Use of Electrical Borehole Imaging Aids in Evaluating Lower Miocene Submarine Channel Complex in Offshore Angola, West Africa

Paul Elliott¹, Antonio Mpanzu², Stephen Van Dalen³, and Janardhan Kurri^4
1Halliburton, Houston, TX
²Chevron (CABGOC),
³Chevron,
⁴Halliburton, Cabinda, Angola

The Halliburton Oil Mud Reservoir Imager (OMRI) tool was successfully tested in West Africa during 2006 in a variety of offshore reservoirs environments ranging from highly porous and permeable sandstones to relatively tight mixed siliclastic and carbonates. The first successful log was run in Block 14 offshore Angola over a Lower Miocene submarine channel complex in March, 2006. This test represents the first run of the OMRI tool in Angola and the first test outside the United States. Two 120-foot conventional cores were also taken in this well which allows direct calibration of the OMRI images with rock data. Preliminary comparison of static and dynamic images to the core and log data set indicates good OMRI image quality over the reservoir with an approximately one inch vertical resolution.
Subsequently, additional OMRI logs were successfully acquired in more resistive reservoir rocks with varying amounts of porosity and permeability in four different fields. Each log provided new and relevant information about the reservoir in question. Additional comparison to core results will be made over time. OMRI generates an electrical image of the borehole based upon the response of 36 micro-resistivity buttons and six calipers arranged in two groups of three. The six calipers act independently to generate a more accurate borehole shape and the six micro-resistivity pads articulate both horizontally and vertically for superior formation contact in rugose borehole conditions. The relative position of the tools sensors is provided by a tri-axial accelerometer. The addition of another oil based imaging device provides the industry with additional options when evaluating boreholes drilled with oil based mud.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece