Abstract:In the process of oil and gas reservoir evaluation using volumetric method, the reservoir volume is obtained by multiplying directly the hydrocarbon-bearing area and effective thickness, while the influence of trap structural morphology is ignored. In this study, the volume integral method is used to obtain the reservoir volume and to evaluate the oil and gas resource with the purpose of getting more accurate reservoir resources by using the rock volume closer to the true value. The Halfayah oilfield of Iraq with abundant data is selected as the research area, the reservoir of which is upper cretaceous Tanuma formation. Seismic data was interpreted and lots of wells were analyzed, which was used to outline the structure contour and build up model of volume integral method. The oil reservoir evaluation was also completed by volumetric method, in which the two parameters of petroleum bearing area and effective thickness were taken as big, medium and small value respectively and 9 combinations were formed. By comparison, the result of volume integral method is very close to the median value or average value of the evaluation result of volumetric method. Finally, it is believed that the volume integral method can reflect the variation of trap form and is more deterministic, while the volumetric method can reflect the range of oil and gas volume and is more flexible.