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 (MgCl2·6H2O, Mg(NO3)2·6H2O Mg(SO4)2·8H2O 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.

Keywords:
drilling fluid chemistry, complex reservoir, precipitation, surface area, methylene blue dye adsorption, drilling fluid selection and formulation, drilling fluid formulation, adsorption, mg salt, freundlich isotherm
Subjects:
Drilling Fluids and Materials, Unconventional and Complex Reservoirs, Drilling fluid selection and formulation (chemistry, properties)
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2019, Unconventional Resources Technology Conference (URTeC)
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