Critical Gas Saturation and Supersaturation in Low-Permeability Rocks

Summary The laboratory methodology for determining critical gas saturation, Sgc, in field depletion processes is still uncertain. Through measurements on low-permeability rocks, we explore some of the key issues affecting laboratory determination of Sgc. Differences between laboratory depletion and external gasdrive experiments are measured and analyzed. We also investigate the relationship between average Sgc from material balance and true Sgc, source of supersaturation, gas nucleation conditions, and dynamics of gas bubble growth in depletion drive experiments. We assess the use of low-bubblepoint oils to reduce experiment time. Finally, we suggest some improvements to laboratory procedures.