Abstract: A fast, efficient and accurate pseudo 2-D inversion scheme for resistivity determination of an anisotropic formation uses data from a tool (3DEX) comprising three transmitters and three corresponding receivers sampling the formation in a plurality of spatial directions. An initial model of the formation including invasion zones is obtained using a conventional multifrequency and/or multispacing logging tool. A pseudo 2-D inversion scheme combines an accurate full 2-D forward solution of the synthetic responses of the earth model with a 1-D approximation of the sensitivity matrix of the horizontally layered anisotropic background model. The timesaving compared to a regular 2-D inversion scheme can be tremendous. The applicability of this scheme is important in cases when borehole and near-zone effects do not allow an interpretation based on 1-D inversion.

Abstract: Measurements made by a multicomponent logging tool in a borehole are inverted to obtain horizontal and vertical resistivities of a formation traversed by the borehole. The model includes layers of equal thickness, each layer having a horizontal resistivity and a vertical resistivity. For a vertical borehole, the inversion is done by first iteratively obtaining the horizontal resistivities of the layer using the Hzz component of the data wherein in successive steps of the iteration, the horizontal resistivity for each layer is multiplied by a ratio of a model Hzz output to the measured Hzz. The vertical resistivity model is set equal to the derived horizontal resistivities and the iterative process is repeated using the ratio of the model Hxx output to the measured Hxx. A similar process is used for boreholes with a known inclination. For such an inclined borehole, the two horizontal components Hxx and Hyy are summed to give a horizontal measurement Hxxyy that is independent of tool rotation.

Abstract: The total porosity of said formation, a fractional volume of the shale, and a resistivity of the shale are determined in a laminated reservoir including sands that may have dispersed shales therein. A tensor petrophysical model determines the laminar shale volume and laminar sand conductivity from vertical and horizontal conductivities derived from multi-component induction log data. The volume of dispersed shale and the total and effective porosities of the laminar sand fraction are determined using a Thomas-Stieber-Juhasz approach. Removal of laminar shale conductivity and porosity effects reduces the laminated shaly sand problem to a single dispersed shaly sand model to which the Waxman-Smits equation can be applied.

Abstract: An improved induction tool for formation resistivity evaluations. The tool provides electromagnetic transmitters and sensors suitable for transmitting and receiving magnetic fields in radial directions that are orthogonal to the tool's longitudinal axis with minimal susceptibility to errors associated with parasitic eddy currents induced in the metal components surrounding the transmitter and receiver coils. Various transmitter receiver combinations are provided to select sensitivity to a desired reservoir formation properties, for example, different orientations xy, xz, yz, 20-40, 20-90, and combinations, such as, Symmetric—symmetric; Asymmetric—symmetric; and Asymmetric—asymmetric. Measurements made with a multi-component logging instrument when used in a substantially horizontal, vertical or deviated borehole in earth formations are diagnostic of the direction of resistive beds relative to the position of the borehole.

Abstract: A fast, efficient and accurate pseudo 2-D inversion scheme for resistivity determination of an anisotropic formation uses data from a tool (3DEX) comprising three transmitters and three corresponding receivers sampling the formation in a plurality of spatial directions. An initial model of the formation including invasion zones is obtained using a conventional multifrequency and/or multispacing logging tool. A pseudo 2-D inversion scheme combines an accurate full 2-D forward solution of the synthetic responses of the earth model with a 1-D approximation of the sensitivity matrix of the horizontally layered anisotropic background model. The timesaving compared to a regular 2-D inversion scheme can be tremendous. The applicability of this scheme is important in cases when borehole and near-zone effects do not allow an interpretation based on 1-D inversion.

Abstract: Data are acquired using multi-array logging tool in a borehole having an angle of inclination to a normal to the bedding plane of earth formations. The multi-array measurements are filtered using angle dependent filters to give a filtered curve corresponding to a target one of the multi-array measurements using angle dependent filters. Correlation coefficients are determined for a set of possible dip angles and a relative dip angle is estimated from the correlation coefficients. This dip angle estimate together with bed boundaries obtained from the multi-array measurements are used for inverting multi-component measurements alone or jointly with multi-array measurements to refine the relative dip angle interpretation and give horizontal and vertical formation resistivity.

Abstract: The total porosity of a formation, a fractional volume of the shale, and a resistivity of the shale are determined in a laminated reservoir including sands that may have dispersed shales therein. A tensor petrophysical model determines the laminar shale volume and laminar sand conductivity from vertical and horizontal conductivities derived from multi-component induction log data. The volume of dispersed shale and the total and effective porosities of the laminar sand fraction are determined using a Thomas-Stieber-Juhasz approach. Removal of laminar shale conductivity and porosity effects reduces the laminated shaly sand problem to a single dispersed shaly sand model to which the Waxman-Smits equation can be applied.

Abstract: Measurements made by a multicomponent logging tool in a borehole are inverted to obtain horizontal and vertical resistivities and formation dip and azimuth angles of a formation traversed by the borehole. The inversion is performed using a generalized Marquardt-Levenberg method. In this generalized Marquardt-Levenberg method, a data objective function is defined that is related to a difference between the model output and the measured data. The iterative procedure involves reducing a global objective function that is the sum of the data objective function and a model objective function related to changes in the model in successive iterations. In an alternate embodiment of the invention, the formation azimuth angle is excluded from the iterative process by using derived relations between the multicomponent measurements.

Abstract: The total porosity of said formation, a fractional volume of the shale, and a resistivity of the shale are determined in a laminated reservoir including sands that may have dispersed shales therein. A tensor petrophysical model determines the laminar shale volume and laminar sand conductivity from vertical and horizontal conductivities derived from multi-component induction log data. NMR data are used to obtain measurements of the total clay-bound water in the formation and the clay bound water in shales in the formation.