‌Solution for Water-Sensitive Swelling and Shrinkage Formation

‌1. Water-Sensitive Swelling and Shrinkage Formation‌

The water-sensitive swelling and shrinkage formation refers to rock formations that exhibit water absorption and swelling phenomena after encountering water. These formations are primarily composed of mudstone and shale layers dominated by montmorillonite and illite-montmorillonite mixed layers.

Formations such as hard shale, clay-cemented formations, or formations cemented by water-soluble minerals are prone to disperse in blocks and peel off when they come into contact with water, resulting in the collapse of the borehole.

2 .Problems Existing in Drilling Construction

 Caving blocks and collapse

The caving blocks returned from the highly water-sensitive formation

3.Drilling Treatment Measures for Strongly Water-sensitive and Dispersive Formations
(1) According to the on-site situation, increase the density of the drilling fluid to balance the formation pressure.
(2) Select film-forming anti-collapse drilling fluid, potassium-based polymer drilling fluid, or dual-polymer anti-collapse drilling fluid, etc.
(3) Add plugging materials or treatment agents with strong cementing properties to the drilling fluid to strengthen the cementation between particles or fragments and enhance the mechanical strength of the borehole wall.

4 . ‌Recommended Drilling Fluid Systems‌

‌Table1. Optimized Drilling Fluid Formulations‌

5.Application Cases ：

The on-site test of the film-forming anti-collapse solid-free drilling fluid system shows that: it has a remarkable effect on protecting the borehole wall, and meanwhile, the quality of core sampling has been significantly improved.

The core samples taken out with the original drilling mud.

The core samples taken out with the film-forming anti-collapse drilling fluid.