Experimental Study on a New Ultrahigh Temperature Shale Inhibitor

Study on high temperature shale inhibitors is of great importance in satisfying the needs of high temperature deep well drilling and in improving the inhibitive capacity of high temperature water base drilling fluids. A new ultrahigh temperature shale inhibitor, HT-HIB, was studied for its high temperature performance and working mechanism through laboratory experiments, such as test of bentonite to yield, hot rolling test, shale core swelling test, pressure transmission measurement, x-ray diffraction to measure the c-spacing of clay, Zeta potential test and thermogravimetric analysis etc. The study has shown that HT-HIB was able to inhibit the hydration, swelling and dispersion of shales, and to contain pressure transmission to some extent, and was superior to the polyamine shale inhibitors presently used in high performance water base drilling fluids. In the experiment, HT-HIB remained stable at 220℃. HT-HIB worked by inserting its amine group at the end of its molecular chain, in a way of monolayer adsorption, in between the crystal layers, thereby destructing the surface hydration structure of the clay particles and squeezing the adsorbed water out of the crystal layers. After adsorbing HT-HIB molecules, the hydrophilicity of clay particles was greatly reduced, and adsorption of water molecules was thus stopped. Furthermore, the solubility of HT-HIB changed with pH of the system, and was thus able to separate out from the system to plug the micro fractures in shales, beneficial to hinder the invasion of water molecules into shales. To summarize, HT-HIB showed excellent inhibitive capacity through synergy of chemical inhibition, wettability reversal and physical plugging. It paves the way to developing the new generation high temperature high performance water base drilling fluids.