Application of aluminum based polyalcohol drilling fluid in Liaohe oilfield.

In Shenbei block of Liaohe oilfield, large soft mudstone exists in the upper formation, leading clay hydration and swelling, then hole shrinkage; in the lower formation, the clay is dispersive, making periodical hole collapse a potential. Complex problems appeared by reason that the conventional drilling fluids were not qualified to stabilize well bore effectively. A strongly inhibitive aluminum-based polyalco-hol drilling fluid was developed to prevent above problems from happening. In virtue of cooperation of aluminum salt and polyalcohol, this fluid provides excellent lubrication and inhibition property. This drilling fluid was used in 3 wells of Shen625-10-22, Shen625-14-34 and Shen625-18-30 with excellent performance, the drilling accidents were reduced, the hole was in gage. Comparing with wells in adjacent blocks using polymer drilling fluid, the average well diameter enlargement rate was reduced by 7. 95%-11. 77%, and the density was lower than that of adjacent wells. Drilling success verified that aluminum based polyalcohol drilling fluid satisfied drilling requirements of Shenbei block with obvious anti-collapse effect.