Wettability alteration in rock reservoirs and its effect in petroleum recovery

Reservoir wettability is controlled by crude oil/rock/brine interactions. Wettability plays an important role in oil recovery because of its effect on fluid location, flow behaviour and residual oil distribution. In mature oil fields, a development programme is initiated to maintain oil production in economic size. Understanding reservoir wettability is a central issue in such field development plans which can be optimised to boost oil production rate. However, there is a considerable uncertainty in understanding the reservoir wettability especially in terms of effect of brine composition and temperature. This thesis serves to minimise such uncertainty. In the present work, several experimental techniques are employed to investigate crude Oil/brine/rock interaction in mineral surface. A protocol of contact angle measurements is developed to mimic the drainage of oil thorough receding contact angle and imbibition of water through advancing contact angle. Experiments are designed carefully to investigate the role of water film, brine composition, asphaltene content, crude oil solvency and temperature in wettability of mineral surface. The consequence of wettability alteration is studied in how fluid behaviour is developed and affects the trapping fluids. A two dimensional glass micromodel gives new visual insights into the type of flow behaviour as a function of brine salinity and temperatures. Furthermore, the role of capillary number is investigated in three distinctive wettability scenarios that exist in oil fields. Real rock surfaces, which are extracted from underground reservoirs in Oman, are studied extensively to understand the role of mineralogy in rock surface. A novel experimental combination between Nuclear Magnetic Resonance (NMR) and capillary imbibition test are utilised to track the wettability alteration in core samples as brine salinity and temperature manipulated. For the first time, the introduction of optical interferometry to petroleum recovery literature is achieved successfully by using vertical scanning interferometry. A detailed investigation of surface profile of crude oil adsorption gives new information on nanoscale wettability. Application of the above-mentioned techniques to different crude oils on different reservoir conditions allows the establishment of fundamental wettability understanding to current enhance oil recovery techniques such as smart water flooding and steam injection. To our best knowledge, some of these finding are reported for, the first time.