To produce a commercially viable oil deposit, there must be a source rock, a reservoir rock, a seal rock, and a trap that denies the oil passage to the surface. The trap is a geologic structure that prevents the upward movement of oil and gas, causing them to accumulate in the reservoir rock. This trap can be formed by various geological features, such as folds, faults, and unconformities. Without a trap, the oil and gas would migrate to the surface and be lost. Therefore, a trap is a crucial component of an oil deposit that can make it economically viable to produce. The other options listed (igneous heater rock, porous filter rock, and large fracture connecting the reservoir rock to the surface of the earth) are not essential components of a commercially viable oil deposit.