Investigation of fly ash effect on rheological and filtration properties of water based drilling fluid

Drilling fluids are an important part of drilling operations and these fluids must have certain properties in order to have a succesful drilling process. Recently, it is aimed to improve the desired properties of the drilling fluids by adding various materials different in composition and size. In this thesis work, fly ash, which is a combustion solid of coal fired power plant, is added into drilling fluids in different concentrations (% w/w) and particle size and the changes in rheological and filtration properties were investigated. For this purpose, 32 μm, 63 μm ve 90 μm subsieve fly ash samples were added in to drilling mud in different concentrations of 1, 2, 3, 4 and 5 (w/v) respectively. Composition of fly ash was determined by XRF and supported by SEM images. Prepared mud systems were tested according to American Petroleum Instıtute (API)'s test procedures and test methods. Plastic viscosity, yield point, apparent viscosity and gel strength are examined with Fann Viscometer as rheological properties, filtrate loss and filter cake thickness were examined with API fluid loss testing equipment as filtration properties. According to experimental test results, fly ash addition improved rheological and filtration properties of drilling fluids and results were found within the limits of API-13A standarts. 1% to 5% fly ash addition for 32 μm fly ash added drilling mud caused 1 cP increase in plastic viscosity and 5 cP increase in apparent viscosity while fly ash addition of 1% to 5% concentration for 90 μm fly ash added drilling mud 6 cP increase in plastic viscosity and 8 cP increase in apparent viscosity. As the amount of fly ash added increased, filtration losses were decreased. The greatest reduction in filtration losses was observed when the smallest particle size (32 μ) was added to muds. It was determined that the filtration cake thickness increased in parallel with concentration and particle size of fly ash added.