Stratigraphy And Sedimentary Facies Study Of Mesozoic In Dongpu And Surrounding Regions

Comprehensive researches on biostratigraphy, lithostratigraphy, seismic stratigraphy andsedimentary cycle indicate that the development degree of various Mesozoic strata differsgreatly in Dongpu and surrounding regions. Triassic rocks distribute widely, mainly in the areasto the west of Lanliao Fracture Zone such as the northern part of Dongpu depression, ShenCounty depression, Tangyi arch, Guantao arch, Guan County depression, Tangyin graben inLinqing Sink, and Jiyuan depression, Zhongmu depression in the south of North Chine basin,etc. Jurassic rocks distribute in Shen County depression, Qiu County depression, Tangyin graben,Handan depression of Linqing Sink and Jiyuan depression, Zhongmu depression, Huangkoudepression in the south of North China basin, and Dongpu depression is lacking. Cretaceousrocks distribute in Qiu County depression, Handan depression, Shen County, Guan Countydepression and Guantao arch of Linqing Sink, Huangkou depression in the south of North Chinabasin and Chengwu depression on Luxi uplift, etc. Cretaceous strata of Jiyuan depression hadless developed. Dongpu depression is lacking.Palaeontological analysis, regional stratigraphic correlation and absolute age testing showthat the geologic age of high resistivity and red beds belongs to Triassic. The concrete geologicage should is the early period of Early Triassic. It may be compared with Lower TriassicLiujiagou formation and Lower Shanggou formation distributed widely in the middle-west partsof North China area.The dark coal-bearing clastic rock in the lower formation of Early-Middle Jurassic hascertain hydrocarbon-forming potential in the surrounding regions of Dongpu. The dark strata ofLower Cretaceous are important potential hydrocarbon source rocks. Reliable Upper Jurassicremains to be discovered in the area. A tremendous regional unconformity surface exits betweenMiddle-Lower Jurassic and Lower Cretaceous.General depositional features of Mesozoic clastic rocks in Dongpu and surrounding regionsare: lightly low maturity of rock's mineralogical composition and middle-lightly high structurematurity;mainly read shaly rocks and less dark ones;drag flow genesis for the sedimentarystructure;mainly two-section type and two-section transition type for grain probability curve,less single-section type and three-section type.The Mesozoic sedimentary facies types in Dongpu and surrounding regions consist oftorrential-alluvial fan facies, fluvial facies and lacustrine facies, etc, in which the fluvial faciescan be also subdivided into channel subfacies, flood-plain subfacies and flood-basin subfacies,and the lacustrine facies can be also subdivided into littoral and shallow-lacustrine subfacies,semi-deep lacustrine subfacies, limnetic subfacies,etc. The sedimentary facies types differ invarious regions and ages. Triassic sedimentary areas are large but there is not sedimentation inthe Luxi uplift region, Neihuang uplift region and Huangkou area. The sedimentary typesinclude fluvial-channel deposit and paludal facies deposit. The Middle-Lower Jurassic sedimentmainly developed in Linqing Sink and Jiyuan depression. The sedimentary types involve fluvialfacies, paludal facies and semi-deep lacustrine-shallow lacustrine facies. The Middle Jurassicsediment mainly developed in Linqing Sink, Huangkou depression and Jiyuan depression. Thesedimentary types are comprised of fluvial facies and lacustrine facies. The lower deposit ofLower Cretaceous mainly developed in Qiu County depression and Huangkou depression. Thesedimentary types are fluvial facies and lacustrine facies. The upper part of Lower Cretaceousmainly developed in Qiu County depression and Huangkou depression. The sedimentary typesconsist of lacustrine facies, torrential-alluvial fan facies and fluvial facies. Upper Cretaceousdeposit mainly developed in Linqing Sink and Jiyuan depression. The sedimentary types includefluvial facies and paludal facies.The cementation of Mesozoic sandstone developed very well in this region, which ismainly carbonate cementation, quartz and feldspar grains growth, authigenic clay mineralgrowth, zeolite family mineral precipitation and sulphate mineral precipitation. The intensecementation greatly reduces the porosity and permeability. The carbonate cementing matters aremainly calcite, iron-bearing calcite and dolomite. Calcite and dolomite mostly show thefine-microlitic texture, which is, being grain in shape, filled between the clastic grains. They aremostly cemented to being pore in form, the individual to being basement in form. The growingquartz mostly developed two episodes. One is that R0 is 0.5-0.7% in shallow zones, which canmake the porosity show a reduction of 1-3%. The other occurs when R0 is 1.3-1.5%, which canmake the porosity show a reduction of 2-5%.Middle Palaeozoic reservoirs in Dongpu and surrounding regions can be divided into fourtypes, combined with the petroleum exploration practice of this region and referred to theexploration practice and researches of low-permeability reservoirs at home and abroad.Reservoir type â…  is the effective reservoirs, reservoir type â…¡ is the potential effective reservoirs,the type â…¢ is the prospective effective reservoirs and the type â…£ is nonreservoir.The reservoirs of various regions differ greatly, in which the reservoirs' preservingproperties are well in Tangyi arch, Qiu County depression and Huangkou depression. And thereservoir type is mainly the typeâ…  . The typeâ…¡ is the main reservoir type in Dongpu depression,and the reservoir type is the typeâ…¡ . The reservoirs' preserving property is poor in Jiyuandepression, and the reservoir type is mainly the type â…£ .Correlated and evaluated to Mesozoic reservoirs in this region, Huangkou depression isconsidered as first-order area, Chengwu depression and Yutai depression are taken assecond-order area, Qiu County depression and Dongpu depression as third-order area, andJiyuan depression as fourth-order area.