Laboratory Study of Low-Ionic Strength-Induced Migration of Clay Particles in Unconsolidated Rocks
Kardasz, Marko; Mileusnic, Nikola; Trimper, Adam
Engineering Honours Project, 2015
Australian School of Petroleum
University of Adelaide
Low salinity waterflooding has been used for enhanced oil recovery (EOR) for the last decade, however its physical mechanisms are not clearly yet understood. Low salinity-induced fines migration is used to cause permeability reduction during mobility-controlled EOR. Variation of water composition results in fines mobilisation, migration and straining and in comparison with conventional EOR methods; low salinity waterflooding requires significantly less investment and may yield high incremental recovery. In the past, experiments have confirmed that ionic strength of the injection fluid significantly effects fines migration and mobilisation. In relation to core clay concentration, there has been great difficulty in studying fines migration due to the high uncertainty of core composition. This increases the complexity of studying permeability reduction caused by clay particles due to fines migration and mobilisation. As the percentage of clay within a core cannot measured, a relationship cannot be construed as to how the percentage of clay and permeability reduction are related.
In order to eliminate the uncertainty regarding initial clay concentration in real cores; experiments were focused on creating a matrix system using an artificial unconsolidated porous media with known clay concentrations. This allowed material balance to be performed, enabling clay recovery factors and clay retention data to be investigated and analysed. The execution of the experiment involved injecting a range of salinities of decreasing ionic strength and permeability reduction was investigated through real-time differential pressure analysis, which indicated a relationship between clay concentration and permeability.
Investigation was focused on the relationship of clays and their effects on an unconsolidated sand matrix to allow us to better understand how clay reacts upon contact with injection water and how the percentage of clay within a core leads to a reduction in permeability and corresponding damage mechanism. Experimentation will continue through refinement of the experiment’s methodology, varying clay concentration, clay type and number of ionic solutions. Further evolution of this research will include creating artificial consolidated cores and finally testing real cores from the field.