Sandstone Distribution Pattern And Reservoir Forming Favourable Target Prediction Based On Delta In Chang6Oil Reservoir Of Yanchang Formation Of Suijing Area,Northern Shaanxi Slope

The delta deposit is the main direction of oil and gas exploration in China, which contains a huge amount of energy and mineral resources. The Ordos basin has a wealth of oil and gas resources, has made many breakthrough for more than30years’ exploration and development, the geological oil reserve increased year by year. However, the overall level of exploration is still low in the Ordos basin.The paper aims at chang6oil reservoir of Yanchang Formation in Suijing Area, on the basis of absorbing the results of previous studies and the data fully. This article analysised the stratigraphic classification and correlation, the sedimentary microfacies, the reservoir characteristics, the reservoir type, the reservoir controlling factors and the distribution law of oil and gas by the theory and method of sequence stratigraphy, sedimentology, petroleum geology, logging geology, reservoir geology, and so on. Based on the above, we predicted the reservoir forming favorable target of chang6oil reservoir in Suijing Area.Chang6oil reservior of Yanchang Formation can be divided into chang61, chang62and chang63by looking for regional correlation marker bed, with cycle comparison and hierarchical control. We completed the stratigraphic classification and correlation systematically by establishing some vertical and horizontal well sections.Chang6oil reservior of Yanchang Formation is a delta deposit in Suijing Area, developed delta plain and delta front. We can identify eight kinds of sedimentary microfacies, which are distributary channel, interdistributary embayment, natural levee, crevasse splay, subaqueous distributary channel, subaqueous interdistributary embayment, subaqueous natural levee and channel mouth bar. The distribution of river channel is NE-SW in accordance with bands.Through the study of core slice, cast slice and mercury penetration, the pore types of chang6oil reservior of Yanchang Formation is mainly secondary solution pore, followed by primary pore. The reservoir is mainly the sandstone of distributary channel and subaqueous distributary channel, which is an axial canal and subtle throat reservoir. The river channel sandstone’s thickness of chang61is4m～20m, and chang62is8m～20m. The distribution of reservoir sandstone and physical properties is the same as that of sedimentary facies. The continuance of sand body is very good in the direction of parallel to the provenance, but is poor in the direction of perpendicular to the provenance.Chang6oil reservior of Yanchang Formation is "continuous" reservoir by analysis. The reservoir is controlled by some factors of sedimentary microfacies, lithologic character, oil source, diagenic metamorphism, and so on. They are mainly distributed in the distributary channel and the subaqueous distributary channel close to the oil source.By the above study, we predicted the reservoir forming favorable target of chang61and chang62in Suijing Area combined with the data of logging, well logging interpretation, testing for oil and production. All this can provide an important basis for the further exploration and development.