing of shallow and deep groundwater. The recharge area in the central, proximal, and medial facies zone consists of 3 groups. Group I is considered water originating from local rainwater infiltration; Group II is considered the infiltration elevation which ranges from 980–1230 m asl; Group III estimated to be derived from the recharge elevation between 750–970 m asl, Group IV are more likely to show symptoms of evaporation or interaction with surface water. The discharge area is characterized by less active groundwater circulation, with dominant HCO3– and TDS value in the distal facies zone. Hydrochemical variation helped the identification of recharge areas in the volcanic facies.

Metamorphic pressure-temperature conditions of the Lützow-Holm Complex of East Antarctica deduced from Zr-in-rutile geothermometer and Al2SiO5 minerals enclosed in garnet

<p>The Zr content of rutile coexisting with zircon and quartz is mainly a function of the temperature condition and is calibrated as Zr-in-rutile geothermometers. Because of their robustness under high-temperature conditions, they have been applied to granulite facies rocks instead of the conventional Fe-Mg exchange type geothermometers to estimate more reliable temperature conditions. However, it is recently pointed out that in order for rutile to retain the primary Zr content, rutile must be chemically isolated from zircon and quartz during cooling. In this context, inclusion rutile separately enclosed in garnet can be considered to retain the primary Zr content at the time of entrapment, only if rutile, zircon, and quartz are all enclosed in a contemporaneous domain of the garnet.</p><p>In this study, we re-examined the pressure-temperature (<em>P-T</em>) conditions of high-grade pelitic gneisses from selected regions (Akarui Point, Skarvsnes, Skallen, and Rundvågshetta) of the Lützow-Holm Complex (LHC), East Antarctica. The LHC has been divided into the upper-amphibolite facies zone, the transitional zone, and the granulite facies zone, based on matrix mineral assemblages of mafic- to intermediate gneisses. Akarui Point is located in the transitional zone and others in the granulite facies zone.</p><p>While previous studies commonly applied the conventional Fe-Mg exchange type geothermometers, we applied the Zr-in-rutile geothermometer of Tomkins et al. (2007) to rutile grains enclosed in garnet that also encloses zircon, quartz, and Al<sub>2</sub>SiO<sub>5</sub> minerals. By utilizing the phosphorus zoning in garnet, we defined contemporaneous domains of the garnet and identified coexisting inclusion minerals in each domain. In this way, coexisting Al<sub>2</sub>SiO<sub>5</sub> minerals and rutile grains were utilized to constrain the <em>P-T</em> condition of each domain of the garnet.</p><p>As a result, samples from Akarui Point, Skarvsnes, and Skallen were shown to have experienced almost the same <em>P-T</em> conditions around the kyanite/sillimanite transition boundary (~ 830-850 °C/~ 11 kbar). This is significantly higher than the previously estimated peak condition of 770-790 °C/7.7-9.8 kbar based on the conventional garnet-biotite geothermometer in the case of Akarui Point. From Rundvågshetta, where ultrahigh-<em>T</em> metamorphism is reported by previous studies, higher-<em>T</em> condition (850 ± 15 °C/0.1 kbar to 927 ± 16 °C/12.5 kbar) than those of other three regions was confirmed from inclusion rutile in garnet enclosing sillimanite. Therefore, the traditional metamorphic zone mapping, which classified Akarui Point as belonging to the transitional zone, does not reflect the highest metamorphic grade attained. It should be noted that the regional <em>P-T</em> conditions estimated from inclusion minerals in this study is that of earlier higher-<em>P</em> metamorphic stage than the regional <em>P-T</em> conditions determined by the metamorphic zone mapping utilizing matrix mineral assemblages. This result indicates that the Zr-in-rutile geothermometer is a powerful tool to reveal the <em>P-T</em> evolution of high-grade metamorphic terrains, when combined with detailed microstructural observations focusing on the relationship between rutile, zircon, and quartz.</p>

Lithostratigraphy and Sedimentological Characteristics of the Calciturbidites of the Babadağ Formation-Tavas Nappe (SW Turkey)

The Lycian Nappes contain slices of ophiolites and sedimentary rocks of various ages that crop out in SW Turkey. They evolved and were emplaced under the effect of the Late Cretaceous-Miocene compressional regime. The Tavas Nappe is part of the Lycian Nappes and contains Jurassic-Eocene sediments. The Babadağ Formation, forming the middle part of the Tavas Nappe, is composed of limestone at the base and various sized calciturbidites with chert intercalations in the upper part. The Standard Microfacies Classification (SMF of FLÜGEL, 2004) indicates that the entire unit was deposited mainly in a deep-shelf environment (Facies Zone – FZ-2), deep-sea (FZ-1), toe of slope (FZ-3) and on the continental slope (FZ-4). Calcite and quartz dominate the bulk mineralogy of the calciturbidites with higher SiO2 and CaO weight percentages than other major oxides. Additionally, the presence of Na2O, K2O, Al2O3, MgO, TiO2 and Fe2O3 is associated with the local sediment input. Tectonism and sea level fluctuations were the main triggering factors of the changes in the original depositional environment of the Babadağ Formation. Additionally, grain size and the amount of sediment input control the calciturbidite type and extension. Si enriched water circulation and Si and Ca substitution were responsible for the abundant chert formation during diagenesis of the units. Post depositional tectonic activities during transportation and emplacement of the nappes resulted in calcite filled cracks that cut both the calciturbidites and cherts. Study of the different nappe slices provides valuable information about syn- and post- depositional changes of the lithostratigraphic units.

Microfacies Characterizations and Paleoenvironment of Upper Part of Qamchuqa Formation from Chwarqauran Section, Sulaimaniyia Area, Kurdistan Region, Iraq

The Qamchuqa Formation was studied in Chwarqauran section, Sulaimanyia, Kurdistan region, Northeastern Iraq. The lithology of the formation contains limestone throughout the whole section except for one bed of dolomite at the Middle part. Twenty-four slides were prepared from 24 rock samples that were taken from this section to discriminate the petrography and fossil content. The petrographic study shows four main microfacies including lime mudstone, wackestone, packstone, and floatstone. Additionally, there are four sub microfacies: bioclast wackestone, miliolid wackestone, bioclast packstone and orbitolinid packstone. However, the fossil content shows the abundance of benthic foraminifera against the planktonic. All the microfacies indicate facies zone 7, 8 and 9A which reflect deposition in the platform interior between the tidal flat to the mid ramp and back reef environment

Paleoredox and Environmental Conditions of Southern Neo-Tethys Deposits in South Iraq (Yamama Formation) by Geochemical Indicators

A geochemical and environmental study was carried out for the sediments of the Southern Neo-Tethys Ocean, represented by the Yamama Formation (Berriasian-Valaganian) in southern Iraq. The formation has a particular reservoir importance. The typical WQ-220 and WQ-280 wells were selected from the West Qurna field. Data of Gamma-ray logs were used for 30 depths of the typical well. Ten core samples were analyzed by X-Ray Fluoresces and total organic matter from both wells. The results showed that shaliness was relatively low, with an average of 16.5%, leading to a decrease in the presence of clay minerals and trace elements because the environment of the Yamama Formation is relatively far away from the coast. Qualitative evaluation of clay minerals was carried out by thorium/potassium ratio, which showed the dominance of illite and smectite. This may be due to an increase in the salinity of the ocean at that time or because potassium bonds are strong enough to resist the diagenesis processes. The origin of shale in the Yamama Formation was studied using the relationship TiO2-MgO+Fe2O3; the sources were passive margin group, oceanic island arc and active continental margin. The redox potential of paleoenvironment was determined by the thorium/uranium ratio, which showed that the beginning of depositional environment was slightly oxidized, but with the increase of sedimentation, it turned into a reduced environment, which indicates a transgression phase of sea level. The results of euxinic affinity, based on the relationship between molybdenum and Total Organic Carbon (TOC), reflect dyoxic facies which is deposited in extremely low but non-zero oxygen content, while the upper was approaching anoxic facies zone. The paleoenvironment of the Yamama Formation was of restricted deep marine water (outer shelf - upper part of the benthic zone) which contained a marine transgression phase because of the opening of Southern Neo-Tethys Ocean in the Valanginian age.

Depositional Environment Analysis Carbonate Rocks in Montasik District

Kecamatan Montasik terdiri dari 2 formasi yaitu Formasi Gunungapi Lam Teuba berumur Pliosen Akhir sampai Plistosen Akhir dan Formasi Anggota Padangtiji berumur Pliosen Awal sampai Pliosen Tengah. Litologi Formasi Anggota Padangtiji terdiri dari konglomerat, batulanau, batupasir gampingan dan batu gamping. Lingkup penelitian ini meliputi kajian tentang kondisi geologi permukaan dan analisis lingkungan pengendapan sedimen karbonat pada lokasi penelitian. Metode yang digunakan dalam penelitian ini yaitu pengambilan data langsung di lapangan dan menganalisis petrologi dan petrografi pada sampel batuan. Litologi pada lokasi penelitian terdiri dari 7 satuan yaitu guguran lava, lava andesit, lapili jatuhan piroklastik, tuf jatuhan piroklastik, konglomerat, batugamping terumbu dan batupasir gampingan. Lingkungan pengendapan sedimen karbonat yang terdapat pada lokasi penelitian terbentuk di laut dangkal (reef) pada kedalaman 0 m - 200 m di bawah permukaan laut. Zona fasies pengendapan batugamping pada lokasi penelitian terendapkan pada zona platform margin sands dan organic buildups. Sedangkan zona fasies terumbu pada lokasi penelitian terdapat pada zona reef front. Montasik district consists of two formations, Gunungapi Lam Teuba Formation aged Late Pliocene – Late Pleistocene and Padangtiji Member aged Early Pliocene – Middle Pliocene. Lithology of Padangtiji Member consists of conglomerate, siltstone, carbonate sandstone, and limestone. The scope of this research includes a study of surface geological conditions and depositional environmental analysis of carbonate sediment. The method used in this study is direct data collection in the field and analyzing petrology and petrography in rock samples. Lithology of the research area consists of lava drop, andesit, lapili pyroclastic, tuff pyroclastic, conglomerate, fosilliferous limestone, and carbonate sandstone. Depositional environment in the research area formed at shallow marine (reef) on 0m-200m depth under sea level. Depositional facies zone in the research area is on the margin sands platform zone and organic buildups, while Reef facies zone contained in reef front zone.Keywords: Geological Mapping, Depositional Environment, Carbonate Rocks, Petrography, Montasik