Experimental observations and numerical modeling of gas lifting in small-diameter pipes in view of unloading liquids from wells with low reservoir pressure

This study aims at developing a simple and efficient gas lifting technology using small-diameter pipes in order to unload liquids from reservoirs with very low pressure. The research program consists of three parts: (a) check the validity of existing models for evaluating gas-liquid flow in small diameter pipes, (b) laboratory investigations of gas/liquid flow in small diameter pipes, and (c) analytical model development.;The experimental program was developed to observe the gas lifting efficiency using three pipe diameters (4, 7.8 and 12mm ID). The effect of surface tension on production efficiency was also investigated by using water-methanol (60:40% vol.) mixture.;Two mechanistic models were developed. The Critical Production Condition (CPC) model simulated the critical depth at which an infinitesimal amount of liquid is produced under specific gas injection rate and submergence. The SDP model simulated the effect of liquid falling back and predicted the liquid production for a given gas injection rate and submergence (reservoir pressure). The CPC model predictions compared reasonably with the experimental data especially for submergences higher than 20%. The SDP model simulated better the experimental data for the 20% submergence and 12mm riser.