Strengthening wellbore fluid techniques for long open-hole

The difficulty of strengthening wellbore fluid for long open-hole in X1 region is concentrated in the leakage in the upper Permian igneous rocks with developed micro fractures, and the shale collapse in the lower Silurian. Drilling fluid maintenance is difficult in the same open hole section. In well X1-1H, 8 leak points were found in Permian, and well leaked for 25 times, losing 2 568 m3 drilling fluid. In well X1, the treatment for mudstone blocking in Silurian took 22.1 days. Polymer gel plugging agent and bamboo fiber were applied to prevent leakage for 30 min at 0.69 MPa. Plugging agents for fractures of 1, 2, 3 mm were designed, which can prevent leakage at 6.9 MPa. We combined isolating membrane with hydration inhibition, introduced film-forming agent and polyamine inhibitor as key agents, and optimized form Amino potassium filming drilling fluid system for Silurian, which has a high pressure filtration volume of 8.8 mL at 150℃. Compared with KCl-polymer sulfonated drilling fluid, shale recovery increased by 15.1%. Applications in wells X1-5H and X1-6H 2 showed a good effect. No leaking occurred when drilling and completing in Permian. Almost 5 000 meters long open-hole did not stick. The average hole enlargement of Silurian was only 9.01%. Strengthening wellbore fluid techniques for long open-hole are significant to cut cost and increase profit in X1 region.