This book detailed the petrophysical effect of clay heterogenities on reservoir properties; placing special focus on the producibility indicators. It gives practical approach to utilizing petrophysical tool as a replacement for core analysis in determining clay distribution patterns in reservoirs, as well as accounting for same in hydrocarbon bearing reservoirs. Real time data from a producing field of the Niger Delta petrolifeous province were utilized. The book is a sure eye opener for research students and a good companion for practicing Geoscientists, who desire to enhance their exploration skills.