Abstract

Clay stabilizers have been used in various forms in oil well treating solutions for over 30 years. Cationic organic polymers have been the most popular type stabilizer in use recently because of their resistance to wash-off and chemical attack, ease of application, and effectiveness in moderate to high permeability formations. Recent studies investigating the effectiveness of such stabilizers in very low to low permeability sandstones have shown them to be less than 100% effective in stabilizing clays to prevent swelling and migration. Results indicate that higher molecular weight polymers can create permeability impairment when injected into these formations. These findings indicated the need for further research into clay stabilizers. This research led to the development of a novel clay stabilizing chemical for low, as well as high, permeability formations. This low permeability clay stabilizer also offers additional benefits in treating low permeability formations by enhancing fluid recovery after fracturing, and preventing the detrimental effects of fracturing fluid gel adsorption onto formation surfaces.

Introduction

Most oil and gas producing formations contain clay minerals that either were originally deposited during sedimentation (detrital clay), or formed later by the action of heat, pressure and time on minerals already present, or precipitated from fluids flowing through the matrix (authigenic clays). The importance of these minerals in the production of oil and gas and the potential permeability damage they can cause have been widely investigated. The two major mechanisms by which these minerals can cause permeability damage are by swelling and by migration. In swelling, clay imbibes water into its crystalline structure and subsequently increases in volume, plugging the pore in which it resides. In migration, clay minerals can be dispersed by contact with a foreign fluid, or can be entrained by produced fluids and transported until a restriction is encountered (usually a pore throat) where the entrained particles bridge, forming a restriction in the capillary. The mechanisms of migration of clays and other fine minerals have also been extensively explored.

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