Clay Minerals and its importance on Hydrocarbon Production Potential in a part of Geleki oilfield of Upper Assam Basin

Prediction of reservoir characteristics becomes a key challenge for hydrocarbon exploration and development. A thorough understanding of clay minerals is important in understanding the reservoir characteristics as well as oil recovery efficiency. The present study is based on the analysis of clay minerals and their role on hydrocarbon production potential in a part of Tipam Reservoir Sand of Geleki oilfield of Upper Assam Basin. The study shows the presence of smectite, kaolinite, illite and mixed-layer. Smectite is the dominant clay mineral and mostly occurs as coating over detrital grains whereas kaolinite occurs as loosely-attached, discrete particles and the mixed-layer occurs as patchy pore linings which are found to play a major role in variation of the reservoir characteristics of the study area. Due to the reduction of intergranular pore volume and creation of microporosity, sometimes it is observed that high irreducible water saturation zones are developed which showing low resistivity value against oil bearing zones and creating problems in log interpretation. Again, kaolinite preferentially adsorbs oil which makes the reservoir rock oil-wet. According to Tang and Morrow (1999) during EOR, especially in Low Saline Waterflooding (LSW), the migration of fines (kaolinite) in sandstone reservoir increases the water wetness in the reservoir rock by exposing new underlying rock surfaces which improves the oil recovery efficiency.