Figure 4 a,b. Microporous grains in Arab Formation carbonates. In thin section, porosity is filled by bluedyed epoxy, calcite is stained pink to red, other minerals are unstained. (a) Thin section photomicrograph of microporous peloids (P) and microporous miliolid foraminifera (M). Microporosity appears as a blue haze within grains (plane-polarized light, unspecified Mesozoic reservoir, Middle East). (b) Thin section photomicrograph of microporous ooid. Microporosity in this grain is denoted by a blue hazy appearance resulting from infiltration of blue-dyed epoxy into micropores in the grain (plane-polarized light, Saudi Arabia, Qatif field, Arab-C).