Proceedings Volume Cover
Society of Petroleum Engineers  
SPE 35159  
Borehole Imaging The Future of Formation Evaluation  
R.L. Sanders, SPE,and K.D. Fuchs, Halliburton Energy Services  
Tool Descriptions and Image Display  
Copyright 1996, Society of Petroleum Engineers, Inc.  
The electrical micro-imaging tool is a six arm pad device with  
twenty-five button electrodes mounted on each pad (Fig. 1).  
Each button electrode emits an electrical current into the for•  
mation for a distance of fifteen inches. The changes in the  
permeability, porosity and lithology of the formations near the  
borehole wall are reflected as resistivity variations in the elec•  
trical current return to the individual electrodes. A system of  
magnetometers references the tool's orientation to magnetic  
north. Utilizing a computer workstation, these resistivity varia•  
tions are processed into a two dimensional image that repre•  
sents the surface ofthe borehole wall with respect to magnetic  
north (Fig. 2). The images are presented in either a gray-scale  
or color display with a standardized color code representing  
the· variation in formation features. Low porosity, low perme•  
ability, and high resistivity features represent the light end of  
the color spectrum. The high porosity, permeable, and low  
resistivity events are scaled as the darker colors.  
This paper was prepared for presentation at the Permian Basin Oil & Gas Recovery  
Conference held in Midland, Texas 27-29 March 1996.  
This paper was selected for presentation by an SPE Program Committee following review  
of information contained in an abstract submitted by the author(s). Contents of the  
paper, as presented, have not been reviewed by the Society of Petroleum Engineers and  
are sUbject to correction by the author(s). The material as presented, does not neces•  
sarily reflect any position of the SocietY of Petroleum  
its .officers,  
Papers presented at SPE meetings are sUbject to publication revIew by Editorial Com•  
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The emerging teclmology of borehole imaging coupled with  
the advances in graphics software will shape the future of for•  
mation evaluation because (1) imaging reveals new opportuni•  
ties for exploration in tIDCOnventional and previously neglected  
reservoirs,(2) imaging exhibits the complex distribution of  
porosity and permeability throughout the reservoir, and (3)  
imaging enhances the knowledge of the physical dynamics of  
the reservoir for improved stimulation techniques.  
Unconventional Reservoirs  
The electrical micro- imaging tool reveals many potential op•  
portunities that are present in unconventional reservoirs but  
may be undetected using standard logging suites. An uncon•  
ventional reservoir is described as a reservoir (1) where the  
presence of natural fractures is the primary reason for the hy•  
drocarbon production, (2) the reservoir is not considered pro•  
ductive in the area, and (3) the completion of the well may  
require unconventional stimulation techniques.  
An unconventional reservoir may be characterized by events  
occurring during the drilling of a well that may not be obvious  
on conventional logging suites. Examples of these events  
would be the incidence ofoil on the mud pits, gas increases on  
the mud log, or unusual drilling breaks without any corre•  
sponding curve responses on the conventional logs. Each of  
these events taken individually may not be considered signifi•  
cant but the sum of all the events would be could be relevant  
in terms ofa commercial discovery.  
Traditional methods of formation evaluation have relied upon  
the interpretation of data recorded from a wireline tool in the  
borehole. While no wireline tool directly measures the porosity  
or the resistivity ofthe formation, these properties have served  
as the basis for analysis offormations for some seventy years.  
The advantage of borehole imaging is the ability to visualize  
the many variations ofporosity types, permeability, and lithol•  
within the rock. Borehole imaging utilizes either  
acoustic or resistivity recording devices to graphically display  
the surface features ofthe borehole wall in the open hole envi•  
rorunent. This paper presents only the 'fesistivity based tool,  
the electrical micro-imaging tool as the source for the follow•  
ing case studies.  
One area of interest in the Permian Basin is the Spraberry  
Trend. The majority of wells drilled in the Spraberry Trend