Reservoir Basin Research Articles

The impact of the complex evaporites features’ on the seismic illumination of the underlying rocks: A case study in the Brazilian presalt

The oil industry utilizes seismic techniques to image the Earth's subsurface. The number of reflected rays generated at a single point that return to the receivers impacts directly the quality of seismic data and, in turn, seismic interpretation. Seismic illumination is used as a quality control measure to find poor coverage zones, which are commonly found in pre-salt reservoirs of eastern Brazilian marginal basins. The Santos Basin has a wide evaporite section featuring some complex structures such as overhangs, mini-basins, salt domes, salt tongues and walls more than 3 km thick. Those structures change the paths of the seismic rays and reduce the coverage of seismic imaging below the evaporite layer in some regions. In this study, a quantitative and qualitative illumination analysis of a pre-salt horizon was performed comparing four different velocity model scenarios and the behavior of the seismic ray path was analyzed. The results show that both stratification and the geometric structures existing in the salt layer have a direct impact on the imaging of the pre-salt reservoirs. Each factor influences imaging in a different way and, when associated, can generate regions of low illumination quality. Consequently, it is of extreme importance to obtain a suitable understanding of the upper salt layer as it will govern the ray paths towards the layers below the evaporites. Furthermore, the mapping of the anomalies generated by the stratification should also be considered in the creation of the velocity model.

ANALYSIS OF WATER QUALITY OF RIVERS AND RESERVOIRS IN CHELYABINSK REGION, SOUTH URAL

Overland water resources of the Chelyabinsk region are presented by the basins of the Tobol, Ural, Volga (Kama) rivers. The total number of rivers exceeds 3.5 thousand, many of them are headwaters. This work assesses a ten-year change of water quality in 3 rivers and 3 reservoirs of the Tobol basin that are as well the source of drinking water for the residential area of the Chelyabinsk region. There are many ferrous, non-ferrous, power and machine-building industry facilities in the region. As a result, most of the rivers in South Ural are affected by industrial and household wastewaters. Any significant improvement of the water quality in the studied rivers has not been monitored for 10 years. The water can be characterized as “polluted” - “very polluted”. The Miass river has the heaviest anthropogenic impact in the Chelyabinsk region. It used to be “extremely polluted”. The given work aims to reveal interrelations between the water quality and the state of the studied water-bodies by means of principal component analysis. Principal component analysis allowed us to distinguish 2-3 periods that are characterized by similar pollution. The environment of rivers under a human-made impact changes adversely and transforms into another ecological state for a couple of years.

Integrated reservoir and basin modeling in understanding the petroleum system and evaluating prospects: The Cenomanian reservoir, Bahariya Formation, at Falak Field, Shushan Basin, Western Desert, Egypt

Robust inferences on understanding the reservoir heterogeneity and processes of the respective petroleum system are essential to reduce risks throughout the petroleum exploration and development phases. In this paper we present integrated static reservoir modeling and basin modeling to better characterise the reservoir rock; hydrocarbon-bearing sandstones of the Cenomanian Bahariya Formation. This reservoir is an element of the petroleum system; whose times of hydrocarbon generation-migration-accumulation, and entrapment, are also to be addressed; in Falak Field, Meleiha Area, Shushan Basin, Western Desert, Egypt. We utilized dataset including seismic profiles and well logs of four wells. Stratigraphic and structural modeling was performed to delineate the reservoir framework, then facies and petrophysical modeling, using stochastic simulation algorithms, was performed to delineate the reservoir architecture. 1D basin modeling was performed to retrieve the geohistory and maturation models of the area. Combining both reservoir and basin models was aimed, in this study, at identifying new petroleum prospects and estimating the volume of hydrocarbons within the reservoir intervals of the study area. According to the constructed reservoir and basin models, we identified three new petroleum prospect areas; to the NE, NW, and southern parts of Falak Field; that lead to reliable consistent inferences reasonably have sound impact on the oilfield development phases of the area.

Quantifying the impact of human activities on water quality based on spatialization of social data: a case study of the Pingzhai Reservoir Basin

Abstract In water pollution source research, it is difficult to quantify the impact of human activities on water quality. Based on pollution load theory and the concept of spatialization of social data, this study integrates land-use type, slope gradient, and spatial position, and uses the contribution of human activities to quantify the impact of farmland fertilizers, livestock and poultry wastes, and human domestic pollution on water quality in the study area. The results show that livestock manure is the largest source of total phosphorus (TP) and total nitrogen (TN) discharges in the research area, and domestic pollution is the largest source of chemical oxygen demand (COD) discharges. The total equal standard pollution load (as well as the load of each pollution source and its pollutant amount) is the highest in the Nayong River Basin and the lowest in the Baishui River Basin. The contributions of human activities to TP and TN have similar spatial distributions. The impact of human activities on COD discharge is minimal. The quantitative results of this model are basically consistent with the actual conditions in the Pingzhai Reservoir Basin, which suggests that the model reasonably reflects the impact of human activities on the water environment of the basin.

БИОГЕННЫЕ ЭЛЕМЕНТЫ (АЗОТ И ФОСФОР) В ХАРАНОРСКОМ ВОДОХРАНИЛИЩЕ

Kharanorsk reservoir is a natural and technogenic object, the environmental condition of which is determined by the influence of natural factors and anthropogenic pressure connected with the operation of a hydroelectric power station. A change in the composition and concentration of nutrients is one of the indicators of the environmental changes in water bodies. The spatial distribution of biogenic elements (nitrogen and phosphorus) in the ecosystem of the Kharanor reservoir was analyzed by means of complex expedition studies. The content of mineral forms of nitrogen shows seasonal dynamics. At the same time, natural components of nitrogen compounds are modified by the anthropogenic impact on the ecosystem of the reservoir associated with the condition of the river Onon waters and warm water discharged from the state district power station. The highest nitrite content was registered in summer. Seasonal changes of nitrate ions concentration are also characterized by a summer increase and an almost uniform distribution of their content over the reservoir basin with only a slight increase in the area influenced by temperature factors and in the area of the pumping station. From April to October, the seasonal concentration of ammonium ions has a tendency to increase. The highest concentration of total phosphorus in the reservoir water is recorded in summer. In autumn phosphate concentration is lower than in spring. In spring, an increase in total phosphorus is associated with intra-water processes of decomposition of organic matter. The analysis of long-term data on the Kharanorsk reservoir hydrochemical regime proves a tendency of decrease in concentration of such substances as phosphates, total phosphorus, ammonium nitrogen, and increase in the content of nitrates and nitrites. Constant recharge of the Haranor reservoir by the waters of the Onon river results in an accelerated renewal of the water mass, which prevents stabilization of the ecosystem in comparison with other natural reservoirs. In this regard, the observed changes in the concentrations of nutrients are to a greater extent features of external influence than characteristics of a longstanding isolated reservoir.

Integrated prediction of deep-water gas channels using seismic coloured inversion and spectral decomposition attribute, West offshore, Nile Delta, Egypt

ABSTRACT In the West Delta Deep Marine (WDDM) concession many important gas reservoirs have been recently discovered. To improve the possibility of discovering new natural gas resources, an integrated prediction method approach is used in this study to identify the deep-water gas reservoirs. Post-stack seismic coloured inversion and the spectral decomposition attribute, combined with composite logs of five wells, are used to indicate the lateral and vertical variations of the gas channels in El Wastani Formation. Data conditioning and petrophysical analysis are performed. Both techniques help and improve visual evidence to detect gas channels. Coloured inverted seismic profile show relatively low impedance zones represent the gas channels. Spectral decomposition attribute solves the problem related to thin gas-sand layers through three different frequency magnitude values. The spatial distribution of the gas-channels properties indicates a good calibration at the well location with the effective porosity in the range of 15–35%. Comparing the results of the coloured seismic inversion with the spectral decomposition attribute, the low-frequency range through the spectral decomposition analysis is consistent with the low impedance values represents the gas channels. Furthermore, the methodology followed in the current study is advantageous to identify the gas reservoirs in various basins with similar geological settings.

Зональные особенности химического состава вод малых рек бассейна Рыбинского водохранилища

The work is devoted to the study of the chemical composition of small rivers in the southwestern part of the territory of the Vologda region, which form the river flow of the Rybinsk reservoir basin. The determination of the chemical composition of water in rivers is carried out by generally accepted methods according to standard procedures. A distinctive feature of the river waters of the studied drainage basin is their significant difference in color and color intensity, total iron ion content, and ratio of basic anions. Most of the catchment area of this territory is represented by swamps and numerous lakes, many of them are sources of small and medium length watercourses. A comparative analysis of the ion-salt composition of the waters of rivers shows a certain similarity in the manifestation of the zonal features of the formation of their chemical composition. The composition of the water of the rivers in its salt part is mainly due to the climatic conditions. The waters of the rivers have a hydrocarbonate and sulphate-hydrocarbonate magnesium-calcium composition and relatively low mineralization. Statistical processing of the results of analytical data shows a high correlation in terms of color, permanganate oxidation and chemical oxygen consumption of the investigated water samples. Nutrients represented by the mineral forms of nitrogen and phosphorus in river waters within the studied catchment basin are determined by similar concentrations. A single directivity has been established in the distributions of the contents of heavy metal ions. From the number of heavy metal ions (iron, manganese, aluminum, copper, zinc, nickel, lead, arsenic, chromium, cadmium), which were determined in the analyzed samples, the excess of water quality standards for fishery water bodies was established of by iron and manganese ions. Excess of the established standards of quality of natural waters for other identified ions was not detected.

Impact of Climate Change on Hydrological Parameters in Dharoi Dam Reservoir Basin, India

Impact of Climate Change on Hydrological Parameters in Dharoi Dam Reservoir Basin, India

СОСТАВ И СТРУКТУРА СООБЩЕСТВ ФИТОПЛАНКТОНА РЕКИ САМАРЫ (БАССЕЙН САРАТОВСКОГО ВОДОХРАНИЛИЩА)

СОСТАВ И СТРУКТУРА СООБЩЕСТВ ФИТОПЛАНКТОНА РЕКИ САМАРЫ (БАССЕЙН САРАТОВСКОГО ВОДОХРАНИЛИЩА)

Wet atmospheric deposition of nitrogen and phosphorus and estimation of their contributions to the lake in typical subtropical reservoir basins

Wet atmospheric deposition of nitrogen and phosphorus and estimation of their contributions to the lake in typical subtropical reservoir basins

Massive mortality of the giant freshwater mussel Anodontites trapesialis (Lamarck, 1819) (Bivalvia: Mycetopodidae) during a severe drought in a Neotropical reservoir.

In 2012, a severe drought struck the southeastern of Brazil compromising the Paraná River Basin reservoirs. Here, we described how this climatic event promoted a massive mortality of the giant freshwater mussel Anodontites trapesialis in Furnas reservoir and reported the consequences of this phenomenon. In November 2012, three quarters of 100 m2 were sampled in this reservoir, where 812 dead shells of A. trapesialis were analyzed and measured (33 ˫ 133 mm). The species showed an aggregated distribution with high density ( X ¯ : 1.0 - 5.5 ind/m2). Despite the massive mortality detected in field, it was possible to find living specimens in a small channel in the studied area, allowing the species to survive the water level fluctuations. Large adult individuals (100 ˫ 124 mm) were more affected by drought than juveniles, accounting for about 90% of the dead mussels analyzed. Two years after the massive mortality event, water level was not reestablished and a terrestrial succession (with elevations in the concentration of organic matter and calcium in sediment) was observed in the studied area. We verified that the damming associated with extreme climatic events affect negatively the populations of A. trapesialis and should be faced as a conservationist problem.

Turbidez y profundidad de disco de Secchi con Sentinel-2 en embalses con diferente estado trófico en la Comunidad Valenciana

<p>Transparency or turbidity is one of the main indicators in studies of water quality using remote sensing. Transparency can be measured <em>in situ</em> through the Secchi disc depth (SD), and turbidity using a turbidimeter. In recent decades, different relationships between bands from different remote sensing sensors have been used for the estimation of these variables. In this paper, several indices and spectral bands have been calibrated in order to estimate transparency from Sentinel-2 (S2) images from field data, obtained throughout 2017 and 2018 in Júcar basin reservoirs with a great variety of trophic states. Three atmospheric correction methods developed for waters have been applied to the S2 level L1C images taken at the same day as the field data: Polymer, C2RCC and C2X. From the spectra obtained from S2 and the SD field data, it has been found that the smallest error is obtained with the images atmospherically corrected with Polymer and a potential adjustment of the reflectivities’ ratio of the blue and green bands (R<sub>490</sub>/R<sub>560</sub>), which allow the estimation of SD with a relative error of 13%. Also the C2X method presents good adjustment with the same bands ratio, although with a greater error, while the correction C2RCC shows the worst correlation. The relationship between SD (in m) and turbidity (in NTU) has also been obtained, which provides an operational method for estimating turbidity with S2. The relationship for the different reservoirs between SD and chlorophyll-a concentration, suspended solids and dissolved organic matter, is also shown.</p>

NeStRes – Model for Operation of Non-Strategic Reservoirs for Irrigation in Drylands: Model Description and Application to a Semiarid Basin

Water availability in dry inhabited environments has usually been promoted by large strategic reservoirs, but small non-strategic ones, built by farmers and communities, are unable to cope with long term droughts and inappropriate for human supply. Nevertheless, small reservoirs promote water spatial distribution and play a major role for livelihood in rural areas. To fill the gap of operation methods for non-strategic reservoirs used for irrigation where water is a limiting factor, the NeStRes model was developed. The model is composed of three modules: i) hydrological: to define the reliability of water withdrawals from the reservoir; ii) agricultural: to simulate crop production based on water availability; iii) economic: to compute the possible income from irrigated agricultural crops. NeStRes was applied to 91 reservoirs of the semiarid Banabuiu River Basin – BRB, Brazil. The simulations indicated that the maximum income from the cultivation of maize is obtained when the reservoirs are intensely used, drying completely in one to two thirds of the time. Adoption of a fixed reliability level of daily water supply (54%, in the BRB) generates at least 85% of the maximum possible income for all simulated reservoirs. This model application suggests a paradigm change in the operation of small non-strategic reservoirs in drylands: to use water for crop production and save the revenue, instead of saving water, which is susceptible to evaporation. Although high reliability level is desired for human supply by strategic reservoirs, non-strategic ones can be more intensely explored to generate income from irrigated agriculture in drylands.

Tight tuff reservoir characteristics and its controlling factors: A comparative study of the Permian Tiaohu Formation and Carboniferous Haerjiawu Formation in the Santanghu Basin, NW China

Tight oil resources have been found in tight tuff reservoirs in many oil and gas bearing basins. The tight tuff reservoir developed in the Santanghu Basin (NW China) has provided an excellent opportunity for further research to enhance our cognition and understanding of tuff reservoir characteristics. This study focuses on the differences in the basic characteristics in petrologic features, reservoir space, and physical properties between the Tiaohu and Haerjiawu formations tuff reservoirs, then determines the formation mechanism causing these differences. (1) The tuff samples of the Tiaohu Formation mainly consist of vitric fragments, and quartz and albite are the major mineralogical components. However, the crystal fragment content is much higher in the Haerjiawu Formation tuff, and albite and anorthite are the major components. (2) Primary pores and the interparticle pores among authigenic minerals formed during alteration are the main pore types for both the Tiaohu Formation and Haerjiawu Formation tuffS. (3) The Tiaohu Formation tuff reservoir is characterized by high porosity (ranging from 10% to 25%) and relatively low permeability (on the order of 0.01–0.50 mD), while that of the Haerjiawu Formation is characterized by lower porosity (<10%) and lower permeability (mainly <0.1 mD). (4) Alteration and compaction processes contributed most to the pore formation in both the Tiaohu and Haerjiawu tuff reservoirs. Hence, the changes in total tuff reservoir porosity can be explained by the evaluation of compaction residual porosity and alteration porosity. The vitric fragments in the Tiaohu Formation originated from acidic or intermediate-acidic volcanic ashes, which are more liable to be altered than the basic volcanic ashes that formed the crystal fragments in the Haerjiawu Formation. Moreover, the Haerjiawu Formation tuff reservoir is buried hundreds of metres deeper than the Tiaohu Formation in general, and thus, experienced stronger diagenetic compaction, which indicates fewer residual pores for Haerjiawu Formation tuff samples. The nature of tuff and the deeper burial depth are the major reasons for the worse physical properties of the Haerjiawu Formation tuff reservoir.

Palaeontological framework from Pirabas Formation (North Brazil) used as potential model for equatorial carbonate platform

Abstract The Pirabas Formation (early to middle Miocene) from the equatorial margin of North Brazil is characterized by a shallow-marine carbonate platform with high fossil diversity and abundant micro- and macrofossil remains. The Pirabas Formation represents a unique carbonate system along the Atlantic margin of South America that developed before the onset of the Amazon delta. We studied the palaeontology and lithofacies of outcrops of the uppermost Pirabas Formation and found that was deposited in a coastal marine environment with marginal lagoons under the influence of a tidal regime and tropical storms. The remains of calcareous algae, molluscs, crustaceans, echinoiderms, bryozoans, solitary corals, fish and marine mammals, together with foraminifera, ostracods and other marine microfossils, shaped a biogenic framework, that together with the post-depositional processes of dissolution of skeletal grains, is responsible for the mean packstone-floatstone porosity of 14.9%. The palaeontological framework and the petrophysical characterization of the carbonate rocks from the uppermost Pirabas Formation outcrop represent a baseline to interpret the entire Pirabas Formation in the subsurface stratigraphic sections (cores) of this important Neogene unit. Considering that carbonate rocks account for ~50% of oil and gas reservoirs around the world, this research provides a model for Neogene tropical carbonate deposits useful for carbonate petroliferous reservoirs in the Brazilian equatorial basins.

Phytoplankton of the Usa River and Its Tributaries (Kuibyshev Reservoir Basin)

Abstract—Data on the status of summer phytoplankton of the Usa River and its tributaries are given. In total 184 taxa of algae with a rank lower than the genus from eight divisions were recorded in algal flora, with Bacillariophyta (43–57% of the composition) and Chlorophyta (23–47%) predominating in the rivers. The abundance range in algocenoses was 0.02–5.2 million cells/L; of biomass, 0.01–1.8 mg/L; the content of chlorophyll-a, was 0.01–3.1 μg/L. The ecological heterogeneity along the watercourse causes significant dynamics in the taxonomic composition, which is characterized by mosaic distribution in different areas, and changes in the quantitative structure of plankton communities. An increase in the species diversity, abundance, biomass, and chlorophyll-a concentration from the source to the mouth of rivers is noted. The ecotone effect in the zone of mixing and transformation of the waters of the lower reaches of the watercourses and Usinskii Bay of the Kuibyshev Reservoir is expressed in an increase in the diversity and amount of algae, an increase in the coenotic role of Cyanoprokaryota and planktonic green algae of the Chlorococcales order, which are dominant in Usinskii Bay. The influence of hydrological conditions, the content of nutrients, and the anthropogenic impact on the formation of algocenoses is discussed. The taxonomic composition, distribution, structural characteristics of algocenoses in the absence of nutrient limiting depend on hydrological factors, and biotopic heterogeneity of natural and anthropogenic origin have been studied, whereas their relation to the content of nutrients in eutrophic conditions has not been revealed. The Shannon species diversity index varied from 0.5 to 2.7 bits/specimen in the river algocenoses. The minimum values were noted on the upstream sections of the rivers; the complexity of the structure is typical for the algocenoses of the mixing zones of the waters of the upper part of Usinskii Bay and the mouths of the Muranka and Tisherek rivers, as well as for the communities of the sections of rivers with anthropogenic impact.

Unwanted appearance of invasive species in the transboundary Irtysh river basin

This paper presents data on the size and weight characteristics of the Amur sleeper (Perccottus glenii) in floodplain reservoirs of the transboundary Irtysh river basin: Bezymyannoe Lake, Amalby Lake, Mangadaevo Lake (Yarkovsky District), and Andreevskoe Lake (Tyumen District) of the Tyumen Region.

Identification of critical erosion prone areas in Temengor Reservoir Basin using Universal Soil Loss Equation (USLE) and Geographic Information System (GIS)

In this study, the Geographic Information System (GIS) was integrated with the Universal Soil Loss Equation (USLE) model to identify the risk of erosion at 360,000 ha in the Temengor Reservoir Basin. GIS was utilized as a tool for generating, manipulating and spatializing data from government agencies for sediment yield modelling and offering spatial input data to the erosion model. Meanwhile, USLE was used to predict the spatial distribution of the sediment yield on the grid basis. The five main parameters used in this study were the rainfall erosivity factor (R), topographic factor (LS), soil erodibility factor (K), crop management factor (C) and practice support factor (P). The R factor was calculated based on the annual rainfall data of the study area. The soil survey data was used to generate the K value and Digital Improvement Model (DEM) of the study area was used to generate LS factor. The values of C and P factors were derived from the land use map. After generating all parameters, analysis was performed to estimate the soil erosion using USLE model with spatial information analysis approach. It was discovered that the average annual soil loss in the study area was 8 t ha-1 year-1 and only 4% of the total area was under extreme erosion risk.

High-resolution sequence stratigraphy of a cretaceous mixed siliciclastic-carbonate platform succession of the Sergipe–Alagoas Basin, NE Brazil

The Sergipe–Alagoas Basin, in northeastern Brazil, has extensive exposures of carbonate rocks that may be studied as analogues to hydrocarbon reservoirs. The outcrops are equivalent to the pre-salt and post-salt reservoirs of the Campos and Santos basins, the most important hydrocarbon exploration targets nowadays in Brazil. Outcrops and well logs of the Riachuelo Formation, the most important for analogue studies of Cretaceous marine carbonate reservoirs of the Campos Basin due to the great variability of facies, are described and interpreted to identify the depositional cycles and stratigraphic sequences. Three unconformities formed during the initial drift phase of the basin are recognized. The depositional setting of the studied section changes from a siliciclastic-dominated continental to shallow-marine mixed siliciclastic-carbonate at the base to a shallow-marine carbonate platform in the upper part. The transgressive–regressive (T–R) sequence model was used for the stratigraphic analysis, leading to a stratigraphic framework of three third-order T–R sequences, with an estimated duration of approximately 2.0, 4.5 and 1.5 Ma, respectively. Consequently, the higher frequency cycles identified in the well logs represent a timing of circa 140,000 years, and are interpreted as fourth-order depositional cycles.

Artificial Neural Networks Method for Prediction of Rainfall-Runoff Relation: Regional Practice

Rainfall and runoff relation is very important on efficient use of water resources and prevention of disasters. Nowadays, different methods of artificial intelligent techniques are applied to determine the rainfall-runoff relations. Artificial Neural Networks (ANN) is used for the present study. Also, Classical methods such as Multiple Linear Regression (MLR) are used. In this study, the data obtained from USA Waltham Massachusetts Stony Brook Reservoir basin was taken. 731 daily data of rainfall, runoff, and temperature were used to generate input data in the Multi Linear Regression and Feed-Forward Back-Propagation Artificial Neural Network models. The results obtained were compared with the actual results.