Impermeable Clay Research Articles

UPDATE OF PETROPHYSICAL AND GEOLOGICAL MODEL OF MIDDLE JURASSIC DEPOSITS DURING WELL MONITORING

Tyumen deposits of the studied subsoil area of Western Siberia were put into operation from the middle of the last century, but active development of the YuS2 formation began not so long ago. Currently, the share of wells planned for the operation of this target in the coming years is growing. There are cases when the well performance does not meet the forecasts, which calls into question the correctness of the model used in the development of the target and the structure of the section itself.For high-quality planning of the production stock, it is necessary to prepare a reliable geological basis. The problem of updating the model and improving its reliability lies in the complex geological structure of the formation, which is characterized by high lateral and vertical heterogeneity, as well as in the absence of the basis for all geological models - seismic studies of the investigated subsoil area.The cross-section of the YuS2 reservoirs is complex for petrophysical and geological modeling and is characterized by low reservoir properties. The reservoirs are represented by thin interbeds of permeable interlayers and impermeable clay, carbonaceous and dense rocks.The article examines the specifics of building petrophysical models of YuS2 formations during development drilling using all available core and borehole data to detail the deposits of the Tyumen formation. The purpose of the work is to create own dependencies for interpretation of well geophysical survey data taking into account sedimentation conditions.To detail the Jurassic section, a comprehensive analysis of lithological and petrographic studies of core material from the point of view of geology and petrophysics was used.Facies analysis of the Tyumen deposits in the absence of seismic studies 3D acts as the main factor improving the quality of the predictive ability of geological models in support of development drilling. Adaptation of the petrophysical model to modern geological and technical conditions of well drilling is shown.An integrated approach to the study of the Tyumen formation deposits based on facies and petrophysical studies made it possible to improve the quality of the forecast of the distribution of the reservoir of formation YuS2 and obtain a detailed model. This will help optimize the placement of the production stock, as well as identify the prospects for the development of deposits in areas not covered by drilling.

Hydraulic fracturing using high-boiling fraction of oil as a fracturing fluid

Background: In recent years, there has been a trend towards deterioration in the structure of residual reserves at the fields of Kazakhstan. A significant part of the reserves is located in low-permeability reservoirs and in the zones not covered by flooding. The main factor negatively affecting the productivity and efficiency of development is the heterogeneity of oil reservoirs.
 Oil-saturated formations are an alternation of permeable oil-saturated sand or limestone and impermeable clay or dolomite layers, lenses and interlayers. Up to 1020 interlayers can be distinguished within the reservoir, which indicates a strong compartmentalization of the reservoirs. Due to the complexity of the structure of oil deposits, it is very difficult or impossible to ensure complete drainage of the entire volume of the deposit and complete coverage of oil displacement by water into production wells through injection wells.
 Aim: Increasing oil recovery in a cost-effective way.
 Materials and methods: Experimental studies of the processes of impact on the bottomhole formation zone with high-boiling oil components were carried out using a laboratory machine for diamond drilling, an installation for determining the permeability of a rock in terms of liquid and gas, an installation for determining oil viscosity, and an installation for pumping fracturing fluid into the reservoir model.
 Results: As a result of applying the hydraulic fracturing method using high-boiling oil components, it is possible to increase the permeability of low-permeability formations and significantly increase oil recovery.
 Conclusion: Due to the geological structure of multi-layer oilfields, water-based gel fracturing fluids to increase oil flow to wells are considered ineffective due to the adsorption of gels with long molecules in the pores of the formation and swelling of the clay particles of the reservoir when they interact with the water-based fluid.

Studi Karakteristik Propertis Tanah di Kecamatan Polen Kabupaten TTS

Knowing soil characteristics is very important for an engineer to ensure the safety of buildings above the ground. Therefore, conducting a soil investigation in the laboratory and field testing The island of Timor, especially in the Polen sub-district, Timor Tengah Selatan district, has fine-grained soil deposits. In the sub-district area, a large dam is being built, namely the Temef Dam and the main road link connecting one city and four regencies on the island of Timor also. This study aims to determine the characteristics of the soil both physically and mechanically through laboratory testing. The results showed that the location in Puna Village was clay of low plasticity, while the Loli Village had high plasticity clay deposits. The higher of soil's plasticity index, the higher the potential for swelling of the soil. The increased swelling potential causes the low shear strength of the soil. Clay with low shear strength cannot support the construction load on it. Therefore, before the construction of the building on it, it is necessary to improve the soil. In addition to its weaknesses, on the other hand, impermeable clay is used in the dam core material, where the location of material extraction is still within reach so that the work becomes economical.

A facies- and sequence stratigraphy-based reservoir model for a carbonate reef complex: South Swan Hills oil pool, Alberta

We present a reservoir model for the South Swan Hills oilfield, Alberta, Canada, developed in a Devonian atoll reef, based on facies analysis and sequence stratigraphy. The analysis illustrates the complex reservoir geometries in such a reef, caused by facies variation from reef margin to reef interior and fluctuations in relative sea level. The latter resulted in cyclic deposition of facies and formation of field-scale sequence boundaries. The model is built on lithofacies analysis from high-resolution core descriptions that recorded lithologies, bioclast type and characteristics, and sedimentary structures. Core descriptions were correlated to well logs, enabling lithofacies to be mapped across the field. Lithofacies distributions permit definition of three distinct reef environments: a reef interior, a reef margin and a terminal shoal. Vertical variability is characterized using sequence stratigraphic interpretations. Two 3rd order and four 4th order sequence boundaries were identified and correlated across the reef. The analysis illustrates the complex reef geometries linked to facies variation from reef margin to reef interior and fluctuations in relative sea level. The latter resulted in cyclic deposition of facies and formation of field-scale unconformities. These and the intervening deposits represent the response to fluctuating sea level.The geological analysis was transformed into a 3-D geocellular model using a sequential indicator simulator. The simulator models lithofacies and, in turn, porosity and permeability distributions based on strong relationships between lithofacies and petrophysical properties for the three representative regions; the interior, margin and terminal shoal. The interior deposits formed forms the bulk of non-reservoir material in the centre of the reef build-up. The margin surrounded surrounds the interior and formed forms a continuous 1–2 km band of reservoir around it. Reservoir thickness is 20–30 m and primarily composed of reef flat deposits. The terminal shoal forms a reservoir body that caps the reef complex, but is disconnected from the bulk of the underlying reef by a thick layer of impermeable clay associated with a sequence boundary. The high-resolution realization displays the geometry and continuity of the reservoir and exposes demonstrates the compartmentalized and variable producibility of the atoll.

Experimental and numerical simulation of solute transport in non-penetrating fractured clay

A set of one-dimensional experimental device for solute transport in non-penetrating fractured clay are developed, which can study the laws of groundwater flow and solute transport under different hydraulic heads, fractured aperture, and thickness of non-penetrating zones. The experimental results show that the solute will quickly reach the bottom of the clay along the non-penetrating fracture, and there is an obvious dominant flow phenomenon compared with the intact clay. According to the experimental data and numerical calculation results, the model parameters of the fracture and each soil layer were identified, and the verified numerical model was used to simulate the solute transport in the non-penetrating fractured clay. The numerical results show that the increase of the thickness for the non-penetrating zone has a significant improvement on the anti-seepage ability of clay, and the increase of the hydraulic head pressure and fractured aperture leads to a faster growth rate of the solute concentration, which indicates that the solute breaks down the lower impermeable clay layer under high head pressure. The research results are of great significance for the bottom anti-seepage layer similar to landfill projects.

Integrating Geophysical, Geochemical and Geotechnical Characteristics to Assess Soil and Groundwater Resources in Ovade, South-South Nigeria

Integrated methods were employed to assess soil and groundwater resources in an oil and gas producing area. Earth resistivity meter was used for the electrical imaging of the subsurface. Physico-chemical, geochemical and geotechnical parameters of soil and groundwater samples were determined. The results of the resistivity data revealed that a high resistive plume with resistivity > 2,000 Ohm-m has penetrated the soil beyond 20 m beneath the surface in some parts. The water samples show mild acidity with pH values in the range 4.3-5.5. Total dissolved solids (TDS) is low 26.55- 38.05 mg/L and conductivity ranges from 55.38-65.60 µS/cm. Iron content in water is fairly high (0.878-0.994 mg/L). Groundwater samples analysis using ultra violet (UV) detector and gas chromatography (GC) show that total petroleum hydrocarbons (TPH) is very low (< 0.01 mg/L and <0.031mg/L) respectively. It can be attributed to the sealing of the confined aquifer by impermeable clay in the case of the groundwater. The average permeability of the soil is 8.098 ´ 10-3cm/s indicating good drainage. The results have shown that shallow boreholes are prone to pollution. Groundwater of the area needs treatment before it can be consumed and integrated methods of investigation should be carried out periodically.

Joint interpretation of electrical and seismic data aimed at modelling the foundation soils of the Maredolce monumental complex in Palermo (Italy)

AbstractThe monumental complex of Maredolce (Palermo) includes an Arab‐Norman castle that stands on the banks of an artificial lake carved out of the calcarenitic rock that rests on impermeable clays. The lake was originally filled with water, thanks to the channelling of a spring. Over time, the lowering of the water table and the high hydraulic permeability of the calcarenites have caused the lake to dry up. A project to renovate the monumental complex has recently been launched. It also provides the study of a possible restoration of the original conditions of the lake. To this end, a multidisciplinary geophysical study was carried out to investigate the geotechnical conditions of permeability of the land outcropping and provides valid technical solutions for waterproofing the bottom of the lake. For this purpose, a joint interpretation was performed using data acquired with different geophysical techniques, such as seismic refraction tomography, electrical resistivity and induced polarization tomography, multichannel analysis of surface waves and horizontal‐to‐vertical spectral ratio of environmental vibration recording. Joint interpretation, supported by cluster analysis techniques, allowed the reconstruction of the geophysical and geotechnical model of the subsoil of the ancient lake, helpful to suggest appropriate techniques for waterproofing the bottom of the lake.

Delineation of shallow structures in the vicinity of Ulu Slim hot spring using seismic refraction and MASW techniques

ABSTRACT Ulu Slim hot spring possesses the highest surface temperature with a reported temperature of 104° C. Hence, the site may be suitable for electric power generation from the geothermal aquifer. In the present work, two seismic techniques are used for shallow structures investigation. The methods are the seismic refraction and the Multi-Channel Analysis of Surface Waves (MASW). The delineation of superficial structures will aid in developing the area without affecting the geothermal system. The instrumentation used for both is similar to a large extent. The main differences are the natural frequencies of geophones used. MASW requires a low natural frequency geophone, whereas seismic refraction uses high-frequency ones. Both techniques are applied at five locations distributed in the 5 km x 5km area. The results obtained from both methods are also tending to confirm with each other. From all profiles, three layers are delineated in the vicinity of the hot spring. The top layer is impermeable clay with an average Vp of 500 m/s and Vs <200 m/s. Underneath this surface layer, the possible aquifer unit characterised by sand, with Vp in the range of 1000 to 2800 m/s and Vs between 200 m/s and 300 m/s. The final layer is the bedrock characterised by a Vp higher than 3700 m/s and Vs greater than 300 m/s. A particularly striking feature of the bedrock structure obtained from our results shows that the bedrock is relatively close to the surface of the vicinity of the hot spring, with a depth of about 5 m. These results confirm the conceptual model proposed for the Ulu Slim hot springs as of granitic origin. Moreover, a plot of the Poisson ratio indicated regions of high water saturation that may represent the hot water pathway to the surface.

Preliminary Investigations for Landfill Siting in Lafia, Nasarawa State of Central Nigeria

Waste management has taken the front purview in recent years due to the evident and attendant effects of indiscriminate disposal of wastes to the environment. This led to the preliminary investigations for the proposed siting of a landfill facility in Lafia and environs of Nasarawa State in Central Nigeria, with the aim of providing valuable information on the suitability for location for the disposal of Municipal Solid Waste (MSW). The combined use of geo-resistivity, geological and hydrogeological investigations were carried out for the study. Ten Vertical Electrical Soundings (VES) of the Schlumberger array was used to investigate the properties of the subsurface lithologies to determine their properties especially, clay, for siting a landfill. Clay, an attenuating material, is significant for siting a landfill facility because it tends to isolate potentially toxic wastes from the environment by slowing down the movement of leachates into groundwater and the environmental. Quantitative interpretation of data of the VES survey using the IPI2win computer software revealed the presence of four to five geologic layers comprising of sandy top soil (247 – 1964Ωm), silty sand (98 – 3488Ωm), clayey-shally/sand (68 – 3922Ωm), saturated clayey sand (31 – 3226Ωm) and loose sand (478Ωm). Clay was found to be abundant in the area and found at depths ranging from 30m to infinity. Geologically, structures like lineaments abound and were analysed; they show a dominant trend in the NW – SE direction from the Rosette Diagram. Lineaments are useful for studies because they are possible conduits where decomposed wastes in liquid form, such as leachates, get transported to pollute groundwater. Hydrogeological studies surveyed Static Water Levels (SWL) measurement from 51 hand dug wells in the study area. The SWL ranges between 5.8m and 37.1m. The data from the SWL was used to construct the absolute water level map in a 3D form to show the flow direction of the groundwater. The study revealed the presence of impermeable clays at VES 1, 2, 3, 9 and 10. This is significant for selection for landfill due to its pollution-prevention properties of groundwater pollution. The investigations carried out in this study show that Shabu, a town located about 8km from Lafia, is likely suitable for siting a landfill facility; because of the abundance of clay at a shallow depth of 30m and with limited preponderance of lineaments.

Reforestation in Venezuela – current situation and future perspectives

The location of the Bolivarian Republic of Venezuela in the tropical region of northern South America, in the Northern Hemisphere, with a total area of 91.64 million ha, of which 49.6 million correspond to natural forests (54.12 % of the national territory). Venezuela shows a series of geographic advantages that allow a rapid growth and development of the trees in comparison with the temperate zones where the growth is extremely slow. However, the occurrence of deforestation processes has intensified in a sustained way in the recent history of the country.&#x0D; In the period from 1920 to 2008, the loss of 26.43% of the forested area has been recorded. Likewise, in the period 1975-1988, deforestation was estimated at 216,000 ha year-1, equivalent to 2.9 million ha in 13 years (Catalan 1992). Deforestation has now increased to worrying levels and according to FAO estimates (2010), in Venezuela, a forested area of more than 288.000 ha year-1 is deforested.&#x0D; In the middle of the 20th century several public and private institutions began an important effort to reforest areas of sandy soils of scarce depth on a bed of highly impermeable clay. With erosion processes generated as a result of strong winds that causes severe damage to the little existing vegetation. It was expected that with the passage of time this region could become a desert in the oriental plains of Venezuela. This is how the Maderas del Orinoco Companies (CVG - PROFORCA), the Venezuelan Corporation of Guayana (CVG), Smurfit Kappa Cartón of Venezuela, San Carlos Forestry Development, Masisa. Propulso, among others, started in different regions of the country the establishment of plantations for various purposes. For this they have used fast growing forest species such as: Pinus caribaea var hondurensis, Eucalyptus Urophylla, Acacia magnium, Caraipa llanorum, Tectonia grandis, Hebea brasiliens, Gmelina arborea, Erisma uncinatum, among others. At present, a reforested area of 650.000 ha has been reached. This has favored the protection of natural habitats by reducing the pressure for exploitation and use of the forests.&#x0D; The legal framework established in the new National Constitution, approved in 1998, is based on decrees of 1825-1829 of the Liberator Simón Bolívar and classifies the territory in diverse forest areas establishing a modern environmental conservation policy. A historical summary and the current legislation with the classification that promises a rational management of the national territory is presented.

Ramp reef depositional facies model for the Mid-Pliocene Golden Gates Reef Member of the Tamiami Formation, South Florida

The depositional setting for northern most Atlantic coral reef development during the Mid-Pliocene Warm Period is a gentle sloping mixed carbonate–siliciclastic ramp. Five core transects document the distribution of the reef complex in an area approximately 65 by 12 km, and nine repetitive depositional facies are identified. Paleoecological and sedimentological evidence documents facies development along a water depth–energy gradient. The mid-Pliocene Tamiami Formation is characterized by coral boundstone developed over level skeletal rudstone depositional units dominated by mollusks. Hyotissa haitensis (Sowerby), one of the last Gryphaeid oysters, is the dominant fossil found in the most continuous skeletal facies and overlies deeper water green clay facies, the only facies with pelagic foraminifera. Ground penetrating radar documents reef depositional topography, onlapping stratigraphy and two episodes of reef growth. Two cycles of deposition are recognized, separated by subaerial exposure. The coral boundstone and the skeletal rudstone exhibit both high primary and secondary porosity and overlie the impermeable clay facies. The upper surface of the coral boundstone lies at ~ 4 m in elevation whereas contemporaneous estuarine deposits are found to the north at elevations of 20–25 m. High porosity bank reef complexes along a shallow dipping ramp provide an alternative to the standard model of reef and porosity development along the outer shelf margin. Understanding the differences in associated facies between these two depositional environments permits better interpretation of observed heterogeneities in subsurface geobodies associated with inner shelf and platform settings.

Increased uranium concentrations in ground and surface waters of the Swiss Plateau: A result of uranium accumulation and leaching in the Molasse basin and (ancient) wetlands?

Increased uranium (U) concentrations are found in certain ground and surface waters of the Swiss Plateau. Analysis of more than 100 public fountains revealed that increased 238U concentrations frequently occur close to the interface between the Lower Freshwater Molasse and the Upper Marine Molasse, cropping out in the western part of the Swiss Molasse Basin. Out of these locations, Mont Vully, situated ca. 20 km west of Berne, was studied in detail. As this hill consists of the two aforementioned stratigraphic Molasse units, it represents an ideal case study. Two springs at the northern slopes of Mont Vully exhibit the highest 238U concentrations with more than 300 mBq/L and were thus monitored for almost two years in order to screen possible seasonal variations. Further water samples were collected from spring captures, creeks and drainage pipes. The pipes drain the farmland north of Mont Vully showing 238U concentrations with more than 600 mBq/L. In order to discover the reason for the duplication in concentration, gamma dose rate measurements were accomplished on the farmland, revealing elevated dose rates of up to 160 nSv/h. These are located above ancient pathways of creeks that originated from Mont Vully. At these locations with elevated dose rates, three shallow sediment drill cores were taken and analyzed for their U content. The sediment cores can essentially be divided into three parts: (i) an upper soil with common U concentrations of about 30 Bq/kg 238U, (ii) an U-rich peat horizon with concentrations of up to 500 Bq/kg 238U, and (iii) an impermeable clay unit that acts as an aquitard with again minor 238U concentrations. Radiocarbon dating of the U-rich peat horizon reveals ages younger than 8.1 kyrs. This study suggests that a wetland was formed on top of the impermeable clay layer after the last glaciation during the Holocene. The stream waters with 238U concentrations of more than 300 mBq/L originating from Mont Vully contributed significantly to the water supply for the development of the wetland. Due to the reducing conditions that are present in wetlands, the dissolved U in the incoming streams was reduced and adsorbed onto organic matter. Accordingly, an entrapment for U was generated, persisting for at least 6 kyrs – a sufficient time to accumulate up to 500 Bq/kg. In the course of the last century, numerous wetlands in Switzerland were drained by capturing streams and installing drainage pipes to make the land suitable for agriculture. This kind of melioration was also done at the wetlands north of Mont Vully resulting in a subsequent change in redox conditions within the soil. The solubility of U depends on its oxidation state and U can be oxidized by oxygen-rich rainwater. The rainwater leached the U adsorbed on the peat yielding 238U concentrations of more than 600 mBq/L. Consequently, the duplication of 238U concentrations in the drainage water as compared to the original concentration that creeks brought into the ancient wetlands has been clarified during this study. Twenty of the analyzed public fountains in the Swiss Plateau exhibited a 238U concentration of more than 50 mBq/L. All of them could have contributed to the formation of a wetland after the last glaciation, which leads to the assumption that the situation at Mont Vully is not a singularity in the Swiss Plateau.

Application of the conductive method in the engineering geology: Ruczaj district in Krak\xf3w, Poland, as a case study

The Ruczaj district in Kraków is the potential building area of high flat blocks for inhabitants. This area is built of the gypsum basement covered by the soil and impermeable clay beds with several meters of thickness. The flat blocks must be set on the textured gypsum layer. In the result of the rainfall and static pressure of the blocks, the water with SO42− increases up to the groundwater level, become the great threat for the flat blocks. The water creates specific hydrogeological conditions occurring in the zone of the building’s foundations. To eliminate the mentioned threat, we should determine precisely the thickness of the soil and impermeable clay as well as the depth of the gypsum basement. Based on the electromagnetic parameters of the geological formations, the Ground Conductivity Meter and DC resistivity methods were used to solve the mentioned problems.

Effective water quantity of multi-source water recharging aquifers in Yufuhe River based on groundwater and surface water semi-coupled modelling

AbstractWith rapid urbanisation, a karst water recharge area of the Jinan spring catchment was damaged. Thus, managed aquifer recharge projects were built in the western Jinan spring catchment to protect the water supply of the spring. Yufuhe River was selected as the study area to compute the effective recharge rate into karst aquifers. This strong seepage zone has a large gradient and undergoes a specific hydrogeological condition in which two strata of a gravel layer and limestone change to three strata of gravel, impermeable clay shale and limestone at the open window of the karst aquifers. A hydraulic model called HEC-RAS was applied to simulate the river stage, and a numerical groundwater model called HYDRUS-3D was adopted to simulate the groundwater mound dynamics and estimate river flow seepage into the aquifers. The effective recharge rates are 64.9%, 65.2% and 68.1% when the buried depths of groundwater are 40, 30 and 25 m. An analysis of the electric conductivity, water table, temperature and water volume data found an effective recharge rate of 68.3%. Results of field monitoring confirmed the accuracy of the numerical simulation and showed that most of the recharged water in the study reach can be effectively recharged into the karst aquifers.

Observations of the ground and structural behaviours induced by a deep excavation in loose sands

Large-scale deep basement excavations are commonly used in metropolitan areas; however, previous studies focused primarily on excavations in impermeable clay instead of permeable sand with high groundwater levels. In this study, a unique opportunity provides a complete picture of the ground and structural behaviours induced by deep excavations in loose to medium sand, which have been rarely studied in the past. With a maximum excavation depth of 16.8 m, the pit was retained by a 0.9-m-thick and 32-m-deep reinforcement concrete diaphragm wall with 4-level struts. The maximum wall displacement (δvh) reached 56 mm at the end of excavation, and the ratio of δvh to the excavation depth was 0.32%. In contrast, the ratio of the maximum surface settlement to the excavation depth was lower, i.e. only 0.2%. Pumping inside the excavation site did not appear to induce a significant impact outside the excavation site due to the retaining wall embedded in a layer of impermeable clay at a depth of 28.5–30.5 m. The plain strain ratio from the observed settlement is interpreted; the ratio indicates a difference of 2–39%. This difference may be connected to the soil anisotropy, or the maximum surface settlement at each monitoring section may not be detected. The wide range of the variance might also be connected with the small measured surface settlements and the difficulty of detecting such small displacements on the ground level in field surveys.

The layered model of the Copahue geothermal reservoir, Argentina

An exhaustive review of the available data related to the reservoir of the volcano-hosted Copahue geothermal system is presented. Reservoir interpretation to date suggests a vapor-dominated nature. However, the review provided reveals the limitations of this model, regarding the transition from shallow argillic to deep propylitic alteration zones, gas geothermometers calibrated to near-neutral pH environment, production tests, and low recharge of the feed zone, among the other features. We propose that a layered model with a shallow vapor zone above a fluid pressurized reservoir better accounts for the known features of the geothermal reservoir. Temperature profiles define the 800-m-thick upper thermal boundary that includes the impermeable clay cap. An argillic alteration layer (smectite + chlorite + illite + kaolinite) with low electric resistivity response, consistent with the presence of smectite, composes the clay cap. A shallow steam cap develops immediately below the impermeable layer. This vapor zone has 200–215 °C, low seismic activity, and high electrical resistivity, and is highlighted by the isothermal segment of the well logs. The bottom part of the reservoir is subjected to controversy because of the lack of direct measurements. The deep liquid-dominated reservoir has a temperature of ~ 280 °C, develops below 1500 m depth under near-neutral pH condition, and probably has a pervasive propylitic alteration, and wairakite + laumontite + chlorite + epidote + prehnite + actinolite is the likely mineral assemblage. Pressure collapse might trigger the development of the shallow steam cap during deflation–inflation volcanic cycles or Pleistocene-to-recent tectonic deformation. This work points out the main weak points of the previous conceptual model, providing an alternative one based on the first comprehensive compilation of data of the Copahue reservoir. Further research, including a deep exploration drilling stage, is required to establish the physicochemical reservoir state precisely and to validate the proposed layered model.

Evaluation of some geophysical and physicochemical characteristics of soil and groundwater resources in Sapele, south-south Nigeria

This study evaluated some geophysical and physicochemical characteristics of soil and groundwater resources in Sapele, Delta Sate of Nigeria using various standard techniques. The results of the resistivity data shows that a high resistive plume with resistivity > 12,000 Ohm-m has penetrated the soils beyond 21m beneath the surface in most parts of the surveyed area. The water samples shows high acidity with pH values in the range 4.6-5.1. Total Dissolved Solids (TDS) is low 46.40- 47.98mg/l and conductivity ranges from 72.80-78.8 μS/cm, There is no incidence of heavy metal pollution, only Iron is high (0.772-0.915mg/l). Total petroleum hydrocarbons-(TPH) as oil and gas revealed by gas chromatography result is below detection level (<0.031mg/l), this can be attributed to the sealing of the confined aquifer by impermeable clay. The average permeability of the soil is 5.514 x 10 -3 cm/s indicating good drainage condition. The results have shown that shallow boreholes are polluted and the soils of the area are acidic. Groundwater of the area need treatment before it can be consumed and periodic integrated methods of investigation should be carried out in the study area. Keywords: Contamination, Groundwater, Imaging, Resistivity, Soil

Seismic reflection and structuring characterization of deep aquifer system in the Dakhla syncline (Cap Bon, North-Eastern Tunisia)

The Dakhla syncline is located in the North-Eastern Tunisia. It is bounded by Abd El Rahmene anticline to the North-West, El Haouaria Graben to the North-East, Grombalia Graben to the South-West and the Mediterranean Sea to the East. The main aquifer reservoirs of Dakhla syncline are constituted by stacks of fluvial to deltaic Neogene sequences and carbonates. The interpretation of eight seismic reflection profiles, calibrated by wire line logging data of three oil wells, hydraulic wells and geologic field sections highlighted the impact of tectonics on the structuring geometry of aquifers and their distribution in elevated structures and subsurface depressions. Lithostratigraphic correlations and seismic profiles analysis through the syncline show that the principal aquifers are thickest within the central and northern part of the study area and thinnest to the southern part of the syncline.Seismic sections shows that the fracture/fault pattern in this syncline is mainly concentrated along corridors with a major direction of NW-SE and secondary directions of N-S, E-W and NE-SW with different release. This is proved by the complexity structure of Eastern Tunisia, resulted from the interaction between the African and Eurasiatic plates. Isochron maps of aquifers systems exhibited the structuring of this syncline in sub-surface characterized by important lateral and vertical geometric and thickness variations. Seismic sections L1, L2, L3, L4, L5 and petroleum wells showed an heterogeneous multilayer aquifers of Miocene formed by the arrangement of ten sandstone bodies, separated by impermeable clay packages. Oligo-Miocene deposits correspond to the most great potential aquifers, with respectively an average transmissivity estimated: Somaa aquifer 6.5 10−4 m2/s, Sandstone level aquifer 2.6 10−3 m2/s, Beglia aquifer 1.1 10−3 m2/s, Ain Ghrab aquifer 1.3 10−4 m2/s and Oligocene aquifer 2 10−3 m2/s. The interpretation of spatial variations of seismic units and the recognition of tectonic structures and their development may reveal some new insights for hydrogeological aspects.

Community Wastewater Treatment with Attached Growth Assisted Constructed Wetland Reactor

Constructed wetlands are systems of artificial wastewater treatment which consists of shallow ponds or channels that have been planted with aquatic plants. The treatment is based on the natural, biological, physical and chemical treatment of wastewater. The technique is reported to be cost effective as compared to other methods. The constructed wetlands have impermeable clay or synthetic coatings and artificial structures for controlling the direction of flow, liquid retention time and the water level. However, there are certain limitations of constructed wetland system, which need improvement for its wide adoptability. As such the effort was made to assist the constructed wetland system with attached growth system with the aim to design an economical and user friendly waste water treatment option for the small community. The laboratory scale model was fabricated using GI sheet of thickness 0.5 mm. The overall capacity of the model was 275 L. The laboratory scale reactor model consisted of four compartments out of which first three compartments were based on attached growth system and the fourth compartment acted as constructed wetland reactor. All the three compartments were packed with different types of artificial, semi-artificial and natural media. The fourth compartment consisted of media packed from bottom as aerocon stone layers 03 in numbers followed by snail shell, followed by a soil layer of 80 mm thick which holds the plants in rows. The reactor was operated as continuous flow reactor with varying detention time and change of different type of media packed in the reactor. The performance of Customized Constructed Wetland reactor was observed under various operating conditions for removal of BOD, COD and TS parameters. The paper presents the details regarding the development of the reactor model, operation of the reactor model and results obtained during the course of study. The paper also cover the discussion regarding the improved performance of reactor noted during the study and adoptability of the developed reactor model for community waste treatment.

Very Low Frequency Electromagnetic Induction Surveys in Hydrogeological Investigations; Case Study from Poland

In 2011, a geophysical survey was carried out in the surroundings of the Jagiellonian University in Cracow, using a Very Low Frequency method. The measurements were designed to determine the reason of frequent flooding of the lowest level of the building. The main objective of the study was to find out from where and in which way the rainwater seeps into the building and how this problem can be solved in the least invasive manner. The aim of geophysical methods was also to provide necessary information that will enable the construction of a hydro-geological model of the local environment. The interpretation revealed the presence of a sandy gutter surrounded by impermeable clay. There is a big resistivity contrast between those layers. Their location and approximate dimensions were determined.