Study and Field Application of a Highly Inhibited Drilling Fluid

Open hole completion of horizontal wells is an effective way of reducing development cost. Based on the analysis of clay hydration mechanisms, an inhibitor able to form a hydrophobic film on the surfaces of a core and to change the wettability of the surfaces of a reservoir has been selected to satisfy a higher requirement for borehole stabilization in open hole completion. The inhibitor was evaluated in laboratory for its ability to change wettability, its relative rate of inhibition and percent recovery of shale cuttings in hot rolling test. A drilling fluid formulated with this inhibitor was optimized. Laboratory experiment results showed that the inhibitor can effectively inhibit surface hydration of clays, and is well compatible with other drilling fluid additives. Percent recovery of cuttings in hot rolling test was increased from 73.2% to 92.42% after optimization. Field practice showed that the inhibitive capacity of the drilling fluid was remarkably improved, and the drilling fluid showed very good resistance to cutting contamination, all of which were beneficial to borehole stabilization and increasing of rate of penetration.