Fines migration is a well known problem in sandstone formations, where clay particles are released when come in contact with fresh water or high pH fluids. In its nature state, each clay platelets is surrounded by an atmosphere of cations. These positive charges neutralize the negative charges of the platelets and hold the platelets in electrostatic equilibrium. Beside the electrostatic interactions between colloidal entities, dispersion forces often called the London-van der Waals forces, which are always attraction forces, exist between particles. To mitigate the migration problem, it was required to control these forces. A new inorganic Al/Zr-based clay stabilizer was used to mitigate fines migration problem. Its effectiveness was proven experimentally in Berea sandstone cores with permeability of 65–100 md, Berea sandstone is rich in kaolinite. It showed also great effectiveness when come in contact with high pH fluids. Coreflood tests were conducted at various temperatures up to 300°F. Effluent samples were collected, and the concentrations of different cations were measured using ICP. Experimental results showed that the stabilizer was effective in mitigating fines migration in Berea cores up to 300°F. The amount of Al/Zr retained in the core effluent was found to be a function of clay content. Various forces acting on clay particles were defined using Derjaguin and Landau, Verwey and Overbeek theory. The mechanism of stabilizing clay using the new chemical is well explained by DLVO theory. The results of this work will help production engineers to design clay stabilizer treatment used in the field.

Quaternary amine-based chemicals have been used for many years as clay stabilizers. An Al/Zr-based clay stabilizer, A, was developed. It showed great effectiveness in mitigating fines migration and overcame the leaching effect of HCl. In this study, Stabilizer A was examined and its performance was compared with two commercial clay ones: tetramethyl ammonium chloride and choline chloride. The type of cores (6 in. length and 1.5 in. diameter) that were used is Berea sandstone of 60-85 md; mainly contained 5 wt% kaolinite. Various coreflood experiments were performed to assess the effectiveness of each of the three stabilizers at 200 and 300°F. Inductively Coupled Plasma was used to analyze the core effluent to measure the concentrations of key cations. During tetramethyl ammonium chloride and choline chloride corefloods, significant amount of fines were noted in the core effluent samples, which means that these stabilizers were not effective. A bad odor of ammonia was noted during mixing of choline chloride with HCl acid. Choline chloride was effective at high concentrations. Stabilizer A showed good behavior during coreflood experiments, and proved to be better than the two commercial stabilizers at low concentrations. Stabilizer A worked very well, and no bad smell or fines were produced. In addition, Stabilizer A is an inorganic-based fluid, environmentally friendly, and does not have any smell; in contrast to quaternary amine chemicals. Unlike previous Al-based stabilizers (hydroxy aluminum solutions), the new stabilizer was not removed by HCl and no decline in permeability was noted following HCl injection.

Clay stabilizers are means to prevent fines migration and clay swelling, which are caused by the contact of formation with low salinity or high pH brines. Previous clay stabilizers including: Al and Zr compounds and cationic polymers have several drawbacks. Al and Zr compounds can be removed by acids. Cationic polymers can cause formation damage in some cases, and their environmental impact is questionable. There is a need to develop new clay stabilizers that can work following acid treatment and are environmentally acceptable.Laboratory studies were conducted on newly developed Al compound. Zeta potential and particle size measurements were used to determine surface charge of four types of clays: kaolinite, illite, montmorillonite, and chlorite; and to optimize clay stabilizer concentration. Coreflood experiments were conducted on Berea sandstone cores (1.5 in. diameter and 6.0 in. length) to assess the effectiveness of the new compound and determine the impact of acids on its performance. Atomic absorption was used to measure the concentrations of Al, Mg, Ca, and Fe in the core flood effluent.The new clay stabilizer was very effective in mitigating fines migration. Zeta potential indicated that the isoelectric point at which complete shields of surface charge of clay particles was achieved at a stabilizer concentration of 0.2 wt%. Coreflood tests showed that this new chemical was effective, and unlike previous Al compounds, it did not dissolve in acids. In addition it is environmentally friendly compound, and also worked very well at 200 o F. The behavior of the new stabilizer was much better when it was prepared in DI water than in brine.

Sandstone formations are exposed to a variety of high pH fluids, including: hydraulic fracturing using high pH borate gels, alkaline-based chemical EOR methods, water-based drilling fluids and cementing filtrate. High pH values can trigger fines migration, and subsequent loss of permeability and well productivity. An Al/Zr-based clay stabilizer was developed to control fines migration at high pH applications. The objective of this study is to assess the effectiveness of this new stabilizer and compare its performance with commercially available stabilizers. Laboratory studies were performed using Berea sandstone (8 wt% clays; mainly kaolinite) cores (6 in. length and 1.5 in. diameter). Tetramethyl ammonium chloride (TMAC) and choline chloride were used for comparison as two commercial clay stabilizers. Various coreflood experiments were conducted to determine the effect of the three stabilizers on core permeability (from 64 – 100 md) at various temperatures up to 300°F. In these experiments, a preflush that included 2 wt% stabilizer was injected and was followed by injection of 2 wt% NaOH solution. The later represented high pH filtrate that can invade the formation during any treatment that includes alkaline fluids. The pressure drop across the core was measured and samples of the core effluent were collected. Inductive Coupled plasma was used to measure the concentrations of Al, Zr, Fe, Ca, and Mg. Lab results indicated that the new clay stabilizer worked effectively up to 300°F. No reduction in permeability was noted in any of coreflood tests using sandstone cores of various mineralogies and initial permeabilities. The concentrations of various cations were found to be a function of core mineralogy. TMAC and choline chloride was not effective when followed by fresh water and incompatible with the high pH fluids. The new stabilizer is environmentally friendly, and can be used in hydraulic fracturing, and alkaline-based chemical EOR methods to mitigate clay related problems.