Complex Artifacts in Resistivity and Acoustic Image Data: Recognition and Use in Borehole Image Interpretation

Borehole image acquired through wireline and lwd logging provide vital high-resolution information to characterize the structural and sedimentological features of subsurface lithology encountered while drilling a well. These images data are very sensitive to the borehole and logging conditions. That is also the reason for creation of image artifacts from borehole image logs.

Image artifacts are features seen on the borehole image logs which are not related to formations logged. They are always present in one form or other, and are routinely dealt with by every image interpreter. Generally, three different major conditions can give rise to such artifacts. The first is while drilling the well bore, and are referred to as drilling-related features. The second type of image artifacts is generated while logging. The parameters used while logging the image tools and borehole conditions give rise to such type of artifacts. The third and final stage of image artifact generation can happen at the processing stage, which is an important stage of data handling to convert the data acquired by the imaging tools to represent actual formation responses. Some of the initial artifacts may be removed during processing, but others may remain or get enhanced if the parameters are not used correctly while processing. These artificial image responses need to be defined properly and dealt with in a very systematic and cautious manner while interpreting image logs. Borehole geologists need to know the origin or the artifacts, i.e., generated due to drilling, during logging, or at processing stage. Once identified and separated, the image data can then be analyzed to extract true formation properties.

Each imaging tool has its own artifacts which can generally be dealt with independently in most cases, however in special cases combining different image data can help identify complex artifacts in a comprehensive way. Several papers describe common artifacts seen on the different image logs, both as individual datasets and as integrated observations. This paper highlights some of the complex image artifacts not described before and can be used as reference in addition to commonly observed artifacts. These have been observed in the image data, acquired in different conditions across complex carbonate reservoirs of Kuwait.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California