ABSTRACT

Wireline log and core measurements form the basis for most of the current petrophvsical evaluation efforts throughout the Former Soviet Union (F. S. U.) by the Western petroleum industry. Understanding specific logging tool response characteristics and applying corrections for the effects of borehole environment can identify valid input data necessary for integrated interpretation methods. Many Russian log analysis textbooks and tool-specific chart books are available for electrical, nuclear and acoustic logs. Their application provides a wealth of insight to the methodologies and algorithms used by several generations of Russian petrophysicists Multiple techniques are needed to quantify Rt, Rxo, and Di. These techniques are based on unfocused and focused electrode and induction electrical measurements. Unfocused electrode (BKZ) methods often must be understood even when focused electrical logs are available, Forward modeling single and multiple inversion and combinations of these methods are used for lateral response interpretation. Published integrated radial geometrical and pseudo-geometrical factor curves for focused electrical logs are used to generate Western-style tornado charts for 1-D invasion modeling. Common nuclear measurements include natural gamma ray, neutron-gamma (capture) neutron-neutron (thermal and epithermal), and gamma-gamma density. Newer neutron logging tools may be configured as single or dual-detector devices. Nuclear logs used for porosity determination require specific knowledge of the tool calibration methods. Environmental corrections are necessary to avoid systematic errors in the estimation of porosity. Some Russian core measurement terminology differs from Western definitions and therefore must be understood for comparison with log measurements. Depth control during core acquisition is a common problem; hence, normalization of log measurements by histogram techniques rather than regression analysis may be appropriate. The rationale for coring and core measurements varies by area and reservoir type. Examples will demonstrate that the application of appropriate Russian tool response functions and environmental corrections can yield the necessary information for informed reservoir assessment.

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