| Lower Paleozoic carbonate rock reservoir of Nanpu sag and adjacent aera is one of the hot spot in oil/gas exploration of Bohai bay. Based on the the materials of study area, selected the Zhaogezhuang profile to analyse the characters of microfacies, sediment enviroment and their spatial distrubution. After indentified the main facies types and sediment features of Yeli-Liangjiashan Formation, estabished the facise-order evolution integrate map of tide-conctrol carbonate slop system of Tanshan aera. Then, anlysised the the correlative facies-zone’s diagenesis which dominant by the dolomitizaton.By the means of the thin section observation of all rock sampes, the analyse of microscopy shape and elemental component in typical rock under environmental scanning electron microscope, and the analyse of Carbon Oxygen stable isotope of the representative sampling, established the appropriate dolomitization models to the correlative facies-zones.Contrasted and concluted the results between the carbon stable isotope analysis, the sediment enviroment and the changes of global sea-level. Discussed the reservior unit compartmentalize and reservior capability of Yeli-Liangjiashan formation by the analysis of sediment microfacies, sediment facies, diagenesis, post-diagenesis and stable isotope analysis.Acquired some coclution as follow:1、According to the key charecters of matrix,gain and rock fabric, and use Flugle’s microfacies identify class about carbonate slop,7microfacies type was recorgnized. In this paper, two newly facies, namely, RMF31and RMF32was recorgnised and added into the type of cabonate ramp facies. Respectively, RMF7:aboundant echinoderms bioclastic packstone and intra-bioclasts mudstone. RMF8:packstone with arillaceous and multi-grians RMF9-BI with ramp-derived ioclastic/intra-packstone/mudstone. RMF9-F:floatstone dominated by ramp-derived rounding intra-clasts. RMF9-A:rounding alga-clasts wackestone/packstone. RMF14:multi-bioclastic packstone/wackestone. RMF18:bioclastic wackestone with ostracods. RMF31:rounding Spatulate float rudite limestone, RMF32:rounding intraclastic-bioclastic grain/wackestone.2、The sediment feature of Tangshan Yeling-Liangjiashan formation continues from the Upper Cambrian, it is belongs to the tide control cabonate rock system of inner slop facies which was made up by lagoon/grain-shoal/restrict plateform sub-facies.3、The evolution serial of Yeli formation is a intergrity third class sequence plateform. Namly, it is begains at at the inner restrict plateform facies of LST, then changed to the open-plateform sub-facies of lower TST, and to the mid-slop facies of the upper HST. Ovber the surfaces of maximum flooding, it changed to HST which marked by middle slop. On the other hand, the Liangjiashang formation shows the character of dominated by the inner slop restrict platform facies.4、Fur types of dolomaite was distinguished in the study area.①intensity dolomitization, coarse crystal, euhedral, ring-zone, clear crystal boundary ouline, with well growth shrink hole between inner and space of grain.②few dolimite, fine crystal, ubhedral to anhedral.③blur edge few dolimite, fine crystal, subhedral to anhedral, adjoint with fine crystal of gypsum and halite.④intensity dolomitization, coarse crystal, euhedral, ring-zone, clear crystal boundary outline, few of growth shrink hole between inner and space of grain, sporadic with fine crystal of gypsum and halite.5-Cncluded two dolomitization models refers tothe resuults of sediment facies and dolomitization character. One is the diagenetic capillary punp draw to evaporation dolomitization model, it mainly occurred in the tide-edge facies and restrict platform facies, and the other is the syngenetic over-evaporation-sea-water condense solomitization model, the former, taken placed in the lagoon facies and grain-shoal facies.6、Whole rock carbonate rock isotope analysis shows that the813C value of Yeli formation dolomite is-7.11‰～0.769‰(PDB), means-2.98‰,δ18O is-9.09‰～-4.65‰, means-6.12‰, and the813C of Liangjiashang formation dolomite is-1.15‰～0.3‰, means-0.57‰,δ18O-8.76‰～7.48‰, means-8.06‰(PDB). The lighter carbon value of Yeli formation indicated that it was forming with normal water, but the higher value of Liangjiashang formation showed the environment of salted medium. Oxygen isotope analysis demonstrated that, the higher negative value of Liangjiashang formation maybe come from the join of meteoric fresh-water after exposure or was affected by the high-temperature during the deep burial enviroment.7、There is a tight relation between the carbon isotope distribution and sediment facies. The maximum carbon value appearenced at RMF31, rounding Spatulate calcirudite, with sediment facies of the inner grain-shoal/restric platform, the minimum value at RMF18, related with the inner slop/open-plateform facies.8、As the result of a integrated3-rd sequence evolution to the Yeli formation went through, the changes of813C value was tightly related with globe sea level eustacy, and the trends of carbon isotope was accordanced to the lower latitude in same period. The813C value of bottom Liangjiashan Formation was rise, but in the middle-uuper parts which dominated by HST, the main facies was inner ramp lagoon and grain-shoal, it rotate around0‰, and without obvious dtift.9、The δ13C value in study area was lighter than other profiles. With the analysis of rock character, sediment system and micro-area when compaired the6events of transgression and regression. It’s convinced that the main reason to the lighter δ13C value should be related with the model of over-nutrition/starvation sea and the organic oxidation mechanism in seafloor. and the lowest neagtive value was explained by the sulphate reduction.10、Paleo-temperature caculated by carbon isotope in the lower Yeli formation was ranged from15℃～25℃. The upper Yeli formation to Liangjiashang formation has the more higher value range of30℃～45℃, and the mid-upper Liangjiashang formation has the lowest range of10℃～15℃. The higher temperature occured at the restrict platform facies to open platform facies, however, the lowest temperature at grain-shoal facies to lagoon facies. Therefor, further study was needed to estimate whether or not the higher temperature of upper Yeli formation to Liangjiashang formation undergo burial diagenesis, which has saddle dolomite and the iron content of dolomite. |
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