This article proposes an approach based on state observers to recursively estimate the friction of pipelines with an extraction. Two specific scenarios, associated with information availability, are treated herein: (1) pressure at the extraction is measurable, (2) extraction measurements are unavailable but the position is known. For both scenarios, measurement availability at the pipeline ends is assumed. The state observers were designed from Liénard type models that represent the fluid dynamics in a pipeline. Such models were extended with the incorporation of the friction factors into their state vectors, such that from the extended models, the observers were constructed. The proposed approach was tested by using data from the commercial software PipelineStudio® and experimental data from a laboratory pipeline of water.