Images are central to the task of exploring for and producing oil and gas (hydrocarbons) from the Earth’s subsurface. To understand their utility, one must look at both how hydrocarbons are formed and how we explore for them. Oil and gas (hydrocarbons) are generally found in the pores of sedimentary rocks, such as sandstone or limestone. These rocks are formed by the burial of sediment over millions of years and its subsequent chemical alteration (diagenesis).