Rheological properties of Aphron based drilling fluids

A new drilling fluid system has been successfully used to drill depleted reservoirs which are known as Aphron based drilling fluids. The rheological behavior of the Aphron based drilling fluid was investigated by experimental tests and data analyses. After generating a typical Aphron based drilling fluid, its viscosity was tested at different temperatures, and the test data was fitted using Power law, Bingham Plastic and Herschel-Bulkley models. It is found that Herschel-Bulkley model is more accurate to describe flow properties for fluids before and after Aphron generation process for all temperatures. Based on Herschel Bulkley model, the shear thinning ability of the fluid increases by increasing temperature, the gel strength and hole cleaning capacity of the fluid increase after Aphron generation, and increasing temperature to high value will not debilitate Aphron drilling fluid performance significantly. The fluid has high viscosity in low shear rate conditions, so that it can provide a strong seal in pore openings to bridge the pores. Aphron bubble growth rate over the time and drainage rates are determined as criteria for Aphron bubble stability. Bubble size growth rate is very low and the longevity is long, and liquid drains in a weak rate in drainage static test, which shows a strong stability of the Aphron based drilling fluid.