【作者】 周振柱；

【导师】 周瑶琪；

【作者基本信息】 中国石油大学 ， 地质学， 2011， 博士

【摘要】 温压场的分布与演化与油气成藏关系密切,在油气藏研究中具有重要的地位。东营凹陷古近系大套膏盐层的存在使其上下形成两个相对独立的含油气系统。“盐下”地层具有优越的油气成藏条件,是深入勘探的重要目标。本论文以东营凹陷油气藏温压场演化为研究主线,结合构造活动、沉积埋藏等常规地质分析,综合研究东营凹陷“盐下”油气藏温压场演化特征及其控制因素,借以探讨“盐下”油气运聚过程、分异成因以及膏盐层对油气成藏的控制作用等。论文主要采用流体包裹体分析来恢复古压力,同时也结合其他的一些常规分析和模拟方法。利用微量元素和稀土元素分析了膏盐层的成因,石盐主要来自深部热卤水,石膏主要来自陆源区古石膏层的风化剥蚀,海侵是重要的盐源,但不是主要的。早期气候干旱,在强蒸发条件下,湖盆水体范围的振荡形成了碎屑岩与膏盐岩的韵律层;后气候趋于湿润,深水条件下盐浓度分层作用是膏盐层沉淀的主要原因。利用镜质体反射率方法恢复了东营凹陷温度梯度演化史,东营凹陷古地温梯度在早期较高,中期持续降低,降低速率有限,晚期虽然下降较快,但是幅度很小,呈现明显的阶段弧形演化趋势。对比分析了声波时差法、盆地模拟法和流体包裹体法在计算压力方面的适用性,声波时差和盆地模拟法适用于盆地(或凹陷)内部泥岩厚度大且断裂活动不太发育的地区,可以很好地表征烃源岩的地层压力,流体包裹体计算的压力能够很好的代表储层中的流体压力。东营凹陷“盐下”深部储层中流体包裹体十分发育,丰8井、丰深1井、丰深2井、丰深10井、坨165井及东风3井样品中均发现了烃类包裹体,而丰深3、丰深4、丰深6、永559、郝科1等井样品中均以盐水包裹体为主,未发现烃类包裹体。实验研究了NaCl-H2O体系在低温下的拉曼光谱学特征,揭示了水合物中两种不同的水分子类型及不同的振动类型,在冷冻过程中,盐水会发生浓度分异,使得利用低温盐水合物单点拉曼特征峰定量分析包裹体中流体盐度的可靠性降低,多点测试统计平均值则能更好的反映流体包裹体的盐度。东营凹陷“盐下”深部储层的盐水包裹体及含烃盐水包裹体均以NaCl-H2O体系为主,说明在油气成藏过程中,与油气共同运移的地层水中的盐类主要为NaCl。实验获得盐水包裹体的均一温度、冰点和盐度以及烃类包裹体的均一温度、气液比,成分,应用PIT模拟软件进行了PVT模拟,同时应用盐水包裹体均一温度-盐度法,计算了流体包裹体捕获的温压条件,结合热史及埋藏史分析,恢复了储层压力演化史。根据流体包裹体模拟结果,划分出了“盐下”深部储层三个油气成藏期和五个压力演化阶段。东营凹陷压力演化主要受控于欠压实作用、生烃增压作用和构造作用,膏盐层主要起到封闭和保持压力的作用。地层的欠压实作用是阶段Ⅰ压力增加的主要因素,后陈南断层的强烈活动使得压力释放。烃类物质的生成和运聚成藏是阶段Ⅱ压力增加的主要因素。地层的抬升剥蚀是阶段Ⅲ压力降低的主要因素,烃类流体活动的减弱是压力降低的促进因素。阶段Ⅳ和阶段Ⅴ与油气的第二期和第三期成藏相对应,油气充注活动的强弱直接影响了储层流体压力的变化。在东风3井的岩盐中发现了大量的烃类包裹体,其均一温度主要集中在60~80℃和90~100℃两个温度区间,表明这一石盐层至少经历了两个期次的烃类流体活动。这说明膏盐层对油气并非具有绝对的封盖能力,深断层的发育可以沟通膏盐层上下两个含油气系统,使物质发生交换。深断裂或盐构造发育区的“盐上”地层是油气藏发育的有利区。论文完善了东营凹陷北部陡坡带“盐下”深部油气成藏的模式。东营凹陷民丰地区“盐下”深部油气藏过程经历了三个阶段:古油藏雏形期(35.0~24.6 Ma)、古油藏成形期(14.0~5.0 Ma)和现今油气藏形成期(5.0~0 Ma),经过三期油气充注,在温度、压力和构造位置等因素的影响下,形成了现今的油气藏分布格局。更多还原

【Abstract】 The distribution and evolution of geotemperature-geopressure has a close relationship with hydrocarbon accumulation. It plays an important role in studying hydrocarbon reservoirs. The very thick paleogene gypsum-salt strata vertically divided Dongying sag into two relatively independent petroleum systems. The formation underlying gypsum-salt strata has advantageous hydrocarbon accumulation conditions, and it is an important goal for further exploration. Based on conventional geological analysis, such as tectonic activities and sedimentary burial, this paper mainly studies the evolution characteristics of geotemperature and geopressure fields of hydrocarbon accumulations below gypsum-salt strata in Dongying sag. Furthermore, aimed at the hydromcarbon reservoirs, we discuss the hydrocarbon accumulation process, differentiation causes and the controlling function of gypsum-salt strata on hydrocarbon accumulation. Combined with conventional analysis and some simulation methods, fluid inclusion analysis was mainly used to analyze paleopressure of reservoirs.This thesis concluded the origin of the gypsum-salt strata with trace elements and REE analysis. The halite of gypsum-salt strata mainly came from deep hot brine, and the gypsum mainly came from the eroding product of terrestrial ancient gypsum layers. Furthermore, transgression of sea played an important, but not major, role in providing salt resource for gypsum-salt strata. When the climate was dry in the early paleogene, the transpiration was very strong. As a result, the lake water oscillation led to the formation of rhythmic layers with clastic rocks and gypsum-salt rocks. Later, when the climate was a little humid, the layering effect of salinity in deep water resulted in deposition of gypsum-salt rocks.Using the data of vitrinite reflectance, this thesis calculated geothermal gradient evolution of Dongying sag. The geothermal gradient, which was high in early stage, decreased at a stable rate in medium stage, and decreased sharply in late stage. The evolution curve tends to be arc-shaped. It analyzed the applicability in pressure calculation of SDT, basin simulation and fluid inclusions. The first two methods are suitable in the interior of basin/sag where is filled with thick mudstone and lack of faults. They can correctly calculate the geopressure of source rocks. The method of fluid inclusions shows the fluid pressure of reservoirs correctly.The deep reservoirs of Dongying sag are abundant in fluid inclusions. Large quantities of hydrocarbon inclusions are found in F8 well, FS1 well, FS2 well, T165 well and DF3 well. FS3, FeS4, FS6, Y559 and HK1 are rich in brine inclusions and lack of hydrocarbon inclusions.An experiment studied the cryogenic Raman spectroscopy of the system NaCl-H2O. It clarified two types of water molecules and different vibrations in each type of water molecules in hydrohalite. Hydrohalite would differentiate with the cooling process. This decreased the reliability of using cryogenic Raman spectra of hydrohalite at one single point to determine the salinities of fluid inclusions. Instead, it is more reliable to use statistical values of Raman peaks of hydrohalite at multiple collecting points. The brine inclusions and hydrocarbon-bearing brine inclusions in the deep reservoirs in Dongying Sag mainly are NaCl-H2O system. This illustrates that the type of formation water along with oil-gas migration in hydrocarbon accumulation process mainly is NaCl-H2O.The experiments provided homogenization temperatures, ice points/salinities of brine inclusions and homogenization temperature, vapour/liquid ratios, composition of hydrocarbon inclusions. PVT simulations of fluid inclusions were completed with PIT simulation software. The capturing temperature and pressure are calculated using PVT simulation of hydrocarbon inclusions and homogenization temperature-salinity method of brine inclusions. Combined with geothermal history and burial history, this thesis illustrated the evolution of reservoir geopressure. According to simulation results, it divided the geopressure history into five stages and identified three stages of hydrocarbon accumulation.The uncompaction, hydrocarbon generation and tectonic activities were the main three factors of the overpressure development in Dongying Sag, and gypsum-salt layers played an important role in preserving the pressure. The principal element of pressure increase in stage I is undercompaction, and the badly activity of Chennan Fault released overpressure. The pressure increase in stage II mainly result from generation and accumulation of hydrocarbon. The uplifting and eroding of formation chiefly lead to the pressure decrease in stage III, and the diminution of hydrocarbon activity also weakened the pressure. The stage IV and V of geopressure evolution were equivalent with the second and third stages of hydrocarbon accumulation, and the fluid pressure varied with the intensity of hydrocarbon activity.Large quantities of hydrocarbon inclusions exist in the halite of DF3 well. This halite layer at least experienced two stages of hydrocarbon activities, because the homogenization temperature concentrated in two intervals of 60~80℃and 90~100℃. This suggests that the sealing ability of gypsum-salt strata is not absolutely effective. Discordogenic faults may communicate the two independent hydrocarbon systems under and upon gypsum-salt strata, and lead to material exchange. The formation upon the gypsum-salt strata along with deep fault and/or salt structure is the important zone for hydrocarbon accumulation.This thesis improved the hydrocarbon accumulation model of deep reservoirs underlying the gypsum-salt strata in northern Dongying sag. There are three hydrocarbon accumulation stages of deep reservoirs in Minfeng area, Dongying Sag: embryo stage of ancient reservoir (35.0-24.6 Ma), shaped stage of ancient reservoir (14.0-5.0 Ma) and forming stage of present reservoir (5.0-0 Ma). After three stages of hydrocarbon injection, the present distribution characteristic of oil and gas reservoirs was formed under the control of temperature, pressure, tectonic position and so on.更多还原