Mitch D. Pavlovic¹, Michael Rabinovich¹

(1) Baker Atlas, Houston, TX

ABSTRACT: Calibration of the Borehole Image Resistivity Using 2D Inversion of Array Induction Logs for Improved Petrophysical Evaluation of Thinly-Laminated Formations

We have applied new modeling/inversion data processing that combines borehole image and conventional formation evaluation data to analyze Gulf of Mexico data set with thinly laminated intervals.

Thinly bedded sand-shale geological sequences are encountered throughout the world, often as low-contrast, low-resistivity pay intervals. The thickness of many individual layers is below the resolution capability of conventional logs. It creates a necessity for using high-resolution borehole image logs, that provide the ability to calculate more accurately net reservoir volumes. Integration of borehole image log data and traditional open-hole log data significantly improves the petrophysical evaluation of laminated shaly sands and often leads to increased net pay.

Recently a new advanced technique for complete log-based reservoir description based on integration of borehole image and conventional logs has been proposed. It includes the determination of several important reservoirs properties such as enhanced porosity, laminar shale volume, and improved water saturation calculation that can predict effective hydrocarbon volumes in thinly bedded geological sequences. 2D inversion of conventional array induction log with enhanced layering from imaging tool allows one to create a thinly laminated 2D model that satisfies both the imaging and induction measurements. Presented results indicate that accurate depth matching between image and conventional logs may be achieved using this approach. The case study from the Gulf of Mexico illustrates the technique.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado