Unplugged or improperly plugged, orphaned or abandoned oil wells have become major environmental concern to crude oil producing and neighborhood communities. They provide potential conduits for fluids to migrate between formations and into the fresh water zones. Emissions can also seep to the surface and potentially cause fire-outbreak or risk to health and property. This can result from inadequate hydraulic conditions leading to excessive buildup of pressure. The Oloibiri Oilfield was abandoned since 1978 without recovery plan to drain the estimated 21.3 million barrels of crude left-over. This had spurred serious concerns due to recent oil/gas well blowout incidents across the Niger Delta region. On this basis, research work became necessary to study and identifies some of these legacy oil and gas wells abandoned for decades with a view to assessing potential leaks and analyzing the risks. The vicinity of 7 out of 21 abandoned Oil/Gas Well Heads were sampled at distances of 0m, 2m, 5m, 10m, 15m, 20m and 25m radius in north, east, south and west directions off the wellheads over a period of 6 weeks. In this report analysis of direct onsite emissions of methane at the radius distances of the abandoned oil and gas well heads at Oloibiri and Otuabagi are presented. The Aeroqual S200 Multi-Gas Monitor was used to instantaneously sample detectible limits of Methane gas leaks (Townsend-Small and Hoschouer, 2021). The study area showed significant excess Methane loads over four (4) to twenty (20) times above the naturally expected atmospheric condition of 2.2 ppm by volume. The sustained buildup in concentration is therefore sufficiently high enough to cause direct or indirect impact on animate life, hence the ecosystem, as the hydraulic pressure of methane and other gaseous emissions in the annular casing continues unabated in the long run.