Akintola, S. A.Orisamika, O. B.2026-04-2920231337-7027ui_art_akintola_apllication_2023.Petroleum and Coal 65, pp. 131-137https://repository.ui.edu.ng/handle/123456789/13844Biodegradable natural products are increasingly investigated for different industrial applications mostly due to wider range of disposal options with minor health, safety and environmental impacts. In the petroleum industry, research into the products of natural polymeric materials to substitute synthetic chemical products used as additives in drilling fluids is aimed at reducing the overall cost and environmental impact of drilling operations. In this study, micronized carboxymethyl starch (CMS) was investigated and compared with carboxymethyl cellulose (CMC) as additive in water–based mud. Natural starch obtained from yam, potato tubers, and rice was modified by carboxymethylation, micronized to different particle sizes, and analyzed using Fourier Transform InfraRed (FTIR) Spectrometry. The rheological properties of the mud were determined at different micro–sizes (63µm and 75µm) and concentrations (0.5, 1.0, 1.5 grams) of the additives, and temperature ranging between 30⁰C to 85⁰C following the American Petroleum Institute recommended practice (API RP 13B–1). The major functional groups identified in the starch products are six–membered ring carbonyl group at 1735cm–1, carboxyl group at 1605cm–1 and 1650cm–1, and methyl group between 1450cm–1 to 1300cm–1. The CMS at 63µm compared favourably with CMC and had approximate average yield point/plastic viscosity ratio of 1.5 above 30oC. The results further showed that CMS is a suitable alternative viscosifier to CMC for water based mud and recommended for field trials.enNatural productsCarboxymethyl starchMicronizedWater–based mudRheological propertiesArticle