Predicting reservoir quality during exploration: lithic grains, porosity and permeability in Tertiary clastic rocks of the

have been supplied with sediment rich in pelitic metamorphic rock fragments, weathered basic igneous rock fragments and micaceous rock fragments by similar drainage systems. We have analysed ata from the Gulf of Thailand and Malay basins to predict reservoir quality in the South China Sea basin. These Tertiary sandstones contain 20-40 % lithic rock fragments hat are rich in clay minerals. There are good correlations between both porosity and permeability and the total clay mineral content. They undergo rapid loss of porosity with depth at a rate commensurate with sandstones bearing 20-40 % ductile grains. The relationship between porosity and permeability is also strongly influenced by the presence of ductile grains. The rapid loss of permeability with porosity is a result of ductile grains being squeezed between therigid grains, blocking pore-throats and leaving isolated, ineffective porosity. Mineral cements eem to be unimportant modifiers of porosity or permeability. The rapid loss of porosity with depth and the decrease in permeability with porosity leads to low permeabilities at shallow depths relative to many other hydrocarbon provinces (e.g. North Sea, Gulf of Mexico, etc.) which have lower ductile grain contents. We have used modelled compaction curves for sandstones with 20 and 40 % ductile grains to predict