Lithofacial Interpretation of the Section in the Core Absence Intervals Using Microimager Data
Authors: Kazantsev Gleb Vladimirovich , Ivanov Alexey Igorevitch 
Published: October 2021

This work is devoted to a new direction for geology – interpretation of studied section of sediments through the analysis of microimager data.

Imager analysis provides important information about the structural and textural features of rocks, nature of stratification, structural occurrence of the section, natural and technogenic fracturing. The use of borehole microimages in geological and field studies allows us to deepen and expand the existing ideas about the geological structure of known hydrocarbon deposits, and the integrated use of images allows us to solve narrowly focused tasks (Rybalchenko et al., 2016). It is worth to notice that today the potential of reservoir microimagers as a geological GIS tool is underestimated (Isotova et al., 1993) (Mathis et al., 1995) (Donselaar et al., 2005). The most widespread development of borehole imagers abroad occurred in the mid-80s of the XX century. Currently, their use is still gaining popularity in Russia. The use of microimages is not limited to the open trunk of a drilled well, technologies that allow obtaining images directly during drilling are available and widely used (Rybalchenko et al., 2016). From the point of view of well productivity, they can be used to characterize such key parameters as the orientation of horizontal stresses, as well as the intervals of anisotropy, secondary porosity, fracturing and possible crack spread during hydraulic fracturing (Climer et al., 2015). Fine structural and textural features of the section can be used for sedimentological analysis, which means the study of sedimentary rocks in order to establish the processes of their formation - the transport of material, the accumulation of sediments and their diagenetic transformations (Nichols et al., 1999). This analysis is based on the principle of actualism and is carried out using the latest results of studying modern sedimentation processes (Prothero et al., 1996).

Imagers are divided into the degree of detail and the scale of measurements:

Microimagers – a number of GIS devices, the result of which are images (well scan) with an axial resolution of no more than 1 cm, with a maximum coverage of the wellbore of at least 75% and having a correction for uneven movement and for the intervals of puffs (FMI, FMI-HD, QGEO, QGEO Slim, TBEI of the Wireline division, and also MicroScope HD devices). Imagers – a number of GIS devices, the result of which is images with an axial resolution of no more than 10 cm and/or with a maximum coverage of the wellbore of at least 50%. (FMS, DOBMI, OBMI, UBI divisions of Wireline, and also MicroScope and GeoVISION devices). Macroimagers – a number of GIS devices, the result of which is images (well scan) with an axial resolution of more than 10 cm (geoVISION, EcoScope).

Imager - a graphical representation of the walls of the well. It is the result of recording a number of GIS devices. In the diagrams, it is a scan of the cylinder from 0 to 360 degrees, oriented to the cardinal directions relative to the true north or relative to the "top" of the well (Top of Hole).

In this paper, authors show the advantages of microimagers over the informativeness of a standard GIS complex and sedimentological core study, and also describes cases when the informativeness of a microimager is not inferior to the informativeness of core data. Authors understand that core is the most important link in the chain of studying the geological structure of the deposit. Nevertheless, it is difficult to characterize the entire interval of the formation using only the core, both for geological and technological reasons. At the same time, imagers can be used not only as a qualitative, but also a quantitative source of visual information (Brown et al., 2015).