Monitoring water alternate gas process using streaming potential

Abstract

Spontaneous potential (SP) is commonly measured during reservoir characterisation. SP signals are also generated during hydrocarbon production due to the streaming potential occurrence. Measurement of SP has been proposed as a method to detect and monitor water encroachment. In principle, SP signals could also be monitored during production from a single well, with pressure support provided by a water alternate gas (WAG) process. The objective of this study is to monitor WAG process by using streaming potential measurement. SP signal will be measured during production by WAG injection. Measurement of streaming potential has been previously proposed to detect the water encroachment towards a production well. The peak of the signal corresponds to the waterfront where there is a change of saturation from ionic water to non-polar hydrocarbon. Similar trend is predicted in the case of WAG where we have several interfaces between the injected water and the injected gas. This project involved experimental work. The investigation comprised physical model design for WAG process, model characterisation, and correlation between SP signals WAG performance. WAG displacement process could be monitored indirectly from the signal acquired. SP measurement is a promising method to monitor the effectiveness of a WAG process. This study is significant because monitoring the progress of water and gas in a WAG process is a key in the effectiveness of this enhanced oil recovery method. Measurement of the streaming potential provides another method besides using tracers to monitor the WAG profile. Better monitoring will lead to more efficient displacement and great benefits in term of economy and environment.