Research and Applications of Anti-Sloughing Drilling Fluid for the “Double Stone” Layers of the Yanchang Tight Sandstone Gas Field

Abstract

Borehole collapse has always been encountered when drilling the Shiqianfeng and Shihezi formations in Yanchang. It was found that the collapses were due to “double layers of stone” which were brittle, strong, porous, and water sensitive, with a high mineral content within their skeleton particles. Water-locking properties and stress sensitivity are potential factors known to induce wall collapse. To resolve this drilling problem in the Yanchang gas field an anti-sloughing drilling fluid system was devised for use in its “double layer of stone”. The system (complex fluid loss—dual inhibition—materialized block) incorporates a multiple cooperative mechanism of drilling fluid to prevent further drilling collapses. The drilling fluid system developed was applied to Yanchang gas field 645, part of the Shiqianfeng group, and resulted in the Shihezi hole enlargement rates reducing from an average of 22.49 and 22.04% to 15 and 12% respectively, with a filtration rate less than or equal to 5 mL, demonstrating that the drilling fluid system had an obvious anti-collapse effect.

Copyright 2017, Shaanxi Petroleum Society.

This paper was prepared for presentation at the 2017 International Petroleum and Petrochemical Technology Conference in Beijing, China, 20–22 March, 2017.

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