钻井液防塌剂的作用方式及分类

为了发挥组成类别不同的防塌剂的协同效应，对防塌剂按作用方式进行了分类。根据防塌剂的一般作用方式，可把防塌剂分为两大类共八个亚类。第一大类为阻止或延缓水从井眼向地层内迁移的防塌剂；第二大类为增加地层矿物颗粒间联结力的防塌剂。第一大类分为六个亚类：（１）水活度降低型；（２）滤液增粘型；（３）封堵型；（４）润湿性改变型；（５）低水化能型；（６）泥饼致密型。第二大类分为两个亚类：（１）桥联型；（２）化学胶结型。对于防塌钻井液，一般必须使用封堵型防塌剂，其它七个亚类则根据岩层特点和钻井液体系的特点加以选用。

ACTING WAYS AND CLASSIFICATION OF ANTI CAVING ADDITIVES FOR DRILLING FLUIDS/

The anti caving additives are classified into two types and then are classified into 8 sub types based on their general acting ways. The first type of additives can be used to prevent or slow down transmission of water from well hole into formations. The second type can bind up mineral particles in formation. The first type includes six sub types of additives: (1)that can decrease water activity of drilling fluids; (2)that can increase the viscosity of filtering fluid; (3)that can block up formation pores and fractures; (4)that can reduce the capilary force on water towards formation; (5)that has low hydration energy; (6)that may form compact mud cakes. The second type includes two sub types: (1)that may link up mineral particles by van der Waals forces; (2)that can adhere mineral particles by chemical bonds. The type of additive that can block up pores is the essential one for anti sloughing drilling fluids generally.