LAUSR

AbstractA grading system for tight sandstone reservoir quality is needed to predict tight oil enrichment areas and assess the resources. To explore the establishment of the grading system, a variety of research methods, such as rate-controlled mercury injection, conventional mercury injection, contact angle measurement, and the mechanical equilibrium principle, are integrated to determine the upper and lower limits of the porosity, permeability, and pore-throat radius of tight sandstones and to establish a quality grading system. Based on the porosity ϕ, permeability K, and pore-throat size r properties of the studied samples from the K1q4 Member, five sandstone classes have been identified. Three of these classes are tight sandstone reservoirs and include (1) high-quality tight sandstone reservoirs (ϕ=9%−12%, K=0.1−1.0  mD, and r=0.063−0.4  μm), (2) effective tight sandstone reservoirs (ϕ=6%−9%, K=0.05−0.1  mD, and r=0.0063−0.063  μm), and (3) low-quality tight sandstone reservoirs (ϕ=4%−6%, K=0.01−0.05 ...