云贵高原水敏凝灰岩在盐溶液中的稳定性

Stability of water-sensitive tuff in salt solution in Yunnan-Guizhou Plateau

水敏凝灰岩快速分解垮塌给勘查钻井带来严重问题。研究凝灰岩在化学溶液中的稳定性对水敏凝灰岩防塌钻井液应用具有重要意义,是防塌应用的必要条件。选取凝灰岩分布广泛的云贵高原地区的几个典型高分解性软弱水敏凝灰岩作为样本,进行凝灰岩在系列盐溶液中稳定性的化学实验,并对部分有较好防塌能力的盐溶液进行浓度系列实验。研究表明:1)较高浓度的盐溶液对凝灰岩的分解具有明显的阻碍作用。钾盐对部分地区凝灰岩有稳定性改性作用。2)不同地区凝灰岩在不同盐溶液中的稳定性不尽相同,对水敏凝灰岩应使用以某盐的饱和盐溶液为基础的混合盐溶液,辅助使用凝灰岩滤液作为基液有很好的防塌效果。水基盐溶液对凝灰岩分解的阻碍时限一般不超过两天,要使防塌钻井液达到实用程度,但还需钻井液含有纳米成膜及控制钻井液中自由水等其它配方成分。3)凝灰岩在盐溶液中稳定的原理是:高浓度盐溶液阻碍了凝灰岩内部可溶盐的溶出,进而起到了稳定凝灰岩的作用。阻止溶出作用是最主要的因素,离子交换改性或双电层效应仅是部分高含黏土凝灰岩的部分稳定性因素。

The rapid collapse of water sensitive tuff brings serious problems to exploration drilling.For the application of water sensitive tuff’s anti-collapse drilling fluid,it is very important to study the stability of tuff in chemical solution,the stability in chemical solution is the necessary condition for drilling fluid.In this paper,several typical highly decomposable and water-sensitive tuffs in Yunnan-Guizhou Plateau were taken as samples to conduct chemical experiments on the stability in a series of salt solutions.And for those salt solutions which have good anti-collapse ability,series concentration experiments were conducted.Studies results indicate that:1)Higher concentration of salt solution has a significant hindrance to the decomposition of tuff.Potassium salt has some stable modification effects on tuff in some areas.2)The stability of tuff in different salt solutions in different regions is not the same.For water-sensitive tuff,a high-concentration mixed salt solution should be used.The time limit for the water-based salt solution to hinder the decomposition of tuff is generally no more than two days.To make the anti-collapse drilling fluid practical,high concentration or even saturated salt solution is essential,but other formulations such as nano-film formation of drilling fluid are also required.3)The principle of tuff’s stability in salt solution is that the high concentration of salt solution hinders the dissolution of soluble salt in tuff,which is the main factor.Ion exchange modification or double layer effect is only part of the stability factor of some high clay bearing tuffs.