Comprehensive Evaluation Of Chang 7 Shale In Huachi Area,Ordos Basin

Ordos Basin Can be divided into six 1st tectonic units.Yimeng uplift in the north,The folded zone in the western margin,Tianhuan Depression in the west,Shanbei Slope in the center,Weibei uplift in the south and Jinxi flexure with in the east.The study area is located in the center of the basin,belongs to the Yixia Slope of Ordos Basin,the west is Tianhuan Depression and the south is near with the Weibei uplift.Yanchang Formation in late Triassic epoch of Mesozoic is a set of gray-green,gray Medium-bedded of fine sandstone,siltstone and dark gray,black shale deposition.The Lower part consists mostly of medium and coarse sandstone sediments,the middle part is a set of Lake-Delta sand and mud interbedded sedimentary,the upper part is fluvial sandstones and mudstones sediments.The Yanchang Formation's top of each other strata is a parallel unconformity.It has Obvious Sedimentary cycles,Bottom-up is divided into five segments,between the various sections are continuous deposition.In order to meet the needs of oil and gas exploration,By lithology,electrical properties,especially in light of the 10 marker bed(K0-K9),Yanchang Formation is divided into 10 reservoir group from top to bottom.Depend on sedimentary cycles and logo layer,chang 7 is divided into chang 73.chang 72 and chang 71 oil layer group.Sand thickness of the three layers is increases from bottom to top,chang 73 is much thinner compared to chang 71 and chang 72,the sand is also small.The abundance of organic matter of chang 7 shale is high.The kerogen microscopic observations suggest that organic matter in the shale consists mostly of amorphous algae,planktonic algae and benthic algae are the most biological sources of chang 7 shale.Kerogen types are ?1 and ?2,Ro in the study area is 0.56%—1.12%,0.83%in average.The oil generation is at Low-mature and mature stage.Shale oil content in the study area is lower,only 0.26%—4.69%,1.15%in average.Speculate that shale there have been have a large-scale hydrocarbon and hydrocarbon expulsion,and there is no large-scale shale oil zone.There is much brittle mineral in chang 7 shale,the content of each layer is more than 40%.The brittle index is relatively high compared to North America.The shale porosity is 0.5%-2%,and the permeability is(1-7)×10-6?m2.The reservoir of study area is lithology reservoir,chang 7 is the Source rocks,Reservoir and also the cover.The sand morphology and sand contaction with shale impact chang 7 reservoir distribution.It is more favorable to explorate shale oil and gas in chang 73.