MOP. A computed log, based on several logging operations. prepared for the purpose of determining the presence and quantity of movable hydrocarbon (usually oil) at difterent parts of a formation. For example:
(1) The first curve of the log will be said to represent the pore volume of the rock framework. It must be determined by a technique in which derived porosity is least influenced by the type of fluid occupying pore volume (sometimes a single porosity curve; i.e., sonic; sometimes computed from several porosity curves).
(2) The second curve will represent the pore volume occupied by the water in the flushed zone (i.e., the product of water saturation in the flushed zone and porosity from the first curve). Focused microresistivity tools are usually used to determine flushed-zone water saturation (e.g., microlaterolog, FoRxo, etc.).
(3) The third curve represents the pore volume occupied by water in the uninvaded zone (i.e., the product of water saturation beyond the depth of invasion and porosity from the first curve). Deep resistivity measuring tools are usually used, such as deep induction tools or deep laterolog tools.
The first curve represents void volume or pore volume. The difference between the first and second curves is related to the volume occupied by immovable hydrocarbon. The difference between the second and third curves represents the bulk volume of movable hydrocarbon. And the third curve represents the bulk volume of water present (including adsorbed water, if part of the original porosity measurement).