One of the most crucial problems that the petroleum industry has been facing for quite some time, is the damage done to the sandstone formations by the produced water that is pumped into the ground during secondary oil recovery. The drastic reduction in permeability of these sandstone beds due to the water-shock, is a great concern in petroleum industry. The changes in produced water composition has made secondary oil recovery difficult. The decreasing permeability of the bed, increases the pumping and equipment cost to a great extent. The control of clay release is essential to the economic and effective operations in many oil fields.
The main topic of this research is the effect of electrolytic composition in produced water on the clay particles pumped into sandstone formations or through sand-filters. Earlier studies [1–5] have revealed that high pH and low salt concentrations of water lead to release of clay from sand-grains. Also, there might be some clay particles injected into the ground with the produced water. These injected clays get captured by the sandstone bed. Both the release and capture of clays changes the porosity of bed and the surface area of sandstone particles and thus, reduces the permeability of the bed drastically. This paper just presents the experimental work done to predict the release of indigenous clay in the sand filter in aqueous phase flow. Future work will concentrate more on actual filtration experiments to release of indigenous clays and capture of injected clays in aqueous phase flow and the release-capture phenomena in two phase flows as well.
In produced water operations, oil companies need to remove particles from the injection water to avoid formation damage. Consolidated Sand Cartridge filters are an inexpensive alternative compared to tradition means of filtering the particles. This work demonstrates the capability and advantages of these filters. The filter has properties similar to that of sandstone and so, results of clay migration study for the filter may be similar to sandstone bed as well. The Consolidated Sand filter is superior compared to conventional cylindrical sand filters in that its outer surface is expanded out into a six-lobe geometry with a larger surface area for filtration. Hence higher flow rates are achieved through the filter at a given pressure drop and the life of filter increases. Also, it has a glue bound sand structure which reduces the release of clay compared to the conventional sand filters. However, the disadvantage of the filter is that it is bulky and heavy and it adds to the disposal cost for the user. This work serves the dual purpose of characterizing the consolidated sand cartridge filter and also, studying the phenomena of clay release and capture in the sand filter to determine the optimum combination of pH and salt-concentration for minimal permeability loss. The phenomenon of clay release and capture is explained on basis of zeta potential of the particles, which characterize the surface charge of the particles.