Ray Impedance Research Articles

Rock physics analysis and Gassmann’s fluid substitution for reservoir characterization of “G” field, Niger Delta

This study investigates the relationship between rock physics and petrophysical parameters in reservoir characterization. The data used for the analysis consist of suites of three wells, intercalated with sand and shale. Two reservoir sands were mapped, and petrophysical analysis was done to evaluate the hydrocarbon potential of “G” field. Elastic parameters such as compressional velocity (Vp), shear wave (Vs), acoustic impedance (AI), LambdaRho (λρ), MuRho (μρ), and bulk modulus (k) were generated and cross-plotted against petrophysical parameters to infer the Facies types. The sand lithology gave a low gamma ray, high resistivity, and low acoustic impedance in contrast to the shale. For the three wells, two reservoirs were observed each, at average depth ranging between 1546 and 1605 m and between 2010 and 2168 m. Cross plots such as Vp/Vs versus AI using gamma ray as indicator, λρ versus μρ using density as indicator, and volume of shale (Vsh) versus water saturation (Sw) using porosity as indicator were carried out for each reservoir to determine and discriminate their porosity and fluid content respectively. Well 2 was observed to be the most productive due to its high hydrocarbon saturation and reservoir characteristics. Gassmann’s fluid substitution was also carried out to understand the behavior of the dry rock; the pores were filled and superimposed on a rock physics template to extrapolate the general reservoir behavior of the field. It was observed that Vp and Rho decrease with increase in Vs for 100% gas saturation, while Vp and Rho increase as Vs remains constant with 100% water saturation.

Cross plotting of Rock Properties for Fluid and Lithology Discrimination using Well Data in a Niger Delta Oil Field

The cross plotting of rock properties for fluid and lithology discrimination was carried out in a Niger Delta oil field using well data from a given oil field. The data used for the analysis consist of suites of six wells. The reservoir was evaluated using gamma ray logs, volume of shale, resistivity and neutron porosity for well-02 and well-06. Sand lithology showed low gamma ray, high resistivity and low acoustic impedance. Cross plotting was carried out and the plots with most outstanding results were Vp/Vs versus AI, λρ Versus Vp/Vs, μρ against Density and λρ versus μρ. For the two wells considered, two reservoirs were observed, one reservoir was observed in well - 02 at a depth of 4600 ft to 5050 ft .and a reservoir was also observed for well - 06 at a depth of 10240 ft to 10600 ft. Crossplotting of rock properties discriminated the wells into lithologies of sand and shale which is typical of Niger Delta. The crossplot also discriminated the fluids into gas, brine and oil. This study has been able to discriminate hydrocarbon reservoirs using well logs in the field of study. Keywords : Hydrocarbon, Reservoir, Well – Logs, Crossplotting, Lithology

Viabilities of seismic ray impedance and elastic impedance for hydrocarbon-sand discrimination

Theoretical evaluation of the elastic impedance (EI) and the ray impedance (RI) reveals that RI has a more reliable value range and is less sensitive to noise than EI. We devised a new measurement [Formula: see text] to estimate the ray impedance from elastic impedance derived by existing techniques. The recovered [Formula: see text] was expressed in the form of a normalization of EI. It solved the range variability problem of EI and had the same interpretation capability as RI. In addition, reflection coefficients represented by [Formula: see text] showed good agreement with the Zeoppritz equation even at postcritical angle of incidence. Tests of these three attributes (RI, [Formula: see text], and EI) were performed on the log data of three different types of reservoir: a typical Class III marine gas-sand, a Class I tight gas-sand, and a Class II oil-bearing sand in thin sand-mud interbedded layers. Although the crossplots of EI against acoustic impedance (AI) showed visually similar characteristics for a gas-sand as that of RI, based on the linear/quadratic discrimination analysis, RI appeared to be more applicable than EI for characterizing gas sands, especially tight gas sands. [Formula: see text], estimated from EI, had a comparable value range to the AI, and retained the interpretation ability of the original RI. Application on real seismic data showed that existing EI inversion results could be improved straightforwardly by means of the introduced transformation.

Electrical Conductivity and Phase Transition Studies in the ZrO<sub>2</sub>-CdO System

The Solid Solution of ZrO2: Cdo Was Prepared by the Conventional Solid-State Reaction. Effect of Dopant Concentration on the Electrical Conductivity of ZrO2Was Studied for Different Compositions at Different Temperatures. the Conductivity Increases with the Addition of Cdo due to the Migration of Vacancies. the Conductivity Increases with Rise in Temperature up to 180°C and Thereby Decreases due to the Collapse of Fluorite Framework. A Second Rise in Conductivity at High Temperature beyond 460°C Is due to the Phase Transition of ZrO2from Monoclinic to Tetragonal. DSC, X Ray Powder Diffraction, Impedance Measurements and FTIR Spectral Studies Were Carried Out for Confirming the Doping Effect and Transitions in ZrO2. the Addition of Cdo to Zro2 Shifted the Phase Transition of ZrO2to Higher Temperatures as Confirmed by the DSC Results. the Occurrence of Single Semi Circle with a Low Frequency Inclined Spike Indicates that the Conductivity Is Mainly due to the Movement of Oxide Ions.

Estimation of body fat composition. Comparison of dual-energy X ray absortiometry, anthropometry and impedance

Estimation of body fat composition. Comparison of dual-energy X ray absortiometry, anthropometry and impedance