Open Hole Petrophysical Assessment of Formation Damage: Concept, Challenges, Possible Applications

This work proposes an original framework for evaluating formation damage (the decrease in near-wellbore permeability) in open hole environment. In comparison to conventional skin factor measurement ways (i.e., pressure-transient analysis, generally performed in cased hole) this approach utilizes different data source – openhole wireline or LWD survey data – and bears different use case in mind, targeting the initial formation damage caused by mud filtrate invasion and micropore plugging by external particles.

The methodology is built around radial modelling of petrophysical properties (resistivity, saturation, porosity, permeability) with the assumption of radial phase flow. As most petrophysical frameworks do, it also requires core analysis to root for accuracy. Final product of interpretation comes as two curves, characterizing equivalent damaged zone permeability and formation skin factor. Taking advantage of well logging fidelity, the skin factor curve provides continuous quantitative assessment of formation damage at the time of logging. Also, it is possible to differentiate the skin by damage mechanisms (accounting for liquid and solid contamination).

The work provides a first comprehensive look upon this methodology, portrays several application examples, outlines and discusses some standing challenges that require further development in order to turn this concept into a proper practical tool.