Geosteering in Unconventional Shales: Current Practice and Developing Methodologies

Abstract

Current well placement in unconventional shale ranges from simple geometric well placement to a gamut of patternrecognition systems and geosteering with geochemical and geomechanical analyses. The wide diversity of systems used leads to uncertainty in the effectiveness of any strategy, with confusion as to the true value or merit of a particular technique. Often, a well-placement strategy is based on what came before, with little regard as to the complexities or differences between reservoirs.This paper reviews the current common practices used in geosteering in shales, for both gas-and oil-producing reservoirs. A brief history of strategy development is outlined, with comments about its perceived effectiveness and value. Examples of successes and failures are examined to attempt to determine the viability of a particular strategy.Finally, alternative approaches and methodologies are reviewed and examined, with comments about the potential application, benefits, and value.

Beyond gamma ray: Determining a geosteering program for a new unconventional reservoir

“…Relative dip picking from gamma-ray images is notoriously unreliable because the depth of investigation for a gamma tool is subject to many factors beyond the control of the interpreter, but as an indicator of relative trajectory, the value is clear. Density images, with higher resolution, can be used for relative dip picking, which aids geosteering, reducing the tortuosity induced by pattern matching (Pitcher and Jackson, 2012).…”

“…The problems from a drilling perspective are complicated by geomechanical instability in the bounding formations, with time-determinant wellbore collapse being a major concern in case a horizontal wellbore exits the target formation. Given these formation characteristics, geosteering systems that commonly are used in unconventional plays that use pattern matching against offset logs (Pitcher and Jackson, 2012) are considered inappropriate as a geosteering solution in this target interval.…”

Elemental geochemistry of the Upper Cretaceous reservoir and surrounding formations applied in geosteering of horizontal wells, Lebăda Field – Western Black Sea

“…One of the first chemosteering applications in unconventional reservoirs took place in the North Sea (Pitcher and Jackson, 2012). In such reservoirs, the information obtained from standard Logging While Drilling (LWD) logs and lithological description of cuttings samples were unsatisfactory.…”