estimation of aquifer transmissivity from dar zarrouk parameters in porous media the aim of this paper is to establish an analytical relationship between the aquifer parameters for porous media and the so called dar zarrouk parameters so that the former can best be estimated from the surface resistivity measurements taking the two fundamental laws viz darcy s law of fluid flow and ohm s law of current flow analytical relationships between transmissivity and transverse resistance as well as transmissivity and longitudinal conductance have been established it was found that the relationship between transverse resistance and transmissivity is more meaningful as the product of hydraulic conductivity and electrical conductivity of an aquifer may be assumed to be constant for an area with a particular geological setting and range of water quality this is verified by analysing the data given by kelly

numerical modelling of self potential signals associated with a pumping test experiment summary the study of electrical signals associated with groundwater flow is a powerful method to determine in a non invasive way the distribution of hydraulic heads in aquifers hence the distribution of the hydraulic conductivity and storativity experimental hydraulic heads and electrical self potential sp signals associated with a pumping test in an unconfined aquifer were reproduced with a numerical model based on the finite difference method for simplicity we assumed axial symmetry around the pumping well we assessed the equivalent hydraulic conductivity and specific storage of the aquifer by fitting the piezometric levels obtained in the course of the pumping against synthetic hydraulic heads produced by the model the current coupling coefficient is obtained from the best fit between the experimental and modelled sp signals at the end of the pumping phase then keeping the previously determined hydraulic parameters the relaxation of both the hydraulic heads and the sp signals were modelled and found to be consistent with the measured values the data show almost linear relationships between the hydraulic heads in the aquifer and the electrical signals recorded at the ground surface these results show that sp signals allow monitoring subsurface flow in the course of pumping experiments

groundwater flow modelling of kwa ibo river watershed southeastern nigeria groundwater flow modelling of the kwa ibo river watershed in abia state of nigeria is presented in this paper with the aim of assessing the degree of interaction between the kwa ibo river and the groundwater regime of the thick sandy aquifer the local geology of the area comprises the quaternary to recent benin formation potential aquifer zones that were delineated earlier using geoelectrical resistivity soundings and borehole data for the area formed the basis for groundwater flow modelling the watershed has been modelled with a grid of 65 rows by 43 columns and with two layers lateral inflow from the north has been simulated with constant heads at the government college umuahia and outflow at usaka elegu in the south the kwa ibo river traverses the middle of the watershed from north to south the river stage data at umudike amawom ntalakwu and usaka elegu have been used for assigning surface water levels and riverbed elevations in the model permeability distribution was found to vary from 3 to 14 5 m day 1 natural recharge due to rainfall formed the main input to the aquifer system and abstraction from wells was the main output a steady state groundwater flow simulation was carried out and calibrated against the may 1980 water levels using 26 observation wells the model computations have converged after 123 iterations under the transient state calibration the highest rainfall and hence groundwater recharge over the 10 year study period was recorded in 1996 whereas the lowest was recorded in 1991 the computed groundwater balance of 55 274 m3 day 1 was comparable to that estimated from field investigations results from the modelling show that abstraction is much less than groundwater recharge hence there is the possibility for additional groundwater exploitation in the watershed through drilling of boreholes copyright 2008 john wiley sons ltd

a semi analytical solution for transient streaming potentials associated with confined aquifer pumping tests we consider the transient streaming potential response due to pumping from a confined aquifer through a fully penetrating line sink confined aquifer flow is assumed to occur without fluid leakage from the confining units however since confining units are typically clayey and hence more electrically conductive than the aquifer they are treated as non insulating in our three layer conceptual model we develop a semi analytical solution for the transient streaming potentials response of the aquifer and the confining units to pumping of the aquifer the solution is fitted to field measurements of streaming potentials associated with an aquifer test performed at a site located near montalto uffugo in the region of calabria in southern italy this yields an average hydraulic conductivity that compares well to the estimate obtained using only hydraulic head data specific storage is estimated with greater estimation uncertainty than hydraulic conductivity and is significantly smaller than that estimated from hydraulic head data this indicates that specific storage may be a more difficult parameter to estimate from streaming potential data the mismatch may also be due to the fact that only recovery streaming potential data were used here whereas head data for both production and recovery were used the estimate from head data may also constitute an upper bound since head data were not corrected for pumping and observation wellbore storage estimated values of the electrical conductivities of the confining units compare well to those estimated using electrical resistivity tomography our work indicates that where observation wells are unavailable to provide more direct estimates streaming potential data collected at land surface may in principle be used to provide preliminary estimates of aquifer hydraulic conductivity and specific storage where the latter is estimated with greater uncertainty than the former

spontaneous potentials and resistivity surveys applied to hydrogeology in a volcanic area case history of the chaine des puys puy de dome france two geophysical methods resistivity soundings and spontaneous potentials sp are used to investigate aquifers in the quaternary volcanic formations of the chaine des puys france the interpretation of the resistivity soundings required a specific work of determination of the resistivity of the formations concerned the basement topography characterized by axial horst and graben structures and perpendicular palaeovalleys was revealed sp was developed experimentally in the field and theoretically it is shown that the sp anomalies can be considered as double layer potentials with their source on the aquifers interfaces the most significant of them is the water table which creates an sp anomaly of similar but inverted form sp anomalies due to flows in unconfined aquifers in palaeovalleys and in volcanic ranges are computed and compared with the observed ones these two methods have determined the extent and the boundary conditions of the different hydrogeological basins and have determined the major drainage axes and the groundwater flow pattern

resistivity and self potential tomography applied to groundwater remediation and contaminant plumes sandbox and field experiments summary geophysical methods can be used to remotely characterize contaminated sites and monitor in situ enhanced remediation processes we have conducted one sandbox experiment and one contaminated field investigation to show the robustness of electrical resistivity tomography and self potential sp tomography for these applications in the sandbox experiment we injected permanganate in a trichloroethylene tce contaminated environment under a constant hydraulic gradient inverted resistivity tomograms are able to track the evolution of the permanganate plume in agreement with visual observations made on the side of the tank self potential measurements were also performed at the surface of the sandbox using non polarizing ag agcl electrodes these data were inverted to obtain the source density distribution with and without the resistivity information a compact horizontal dipole source located at the front of the plume was obtained from the inversion of these self potential data this current dipole may be related to the redox reaction occurring between tce and permanganate and the strong concentration gradient at the front of the plume we demonstrate that time lapse self potential signals can be used to track the kinetics of an advecting oxidizer plume with acceptable accuracy and if needed in real time but are unable to completely resolve the shape of the plume in the field investigation a 3d resistivity tomography is used to characterize an organic contaminant plume resistive domain and an overlying zone of solid waste materials conductive domain after removing the influence of the streaming potential the identified source current density had a magnitude of 0 5 a m 2 the strong source current density may be attributed to charge movement between the neighboring zones that encourage abiotic and microbially enhanced reduction and oxidation reactions in both cases the self potential source current density is located in the area of strong resistivity gradient

geoelectric sounding for the determination of aquifer characteristics in parts of the umuahia area of nigeria seventeen schlumberger vertical electrical soundings ves were carried out in parts of the umuahia area of nigeria using a maximum current electrode separation of 1 km the data were interpreted using a conventional partial curve matching method to obtain initial model parameters which were used in a computer program to obtain final parameters three soundings were made at existing boreholes for comparison aquifer parameters of hydraulic conductivity and transmissivity were obtained by analyzing pumping test data from existing boreholes the results of the interpretation revealed three distinct geoelectric layers overlying a conductive geoelectric basement based on the model obtained aquifer hydraulic conductivity and transmissivity were calculated the hydraulic conductivity calculated agreed closely with that determined from pumping test data the results of the present study also indicate that the entire area is divided into two zones each of which is homogeneous in hydraulic properties and wate

palaoecologic trends and petroleum potential of upper carboniferous coal seams of western germany as revealed by their petrographic and organic geochemical characteristics abstract petrographic compositions of microscopically homogeneous vertical sections in coal profiles from the ruhr basin northwestern germany are reported the studied coal seams of late westphalian age are between 0 4 and 2 4 m thick mean vitrinite reflectivities in the range of 0 1 0 thus indicating high volatile a bituminous coal changes in the organic facies within the coal profiles are common and can be linked to changes of plant communities and preservation conditions in the depositional environments also associated variations in mineral content are usually found although patterns of changes in maceral and mineral contents are complex some general trends have been observed continuous development from seat earth to coal with vitrinitic roots and detritic liptinites and inertinites representing the initial stage of peat and coal evolution just above the base thick vitrinite rich sections with abundant mudstone layers are overlain by inertinite rich sections with low mineral and high sporinite contents the latter may represent highly degraded oxidized peats that accumulated at morphologically elevated areas deposition of clastic roof strata had only a minor influence on organic facies coals and dispersed organic matter in these clastic rocks are in the main similar in maceral group composition organic geochemical characterization of selected lithotypes revealed significant differences between coals and dispersed organic matter this can be explained by trapping of generated hydrocarbons in the coals differences in elemental compositions of coals of the same organic facies at different ranks vitrinite reflectance of 0 70 and 0 92 respectively reflect a loss of about 20 wt co 2 bitumen water during this maturation stage gas chromatographic mass spectrometric analyses of the saturated hydrocarbon fraction in solvent extracts separated from selected samples reveal that all samples contain the same classes of compounds namely straight chain alkanes hopanoids and isoprenoids but that there is a significant difference in the relative abundance of these classes of compounds in the different coals

numerical simulation of electrokinetic potentials associated with subsurface fluid flow a postprocessor has been developed to calculate space time distributions of electrokinetic potentials resulting from histories of underground conditions pressure temperature vapor saturation concentrations of dissolved species flow rate etc computed by unsteady multidimensional geothermal reservoir simulations electrokinetic coupling coefficients are computed by the postprocessor using formulations based on experimental work reported by ishido and mizutani 1981 the postprocessor was applied to both numerical modeling of natural self potential sp anomalies in geothermal fields and production induced sp changes the essential features of the sp anomalies and sp changes which have actually been observed in real geothermal fields are reproduced reasonably well in these calculations for both single phase liquid and two phase vapor liquid geothermal reservoirs the postprocessor was also applied to predicting the magnitude of electrical earthquake precursory signals caused by dilatant strains taking place within a narrow vertical fault zone if the rate of porosity increase is high enough to induce substantial pore pressure decrease two phase flow develops in the fault zone and produces observable signals at the ground surface if a high conductivity channel connects the near surface region and the deep fault zone

electrokinetic spontaneous polarization in porous media petrophysics and numerical modelling abstract the behaviour of streaming potential is directly related to movement of groundwater the responses for typical subsurface flows are modelled to investigate possibilities of spontaneous polarization sp when performing quantitative data interpretation the physical properties of geomaterials related to streaming potential are described a magnitude range of streaming current coefficient is assessed for geomaterials and found to be from 10 10 to 10 8 a pa m depending on water salinity and rock composition the electrical sources of sp caused by groundwater flow in saturated media are theoretically described it is shown that sp is completely defined by three types of electrical sources situated 1 on boundaries where water enters or quits porous media 2 in areas with transient regime and 3 on the boundaries of rocks with different properties hydraulic conductivity streaming current coefficients and electrical conductivity a 2d computer program based on the method of finite difference was created to provide numerical successive modelling of both groundwater flow and sp using sill s geophysics 48 1983 76 approach first the water heads are calculated then electrical sources of sp are obtained on the basis of the calculated heads and coefficient of streaming current finally the sp is obtained on the basis of calculated electrical sources and subsurface electrical conductivity numerical examples illustrating sp responses of infiltration of barrage with different electrical conductivity and of well pumping are discussed field data obtained at the site containing the dam between superficial artificial reservoir and the river are interpreted on the basis of numerical modelling the discussed method can be mainly used for additional calibration of groundwater flow models

relating hydraulic and geoelectric parameters of the jayant aquifer india abstract geoelectrical soundings with schlumberger arrays were carried out close to nine pumping test sites in the jayant project a part of the singrauli coalfields madhya pradesh india to relate geoelectric parameters to hydraulic parameters such as hydraulic conductivity and transmissivity the interpretation of the sounding data was carried out using partial curve matching and the final model parameters were obtained using the computer program aimresi water samples collected from different pumping test sites were analyzed to obtain water resistivity the relationship between transmissivity and normalized aquifer resistivity is discussed in this paper normalized aquifer resistivity is a very good predictor for transmissivity in this aquifer

self potential signals associated with variations of the hydraulic head during an infiltration experiment 1 a field experiment was performed to monitor the variations of the hydraulic head in the vicinity of a ditch during a water infiltration experiment and using the self potential method the coupling between electric and hydraulic flows is electrokinetic in nature the electrical signals are measured at the ground surface with a set of ten non polarisable petiau pb pbcl2 electrodes over a section perpendicular to the ditch the electrical potential is linearly related to the depth of the water table which is here quite shallow between 1 to 2 m a rough estimate of the electrokinetic coupling coefficient obtained in the field is 10 mv per meter of hydraulic head 1000 mv mpa 1 of pore fluid pressure the order of magnitude of this estimate agrees with a laboratory experiment performed with a soil sample from the test site the good correlation found between electrical potential and hydraulic head variations opens the door to direct tomography of hydraulic head fluctuations with many innovative applications in hydrogeology especially because the potential depth to which this method could be applicable is high several hundred meters

joint inversion of steady state hydrologic and self potential data for 3d hydraulic conductivity distribution at the boise hydrogeophysical research site we combine sedimentological hydraulic and geophysical information to characterize the 3d distribution of transport properties of an heterogeneous aquifer we focus on the joint inversion of hydraulic head and self potential measurements collected during an extensive experimental campaign performed at the boise hydrogeophysical research site bhrs boise idaho and involving a series of dipole tests while hydraulic head data obtained from piezometric readings in open wells represent a depth averaged value self potential signals provide an estimate of the water table location the aquifer is conceptualized as a multiple continuum where the volumetric fraction of a geo material within a cell of the numerical flow model is calculated by multiple indicator kriging the latter is implemented on the basis of available sedimentological information the functional format of the indicator variograms and associated parameters are estimated on the basis of formal model identification criteria self potential and hydraulic head data have been embedded jointly within a three dimensional inverse model of groundwater flow at the site each identified geo material category is assumed to be characterized by a constant hydraulic conductivity the latter constitute the set of model parameters the hydraulic conductivity associated with a numerical block is then calculated as a weighted average of the conductivities of the geo materials which are collocated in the block by means of multiple indicator kriging model parameters are estimated by a maximum likelihood fit between measured and modeled state variables resulting in a spatially heterogeneous distribution of hydraulic conductivity the latter is effectively constrained on the sedimentological data and conditioned on both self potential and borehole hydraulic head readings minimization of the maximum likelihood objective function allows estimating the relative weight of measurement errors associated with self potential and borehole based head data the procedure adopted allowed a reconstruction of the heterogeneity of the site with a level of details which was not obtained in previous studies and with relatively modest computational efforts further validation against dipole tests which were not used in the inversion procedure supports the robustness of the results

theory of transient streaming potentials in coupled unconfined aquifer unsaturated zone flow to a well a semianalytical solution is presented for transient streaming potentials associated with flow to a pumping well in an unconfined aquifer taking into account the effect of flow in the unsaturated zone above the water table flow in the unsaturated zone is modeled with a linearized form of richards equation using an exponential model for soil moisture retention and unsaturated hydraulic conductivity archie s law is invoked for unsaturated electrical conductivity the unsaturated electrokinetic coupling coefficient is modeled with a decaying exponential where the maximum value is at and below the water table the coupled flow and electrokinetic problem is solved using laplace and hankel transforms the results of the model predicted behavior are presented and compared to that observed in laboratory simulations of pump ing tests the early time polarity reversal predicted the model is observable in the experiments other non monotonic streaming potential behaviors predicted by the model are also evident in experimental measurements the model is used to estimate hydraulic parameters from sp data and these compare well to those obtained from drawdown data for example a hydraulic conductivity of 3 6 3 10 24 m s is obtained from sp data compared to 3 4 3 10 24 m s from drawdown data

hydrodynamic parameters estimation from self potential data in a controlled full scale site abstract a multi physical approach developed for the hydrodynamic characterization of porous media using hydrogeophysical information is presented several pumping tests were performed in the hydrogeosite laboratory a controlled full scale site designed and constructed at the cnr imaa consiglio nazionale delle ricerche istituto di metodologia per l analisi ambientale in marsico nuovo basilicata region southern italy in order to obtain an intermediate stage between laboratory experiments and field survey the facility consists of a pool used to study water infiltration processes to simulate the space and time dynamics of subsurface contamination phenomena to improve and to find new relationship between geophysical and hydrogeological parameters to test and to calibrate new geophysical techniques and instruments therefore the hydrogeosite laboratory has the advantage of carrying out controlled experiments like in a flow cell or sandbox but at field comparable scale the data collected during the experiments have been used to estimate the saturated hydraulic conductivity k s ms 1 using a coupled inversion model working in transient conditions made up of the modified richards equation describing the water flow in a variably saturated porous medium and the poisson equation providing the self potential v which naturally occurs at points of the soil surface owing to the presence of an electric field produced by the motion of underground electrolytic fluids through porous systems the result obtained by this multi physical numerical approach which removes all the approximations adopted in previous works makes a useful instrument for real heterogeneous aquifer characterization and for predictive analysis of its behavior

petrology and genesis of upper carboniferous seams from the ruhr region west germany abstract the petrology of 21 seam profiles of upper carboniferous age westphalian c and b has been studied in order to determine their depositional environments and diagenetic history the youngest profile was drilled at a depth of 790 m and is mainly overlain by cretaceous sediments the oldest seam was reached at a depth of 1470 m the seam thicknesses vary from 0 4 to 2 5 m the main petrographic compounds are vitrinite intertinite liptinite and minerals the last group occurs as clay bands with illite kaolinite minor chlorite and minor quartz contents or as crack or pore filling calcite fe dolomite siderite pyrite or marcasite or as syngenetic siderite concretions and pyrite crystals the percentages of the different macerals and minerals vary mainly because of different depositional environments diagenetic loss or genesis of compounds is a less important factor in their distribution three types of profiles are distinguished by their different petrologies type i is most abundant and contains much vitrinite many clay bands and syngenetic iron sulfides whereas type iii is rich in inertinite and certain characteristic spores type ii is intermediate but generally contains only low percentages of minerals generally this type is vitrinite rich in the lower and inertinite rich in the central and upper parts of the profiles spores and other liptinites are much better preserved in all the seams than in clay partings or in siltstones and sandstones above and below the seams the seams are interpreted to be former autochthonous peats type i profiles are probably derived from swamps which were sometimes inundated and covered by overbank deposits type ii and iii seams represent former peats which were not inundated by rivers and partly grew under the influence of more oxidizing conditions therefore they contain more inertinite and less sulfide and clay bands they can be interpreted as former raised bogs diagenetic changes are expressed as increases of vitrinite reflectances from 0 65 to 1 0 and of liptinite reflectances a red shift of fluorescence of liptinites was found increasing amounts of exudatinite and micrinite and decreasing amounts of fluorinite and resinite were found minerals seem to be less affected by diagenesis illite crystallinity for example remains poor

theory of transient streaming potentials associated with axial symmetric flow in unconfined aquifers summary we present a semi analytical solution for the transient streaming potential response of an unconfined aquifer to continuous constant rate pumping we assume that flow occurs without leakage from the unit below a transverse anisotropic aquifer and neglect flow in the unsaturated zone by treating the water table as a moving material boundary in the development of the solution to the streaming potential problem we impose insulating boundary conditions at land surface and the lower boundary of the lower confining unit we solve the problem exactly in the double laplace hankel transform space and obtain the inverse transforms numerically the solution is used to analyse transient streaming potential data collected during dipole hydraulic tests conducted at the boise hydrogeophysical research site in 2007 june this analysis yields estimates of aquifer hydraulic parameters the estimated hydraulic parameters namely hydraulic conductivity transverse hydraulic anisotropy specific storage and specific yield compare well to published estimates obtained by inverting drawdown data collected at the field site

organic matter maturation under the influence of a deep intrusive heat source a natural experiment for quantitation of hydrocarbon generation and expulsion from a petroleum source rock toarcian shale northern germany four shallow boreholes were drilled in the hils syncline northern germany in order to determine quantitatively the amount of hydrocarbons generated and expelled during maturation of a typical kerogen type ii bearing source rock the holes penetrated the carbonceous lias shales posidonia shale lower toarcian and part of the adjacent dogger and lias mudstones the maturity of the organic matter in the cores recovered ranges from immature 0 48 r0 to overmature 1 45 r0 due to location of the hils syncline in the vicinity of the vlotho massif which is deep seated intrusive body facies variations of the lias within the short geographical distances in the study area are negligible organic matter mass balance calculations were based on detailed organic geochemical analyses of residual material in the lias shales kerogen bitumen etc and on the evidence of a uniform initial composition of these sediments in the study area dead carbon determinations supported this latter criterion but were not used as a parameter in the calculations about 50 of the initial kerogen was transformed into oil gas and inorganic compounds during the vitrinite reflectance increase from 0 48 to 0 88 ro and only marginally more during the maturity increase from 0 88 to 1 45 ro only a small portion of the generated material remained in the source rock even at a relatively early stage of generation 0 68 ro expulsion efficiency of oil plus gas reached a value of 86 at the end of the main generation stage 0 88 ro

three dimensional modelling of streaming potential summary the self potential sp method responds to the electrokinetic phenomenon of streaming potential and has been applied to hydrogeologic and engineering investigations to aid in the evaluation of subsurface hydraulic conditions to enable the study of variably saturated flow problems of complicated geometry a 3 d finite volume algorithm is developed to evaluate the sp distribution resulting from subsurface fluid flow the algorithm explicitly calculates the distribution of streaming current sources and solves for the sp given a model of hydraulic head and prescribed distributions of the streaming current cross coupling conductivity and electrical conductivity the forward solution is verified by comparing it with an analytical solution for a point source of flow and measured data taken at the surface of a homogeneous embankment we apply the forward model to a synthetic pumping well example to illustrate that heterogeneous physical property distributions can result in significant charge accumulation the sign and magnitude of this secondary charge is determined by the physical property and potential gradients at the interface and can complicate the interpretation of sp data when a single primary flow source is assumed the 3 d character of the sp response to seepage through an embankment and foundation is illustrated in a preliminary study of sp data collected at a dam site in british columbia

estimating aquifer hydraulic properties from the inversion of surface streaming potential sp anomalies 1 electrokinetic effects of water flow during pumping tests have been shown to generate surface streaming potential sp anomalies of several tens of mv that are well correlated with the geometry of the water table it follows that sp measurements can be used to estimate aquifer hydraulic properties we have developed an inversion scheme for surface sp data generated by flow pumping and found that we are able to estimate the hydraulic conductivity and the depth and the thickness of the aquifer we applied our inversion scheme to the data from bogoslovsky and ogilvy 1973 and found a hydraulic conductivity of 10 5 m s 1 an aquifer thickness of roughly 28 m and an electrokinetic coupling coefficient of 1 mv m 1 these values are in the range of what is expected for this kind of environment

self potential modeling from primary flows this paper discusses a new method for the investigation of self potentials sp based on induced current sources the induced current sources are due to divergences of the convection current which is driven in turn by a primary flow either heat or fluid as a result of using this approach there is a shift in emphasis toward the vector flow field and its interaction with current cross coupling structure when compared with the total potential approach of nourbehecht 1963 which emphasized the primary flow potential and the voltage cross coupling this shift in emphasis is advantageous because it is analogous to the actual physical processes for example fluid flow in the ground gives rise to drag convection currents and the interaction of the convection currents with the electrical structure gives rise to the electrical potentials sp this simple physical picture should aid in developing a better intuitive understanding of the generation of sp effects the convective current approach is easily ada

comparative organic petrology of interlayered sandstones siltstones mudstones and coals in the upper carboniferous ruhr basin northwest germany and their thermal history and methane generation in the coal mining ruhr area upper carboniferous rocks ca 4000 m consist of interlayered sandstones siltstones mudstones and coals they were deposited in a tropical paralic environment where alternating fluvial sedimentation occasional marine ingressions and swamp growth resulted in an irregular cyclic succession the total sedimentary package contains on an average 6 vol of organic matter about 70 vol of the organic matter occurs in coal seams the rest as dispersed organic matter in clastic rocks the organic matter is autochthonous in the coals and allochthonous in associated sandstones and siltstones it consists of about 70 vitrinite 20 inertinite and 10 liptinite the overall maceral group composition is the same for coals and dispersed organic matter this surprising similarity is caused by a nearly exclusive input of land plant derived organic matter to swamps and fluvial systems and a similar degree of preservation highest average liptinite contents of total macerals were found in unrooted mudstones highest average inertinite contents in coarse grained siltstones and highest average vitrinite percentages in sandstones

groundwater exploration in rural scotland using geophysical techniques identifying the location size and characteristics of small aquifers is becoming increasingly important in scotland with the growing demand for groundwater to supply isolated rural communities these small localized aquifers are found within superficial deposits such as alluvium blown sands and raised beach deposits and in fracture zones in the underlying bedrock geophysical techniques offer a rapid and inexpensive method of characterizing these aquifers electromagnetic techniques using em34 and em31 instruments have proved useful in identifying variations in the thickness of superficial deposits and detecting buried channels for example at palnure sw scotland ground penetrating radar has been used at several locations including the island of coll to detect the boundary between bedrock and alluvium or blown sand more detailed techniques such as resistivity soundings seismic refraction and resistivity tomography have been used to identify fractures in basement rocks and help calibrate the other methods for example at foyers near loch ness magnetic profiling has also been used to locate dykes acting as hydraulic barriers within permian aquifers in the west of scotland

principles of electrography applied to self potential electrokinetic sources and hydrogeological applications 1 the electrical potential field passively recorded at the ground surface of the earth and termed self potential can be analyzed to determine the shape and the depth of the piezometric surface the coupling between hydraulic flow and electrical current density is electrokinetic in nature the electrokinetic coupling coefficient entering into the integral equation relating the depth of the water table to self potential signals is analyzed for various types of porous materials it is simply related to the electrical conductivity of the pore water in steady state conditions each element of the water table can be seen as an elementary dipole with an inclination locally perpendicular to the water table and strength proportional to the water table elevation then we propose three methods to obtain the shape and range of possible depths of the water table from the study of the self potential distribution recorded at the ground surface the nonuniqueness of the solution is removed if one knows either the electrokinetic coupling coefficient or the water table at one location and under the assumption of the spatial homogeneity of the electrokinetic coupling coefficient two field cases are discussed to show the success of the proposed methods for estimating the shape and depth of the water table at two different scales of investigations they concern the study of self potential signals associated with the shape of the water table in the vicinity of a pumping well and in the flank of the kilauea volcano

self potential signals induced by periodic pumping tests 1 we measured the variations of the self potential sp during periodic pumping tests performed at a test site located near a freshwater reservoir kemnader see bochum germany successions of injection and production intervals were applied in a borehole penetrating a jointed sandstone aquifer we report the sp observations for tests with periods ranging between 10 and 60 min and flow rates between 10 and 25 l min 1 the sp responses at the surface exhibit the imposed period but are not truly harmonic contrary to the hydraulic pressure and sp measured in monitoring wells in the grassy zone around the injection well the amplitude of the sp signals decreases with distance from the injection well around one order of magnitude at 10 m in rough agreement with predictions for radial flow in a homogeneous medium around an infinite source the shape of the sp responses also evolves with distance fourier spectral analysis reveals that the surface signals generally contain two main components at the main period and at half the period with the relative weight of the subperiodic components increasing with distance furthermore the characteristics of the sp responses depend on whether the boreholes are left open or closed by packers the comparison between surface and borehole measurements suggests that nonlinear phenomena are acting probably related to the saturation and desaturation processes occurring in the vadose zone

estimation of hydraulic conductivity and water table map in a large scale laboratory model by means of the self potential method 1 the goal of this paper is to estimate the position of the water table and hydraulic conductivity of a homogeneous porous medium by means of the self potential method the hydrogeophysical experiments were carried out at the hydrogeosite laboratory of the istituto di metodologie per l analisi ambientale consiglio nazionale delle ricerche marsico nuovo italy the laboratory is a large scale model sized 10 7 3 m3 that is filled with a homogeneous medium made up of quartz rich sand with a medium high hydraulic conductivity in the order of 10 5 m s 1 self potential signals generated by the groundwater flow during a pumping test were measured on the ground surface on both the pumping and the recovery phases a novel methodology to estimate the hydraulic conductivity from self potential measurements is proposed hydraulic conductivity very close to that calculated from hydraulic data by means of neuman type curves has been obtained by solving the electrical flow equation through a linear least squares method moreover a kriging with external drift geostatistical methodology has been proposed to estimate the hydraulic head distribution the advantages given by this geostatistical method are that 1 hydraulic head distribution can be estimated without any previous electrokinetic coupling coefficient calculation and 2 the method is valid for either linear or nonlinear relationships between self potential and hydraulic head gradients an original finding of this work is that the relationship between self potential signals and drawdown around a pumping well is not always linear linearity applies only when the groundwater velocity is low but high nonlinearity occurs when hydraulic head gradient rises up kriging with the external drift method could be used for the inversion of the hydraulic conductivity distribution in a real heterogeneous aquifer by means of an appropriate conditioning technique

estimation of hard rock aquifers hydraulic conductivity from geoelectrical measurements a theoretical development with field application summary based on the analogy between darcy s law for groundwater flow and ohm s law for electric current flow a methodology has been developed to estimate the hydraulic conductivity and transmissivity of hard rock granite aquifer from geoelectrical parameters the common parameter aquifer thickness t has been used to combine the two relations and form an analytical equation mathematical relation shows a negative correlation between hydraulic conductivity and aquifer resistivity and a positive correlation between transmissivity and longitudinal conductance the methodology has been calibrated and validated in hard rock granite aquifers in india the good agreement between aquifer hydraulic conductivity k and transmissivity t obtained from the resistivity sounding parameters and those obtained from pumping test analysis proves the potentiality of the methodology it has been applied to estimate the k and t from the surface electrical resistivity parameters and results were utilized to prepare the k and t maps of maheshwaram watershed in hard rock terrain in india

nature of source material for hydrocarbons in cooper basin australia the cooper basin which produces a large proportion of australia s natural gas also includes small oil fields source rocks for the hydrocarbons are believed to be the terrestrial coal measure sediments of the permian gidgealpa group dispersed organic matter in the sediments of the gidgealpa group in the patchawarra trough cooper basin ranges between 1 and 5 by volume through seven formations less than 10 of the dispersed organic matter is exinite and less than 30 is vitrinite if these two macerals only are considered as source material for the liquid hydrocarbons none of the formations contains the 0 5 organic carbon currently deemed necessary for a sediment to be classified as a source rock if inertinite is regarded to have generating potential then most of the formations rate as good to excellent source rocks recent studies on vitrinites and inertinites from a variety of coal seams suggest that if vitrinite is accepted as a possible source of liquid hydrocarbons then inertinite is equally prospective consequently dispersed inertinite in the gidgealpa group sediments is proposed as one of the sources for the liquid hydrocarbons in the cooper basin

sequential aquifer tests at a well field montalto uffugo scalo italy 1 this paper investigates our ability to characterize an aquifer using a sequential aquifer test in a well field that consists of six wells during the test we pumped water out from the aquifer at one well and monitored the water level changes at the rest of the wells to obtain a set of five well hydrographs by pumping at another of the six wells we obtained another set of five hydrographs this procedure was repeated until each of the six wells was pumped we then analyzed the six sets of hydrographs using the classical drawdown time the drawdown distance and the drawdown distance time methods results of the analysis confirm recent findings that the transmissivity estimates vary significantly at early time and stabilize at late time at late time the estimated values from all hydrographs are similar overall but vary slightly according to the locations of the pumping and observation wells in contrast storage coefficient estimates stabilized rapidly to distinct values associated with the well locations we subsequently used a hydraulic tomography approach to include all hydrographs from the sequential aquifer test to estimate the spatially varying transmissivity and storage coefficient fields the estimated fields appear to be realistic they reflect the geologic setting and the behaviors of the well hydrographs although more definitive confirmation is needed

modeling of streaming potential responses caused by oil well pumping the occurrence of streaming potentials is directly related to movement of fluids in the subsurface to investigate whether streaming potential measurements in boreholes and at the surface can be used to monitor subsurface flow and detect subsurface flow patterns in oil reservoirs we model streaming potential responses caused by oil well pumping in monitoring wells and at the earth s surface since the model parameters permeabilities cross coupling properties and electric conductivities depend on a few basic rock physics parameters such as brine conductivity amount of water saturation and porosity the model parameters are evaluated self consistently using rock physics models using a threedimensional 3 d finite difference algorithm the governing differential equations that are drawn from nonequilibrium thermodynamics are solved numerically in three self consistent steps solution of the hydraulic problem computation of the streaming current sources based on the principle of conservation of char

a review on modeling inversion and interpretation of self potential in mineral exploration and tracing paleo shear zones abstract this study discusses the improvements of different modeling and inversion approaches to self potential sp anomaly associated with shallow and deep subsurface imaging the study also focuses on the fundamental foundations of self potential which have been advanced with time and event cause system and application in different investigation fields in addition a point by point forward modeling of different subsurface idealized geological bodies is discussed various sp techniques utilized for interpretation have likewise been examined for each use of sp anomaly besides the uncertainty associated with the understanding of self potential interpretation has also been discussed additionally the above studies were used to examine the diverse subsurface idealized geologic bodies deciphered from different inversion and elucidation strategies combinations of 17 real field illustrations were examined and a similar investigation was conducted for different interpretation strategies moreover a similar study was carried out to gain insights to mineralized bodies associated with different subsurface structures and the depth of the ore body and the rest of the model parameters are also discussed a correlation between the field information and the interpreted model information is shown considering different elucidation techniques wherever information was available the significance of this type of study is its multi purpose application in investigating various subsurface problems related to mineral exploration and tracing paleo shear zones this study would be very useful to scientists investigating the use of self potential in mineral ore investigation and in tracing paleo shear zones in continental crust

monitoring of an infiltration experiment using the self potential method 1 an infiltration test was performed from a ditch with the purpose of monitoring the evolution of the piezometric levels using self potential measurements made at the ground surface we used a set of 18 piezometers and a network of 41 nonpolarizable pb pbcl2 electrodes the variations of the self potential signals are linearly correlated to the piezometric level changes with an apparent voltage coupling coefficient of 5 5 0 9 mv m 1 we measured independently of this infiltration test the three material properties entering the macroscopic field equations they are the resistivity distribution of the soil its mean hydraulic conductivity and its intrinsic streaming potential coupling coefficient 5 8 1 1 mv m 1 then we modeled numerically the infiltration test and the associated self potential signals using a two dimensional finite difference code the numerical model reproduces fairly well the observed results this investigation demonstrates the effectiveness of the self potential method in field conditions to monitor small variations 0 60 m of the water table it offers for the first time a test of the electrokinetic theory in the field with independent evaluation of the material properties entering the field equations

correlation of geoelectric data with aquifer parameters to delineate the groundwater potential of hard rock terrain in central uganda knowledge of aquifer parameters is essential for management of groundwater resources conventionally these parameters are estimated through pumping tests carried out on water wells this paper presents a study that was conducted in three villages tumba kabazi and ndaiga of nakasongola district central uganda to investigate the hydrogeological characteristics of the basement aquifers our objective was to correlate surface resistivity data with aquifer properties in order to reveal the groundwater potential in the district existing electrical resistivity and borehole data from 20 villages in nakasongola district were used to correlate the aquifer apparent resistivity e with its hydraulic conductivity ke and aquifer transverse resistance tr with its transmissivity te ke was found to be related to e by text log k text e 0 002 rho text e 2 692 similarly tr was found to be related to t by text tr 0 07t text e 2260 using these expressions aquifer parameters tc and kc were extrapolated from measurements obtained from surface resistivity surveys our results show very low resistivities for the presumed water bearing aquifer zones possibly because of deteriorating quality of the groundwater and their packing and grain size drilling at the preferred ves spots was conducted before the pumping tests to reveal the aquifer characteristics aquifer parameters to and ko as obtained from pumping tests gave values 29 424 7 m2 day 374 3 m day 9 801 1 m2 day 437 0 m day 31 852 4 m2 day 392 9 m day the estimated aquifer parameter tc and kc when extrapolated from surface geoelectrical data gave 7 142 9 m2 day 381 9 m day 28 200 0 m2 day 463 4 m day 19 428 6 m2 day 459 2 m day for tumba kabazi and ndaiga villages respectively interestingly the similarity between the kc and ko pairs was not significantly different we observed no significant relationships between the tc and to pairs the root mean square errors were estimated to be 18 159 m2 day and 41 4 m day

fluvial channel and overbank deposits from the westphalian of the durham coalfield ne england the westphalian upper carboniferous coal measures of the durham coalfield in ne england were deposited in lower and upper delta plain environments distributary channels crossed the plain and were separated by shallow interdistributary lakes and bays detailed observation of three dimensional 3 d opencast surface mine exposures in collaboration with subsurface borehole analysis has revealed the existence of five varieties of channel deposits and two associated overbank facies within the durham coal measures major distributary channels were the major avenues of sediment transport across the coal measures plain were variably sinuous mostly 1 2 km wide and deposited elongate belts of sand mostly up to 5 km wide proximal major crevasse splay channels formed by the breaching of major channel banks during flood events were straight sand filled and up to 400 m wide minor distributary channels formed by the sustained operation of such crevasses varied from straight to highly sinuous and deposited shoestring sand mud belts up to a few hundred metres wide minor crevasse channels generally straight and up to 50 m wide were formed through bank breaching of minor and in a few cases major distributaries distal feeder channels formed down palaeocurrent extensions of minor distributaries which supplied interdistributary minor delta subsystems were generally straight and up to 200 m wide of the two types of channel overbank levee deposits recognized one comprising thinly interbedded fine grained sandstone and siltstone claystone is mostly though not exclusively associated with major distributary channels the other consisting of massive siltstones with regularly spaced thin claystone bands is uniquely developed at the margins of minor distributary channels the lower part of the westphalian a succession in the northern pennines records a change in the depositional environment upwards from a lower to upper delta plain through this transition major channel deposits show evidence of having evolved from being of dominantly low sinuosity to being more variable in morphology channel sedimentation was profoundly influenced by regular possibly seasonal variations in flow stage and sediment load

permeability dependence of streaming potential coefficient in porous media in theory the streaming potential coefficient depends not only on the zeta potential but also on the permeability of the rocks that partially determines the surface conductivity of the rocks however in practice it is hard to show the permeability dependence of streaming potential coefficients because of the variation of zeta potential from sample to sample to study permeability dependence of streaming potential including the effects of the variation of the zeta potential and surface conductance due to the difference in mineral compositions between samples we perform measurements on 12 consolidated samples including natural and artificial samples saturated with 7 different nacl solutions to determine the streaming potential coefficients the results have shown that the streaming potential coefficients strongly depend on the permeability of the samples for low fluid conductivity when the fluid conductivity is larger than than 0 50 s m for the natural samples or 0 25 s m for the artificial ceramic samples the streaming potential coefficient is independent of permeability this behavior is quantitatively explained by a theoretical model

a transient method for measuring the dc streaming potential coefficient of porous and fractured rocks high quality streaming potential coupling coefficient measurements have been carried out using a newly designed cell with both a steady state methodology and a new pressure transient approach the pressure transient approach has shown itself to be particularly good at providing high quality streaming potential coefficient measurements as each transient increase or decrease allows thousands of measurements to be made at different pressures to which a good linear regression can be fitted nevertheless the transient method can be up to 5 times as fast as the conventional measurement approaches because data from all flow rates are taken in the same transient measurement rather than separately test measurements have been made on samples of berea and boise sandstone as a function of salinity approximately 18 salinities between 10 5 mol dm3 and 2 mol dm3 the data have also been inverted to obtain the zeta potential the streaming potential coefficient becomes greater more negative for fluids with lower salinities which is consistent with existing measurements our measurements are also consistent with the high salinity streaming potential coefficient measurements made by vinogradov et al 2010 both the streaming potential coefficient and the zeta potential have also been modeled using the theoretical approach of glover 2012 this modeling allows the microstructural electrochemical and fluid properties of the saturated rock to be taken into account in order to provide a relationship that is unique to each particular rock sample in all cases we found that the experimental data were a good match to the theoretical model

three dimensional inversion of self potential data used to constrain the pattern of groundwater flow in geothermal fields 1 we propose an algorithm to invert self potential signals measured at the ground surface of the earth to localize hydromechanical disturbances or to the pattern of groundwater flow in geothermal systems the self potential signals result from the divergence of the streaming current density groundwater flow can be either driven by topography of the water table free convection or deformation of the medium the algorithm includes the electrical resistivity distribution of the medium obtained independently by dc resistance tomography or electromagnetic methods or by coding the assumed geology in terms of distribution of the electrical resistivity accounting for the effect of the temperature and salinity distributions and possibly constraints from borehole measurements inversion of the distribution of the source current density from ground surface and borehole self potential measurements is achieved by solving the inverse problem using tikhonov regularization solutions that are compatible with the physics of the primary flow problem by introducing assumptions regarding the smoothness or the compactness of the source and the three dimensional distribution of the electrical resistivity of the system the inverse problem can be solved in obtaining the three dimensional distribution of the current source density in the ground however an annihilator can be added to the inverted source geometry without affecting the measured self potential field annihilators can be obtained from boundary conditions synthetic models and a sandbox experiment are discussed to demonstrate the validity of the algorithm an application is presented to the geothermal field of cerro prieto baja california mexico using literature data inversion of the self potential and resistivity data allows observing a plume of hot groundwater rising to the ground surface in the central part of the investigated area and discharging to the ground surface in the southwest part the temperature anomaly associated with the existence of this plume is independently observed by interpolating borehole temperature measurements we found a good agreement between the distribution of the temperature and the inverted source current density the proposed method appears therefore as a noninvasive method for remote detection and three dimensional mapping of subsurface groundwater flow

steranes and triterpanes generated from kerogen pyrolysis in the absence and presence of minerals abstract steranes and triterpanes generated from pyrolysis of immature monterey formation kerogen in the presence and absence of calcite illite and montmorillonite reveal results that are both consistent and divergent with published data that reflect the use of these biological markers as maturation indicators the extent of isomerization of biomarkers generated from pyrolysis of kerogen at 300 c for 2 hours at c 20 in 14 h 17 h steranes at c 22 in 17 h 21 h hopanes and of 17 h 21 h hopanes correspond to early diagenetic stages in rock extracts from sedimentary basins isomerization increases with heating time and after 1000 hours attains values which correspond to the catagenetic stage in sedimentary basins or equivalent to that of mature oil stepwise pyrolysis of the kerogen indicates faster isomerization rates for steranes and triterpanes in the bitumen than for those retained in the kerogen structure confirming earlier studies presence of a mineral matrix can influence the isomerization of steranes and triterpanes considerably comparisons with results from kerogen heated alone for a given maturation stage show that calcite inhibits illite catalyzes slightly and montmorillonite has a pronounced catalytic effect on these reactions this effect results in early isomerization of steranes and hopanes corresponding to the catagenetic stage in the presence of montmorillonite while kerogen or kerogen with calcite held at the same temperature 300 c and time 10 hours only yield isomerized products which correspond to a diagenetic stage further illite and montmorillonite affect various isomerization reactions differently the fastest reaction is the isomerization at c 20 in 14 h 17 h steranes followed by that at c 22 in 17 h 21 h hopanes and the slowest is the formation of 14 h 17 h steranes these results show that maturation measurements of rock or oil samples from sedimentary basins which use biological markers have to take into account the mineral matrix effects which have been largely ignored until present