Wettability effects on oil recovery mechanisms in fractured chalk

This thesis is a part of the ongoing project, “Oil recovery from fractured chalk reservoirs”, which is a collaboration between the Reservoir Physics Group at the University of Bergen and ConocoPhillips Research Center in Bartlesville, Oklahoma. The project was initiated in 1990 and for the last 15 years about 30 Master and PhD candidates have graduated and, mainly employed by the oil industry. Dedicated candidates combined with professional guidance and stable funding has been a key to the success of this long term research project. Early work in this project report experiments on large chalk blocks subjected to water floods. The dynamics of the water front propagation during water floods were monitored by nuclear tracer imaging for homogeneous whole blocks and when fractured. The impact of the fractures on the water flood could then be investigated. Emphasis was on the effect of wettability condition on the recovery mechanism. In addition to the saturation monitoring system, attempts to measure the pressure difference across different fractures in the block were made with varying degree of success. Based on the findings of the earlier work, emphasis for further research as a part of this thesis work was chosen: 1. Improve the aging technique to obtain reproducible, uniform and relevant wettabilities 2. Improve imaging in order to study the details on fluid transfer across open fractures at different wettability conditions