Summary In petroleum exploration, reservoir navigation is used for reaching a productive reservoir and placing the borehole optimally inside the reservoir to maximize production. For proper well placement, it is necessary to calculate in real-time the parameters of the formation we are drilling in and the parameters of formations we are approaching. On the basis of these results, a decision to change the direction of drilling could be made. Modern logging-while-drilling (LWD) extra-deep and azimuthal resistivity tools acquire multicomponent, multispacing, and multifrequency data that provide sufficient information for resolving the surrounding formation parameters. These tools are generally used for reservoir navigation and real-time formation evaluation. However, real-time interpretation software is very often based on simplified resistivity models that can be inadequate and lead to incorrect geosteering decisions. The core of the newly developed software is an inversion algorithm based on transversely isotropic layered Earth with an arbitrary number of layers. The following model parameters are determined in real time: horizontal and vertical resistivities and thickness of each layer, formation dip, and azimuth. The inversion algorithm is based on the method of the most-probable parameter combination. The algorithm has good performance and excellent convergence because of its enhanced capability of avoiding local minima. This capability enables interpretation of real-time resistivity data, including azimuthal and extra-deep measurements. A graphical user interface (GUI) was developed to provide an interactive environment for each stage of the resistivity data interpretation process: preview of input resistivity logs, initial preprocessing and filtering of raw data, creation of initial guess, running inversion and viewing inversion results, and quality-control indicators. Applications of the developed software will be shown on a series of synthetic examples and field data from the North Sea and Gulf of Mexico (GOM). This newly developed software is currently in use for real-time reservoir navigation and post-well analysis.
The features of numerical VEMKZ data interpretation in deviated and horizontal wells entering oil-saturated and water-saturated formations are observed. On the basis of mathematical modeling of VEMKZ signals for typical hole path of horizontal wells the effects caused by crossing bed boundaries and thin layers with high resistivity are shown. The influence of electrical anisotropy on signals has been investigated. The influence of borehole rugosities and tool eccentricity was studied. The programs of numerical modeling have been developed at Institute of Petroleum Geology and Geophysics (IPGG) Siberian Branch of Russian Academy of Sciences. Algorithms and methodological procedures are used for numerical interpretation of VEMKZ data (including SKL set data) in case of thin reservoir, electrically contrasting shoulder beds and thin interlayers. The eccentricity, borehole rugosity, sine-shaped and spiral well bore influence on signals was investigated in case of typical hole and tool diameters, the programs of numerical correction have been developed. The fact that influence of electrical anisotropy in deviated well causes apparent resistivity increase is demonstrated. Numerical inversion VEMKZ data obtained in well entering terrigenous reservoir under-lied by thin layer with high resistivity have been processed. Starting model for inversion is generated by taking direct current data into account. Examples of real VEMKZ data interpretation are demonstrated. For investigations in deviated and horizontal wells the approach for finding true formation resistivity in thin reservoir using high-frequency induction measurements was proposed. This approach based on numerical signal modeling for deviated tool in horizontally-stratified earth. Algorithms for electrical anisotropy evaluating and thin-layer parameters estimating are observed.
Algorithms and software for numerical modeling and inversion of electromagnetic logs in the wells drilled with biopolymer and oil-based mud are developed. The algorithms are based on linearized solutions of the forward and inverse problems of electromagnetic logging and permit fast modeling of induction logs and efficient recovery of electric conductivity around the well. Mathematical modeling is based on numerical-analytical solution of the 2D forward problem taking into account high conductivity contrast between the well and the formation. Linear inversion is based on SVD-decomposition of information matrix. The results of numerical modeling and inversion of synthetic and field logs at the intervals of fluid-saturated terrigenous and carbonate formations drilled using biopolymer and oil-based mud are given.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.