The Study On Reservoir Distribution Characteristics And Prediction Of Favorable Zones For Oil In Yangmijian-Dalugou Area

Chang 2 and Chang 6 reservoir of Yanchang Formation in Yangmijian-Dalugou Area are the main oil layers in the region, however, the oil reservoir studies are merely a simple description of reservoir characteristics, or just confined to the reservoir characteristics of a small block. There are no systemic analysis and research on the whole region reservoir geometry, spatial distribution, microfacies, micro-pore structure characteristics and oil reservoir control factors in Yangmijian-Dalugou Area,that is difficulty to meet the needs of the exploration work.The research of reservoir distribution, analysis of reservoir control, prediction of favorable zones for oil in Yangmijian-Dalugou Area are studied In this paper, using integrated research methods of the macro and micro integration, regional geological data and single well geological data integration, geological studies and logging technology integration, and applying the analysis and test information of particle size analysis, cast sheet, scanning electron microscopy and high pressure mercury-injection. The geological basises for further exploration and development of the oil field are provided by this research.these main results are achieved after the research:1 The deposition system in Yangmijian-Dalugou Area is identified based on lithology, sedimentary structures, paleontologic evidence, sedimentary cycles, logs, drilling core, and other informations. It is mainly braided river subfacies of river depositional system in Chang 2 depositional stage. The sedimentary microfacies types of the river channel, channel sand bar, abandoned channel, and floodplain can be identified further.It is mainly delta front facies of delta depositional system in Chang 6 depositional stage. The sedimentary microfacies types of the distributary channel, mouth bar, interdistributary bay can be identified further. 2 By the statistical analysis of cast sheet, ithe intergranular pore is the main pore type of Chang 2 reservoir, with areal porosity of 11.8%. Feldspar dissolved pore and debris dissolved pore are followed by. The intergranular pore and dissolved pore are main pore types of Chang 6 reservoir, with respective areal porosity of 2.62% and 2.33%, and the dissolved pore are mainly laumontite dissolved pore and feldspar dissolved pore.3 The diagenesis of Chang 2 and Chang 6 sandstone reservoir of Yanchang Formation are complex, and the diagenesis phenomenon are rich. The common types of diagenesis are compaction, cementation, and denudation. The damage to the porosity by compaction and cementation is big. Clay minerals cements and carbonate minerals cements are the main reason for the deterioration of reservoirs. The denudation has more contribution to the reservoirs. Especially, the secondary porosity formed by feldspar and laumontite dissolution is the important factor in improving the accumulation performance of reservoirs.4 The quality of oil content is mainly controlled by sedimentary facies, reservoir properties and structures. Chang 2 reservoirs are mainly lithologic oil pools and structure-lithology reservoir caused by differential compaction. Chang 6 reservoirs are mainly lithologic oil pools which are formed by sandstone piching or tight sand shielding on the updip direction of sandstone.5 The favorable oil zones of Chang 2 reservoir mainly locate in the thick sand deposition of braided river channel, reservoir with better properties, or tectonic uplift sites caused by differential compaction. The favorable oil zones of Chang 6 reservoir mainly locate in the distributary channel deposition of delta front, reservoirs with strong denudation, and the sites with better properties.