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 2 wt. percent authigenic clays dominated by kaolinite and illite/montmorillonite mixed layer clays. To improve well productivity, a well stimulation treatment has been conducted on the producing wells in this field. The treatment introduces 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 design an effective clay stabilizer treatment. The work included performing coreflood experiments using reservoir cores at reservoir conditions (180 F and overburden pressure of 1500 psi). The critical salt concentration (defined as the salt concentration below which there is loss of permeability) was first determined. Several commercial clay stabilizers, cationic polymers, were evaluated. The effects of stabilizer concentration (0 to 2 vol. percent.), soaking time, and acids (15 wt. percent HCl) on core permeability were investigated in detail. The experimental results indicated that the critical salt concentration (KCl brine) was nearly 5 wt. percent. Severe loss of permeability was observed when brines of lower salt concentrations were injected into reservoir cores. The effectiveness of clay stabilizer was found to be a function of chemical type and concentration. Some of the chemicals tested were not effective at concentrations less than 1.5 vol. percent. Others were effective clay stabilizers, but caused loss of injectivity at higher concentrations (2 vol. percent). After conducting a thorough investigation, 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. This problem was solved by good mixing of the stabilizer and proper filtration. Hydrochloric acid did improve the performance of at least of the clay stabilizers examined. Based on lab testing, a cost effective clay stabilizer was tested in the field at a concentration of 2 vol. percent. Field results indicated that the chemical did not cause loss of injectivity, and minimized formation damage due to fines migration and clay swelling. P. 613

A Collective Clay Stabilizers Review

“…The COP limitations are mainly concerning the large size of these molecules when pumped in low permeability formations, which would induce plugging, especially in formations with permeability below 30 md. (Himes et al 1991;Nasr-el-din et al 1999;El-Monier and Nasr-El-Din, 2013;Nasr-El-Din et al 1998;Baltz et al 1989).…”

“…Depending on the quantity and nature of the clay, simple inorganic salts may not be enough to stabilize them (Fink, 2012). The problem with salt treatments is that their effects are temporary, as well as difficulty in handling and mixing of large quantities (Fink, 2012;Nasr-El-Din and Al-Mulhem, 1998). Moreover, high salt concentrations can negatively affect the performance of breakers and crosslinkers in fracturing treatments (Ataur et al 2013).…”

“…The polymers used to stabilize clay will have functional groups of positive polarity that adsorb onto the clay at multiple sites. The adsorbed polymer with multiple attachments to the rock surface will resist exchange with other cations in solution (Nasr-El-Din and Al-Mulhem, 1998). Moreover, the functional groups in polymers allow a higher valency than the cations from salt treatments.…”

Correlation of magnetic resonance (EPR, ssNMR) parameters and crystal-microstrain in marbles as a tool to probe their provenance

“…Insertion of divalent cations, such as Mg 2+ , Mn 2+ , Fe 2+ and Fe 3+ , creates defects in the calcite microstructure. 12 Thus, techniques such as instrumental neutron activation analysis (INAA), 13 trace element analysis, 14 analysis of stable-isotope ratios using mass spectroscopy, 15 cathodoluminescence, 16 and X-ray diffraction (XRD), 17 have been utilized as high-resolution tools to analyze the composition, structure, and ultimately the origin and geochemical itinerary of white marbles. Magnetic resonance spectroscopies, i.e.…”

Evaluation and prevention of formation damage in offshore sandstone reservoirs in China

“…Several field case histories demonstrated that KOH can mitigate the effects of both clay swelling and fines migration and a single KOH treatment is effective over the economic life of the well. Nasr- El-Din et al (1998) conducted an experimental study to design an effective procedure of treatment with clay stabilizer. The effects of stabilizer concentration, soaking time, and acids on core permeability were investigated in detail.…”