LOW SALINITY WATER FLOODING

It was discovered fairly recently that higher oil recovery was observed when a low salinity brine was injected as compared to water with salinities of 35,000 ppm (seawater) and higher. Much of the research has been in the laboratory through core floods. Several field trials have been implemented recently by BP in the North Slope of Alaska in the Endicott Field.

Because LowSal is new technology, operators and researchers are still trying to understand the mechanisms of incremental oil recovery. Here is a summary of the proposed microscopic mechanisms which result in incremental oil production:

• Wettability modification by multi-component ion exchange, which decreases oil ionic bonding to the pore minerals.
• A pH-induced in-situ surfactant generation, interfacial tension reduction and emulsification.
• Fines migration and stripping of oil bearing fines from the pore walls.
• Plugging of predominantly water saturated pores causing diversion of injected water into less swept pore space.

The LowSal (Low Salinity WaterFlooding) method option offers both secondary and tertiary recovery benefits. In fields where significant pore volumes of aquifer water throughput have been observed, the EOR benefits of LowSal are tertiary, the 3% to 14% of OOIP range.

It’s important to note that the clay content of core materials and of the reservoirs targeted for LowSal is extremely important.