Design and Synthesis of Shale Stabilizing Polymers for Water-Based Drilling Fluids

Abstract

ABSTRACT Troublesome shales can cause costly downtime due to stuck pipe, hole-fill and even hole abandonment. Much research effort has been expended in an attempt to better understand shales and their interaction with drilling fluids. A combination of cations with water soluble polymers are known to effectively stabilize many shale formations including combinations of potassium chloride with partially hydrolyzed polyacrylamide (PHPA). This paper will focus on general aspects of how PHPA and other polymers stabilize shales. In the stabilization of shales by various chemical agents, the specific mechanism by which polymers stabilize shales has not been studied in detail. A shale stabilizing mechanism based on polymer adsorption onto clay surfaces and how solution properties of polymers affect this mechanism, will be proposed. Several simple approaches to the design and the synthesis of improved shale stabilizing polymers for water based drilling fluids will be discussed. A commonly used shale disintegration test has been modified for use in screening many shale stabilizers. This test method is capable of generating statistically reproducible results and has provided some mechanistic information on shale stabilizers. Such information is valuable and has led to the design and the synthesis of a new improved polymer useful for shale stabilization in water-based drilling fluid systems.