Mitigation of terrain induced slugging using mixer devices

The present work focuses on experimental evidence of slug mitigation via various devices. The slug mitigation potential of a number of mixers was tested using a laboratory scale air/water setup to compare their effect on the incoming slugs just upstream of the separator inlet. Dedicated methods and key performance indicators were developed to characterize the slug properties and evaluate the mixers effectiveness. Such mitigation is especially interesting for the purpose of producing oil and gas from thin oil rims, in which wells are often drilled following the geological structure of the oil-bearing layer. These wells consequently contain many long, near-horizontal sections, through which the transport of the oil gas mixture often takes the form of slug flow, i.e. Large volumes of liquid travelling at the velocity of the gas phase. As the gas cannot bypass the slugs, they are generally produced to the topside facilities, where they have a detrimental effect on the mechanical integrity of the equipment and on the metering accuracy due to their large volume. Mitigating slug flow has therefore great potential in optimizing the production from thin-oil rims on the short term. The present study shows that consistent reductions can be obtained on pressure fluctuations due to slugging, highlighting the benefit of these devices. It was observed that the slug speed could be significantly reduced, as well as the liquid hold-up within the slugs, especially when gas lift is used in conjunction with the devices. The physical mechanisms behind these effects are isolated, leading to optimization of the device geometry, for application to full scale. The demonstrated potential of the mixer devices can yield a quantifiable reduction of the impact of slugging on mechanical integrity and metering accuracy. As a consequence, production limitations due to slugging problems can be alleviated, resulting in potential for increase in oil production rates from thin oil rims.