| The paper mainly discussed the diagenesis and its control factors of sinian reservoirs in DingShan structure and AnPingDian-GaoShiTi structure, southeast and middle of Sichuang basin, then drew its porosity evolution.Using the characteristics of biological maker in simian reservoirs bitumen, oil source could be identified. Based on apatite fission track analysis and Easy%Ro chemical kinetics model, geothermal system of Sinian—Lower Palaeozoic could be simulated.The palaeopressure could be recovered by the analysis of fluid inclusion and stimulation of PVTX thermodymamic when these inclusions were captured. So the natural gas in sinian reservoirs exist as Water-soluble gas due to the condition of the particular temperature and pressuer.In the sinian-lower palaeoozoic reservoir, Based on the relative order of fillers in hole,bore and fracture, combining with characteristic of fluid inclusion and isotope of Sr, C and O, the sequence and stage of charging of fluid could be determined. The paper pays attention to the mechanism of gas accumulation in sinian reservoirs, and reveal the dynamics relationships matched with each other in the time-space scales during the hydrocarbon generation, migration, accumulation,dissipating, reservoir evolution and trap formation, and then build the evolution and model of hydrocarbon generation, accumulation of muti-stage and sum up the mechanism and feature of hydrocarbon accumulation systematically in sinian of Sichuan Basin.(1)The diagenesises of Zinian reservoir mainly include dolomitizaton, recrystallization, silication, gypsification,denudation, packing action, and so on, which could be categoried into thirty-four diagenesis. Dolomitizaton impact on the reservoir quality of Denying Formation, but silication which happened at late period effected the reservoir quality more seriously. Porosity increased because of karstifacition resulted from tectonic movement and organic acid, while recrystallization could resist part of cementation which can lead to decrease of porosity in diagenesis stage.That was why pore space in Zinian reservoirs could be maintained. Sinian reservoirs underwent a long time burial and the multitudinous diagenesises which made the porosity evolution complicated. There were similarity between each other in different tectonic belts due to their similar diagensises and fluid charging. (2)There were there-stage cataclasises in Zinian:the first stage developed big,middle-low angle fracture in middle-deep burial; the second stage formed fracture in deep burial after organic matured but before Himalayan epoch;the third stage developed gash fracture from tectonically relaxation in the phase of dry gas or earlier. Cataclasises could increase porosity in the early time when emposieus were infilled and improved permeability of reservoir.(3) Research on reservoir bitumen and possible source rock of Zinian-lower palaeozoic,their biomarker indicated that, 1)in Anpingdian-Gaoshiti tectonic belt, source rock in Cambrian was in anoxic and deoxidated environment having some salinity when it was deposited, and living beings were such low aquatic life as homoneneae; All of the bitumen in Ordovician, Cambrian and Sinian could be compared with mudstone in Cambrian by fingerprint, as concluded that the bitumen came from mudstone in Cambrian.Reservoir bitumen in Permian in Well Hechuan12 probably came from Silurian mudstone, and that in Xixiangchi group of Cambrian come from mudstone in Cambrian. All of Zinian reservoir bitumen of Dingshan Structure in southeast Sichuan area came from mudstone in Cambrian.Bitumen in debris of Shenglengshui Formation of Cambrian have no affiliation with Cambrian mudstone, which likely came from Longmaxi Formation of overlying Silurian. So Cambrian reservoir bitumen show the feature of multiple source.(4)As for bitumen of post-high maturity, sterane isomerization parameter came about reversal, which cannot be identified the maturity. Research indicated such biomarkers parameter as Ts/(Ts+Tm) or Ts/Tm could distinguish that bitumen of different maturity and depositonal environment. These parameters accorded with variance of Pr/nC17-Ph/nC18 and bitumen reflectance which can also reflect the relative maturity.(5) Based on apatite fission track and Easy%Ro chemical kinetics model, palaeogeothermal could be calculated in well Dingsan 1 and Well Anping 1. The geothermal gradient of Cambrian and Sinian varied from decreasing to increasing, and to decreasing again. The burial history of strata and thermal evolutionhsitroy of source rokcs was reconstructed. Laser Raman spectroscopy analysis for fluid inclusion in reservoirs of Cambrian in Well Dingsan 1, and of Sinian in Well Anping 1 .These indicated that a part of methane in reservoir was soluble, they existed in the saline water in the form of soluble-water gas. Using fluid inclusion homogenization temperature and analog inclusion pressure, dissolving capacity of methane in water can be confirmed. Combined with burial history, evolution of temperature and pressure with filling sequence of mineral in core hole, bore and fissiure, the formation and capture of water-soluble gas can be displayed.(6)Based on filling sequence of mineral in core hole, bore and fissure, and the isotope of Sr,C,O, Sinian-Lower palaeozoic reservoirs underwent fluid charging at least six stages.From the first stage to the forth stage, mineral recorded the process of burial. From the fifth to the sixth stage, mineral recorded the paration processse of gas and water and the separation process of saline water and bitumen, bitumen depositing.The sequence of fluid charging represented the full sequence of fluid charging from deep burial to uplifting.(7)Isotope of Sr,C,0 of mineral in core hole,bore and fissiur revealed that the saline water wasn't from adjacent rock but allogenetic. Reservoir in Sinian presented multi-phase chargings, while that in overlying Cambrian and Ordovician probably appeared to be only one stage of fluid charging. Hydrocarbon and saline water in different layers coming from the same source, suggested that fault and fractures play the part of the main conduction systems which fluid migrated vertically.(8)Sinian oil and gas reservoir evolved through such stages of DingShan structure,①Palaeo-oil pools formed in late Silurian.②Palaeo-oil pools were destroyed by the uplift and denudation in Caledonian event.③From early Permian to early-middle Triassic, source rock in Cambrian generated hydrocarbon secondly.④From middle-late Triassic to middle-late Jurassic, oil cracking to gas happened and water-soluble gas formated.⑤At the end of late Cretaceous, natural gas exsolution took place and palaeo-gas pools were destroyed. Zinian hydrocarbon accumulation in Anpindian-Gaositi tectonic belt was similar to that of Well Dingshan structure. But natural gas appeared to be lost, transferred and redistributed when its exsolution came about due to uplifting since late Cretaceous, which leaded to remnant gas pool in Anpindian-Gaositi tectonic belt.(9)Sinian-low Palaeozoic gas accumulating experienced from palaeo-oil pools to palaeo-gas pools, and adjustion and reformation, which were characterd as by①palaeo-oil pool developed and was destructed when hydrocarbon generated from source rock in the early stage;②the second hydrocarbon generation leaded to multi-stage hydrocarbon accumulation early when organic matter maturation, hydrocarbon generation and expelled during Permian and Triassic;③In the middle Jurassic or before, oil cracking to gas and bitumen formation due to deeply burial, result in high temperature of gas pool and oil transformation to gas.④In the Himalayan, strcture trap formation, and the uplifting and denudation lead to late accumulation of hydrocarbon, which features mainly are uplifting, denudation, energy field adjustion, gas exsolution from water, gas pools at later destruction and gas redistribution.
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