Publications

Original Gas In Place (OGIP) is important in Reservoir Engineering. Many methods have been developed to increase confidence and reduce uncertainty in estimates of OGIP. Limitations from earlier methods have been overcome by new methods. This inspires reservoir engineers to make sure they estimate the true OGIP of their Gas Reservoir. Before starting with analysis, the most important thing to be remembered for all reservoir engineers is the quality of data collection. As people say: junk in equals junk out. So a good reservoir engineer will take the longest time in data diagnostics and validation. OGIP estimates based on production data analysis such as P/Z plots is a well-established technique. However, it can yield the wrong OGIP if we don’t account for the drive mechanism of the reservoir, especially for water drive reservoirs and over-pressured gas reservoirs. The Melibur gas field has been producing gas from an over-pressured reservoir (10.5ppg at 570 feet) since 2002. In this paper, we will discuss estimation of OGIP of over-pressured gas reservoirs using modern flowing production data analysis. The flowing material balance, Blasingame type curve and analytical model history matching will be conducted. In order to gain confidence in the analysis, first the data diagnostic will be applied. Then an analytical over-pressure gas reservoir model was constructed and the generated data was input into the analysis software to know how it looks in each of the listed methods. This analysis gave us a new OGIP and more reliable production forecast. It also gave us a new point of view on analyzing production data of over-pressured gas reservoirs.