The impact of entrained gases on net oil measurement is addressed and quantified for three common approaches for determining net oil: coriolis meters, resonant microwave oscillators and microwave absorption devices. Entrained gases are often encountered in the liquid leg of gas – liquid separator based measurement approaches and, if unrecognized, can result in significant error in net oil.

The measurement principles of the three types of watercut meters considered are described. Each watercut measurement device continues to provide a measurement in the presence of gas. However, the interpretation of net oil content of an oil / water mixture with free gas present can be significantly impacted without specific knowledge of the gas volume fraction. The errors in oil cut introduced by unrecognized entrained gases are outlined using simplified models for each type of watercut measurement device considered.

An approach is proposed to utilize SONAR-based gas volume fraction meters in conjunction with the watercut devices to provide accurate net oil determination in the presence of entrained gas. Laboratory and field data evaluating the proposed approach are presented, demonstrating both the impact of entrained gases on net oil measurement and the practicality of accounting for the free gas to enable accurate net oil measurement, independent of small gas volume fraction levels.