Molecular Structure and Performance of Oligomeric Amine Shale Inhibitor

Oligomeric amines were investigated for the effect of their molecular structures on their inhibitive capacity, API filter loss and adsorption behavior. The presence of hydrocarbon and amino groups in the oligomeric amine molecules results in an increase in the API filter loss of a mud treated with oligomeric amine, although the effect of amino group is weaker than that of the hydrocarbon group. The ether group and carboxymethyl group reduce the filter loss of a mud. Amino group is the strongest adsorption group, followed by ether group and hydrocarbon group. Carboxymethyl negatively affect the adsorption of mud additives. All the oligomeric amines, when adsorbed, form single layer on the surface of clay particles, which is beneficial to the formation of a minimum spacing between the unit layers of clay, thereby preventing clay from swelling. A polyamine additive, RZPA, made from polyetheramine D230, the best amine shale inhibitor, was used in drilling the well Jiangsha33-8 in Deyang, Sichuan. Good inhibitive capacity was found when drilling water sensitive shales. Hot rolling test showed that RZPA had percent recovery of shale samples between 73% and 81%.