Endre Turai

Interval inversion of borehole data for petrophysical characterization of complex reservoirs

Wireline logging surveys are routinely used for the reconnaissance and quantitative characterization of multi-mineral hydrocarbon structures. The interpretation of well-logging data, however, is quite a challenging task, because the conventionally used local inversion procedure becomes either an underdetermined or a slightly overdetermined problem that may result in poor parameter estimation. In order to determine the petrophysical model composed of several parameters, such as specific volumes of matrix components, water saturation, primary and secondary porosity and numerous zone-parameters, in a more reliable way a new inversion methodology is required. We suggest a joint inversion technique for the estimation of model parameters of multi-mineral rocks that inverts data acquired from a larger depth interval (hydrocarbon zone). The inverse problem is formulated assuming homogeneous intervals within the zone to get a highly overdetermined inversion procedure. The interval inversion method has been applied to shaly sandy hydrocarbon reservoirs, in this study, that is used for the estimation of petrophysical parameters of complex reservoirs. Numerical results with synthetic and field data demonstrate the feasibility of the inversion method in investigating carbonate and metamorphic structures.

Factor analysis of borehole logs for evaluating formation shaliness: a hydrogeophysical application for groundwater studies

The calculation of groundwater reserves in shaly sand aquifers requires a reliable estimation of effective porosity and permeability; the amount of shaliness as a related quantity can be determined from well log analysis. The conventionally used linear model, connecting the natural gamma-ray index to shale content, often gives only a rough estimate of shale volume. A non-linear model is suggested, which is derived from the factor analysis of well-logging data. An earlier study of hydrocarbon wells revealed an empirical relationship between the factor scores and shale volume, independent of the well site. Borehole logs from three groundwater wells drilled in the northeastern Great Hungarian Plain are analyzed to derive depth logs of factor variables, which are then correlated with shale volumes given from the method of Larionov. Shale volume logs derived by the statistical procedure are in close agreement with those derived from Larionov’s formula, which confirms the validity of the non-linear approximation. The statistical results are in good accordance with laboratory measurements made on core samples. Whereas conventional methods normally use a single well log as input, factor analysis processes all available logs to provide groundwater exploration with reliable estimations of shale volume.RésuméLe calcul de réserves d’eau souterraine dans des aquifères sablo-argileux nécessite une estimation fiable de la porosité efficace et de la perméabilité; la quantité d’argilosité comme paramètre relatif peut être déterminée à partir de l’analyse des logs de forage. Le modèle linéaire communément utilisé, associant l’index d’émission gamma à la teneur en argiles donne souvent une estimation grossière du volume d’argiles. Un modèle non linéaire est suggéré, qui est dérivé de l’analyse factorielle des données de logs de forages. Une étude antérieure de forages pour hydrocarbures avait révélé une relation empirique entre les scores de l’analyse factorielle et le volume d’argiles, indépendamment de l’emplacement du forage. Les logs des trois forages d’eau exécutés au Nord Est de la Grande Plaine Hongroise sont analysés pour déduire les variables des logs pour l’analyse factorielle, qui sont ensuite corrélées avec le volume d’argiles donné par la méthode de Larionov. Les logs de volume d’argiles dérivés de la procédure statistique sont en accord étroit avec ceux dérivés de la formule de Larionov, ce qui confirme la validité de l’approximation non linéaire. Les résultats statistiques sont en bon accord avec les mesures de laboratoire faites sur des carottes. Alors que les méthodes conventionnelles utilisent normalement le log unique d’un forage comme entrée, l’analyse factorielle considère tous les logs disponibles pour fournir une exploration des aquifères avec une estimation fiable du volume des argiles.ResumenEl cálculo de las reservas de agua subterránea en acuíferos de arenas arcillosas requiere una estimación confiable de la porosidad eficaz y de la permeabilidad; la magnitud de la arcillosidad como una cantidad relacionada puede ser determinada a partir de análisis de registros de pozos. El modelo lineal convencionalmente usado, que conecta el índice de rayos gamma natural con el contenido de arcilla, a menudo da sólo una estimación grosera del volumen de arcilla. Se sugiere un modelo no lineal, desarrollado del análisis factorial a partir de datos de registros de pozos. Un estudio anterior de pozos hidrocarburíferos reveló una relación empírica entre los factores determinantes y el volumen de arcilla, independiente de la localización del pozo. Se analizaron los registros de de tres pozos de agua subterránea perforados en el noreste de la planicie Great Hungarian para deducir los registros en profundidad de los factores determinantes, los cuales fueron luego correlacionados con los volúmenes de arcilla dados a partir del método de Larionov. Los registros del volumen de arcilla deducidos por el procedimiento estadístico están en cercana coincidencia con aquellos derivados de la fórmula de Larionov’s, lo cual confirma la validez de la aproximación no lineal. Los resultados estadísticos están en un buen acuerdo con las mediciones de laboratorio hechas sobre muestras testigos. Mientras que los métodos convencionales normalmente usan un solo registro de pozo como entrada, el análisis factorial procesa todos los registros disponibles para proveer a la exploración de agua subterránea con estimaciones confiables del volumen de arcilla.KivonatAz agyagos homok tárolók édesvíz-készletének számítása az effektív porozitás és a permeábilitás megbízható becslését igényli; a karotázs szelvények kiértékeléséből meghatározható az agyagtartalom, mint ehhez kapcsolódó mennyiség. A hagyományosan alkalmazott lineáris modell, mely a természetes gamma indexhez köti az agyagtartalmat, gyakran csak durva becslés ad. A cikkben egy nemlineáris modellt javaslunk, amely mélyfúrási geofizikai szelvények faktoranalíziséből származik. Egy korábbi, szénhidrogén-kutató fúrásban történő alkalmazás terület-független tapasztalati összefüggést mutatott a faktor értékek és az agyagtartalom között. Jelen cikkben az Alföld észak-keleti részén fúrt három vízkutató fúrás szelvényeit dolgozzuk fel, abból származtatjuk a faktorok mélységszelvényeit, majd azokat a Larionov módszerrel kapott agyagtartalom szelvényekkel hasonlítjuk össze. A statisztikai módszerrel kapott agyagtartalmak jó egyezést mutatnak a Larionov egyenlettel számítottakkal, amely megerősíti a nemlineáris közelítés érvényességet. A statisztikai eredmények jó összhangban állnak magmintákon végzett laboratóriumi mérések eredményeivel. Míg a hagyományos módszerek általában egyetlen fúrólyuk szelvényt használnak fel bemeneti adatként, addig a faktoranalízis az összes rendelkezésre álló szelvényt feldolgozza, mellyel a vízkutatás számára megbízható agyagtartalom becslés valósítható meg.ResumoO cálculo das reservas de água subterrânea em aquíferos de areia argilosa requere uma estimação fiável da porosidade efetiva e da permeabilidade; e do teor de argilas, como uma quantidade relativa pode ser determinada a partir da análise de testemunhos de sondagem. O modelo linear convencional usado, correlacionando o índice de raio-gama natural com o conteúdo de argila, dá muitas vezes apenas uma estimativa grosseira do volume de argilas. É sugerido um modelo não linear, derivado do fator de análise dos dados dos testemunhos de sondagem. Um estudo anterior de furos de hidrocarbonetos revelou uma relação empírica entre os resultados fatoriais e o volume de argilas, independentemente dos locais dos furos. São analisados os testemunhos de sondagem de três furos de água subterrânea perfurados no nordeste da Grande Planície Húngara, a fim de obter perfis de profundidade das variáveis fatoriais, os quais são depois correlacionados com os volumes de argila dados pelo método de Larionov. O volume de argilas obtido por procedimento estatístico está de acordo com os obtidos a partir da fórmula de Larionov, a qual confirma a validade da aproximação não linear. Os resultados estatísticos encontram-se de acordo com as medições de laboratório feitas em amostras de testemunhos. Enquanto os métodos convencionais usam normalmente um furo simples como entrada, a análise fatorial processa todos os testemunhos disponíveis, a fim de providenciar a exploração de águas subterrâneas com estimações mais fiáveis sobre o volume de argilas.

In-mine geoelectric investigations for detecting tectonic disturbances in coal seam structures

The methods of in-mine seam-sounding and transillumination (geoelectric tomography) for the detection of tectonic disturbances of coal seams were developed by the Department of Geophysics of the University of Miskolc in the 1970–80’s with the effective support of the former “Borsod” Coal Mines Ltd.The paper gives an overview about the theory of seam-sounding and a special geoelectric tomographic inversion, and introduces the in-mine geoelectric seam-sounding and transillumination measurement systems using vertical electrode dipoles. In the second part the paper, the results of an in-mine geoelectric measurement are presented, which was carried out in order to detect tectonic disturbances of the Miocene aged coal seams situated in Slovakia. As results of the geophysical investigation, the authors forecasted the tectonic features in the coal seam. The company confirmed the results by independent information about seam disturbances and tectonic features arising from the excavation of the investigated area.

Geoelectric Characterization of Thermal Water Aquifers Using 2.5D Inversion of VES Measurements

This paper presents a short theoretical summary of the series expansion-based 2.5D combined geoelectric weighted inversion (CGWI) method and highlights the advantageous way with which the number of unknowns can be decreased due to the simultaneous characteristic of this inversion. 2.5D CGWI is an approximate inversion method for the determination of 3D structures, which uses the joint 2D forward modeling of dip and strike direction data. In the inversion procedure, the Steiner’s most frequent value method is applied to the automatic separation of dip and strike direction data and outliers. The workflow of inversion and its practical application are presented in the study. For conventional vertical electrical sounding (VES) measurements, this method can determine the parameters of complex structures more accurately than the single inversion method. Field data show that the 2.5D CGWI which was developed can determine the optimal location for drilling an exploratory thermal water prospecting well. The novelty of this research is that the measured VES data in dip and strike direction are jointly inverted by the 2.5D CGWI method.

Pressure dependence of seismic Q – a microcrack-based petrophysical model

The pressure dependence of the quality factor of acoustic waves is an extensively explored rock physical problem. To reasonably interpret laboratory measurements, a petrophysical model is required which provides the physical explanation of the nonlinear pressure dependence of the seismic quality factor. In this paper we highlight important features of seismic wave attenuation and propagation under varying pressure which contribute to creating a petrophysical model. The model is starting from the idea that microcracks are opened and closed under varying pressure. Within the confines of the model, differential equations are set up describing the relationship between microcrack density and confining pressure as well as between quality factor and microcrack density. Combining these equations, a three-parameter expression is derived which has clear physical meaning. We found that the pressure dependence of the quality factor can be well described by a threeparameter exponential equation in the form Q = Q0 ΔQ0 (1-exp(−λσ)) which gives also the physical meaning of pressure versus quality factor connection. The physical explanation of each parameter is clarified in the paper, i.e. Q0 is the quality factor at zero pressure, ΔQ0 is the possible range of quality factor and λ is a new petrophysical parameter (the logarithmic stress sensitivity). The model was applied on measurement data sets adopted from the literature. The material parameters of the model were determined by using linearized inversion method and the laboratory measurements were compared to the theoretical data. The theoretical data matched accurately with measured data proving that the petrophysical model applies well in practice.

2D inversion processing of geoelectric measurements with archaeological aim

The paper presents the opportunities of archaeological applications of the geoelectric geophysical methods. The electrical conductivity properties of buried archaeological objects (wall relics, roads, channels, graves, metal objects, etc.) measurably differ from the electrical conductivity properties of soils and rocks covering archaeological objects. So these archaeological objects are detectable with geoelectric measurements performed on the surface of the Earth.The paper outlines the relation between the electrical parameters of individual archaeological objects and the medium covering them; and it supports the archaeological adaptability of geoelectric methods with the presentation of the results of field measurements.

Examination of rainfall data for 110 years using spectral and wavelet analysis

The aim of our research was to better understand the spectral characteristics of precipitation variability, because through infiltration, this is the most important source of groundwater recharge. ...

Interpretation of IP Measurements Using an Inversion Based TAU-Transform Method

The paper presents the TAU-Transform of the Time-Domain IP curves and gives an approximate solution for TAU-transformation using inverse problem theory. A method for estimation of the type and the measure of soil contaminations will also be introduced. The determination of the contamination type (metallic or chemical) comes from the time constant spectra. The estimation of the soil contamination is based on the waited amplitude values of the time constant spectra. The application of the method is demonstrated in a contaminated industrial area in Hungary.

Quick imaging of MT data using an approximate inversion algorithm

An approximate inversion method is proposed for the imaging of MT data measured above 2-D geological structures. In discretizing the model parameters a series expansion formula is used with interval-wise constant functions or Chebishev polinomials as basis functions. The expansion coefficients serve as the unknown parameters of the inverse problem. All the data sets collected at various sites along the measurement line are integrated in a single inversion procedure in which the solution of the forward problem is approximated by the well-known 1-D magnetotelluric formulae with the use of the local values (at the measurement site) of the laterally changing model parameters. The imaging method is tested by means of synthetic data set calculated on a 2-D geological model in both TM and TE mode. Our numerical tests show that the proposed imaging procedure gives quick and highly acceptable parameter estimation.

TAU-Transformation of Time-Domain IP Data Measured Above a Hungarian Refuse Dump

e values of the time constant spectra. This method was tested over several contaminated sites. In this extended abstract we show a new interpretation result measured over a refuse dump in Hungary near Felsőtelekes. The analysis of the IP data shows that there are some very high contaminated parts in waste-rock bodies. The types of the polarization were mainly redox and metallic.