URTEC-198301-MS Swelling Inhibition of Bentonite Clay by MgOH 2 Precipitation Using Different Mg Salts Archana Patel, Brian Towler, Victor Rudolph, and Thomas Rufford, University of Queensland Copyright 2019, Unconventional Resources Technology Conference (URTeC) This paper was prepared for presentation at the SPE/AAPG/SEG Asia Pacific Unconventional Resources Technology Conference held in Brisbane, Australia, 18 – 19 November 2019. The URTeC Technical Program Committee accepted this presentation on the basis of information contained in an abstract submitted by the author(s). The contents of this paper have not been reviewed by URTeC and URTeC does not warrant the accuracy, reliability, or timeliness of any information herein. All information is the responsibility of, and, is subject to corrections by the author(s). Any person or entity that relies on any information obtained from this paper does so at their own risk. The information herein does not necessarily reflect any position of URTeC. Any reproduction, distribution, or storage of any part of this paper without the written consent of URTeC is prohibited. Abstract Inhibition of smectite clay swelling by precipitation of Mg(OH) 2 between clay layers and on the surface of clays is discussed in this paper. The precipitation was carried out using different Mg salts (MgCl 2 ·6H 2 O, Mg(NO 3 ) 2 ·6H 2 O Mg(SO 4 ) 2 ·8H 2 O and NaOH as a base. The change properties after precipitation were studied by X-ray diffraction and methylene blue dye examination. The swelling tests were carried out using vial test method. It was evident from XRD that, after precipitation, bentonite resembled chlorite structure. It is noticed that the adsorption capacity of the samples increased after precipitation due to an increase in the surface area of samples. The samples precipitated with Mg(OH) 2 with Mg:OH ratio more than 8 did not swell in the formation water and showed a more prolonged treatment effect. The Mg(OH) 2 precipitated on the external and internal surface of bentonite. The internally precipitated Mg(OH) 2 could be responsible for the change in the clay structure and inhibit water adsorption between layers of clay structure, while Mg(OH) 2 precipitated on the surface of clays stops water adsorption leading to swelling inhibition. The precipitation was further carried out on mudstone sample, and swelling was observed via micromodel test. Introduction Clay swelling is a severe problem in petroleum reservoirs leading to fines generation, which causes several other operational issues like pump failure, process shutdown, and reduced permeability in petroleum reservoirs. Several commercial clay stabilizers are currently used in the field like KCl, NaCl and polymers but due to their disadvantages their use is limited, and research is focused on long term solution to inhibit clay swelling rather than fines trapping. The objective of this study is to inhibit clay swelling by changing the clay structure via metal hydroxide precipitation between the clay layers. The precipitation of Mg/ Al/Fe hydroxide between the clay layers of montmorillonite is a simple process which happens during weathering leading to mineral transformation from montmorillonite to chlorite. The chlorite is nonswelling clay, so if montmorillonite structure is changed to chlorite; the swelling can be prevented. The chloritization of montmorillonite is already studied and reported in open literature a long time ago to understand the formation of chlorites from montmorillonite but never focused as a tool to inhibit swelling. In this study,