Seismic Sedimentary Facies Of The Middle-lower Combination Of The Yanchang Formation Of The GF Area

With the improvement of oil and gas exploration levels,it has been put forward with higher requirements in submitting control and forecasting reserves.All along,researches on the major oil reservoirs of Chang 8 and Chang 6 in the GF area of the northwestern Ordos Basin have mainly focused on the geological strata,focusing on well logging and geological theoretical studies,and are relatively macroscopic.However,it is rarely combined with seismic data.Thus,it cannot meet the requirements for the division of sedimentary microfacies.In this paper,the middle-lower combination?Chang 8₂,Chang 8₁,Chang 6₃,Chang 6₂?of the Yanchang formation in the GF area of the northwestern Ordos Basin was studied.Seismic sedimentology and geophysics were used to study high-quality 3D seismic data.Based on the results,a large number of geological and drilling data were integrated for analysis.Establishing the corresponding relationship between the seismic facies and the logging phase by calibrating the well and seismic data,dividing the stratum,and describing the sedimentary faciesoftheresearchtargetlayer;then,usingthe“seismicmodel guidance—qualitative-semiquantitative-quantitative”way of the reservoir thickness to describe the sand body morphology,extract and fuse seismic attributes,quantificationally predicte distribution of sand bodies;Finally,according to the main control factors of reservoir enrichment to chose favorable zone.The results of the study indicate that the Chang-8 reservoir component is a section with a Chang of 8₁ and a Chang of 8₂.The Chang-6 reservoir group can be divided into three layers of Chang 6₁,Chang 6₂,and Chang 6₃?due to the Chang 6₁ has small area and thin thickness,and bad connectivity,this article does not do a detailed study?.The sedimentary facies are mainly delta front subphase sediments,and 5 kinds of sedimentary microfacies are identified,including underwater distributary channel,sub-distributary bay,estuary dam,leading edge litter sand or far sand dam;It is believed that the distribution of sand bodies is controlled by sedimentary systems.The sand bodies are mainly distributed in the north-south-southeast and north-north-south phase belts;Combined with exploration results,analyzed and compared the oily nature of the deltas in each period to believe that the sedimentary environment was the geological basis for the reservoir's reservoir performance.After analysis,it is believed that the enrichment of the Yanchang formation in the study area is obviously controlled by the sedimentary systems of continents and lacks,and it is optimally configured by the large dips and faults of the west diversion,forming structural-lithologic and lithologic reservoirs.Finally,a total of 29 categories of favorable areas are classified as being classified as category I and 8 as category II,with a total predicted area of 72.1 Km².