Modification of Shale Inhibition Properties using Novel Drilling Fluids with Gemini Surfactant and Associative Polymer as Additives

Abstract

Drilling fluids are known as specialized fluids to modify rheology, filtration, fluid loss control, and shale inhibition properties for drilling applications in the oil and gas industry. Various additives are employed to change the properties based on the requirements of the drilling well and to meet the objectives of the drilling process. Additives such as polymers are used for rheology modifiers, fluid loss control modifiers, and shale inhibition control modifiers. Apart from polymers, a novel class of Gemini surfactants is also employed to modify the shale inhibition characteristics. In this work, a combined effect of polymer and Gemini surfactant was studied on the shale inhibition characteristics. Various drilling fluid formulations were prepared by adding 0.25 to 0.4% concentration of associative polymer and 0.25% concentration of Gemini surfactant. All the drilling fluids were prepared based on the American Petroleum Institute standards. Two major tests were performed to investigate the effectiveness of prepared drilling formulations for shale inhibition properties. These tests include steady shear rheology and linear swelling tests in the presence of real samples of shale pallets. The rheology of drilling fluids including polymer solutions and polymer surfactant solution was measured over a wide range of shear rates ranging from 0.1 (1/s) to 1000 (1/s). The shear stress and viscosity of the polymer solution increased by increasing the concentration of the polymer. However, the shear stress and viscosity of polymer solutions are slightly affected with the addition of surfactant solutions. It was observed that high-concentration polymer solutions were less likely by the surfactant solution. The linear swelling tests were performed with pure polymer and surfactant solutions along with the polymer-surfactant combined solution over a period of 48 hours. The linear swelling of shale pellets in the Presence of DI water was maximum while the swelling of shale pallets in the presence of polymer solution, surfactant solution, and polymer-surfactant solution was greatly reduced as compared to the swelling in DI water. The linear swelling of shale pallets in the polymer-surfactant solution (0.4%) - (0.25%) was approximately 107%. The associative polymer and Gemini Surfactant have positive pendant groups and long alkyl chains in their structures. The positive pendant groups attach with the clay content in the shale while long alkyl chains encapsulate the shale minimizing the interaction of water with shale. Therefore, the synergistic effect of both polymer and Gemini surfactant improves the shale inhibition characteristics. This combination of associative polymer and Gemini Surfactant would be potential additives for drilling fluids to modify shale swelling and hydration inhibition characteristics.