21-07-2014

The use of coatings for deliquifying gas wells

Background
As reservoirs become depleted, the reservoir pressure and subsequently the gas velocity in the wells decreases. At some point, the gas stream is no longer able to carry out all liquid to the surface. This leads to the formation of a liquid column in the well, which hampers gas production and ultimately results in termination of production.

Laboratory studies have recently demonstrated that the predominant cause of liquid loading is the formation and downward flow of a liquid film on the tubing. Based on this novel understanding of the liquid loading phenomenon, experiments have been carried out at laboratory scale where it was demonstrated that the liquid loading effect can be counteracted by application of a hydrophobic coating on the inside of the tubing. These experiments were performed in 20 mm and 50 mm set ups and under various inclination angles.

These ‘proof of principle’ experiments were sponsored by Shell. For these experiments, a coating was used that is not durable under field conditions. This coating proved to have a very beneficial effect on the liquid loading behaviour. However, the exact functional requirements (surface tension, roughness, etc.) that are necessary to show this effect are not fully understood. Also the requirements with respect to (functional) durability (erosion, fouling, degradation etc.) are not established yet.

This project aims to identify the necessary coating requirements to show the desired effect on liquid loading behaviour. In a next step a coating can be selected (or if needed developed) based on these requirements.

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