Water-bearing Rocks Research Articles

Stochastic discontinuum analysis of hydrocarbon migration probability around an unlined rock cavern based on the discrete fracture networks

This paper presents a framework for application of stochastic discontinuum method for evaluating the uncertainty of hydrocarbon migration around an unlined rock cavern (URC) in water-bearing rock formations. The occurrence of hydrocarbon migration in fractures around the URC was calculated by using a numerical technique based on the migration tracing algorithm and pathway analysis through discrete fracture network (DFN) realizations. The numerical modeling of hydrocarbon migration and uncertainty analysis of fluid flow processes were performed for different arrangement of hydraulic boundary conditions with respect to water curtain pressure head (WCPH) and height of oil in the cavern. The results of numerical simulations demonstrate that the uncertainty and spatial distribution of hydrocarbon migration around URC are very sensitive to the hydraulic boundary conditions, and the geometrical configuration of fractures. The migration probability of both gas and oil decreases non-linearly by increasing the WCPH; however, the rates of decrement for oil and gas are completely different. The maximum migration probability of gas and oil occurred in the case of minimum and maximum height of oil in the cavern, respectively. For most of the hydraulic boundary conditions, the distance and probability of migration for gas are much higher than those for oil. The zones prone to gas and oil migration are mainly concentrated in the neighboring area of the cavern roof and vertical walls, respectively. However, due to the heterogeneous flow system and irregular interconnected fracture networks, the gas and oil migration are possible in the regions below the oil level and below the water bed, respectively. Moreover, the mean and standard deviation of total length and number of migrated fractures around the URC decrease by increasing the WCPH. In addition, both the number of gas migrated fractures and gas escape probability decrease by increasing the height of oil in the cavern. These findings might prove useful for taking optimal decisions in an uncertain framework and for a better design analysis of unlined rock cavern.

FACTORS AND DYNAMICS OF VARIABILITY OF ZMEINYI ISLAND ROCKS FILTRATION PROPERTIES

Problem Statement and Purpose. Transmissivity (T) is one of the most important parameters in determining aquifer productivity and generally estimated from pumping tests. This study (for the period 01.2005-04.2008) focuses on the transmissivity behavior dynamic for pressure fractured-rock aquifer in the Devonian deposits of the Zmeinyi island. It presents a temporal variations in transmissivity under the influence of sea level, distance Earth-Moon and axial rotation of the Earth.Data & Methods. In the paper have studied the data from the experimental pumping test of the exploited well No 2, situated in the northwestern part of Zmeinyi island, having a depth of 50 m. Time-recovery plots (270 plots) were analyzed by using Theis Jacob method to obtain transmissivity. The geologic setting in the study area is generally composed of the Paleozoic deposits, including the Silurian and Devonian, as well as the Cenozoic formations. The lithology of the aquifer varies widely and includes conglobreccia, sandstone, conglomerate, mudstone and siltstone. By results of well logging tests for water-bearing rocks the following thickness intervals were established: 38.0-54.6 m; 57.6-74.0 m; 80.8-109.4 m. Within the upper interval represented by conglomerates, there are two aquifer subhorizons, separated by weakly fractured rocks, that is by relatively waterproof layer. A comparison of water-bearing rocks depth intervals and static water levels shows that ground water in the upper subhorizon is under pressure.Results. On the basis of a cross-spectral analysis of time series (using frequency transfer functions, coherence spectra and phase difference) correlations were revealed between variations of transmissivity and the following factors: sea level, mean Earth-Moon distance, Earth rotation speed. Variations in the correlation between transmissivity and factors influencing it allow assessing stress-strain state of water-bearing rocks. The results obtained from cross-spectral analysis showed that in the low frequency range, transmissivity is related to these factors linearly. In the range of periods from 5.5 to 11 days the Earth-Moon distance increases, the transmissivity value decreases and vice versa, with decreasing Earth-Moon distance (T) increases. For the same periods for accelerated motion of the Earth (T) increases, and vice versa, a decrease in Earth’s rotation speed is accompanied by a decrease of (T). For the sea level, for periods from 5.5 to 11 days, transmissivity is in the antiphase with sea level variations. The increase in sea water level corresponds to a decrease of (T) and decrease of sea water level corresponds to increase of (T).

Anchorage mechanism and pullout resistance of rock bolt in water-bearing rocks

The purpose of a rock bolt is to improve the mechanical performance of a jointed-rock mass. The performance of a rock bolt is generally evaluated by conducting a field pullout test, as the analytical or numerical evaluation of the rock bolt behavior still remains difficult. In this study, wide range of field test was performed to investigate the pullout resistance of rock bolts considering influencing factors such as the rock type, water bearing conditions, rock bolt type and length. The test results showed that the fully grouted rock bolt (FGR) in water-bearing rocks can be inadequate to provide the required pullout resistance, meanwhile the inflated steel tube rock bolt (ISR) satisfied required pullout resistance, even immediately after installation in water-bearing conditions. The ISR was particularly effective when the water inflow into a drill hole is greater than 1.0 l/min. The effect of the rock bolt failure on the tunnel stability was investigated through numerical analysis. The results show that the contribution of the rock bolt to the overall stability of the tunnel was not significant. However, it is found that the rock bolt can effectively reinforce the jointed-rock mass and reduce the possibility of local collapses of rocks, thus the importance of the rock bolt should not be overlooked, regardless of the overall stability.

ОЦЕНКА ИЗМЕНЕНИЯ КОЛЛЕКТОРСКИХ СВОЙСТВ ВОДОНОСНЫХ ПОРОД ПРИ ХРАНЕНИИ ГАЗООБРАЗНЫХ УГЛЕВОДОРОДОВ

The current economic and energy situation in industrial regions of Ukraine, along with need to address the problems of importing and developing its own natural gas deposits, predetermines the need to establish the suitability and search for aquiferous geological structures for accumulation of seasonal reserves of gaseous hydrocarbons. Based on the analysis of geological-structural and hydro-geodynamic conditions, West Donbass was divided into districts and Leventsovskaya geological structure was chosen, in a section of which the Permian-Triassic aquifer is located. Dedicated reservoir is represented by greenish-gray, quartz-feldspar coarse-grained sandstones with interlayers of strongly kaolinized sands and comparatively homogeneous in physico-mechanical properties and granulometric composition. The waters contained in it are characterized by an increased mineralization, high rigidity and are completely unsuitable for domestic and technical purposes. Interpretation of data from the experimental filtration works performed on a site, carried out on a basis of adequate hydrogeological and technological schematization, analytical calculations and graphoanalytical method, showed that the coefficients of filtration and piezoconductivity of an aquifer vary, respectively, from 1.51 to 3.66 m/day and 4.5 to 9.1·106 m2/day. The calculated values of filtration parameters allow considering this reservoir as promising water-bearing gas storage and can be used to determine its capacitive characteristics. To assess the degree of influence of accumulated gas on filtration properties of the dedicated reservoir and the hermeticity of the assumed storage, a series of special laboratory experiments was conducted, based on a reproduction of a long-term contact of gaseous hydrocarbons with samples of water-bearing rocks under pressure and periodic determination of their permeability in a TriSCAN stability meter. The studies have established a significant (15-20%) increase in absolute permeability of an aquifer and underlying rocks when hydrocarbon gases are stored within. It is shown that the destructive changes of a rock matrix caused by aggressive gas impact occur in a near-surface zone with a thickness of several millimeters and will not create a threat of depressurization of the storage during a designed period of operation.

Blast Induced Crack Propagation and Damage Accumulation in Rock Mass Containing Initial Damage

Blast induced rock mass damage and crack propagation play important roles in structure safety and stability in mining, quarrying, and civil constructions. This paper focuses on the effect of small blasthole diameter blast on crack propagation and damage accumulation in water‐bearing rock mass containing initial damage composed of inherent geological discontinuities and previous multiblast induced damage. To elucidate this effect, theoretical analysis of calculation method for several important blast influencing factors is firstly presented. Secondly, definition of a practical damage variable using ratio of longitudinal wave velocity in rock mass before blast occurrence to that after blast occurrence and derivation of a damage accumulation calculation equation accounting for initial damage and blasting effect are described. Lastly, a detailed description of the conducted in situ blast tests and plan layout of the sonic wave monitoring holes is reported. The results indicate that blast activates and then extends the initial cracks in rock mass, leading to accumulation of rock mass damage. The rock mass damage accumulation can be conveniently quantified using the proposed damage variable. When the damage variable reaches its threshold of 0.19, occurrence of damage in the surrounding rock mass is indicated. It is also found that the blast induced rock mass damage extent and the blast induced vibration velocities decrease nonlinearly with increasing the distance between blast source and monitoring position.

Interpretation of environmental tracer data for conceptual understanding of groundwater flow: an application for fractured aquifer systems in the Kłodzko Basin, Sudetes, Poland

ABSTRACT Environmental isotopes and hydrogeological data have been used for the construction of a conceptual model of fresh groundwater flow in the Kłodzko Basin, Sudetes, Poland. The model has allowed the verification of a groundwater circulation scheme resulting from the general morphological assumptions and the recharge role to the surrounding mountains. Combined interpretation of the tritium ages and the isotopic altitude effect allowed determining the volume of water-bearing rock V r and hydrogeological parameters of systems drained by springs and wells. Prior to the final determination of the recharge zone of individual objects, calculations were made for the thickness of the flow zone (h) and the distance from the recharge zone to the drainage point (L). The recharge areas for springs are located within a distance of 1–1.5 km and are characterized by a width of 0.75–1.65 km. The recharge area of wells is located in significantly longer distances of 2.1–12 km but yet definitely lower width. The recharge of groundwater from the Western direction seems to be obvious for all the wells and springs located westward from Nysa Kłodzka River. The eastern component of the recharge appeared during the interpretation of the well in Długopole. Dedicated to Professor Peter Fritz on the occasion of his 80th birthday

On the non-Darcian seepage flow field around a deeply buried tunnel after excavation

When a tunnel is excavated in a water-bearing rock mass, groundwater may flow toward the tunnel and cause some adverse effects. Although the non-Darcian hydraulic characteristics of fractured rock masses have been extensively studied by laboratory and field tests, the non-Darcian seepage flow was seldom taken into account in engineering practice so far. This paper investigates the non-Darcian seepage flow around a deeply buried tunnel after excavation. In-situ water injection tests were conducted to investigate the hydraulic characteristics of the rock mass, and a formula was derived to quantify the non-linear hydraulic conductivity from the test data. A numerical method based on non-linear finite element method was then proposed to simulate the non-Darcian seepage flow toward the tunnel. By comparing the numerical results of non-Darcian seepage flow with the results based on a traditional Darcian assumption, it is found that the difference of hydraulic head distribution is slight, but the difference of flow velocity and total discharge is obvious. The Darcian assumption provides rational discharge estimation only when the actual flow velocity around the tunnel is similar to the flow velocity in in-situ tests; however, the non-Darcian assumption is able to obtain a more rational result especially when the number of test pressure steps used in in-situ tests is limited.

The Implementation of 2-D Resistivity Method in Verifying Paleozoic Aquifer Properties at Bukit Chondong, Perlis (Malaysia)

The research was conducted using 2-D resistivity in verifying Paleozoic aquifer. Since most geologic materials behave as electrical insulators, surface measurements of earth resistivity are controlled by the electrolytic ability of interstitial water. The subsurface distribution of water is controlled by the porosity of the formations. The study area is at Bukit Chondong, Beseri, Perlis. Bukit Chondong is made of sedimentary rock which mostly is sandstone. Bukit Chondong is from uppermost of the Kubang Pasu Formation that represented by a thick unit of grey mudstone interbedded with sandstone. The Kubang Pasu Formation was influenced by shallow marine during the early age. Paleocurrent and fossils traces were found on the mudstone at the study area. The area is suspected to be a Paleozoic aquifer because the sandstone can be a productive aquifer with diffuse flow. The water movement in sandstone is through the fractures and joints. Most of the water stores and transmits in sandstone. The interbedded sandstone and mudstone is one of the aquifer characteristic. Sandstone and mudstone are water-bearing rocks and low-permeable rocks respectively. The data was processed according to the geological information of the study area since there was an outcrop. The study area have low resistivity value which both sandstone and mudstone give less than 800 Ohm-m due to the water content (Sulphide and clay).

EFFECTS OF THE JANUARY 30, 2016, Mw=7.2 ZHUPANOVSKY EARTHQUAKE ON THE WATER LEVEL VARIATIONS IN WELLS YUZ-5 AND E-1 IN KAMCHATKA

This paper describes the water level variations in wells YuZ-5 and E-1 inKamchatkaduring the Zhu­panovsky earthquake that occurred on January 30, 2016 (M w =7.2, Н =180 km). The distances from the Zhupanovsky earthquake epicenter to wells E-1 and YuZ-5 were 70 and 80 km, respectively. In well YuZ-5 , the water level raised by 9.4 cm during 45 minutes after the seismic wave arrival. This effect was caused by a combination of a co-seismic rise in the water level due to the volumetric compression of the water-bearing rocks during fracturing in the earthquake source and an impulse increase in the fluid pressure near the wellbore during the seismic shocks. We estimated the amplitude of the coseismic water level increase (D h =7.3 cm) and the strain value resulting from the volumetric compression of the water-bearing rocks, which is consistent with the estimated value of the coseismic volumetric deformation in the area of the well at the depth of 500m: D 1 = –4.5×10 –8 . This estimation was based on the model of the dislocation source in the homogeneous isotropic elastic half-space with the parameters of the Zhupanovsky earthquake focal mechanism. After the earthquake, the water level dropped for three months at an amplitude of about ~40 cm. In order to estimate the radius of the well sensitivity to the pressure drop source, we used the model of water level lowering that followed the pressure drop in the aquifer at a distance to the well as a result of the improved filtration properties of the water-bearing rocks after the seismic shocks. The estimated radius of the well sensitivity, R is 450 m. For 3.5 months before the Zhupanovsky earthquake, ~20 cm increase in the water level was observed, which is anomalous in comparison with the average seasonal variations of the water level, as shown by the long-term observations. In our opinion, such a rise in the water level occurred in the process of the earthquake preparation, and can thus be viewed as its precursor. In well E-1, a sequence of water level changes manifested a hydrogeodynamic precursor: the water level dropped at an increased rate for 21 days before the earthquake, and raised at an amplitude of 3.7 cm during one month after the earthquake. The hydrogeodynamic precursor detected in real time gave grounds for forecasting a highly probable strong earthquake at a distance of up to 350 km from wells E-1 within a month. This forecast was reported to the Kamchatka Branch of the Russian Expert Council (KB REC) on January 21, 2016. The Zhupanov­sky earthquake occurred on January 30, 2016, and its magnitude, time and location correlated with the prediction. The case of this earthquake shows that the Kamchatka Branch of the Federal Research Center ‘Geophysical Survey of RAS’ has the system of water level observations and data processing, which is capable of diagnosing (close to real time and retrospectively) different types of hydrogeoseismic variations in the water level in wells in case of strong seismic events, and detecting the hydrogeodynamic precursors of strong earthquakes.

Distribution and speciation of iodine in drinking waters from geochemically different areas of Bryansk region contaminated after the Chernobyl accident in relation to health and remediation aspects

Chemical composition of drinking water from different sources was studied in private farms distributed in areas of the Bryansk region contaminated by radionuclides after the Chernobyl accident. Concentration of major ions showed clear relation to water-bearing rocks and local anthropogenic contamination (e.g. N, P). Drinking water was in general impoverished in I (Ме=5.76μg/l that is below the lower limit of sanitary standard equal to 10μg/l). Thermodynamic modeling based on chemical composition of the samples showed that the predominant form of iodine is iodide and it forms mineral complexes CaI+, CaI2, MgI+, MgI2, etc. that explains iodine concentration on carbonate barrier in soils and rocks. Complexes' formation may have contributed to radioiodine retention in water during its fallout with further natural decontamination of aqueous phase during water filtration through soils and sediments enriched in carbonates and organic matter. Comparison with distribution of thyroid cancer cases among rural population revealed a tendency of the inverse relation between the number of cases and iodine content in dug well waters; the finding needs further investigation.

Heat-Induced Electrical Variation of Water-Bearing Porous Rock in Coal Fire Area

Heat-Induced Electrical Variation of Water-Bearing Porous Rock in Coal Fire Area

Effect of pore water of fine sediments on the ecological conditions of hydrosphere under oil-and-gas technogenesis conditions

Experimental models are used to study the poorly known function of pore waters, i.e., their role in hydrosphere pollution. This issue is studied as applied to modern bottom sediments, soil-forming grounds of the aeration zone, and impermeable clays in aquifers. The natural and technogenic geodynamic loads, accompanied by compaction and destruction of water-bearing rocks, are shown to intensify the processes of pore water pressing with the release of rock-forming elements, heavy metals, and organic substances into bottom water layers in water bodies, free soil or intermediate waters. This results in an environmental damage to water bodies, which could be used for drinking water supply and fishery. This study is of particular importance in areas of present-day oil and gas production.

Underground water in Sukhodol Bay area (South Primorye)

The paper describes the specific chemical groundwater composition in Sukhodol Bay (eastern Ussuri Bay). The equilibrium between groundwater and carbonate-aluminosilicate minerals in water-bearing rocks was calculated. It was established that a fraction of the studied water was calcite saturated. However, dolomite and magnesium undersaturated groundwater is non-equilibrium with primary aluminosilicates.

Geological-hydrogeochemical characteristics of a “silver spring” water source (the Lozovy ridge)

Geological and hydrogeological characteristics of the Lozovy ridge (Southern Primorye) are studied, as far as karst phenomena are widely distributed within its boundaries. Water-bearing rocks of the karst water source “Silver Spring” (“Serebryany Klyuch”), which is located near the bottom of the “Bear’s fang” (“Medvezhiy klyk”) cave, are investigated. It is found that karst rocks are presented by calcite (CaCO3), and an accessory mineral is barite (BaSO4). It is determined that among the trace elements forming the composition of carbonate water-bearing rocks the maximum concentrations are typical for Sr, Ba, Fe, Al, Za, Mn, Cu, and Ni. Also, the chemical composition of the waters taken from the “Silver Spring” water source is studied. These waters are fresh, hydrocarbonate, calcium, and weakly alkaline. Among the elements of the spring, such elements as Sr, Ba, Fe, Al, Zn, Mn, Cu, and Ni have the maximum concentration. The other elements have concentrations less than 1 µg/l.

Ground and Intermediate Water Equilibrium with Water-Bearing Rock Minerals (Moldova) under Anthropogenic Impact

The calculation results of ground water equilibrium with the major water-bearing rock minerals (Moldova) are presented under the condition of anthropogenic impact. As a calculation model the HydroGeo software is used. It is shown that both “ground water-rock” and “intermediate water-rock” systems are in equilibrium with a number of minerals.

Chemical Composition of Bottom Sediments in Small Mountain Rivers (Altai, the Russian Federation)

The article deals with the chemical composition of bottom sediments in the small mountain rivers Aktru, Tyute, and Uznezya (Altai, Russia). It is established that as compared to small and middle plain rivers in Taiga zone, Siberia bottom sediments of the Aktru River contain less amount of K, Na, V, Cr, Mn, Ni, Al, Si, Ti, Sr, approximately the same – Fe, Co, Cu, Zn, Pb and more – As, Ca, Mg. It is suggested that there is a sharp increase of relative Al, Na, K and Si shares from the upland to lowland due to both weathering products accumulation of primary alumosilicates in bottom sediments and export of Ca and Mg from them when dissolving carbonate minerals. Composition transformations of bottom sediments is non-linear and considerably depends on composition of underlying and water-bearing rocks and water exchange intensity that manages time, conditions, and stages of interactions in “water – organic matter – rock” system.

Groundwater of Abu Dhabi Emirate: a regional assessment by means of remote sensing and geographic information system

Mapping of geological, topographical, and hydrological elements is critical for understanding and assessing the regional hydrological setting in an arid region. In this study, a synergistic approach has been developed, which uses a combination of remote sensing data and geographic information system (GIS) to map factors controlling groundwater recharge, discharge, and quality across the Abu Dhabi Emirate. The Spectral Angel Mapper (SAM) algorithm, which uses a n-D angle to match the pixels to reference spectra, was used to map new water-bearing rocks, and the deterministic eight-node (D8) algorithm, which allows flow to only one of the eight neighbors based on the direction of steepest descent, was used to map paleochannels. The terrain category was applied to simulate seawater intrusion from digital elevation model (DEM). New maps of lithology, normalized difference vegetation index (NDVI), and paleochannels were derived and interpreted from multi-sources of remote sensing data. The study indicated that the area was produced by a fluvial and eolian process and recharged by local, intermediate, and regional flows. The results showed that the Oman and Hafeet Mountains are the natural sources of groundwater recharge as well as HCO3, Ca, Na, and Mg in groundwater. The mapped factors were spatially correlated with hydrologic anomalies observed in groundwater wells. The integrated approach is timely, cost-effective, and can be used in arid regions for numerical modeling as well as water balance analysis.

THE ROLE OF HYDROGEOCHEMICAL FACTORS IN KARST PROCESSES ON THE TERRITORY OF RIVNE NPP

The purpose of the research is to identify the complex impact of hydrogeochemical factors to karst processes and estimation of its magnitude. Methodology. Methods of non-parametric Spearman rank correlation coefficient and multiple linear regression were applied for data processing and statistical connection searching. Finding. The availability of statistically significant reverse connection between Ca2+ in the groundwater of Upper Cretaceous aquifer and values of hydraulic conductivity and temperature were established after the data estimation as well as direct connection between Ca2+ in research aquifer and its pH values. Results. The results of the research can be interpreted as follows. Statistically significant reverse relationship between Ca2+ in research aquifer and values of hydraulic conductivity exists because of slow groundwater movement and prolonged contacting with water-bearing rocks. As follows, much more Ca2+ migrate to groundwater. Availability of significant reverse connection between Ca2+ in the groundwater of Upper Cretaceous aquifer and its temperature can be explained through: a) ability of carbon dioxide to dissolve faster in cold water and to transform carbonates to bicarbonates; b) possible divergence from regional trend; c) lack of data and small research area.The direct correlation between Ca2+ in research groundwater and pH values indicates that bicarbonates, formed by the interaction carbonate rocks with groundwater, dissociate into Са2+ and НСО3-, thereby preventing СаСО3 forming and carbon dioxide releasing. As a result the environment changes from acidic to alkaline. Considering all of the above we can conclude, that hydrochemical, temperature and hydraulic factors enhance the carbonates dissolution and therefore karst processes.

Geoelectric response of porous media in water and grout injection processes

Significant changes in spontaneous potential and exciting currents are observed during water and grout injection in a simulated porous media. Obvious correlations between the seepage flow field and the electric field in the porous media are identified. In this work, a detailed experimental study of geoelectric field variation occurring in water migration was reported by analyzing water and grout injection processes in a simulated porous media. The spontaneous potential varies linearly with the thickness of unsaturated porous media. Very interestingly, the spontaneous potential generated in the second grout injection exhibits some “memory” of previous grouting paths. The decreases in spontaneous potential observed during grout injection is very probably due to that the spontaneous potential variations are primarily caused by electro-filtration potential, as indicated by the far larger viscosity of grout compared to that of water. The geoelectric response can be utilized to effectively identify the grouting paths in water-bearing rocks.

Geospatial Information and Environmental Isotopes for Hydrogeological Evaluation: Ras Alam El Rum, Northwestern Coast of Egypt

The present study demonstrates the potential of the geospatial information as well as isotopes and chemical analyses to elucidate the hydrogeological setting of the study area. The main objective of this research is to identify factors affecting the occurrence and quality of groundwater in the study area. The Ras Alam El Rum is the pilot area chosen in the northwestern coast of Egypt to evaluate the carbonate aquifer with emphasis on the Middle Miocene aquifer, which has been explored recently. The average of annual precipitation and surface runoff amounts were estimated to indicate possibility of groundwater recharge, where the water-bearing rocks are mainly fractured. The isotope data indicate that the groundwater was derived from rainwater, the recharge source is local precipitation, and no indication of seawater intrusion was recorded. The salinity of the groundwater is attributed to interaction between the water and aquifer rocks represented by limestone, dolomitic limestone, and marl. The mineral indices obtained from the geochemical model reveal that the groundwater is over-saturated with aragonite, calcite, dolomite, strontianite, and barite. The hydrogeological evaluation of the study area led to recommendations to determine of the suitable areas for exploration of the Middle Miocene aquifer and to protect groundwater from deterioration.