On movable fluid saturation of tight sandstone and main controlling factors —case study on the Fuyu oil layer in the Da'an oilfield in the Songliao basin

Abstract

Saturation of movable fluid is the key parameter for the potential tight oil production. With high accuracy rate, NMR technology can obtain fluid saturation statistics accurately, but due to its high cost and long term, NMR cannot be widely applied. Therefore, based on core observation, thin slices, scanning electron microscopy, CT image scanning, this paper set a precedent and proposed to combine nuclear magnetic resonance technology and constant velocity mercury injection technology together to quantitatively study the saturation of movable fluid and main controlling factors in tight sandstone reservoirs. The results showed that pore structure has great influence on movable fluid saturation, among which, total mercury saturation, median pressure, and throat radius are predominant. Diagenesis and sedimentation can affect the mobility of reservoir fluids. With an increasing burial depth, compaction, cementation, and metasomatism deteriorate the fluidity of the reservoir, while dissolution improves the fluidity. Channel microfacies, overflow sand microfacies, rupture channel microfacies, and natural dike microfacies are mainly distributed in the study area. Estuary bar microfacies are mainly dominated by type II and III reservoirs, while sheet sand microfacies are mainly distributed with the type III reservoir.