Time-lapse 2D Seismic Steamflood Monitoring - A Case Study from Offshore Republic of Congo, the Emeraude Field

Heavy oil reservoirs are one of the main energy resources in the world. Drainage is challenging, as it usually requires enhanced recovery mechanisms, such as steam injection, which improves oil mobility. Steam flood monitoring techniques include time-lapse seismic, which results in an understanding of aerial patterns of fluid movement which cannot be inferred from well measurements alone. If acquisition of a 3D seismic survey is problematic due to the surface infrastructure or is prohibitively expensive, a 2D time-lapse campaign may provide an alternative, cost effective technique to monitor changes away from the injector and producer wells. This case study is from a steamflood pilot on the Emeraude field (Offshore Congo). Pre-survey analogue and basic rock physics studies suggested that time shifts due to steam injection should be detectable on seismic. A 2D time-lapse seismic programme was designed and acquired and has proved successful in detecting travel time changes around the steam injectors. Quantitative studies include the inversion of the observed time-lapse response via a first order blocky petro-elastic model. This results in a flooding map which aids history matching during reservoir simulation. Success of the first 2D time-lapse campaign has encouraged the acquisition of further 2D seismic repeat/monitor surveys.