This paper aims at linking the literature on the natural resource curse with the studies on public investment management. It seeks to bridge these bodies of literature through a case study that focuses on the subnational scale and takes into account political economy. The case is an oil-rich Colombian municipality, Arauca. The level of competition in public bidding processes undertaken by the mayoralty of Arauca was muted between 2005 – 2015. Arauca exhibited an extremely high level of single-bidder-ratio (96%) and a very low average number of bids submitted per open tendering process (1.05). The paper explores the factors and processes that contributed to explain this outcome. Qualitative and quantitative data was triangulated to address three aspects of the implementation of investment projects in Arauca: (i) transparency in public management; (ii) integrity in public procurement; and, (iii) the adverse effects of the oil-fuelled armed conflict on local democracy and the municipal procurement processes. The paper reports significant shortcomings in the implementation stage of investment projects in Arauca linked with these three components. After three decades of receiving a windfall of oil revenues, Arauca's subnational government was not able to develop strong institutional arrangements to invest the revenues from resource extraction.