B. P. Sarma1 and M. K. Singh2
1Ganga Valley Project, Oil India Limited, Noida, India
2HLS India Limited, New Delhi, India
ABSTRACT: The Detection, Identification & Characterization of Fractures- Secondary Porosity in Tight and Compact Siliclastic Rocks in Well Bilaspur-1, Ganga Basin, India, Utilizing the Acoustic Imaging Log - A Case Study
Oil India Limited (OIL), a Government of India Undertaking initiated exploration activities for oil and gas in the western part of Ganga basin, northern India during the early nineties over a Petroleum Exploration License (PEL) area of about 46,000 sq. km.
Integration of the various geoscientific studies such as high resolution aeromagnetics, remote sensing utilizing Landsat Imageries, geomicrobial and geochemical, besides 2-D seismic led to the drilling of the 1st wild cat exploratory well by OIL in the northwestern part (Rampur Low) of Sarda Depression in Ganga basin, India.
In continuing efforts towards producing more thorough and meaningful description / inferences of the formations as well the borehole features, Acoustic Imaging was run in the interval 2760 - 3160m in the Quartzitic sandstone section within the Vindhyans (Precambrian - Cambrian) which exhibited very low primary porosity although moderate to heavy mud loss during drilling through this section has indicated the presence of possible fractures.
Analysis of field log images for both fractured and thin-bedded formations are presented in this paper. Detection and characterization of various types of fractures using Acoustic Image log has also been enumerated in this paper which has resulted in the development of secondary porosity system in the Quartzitic sandstone section within Vindhyans in OIL's Bilaspur-1 well.
The identification as well as reasoning for heavy mud loss could be ascertained along with imaging details. Additional application has been found in the description of borehole features such as induced fractures. High-resolution acoustic caliper gives a measure of borehole rugosity as is observed in tight Quartzite formations. Acoustic Imaging has proved to be an impressive addition towards the quest for increasing details and precision of wireline logging techniques for evaluating hydrocarbon potential particularly in tight and compact formations.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado