Research On Reservoir Characteristics Of Chang 3 Oil-bearing Formation In Zhenbei-Yanwu Area Of Ordos Basin

The sand body of Chang 3 oil-bearing formation was developing in Zhenbei-Yanwu Area of Ordos Basin. As a result of poor exploration, the study of predecessors on the reservoir of Chang 3 oil-bearing formation were few, especially, there is no further study on the Reservoir Characteristics of Chang 3 oil-bearing formation. Based on the former's research and effectively utilizing the first data of core observation,well logging,geological borehole log and the techniques of modern laboratory analysis, the Chang3 oil-bearing formation zone of Yanchang formation reservoir, Upper Triassic of the Zhenbei-Yanwu area in Ordos Basin, had been analyzed synthetically and evaluated the reservoir with grey analysis method,through drawing the map of sedimentary facies and sand body distribution and physical property's plane distribution, and so on related geological graphic document.It showed that the lithotypes were debris-feldspar and feldspathic lithic sandstone which had the characteristics of low compositional maturity and high texture maturity; clastic particles were generally fine-grained structure; cement were mainly carbonate; the study area mainly developed the sedimentary system of the meandering river delta, which can be divided into the delta plain subfacies and the delta frontal subfacies. In the plane, the above subfacies can be divided into distributary channel, inter-channel depressions, subaqueous distributary channel and inter-channel bays; The stage of diagenesis was at the early period of mature sub-member of middle diagenetic stage; the mainly types of diagenesis were Compaction,Solution,Cementation,Dissolved and so on. It indicated that heterogeneity was strong and gradually weakened from old to new in the Chang3 layer of reservoirs in the Ordos Zhenbei-Yanwu area; Physical Properties of reservoir were poor and had low porosity and permeability; The sedimentation and diagenesis had played important roles in evolution of reservoir.According to the above study, we evaluated the reservoir of Chang3 with grey analysis method. There were four types of reservoir formation in this area. Typeâ… andâ…¡were the favorable ones and mainly distribute in the center of the distributary channel and subaqueous distributary channel. Typeâ…¢was comparatively favorable and distributed in the edge of the distributary channel and subaqueous distributary channel. The method was used to classify and evaluated reservoirs and the results were compared with the oil testing result. The two sets of results were highly consistent with each other. The analyses showed that this method was practical in reservoir comprehensive assessment.