1887

Abstract

Russian log interpretation has become an important and integral part of well log interpretation for major oil companies in search of oil in the former Soviet Union (FSU). In this work we address some of the major characteristics of common Russian resistivity logs especially BKZ logs and the difficulties associated with Russian log interpretation. Russian resisitivity log data primarily consist of focused (BK) and unfocused (BKZ) galvanic responses and induction tool responses. Russian log interpretation poses different kinds of problems compared to conventional western log interpretation due to the asymmetric and nonlinear nature of the tool responses. Traditionally, conventional resistivity interpretation is performed using charts. Chart interpretation is accomplished point by point and does not take into account asymmetric tool responses and bed-thickness effects. Other chart interpretation tools for Russian logs such as EKAR take into account layering effects, but require extensive interaction from the user, and do not provide uncertainty estimation for the results. Recent advances in computer hardware and development of fast forward modeling algorithms have allowed for the application of inversion algorithms in the interpretation of such well logs. We performed a 1-D and 2-D resistivity inversion on a Russian data set simulated for a benchmark Oklahoma formation model with conductive invasion in resistive layers. A joint inversion was performed using three unfocused galvanic curves (GZl, GZ2, and GZ3), a focused galvanic BK log (LL3-type device), and an induction (IK) curve using a Levenberg-Marquardt algorithm to estimate formation resistivity (R), invaded zone resistivity (Rxo) and invaded zone length (Lxo) for each layer. The mean squared difference between the simulated and synthetic data was used as the cost function. The inversion algorithm was successful in estimating the true model parameters from the Russian resistivity logs, including BKZ data.

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/content/papers/10.3997/2214-4609-pdb.299.119
1997-11-07
2024-03-29
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