Evaluation of Clay Stabilizers for a Sandstone Field in Central Saudi Arabia

Abstract

An oil field in central Saudi Arabia produces super-light crude from a sandstone reservoir. The formation contains up to 7.0 wt% authigenic clays dominated by kaolinite and illite/montmorillonite mixed layer clays. To mitigate sand production and improve well productivity, a frac pack stimulation treatment was conducted on most producing wells in this field. The treatment introduced several fluids, which might invade the formation and induce formation damage.An experimental study was conducted to determine potential formation damage due to fines migration and clay swelling, and to design an effective clay stabilizer treatment. The work included performing coreflood experiments using reservoir cores under reservoir conditions. The critical salt concentration ͑defined, as the salt concentration below which there is loss of permeability͒ was first determined. Several commercial clay stabilizers, cationic polymers, were evaluated. The effects of stabilizer type, concentration and acids on core permeability were investigated in detail.The experimental results indicated that the critical salt concentration ͑KCl brine͒ was nearly 5 wt%. Severe loss of permeability was observed when brines of lower salt concentrations were injected into reservoir cores. The effectiveness of clay stabilizers was found to be a function of chemical type and concentration. Some of the chemicals caused loss of injectivity at higher concentrations. It was found that these chemicals did not readily dissolve in water and formed fish eyes. When these chemicals were injected into reservoir cores, they formed an external filter cake, which caused loss of permeability. Good mixing of the stabilizer and proper filtration solved this problem. Hydrochloric acid at 15 wt% did improve the performance of at least one of the clay stabilizers examined.Based on lab testing, a cost effective clay stabilizer was tested in the field. Field results indicated that the chemical did not cause loss of injectivity, and minimized formation damage due to fines migration and clay swelling. cating the presence of quaternary ammonium chloride. CS-B contained a small amount of the chloride ion, most likely from an inorganic source ͑NaCl͒. CS-C did not contain a significant

A Review on Chemical Sand Production Control Techniques in Oil Reservoirs

“…The swelling of clay rocks closes the pores and channels and drastically reduces permeability. Besides, these types of rocks extensively lose their strength under the influence of acids in the acidizing process and quickly start to produce sand. , For the reasons mentioned above, clay stabilizers have received much attention in preventing sand production and migration by consolidating natural bonds between clay rocks and preventing the swelling of clay rocks . Clay stabilizers can be classified as shown in Figure .…”

“…76,81 For the reasons mentioned above, clay stabilizers have received much attention in preventing sand production and migration by consolidating natural bonds between clay rocks and preventing the swelling of clay rocks. 82 Clay stabilizers can be classified as shown in Figure 7.…”

Clay stabilization

“…Cationic organic polymers can cause formation damage in some cases [80]. Their environmental impact is also questionable [81].…”

Optimization and Evaluation of Stabilizers for Tight Water-Sensitive Conglomerate Reservoirs

“…To prevent the swelling of montmorillonite, KCl or NH 4 Cl is typically used. This is because potassium ions and ammonium ions have similar sizes to vacancy sizes in the interlaminar spaces of the montmorillonite crystal; once these cationic ions enter the interlaminar spaces, the electrostatic force can maintain the crystal structure and prevent water from invading. − …”