一种新型的油包水合成基钻井液

A New Type Water-in-oil Synthetic Drilling Fluid

我国页岩气资源勘探开发已全面铺开。页岩失稳坍塌是目前困扰中国页岩气水平井大规模钻探的关键因素之一。合成基钻井液因其强抑制性强,在国外被广泛用于页岩气水平井钻井。借鉴国外相关经验,设计实验优选出油包水合成基钻井液的配方:矿物油(OA)+白油(OB)+水+3.0%乳化剂(纳米级SiO_2)+1.6%醋酸钾+1.0%有机土+3.0%降滤失剂+2.0%润湿剂+重晶石。以在实验室内合成低毒、价廉的矿物油OA和白油(OB)为基础油不仅能够降低成本,而且可以生物降解,对环境污染小。采用纳米级SiO_2做乳化剂,不仅有很好的粘结性、耐高温性、成膜性,而且对高速搅拌下产生的气泡有一定的消泡作用。采用醋酸钾替代氯化钙作为水相抑制剂,既增强了体系的抑制性又简化了配制工艺。该钻井液体系加重至2.40 g/cm^3的流变性能良好,破乳电压较高;在130℃条件下热滚老化后流变性及破乳电压变化都不大。该体系很适合用于高地层压力梯度的四川盆地页岩Ⅰ区块(下志留统龙马溪组下部—上奥陶统五峰组约86 m层段)含气泥页岩段目的层的开发。其良好的润滑性能也有利于在该区块进行大位移水平井开发。

Exploration and development of shale gas resources has been in full swing. Shale instability collapse is currently plaguing one of the key factors in Chinese shale gas drilling. Synthetic drilling fluids are widely used in overseas shale gas horizontal drilling because of strong inhibition. Based on foreign experiences, through design experiments, preferable synthetic oil-in-water formulation of drilling fluid was obtained as follows： mineral oil（OA） ＋ white oil（OB） ＋ water ＋ 3.0% emulsifier（nano-SiO_2） ＋ 1.6% potassium acetate ＋ 1.0% ＋ 3.0% organic soil fluid loss additive ＋ 2.0% wetting agent ＋ barite. Using inexpensive OB and OA with low toxicity can reduce costs, and they are biodegradable and have lower pollution. Nanoscale SiO_2 is used as emulsifier, it has good adhesion, heat resistance, film, also has a certain anti-foaming effect. Instead of calcium chloride, using potassium acetate as an aqueous phase inhibitor can enhance the inhibitive capacity of system and simplify the preparation process. The drilling fluid has good rheological property and the higher breaking voltage; Rheology and demulsification voltage changes are not large at hot rolling of 130 ℃ condition. The system is very suitable for the Sichuan Basin shale blocksⅠthat is high formation pressure gradient. Its good lubrication properties also are conducive to the development of large displacement horizontal wells in the block.