Compressor application for extending production life cycle in mature fields

Abstract

Mature gas fields are subject to network backpressure fluctuation causing liquid loading condition. The liquid loading, theoretically, occurs when the gas velocity is below its critical velocity which commonly happens in mature fields when rates become »low«. Based on Turner or Coleman’s equations, the critical velocity is proportional to the wellhead flowing pressure. This means, when the wellhead pressure increases as the result of higher external (sales) pressure, then the critical velocity will be higher. This condition will give a »pseudo« production decline of the wells. Gas compression is among the best fit-for-purpose solution to overcome the above challenges. Gas compression will help to reduce the wellhead flowing pressure which increases the gas velocity above the critical velocity as well as the well gas rate by lowering the bottomhole flowing pressure. The wells will be capable of unloading the liquid inside the wellbore and the reservoir will suffer a higher pressure drawdown. Moreover, the wells will not be impacted by the external pressure fluctuation as long as this latter is below the compressor discharge pressure. Gas compression has been implemented in Laslau Mare mature gas field to extend the production life cycle. 5 wellhead compressors have been installed since 2010 and 1 group compressor since 2014. Both types of compressor show positive results. This paper explains the application of compressor in Laslau Mare field starting with candidate selection up to cash flow analysis. A big emphasis will be given to the compressor/ well performance