Research On Characters And Enrichment In Yan8Reservoir Of Yongning Oilfield Hechuan-Yongning Block

The Ordos Basin is the second largest sedimentary basin on land in China whichpreserves abundant oil and gas resource. Yongning Oilfield is located in central and southernof the slope of shanbei, Ordos Basin, the overall stratigraphy of a west dumpling s lope, itsdevelopment of a series of low-amplitude nose-fold structures. In order to provide thescientific prediction of the geology on expanding exploration and forecasting oil favourableobject, it is necessary to meticulously research the relationship between the reservoircharacteristic and the oil enrichment of Yongning Oilfield. This study aimed at the Yan8oilreservoir in the Hechuan-Yongning block of Yongning Oilfield, the use of sedimentology,petroleum geology, structural geology, reservoir geology, geophysical logging, etc. theory,with a large number of logging, drilling, core logging, test oil and test-mining information,combined with a variety of testing methods and analysis tools, thoroughly and systematicallystudied on the area stratigraphy, tectonics, sedimentary microfacies types and distributioncharacteristics, reservoir characteristics.The result shows that Yan8oil reservoir is thetrangressive lacustrine-deltaic depositional system, sedimentary subfacies is delta front, andthe main microfacies are underwater distributary channel, interdistributary bay.Yan8reservoir sandstones the colors are from grayish to grey, the grain size includes fineto medium-fine grained feldspathic sandstone, and fine-grained feldspar sandstone. The maindiagenesis of the study area were compaction, pressure solution, cementation, dissolution andso on, the reservoir diagenesis of the research area had reached late diagenesis A period.The average porosity of16.35%, the average permeability of56.5×10-3μm2. Yan8oil-bearing zone has a positive correlation of porosity and permeability, from the halflogarithm map, we can learn that the relationship between porosity and permeability indicatespositive linear correction; and that the permeability increases with the porosity. Pore types aremainly the inter-granular pores and dissolved pore, the residual inter-granular pores. Themainly combination porosity are between the grains, dissolve hole-between grains, compositesolution pores-micro holed etc. The main types of study area are pore combination with alarge hole in the thin throat and the small hole in the thin throat, and less little hole in themiddle throat. Through the evaluation of the reservoir, we mainly obtained: the main reservoirfor the Yan8are medium to high permeability reservoir and low permeability reservoir.The type of reservoir is tectonical and lithology reservoir. The reservoir is in the dualcontrol of both sedimentary facies and tectonic. Finally, combined with the reservoir characteristics and the affecting factors of oil and gas enrichment, and on the basis of ofsedimentary facies belt, the lung structure, sand body distribution, the review of old well dataand test data, the thesis predicts10favorable blocks of Yan8reservoir. Among them, there are4blocks in Yan81reservoir and6in Yan82reservoir. These provides the basis for thefollowing step of oil-gas exploration.