Technical challenges and solutions of drilling fluid techniques in Silurian in Tuoputai 3 block of Tahe oilfield

Sandstones and mudstones interbedded in the Silurian Kepingtag Formation in the Tuoputai 3 block of Tahe oilfield, about 340-420 m thick for each layer and generally buried at a well depth of 5 570-6 200 m. The interlayer thickness and burial depth gradually increased from north to south. By analyzing the lithology of the Kepingtag Formation and the causes for wellbore instability and well leakage, combining with the laboratory evaluations of inhibitors and anti-collapse plugging agents, we proposed a formula for potassium amine anti-collapse drilling fluid, which is suitable for the Tuoputai 3 block. Some detailed measures to solve collapse and leakage were put forward, combining physical anti-collapse methods with chemical ones. Segmental static plugging and drilling plugging were focused on. A combination of high softening point emulsified asphalt and rigid particle was applied to solve collapse. Velocity was controlled and drilling fluid was circulated when drilling up and down. This drilling fluid system achieved good effects in well TP346X. The drilling diameter of the Kepingtag Formation was improved by 7.45%. Collapse was significantly reduced and there was no leakage or other complex situations.