SPWLA Glossary

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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 log|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 log|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 log| 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 water|bulk volume of water]] present (including adsorbed water, if part of the original porosity measurement).