【作者】 孙玮；

【导师】 刘树根；

【作者基本信息】 成都理工大学 ， 矿产普查与勘探， 2008， 博士

【摘要】 四川盆地元古宇-下古生界(简称下组合)已进行油气勘探50多年,累计钻探井五十多口(威远气田以1口井计),并主要分布于乐山-龙女寺古隆起范围和周边造山带地区。下组合在四川盆地内获气田1个(威远气田),震旦系探明储量408.6×10~8m~3(2000年),寒武系威远气田已获气井五口(威42、威52、威78、威92井和水2井);含气地区1个(资阳含气区),控制储量102x10~8m~3;其它地区见气显示井6口(Z-4口,O-2口)。目前,除威远气田外,完钻层位在震旦系-志留系的几十口探井中,仅有五口井(资3井、东深1井、河深1井、五科1井和太13井)是工业气井,成功率不超过10%,勘探效果不够理想。论文首先通过对四川盆地隆升过程分析,研究下组合能量场的演变历史和烃态变化进程。四川盆地及周缘地区在喜马拉雅期发生了强烈的隆升运动。隆升速率超过100m/Ma,隆升幅度超过4200m。其隆升过程可分成三阶段。第一阶段:晚白垩世-古近纪,差异隆升阶段,大部份地区处于隆升状态,但隆升的速率有差异;第二阶段:整体隆升阶段,全盆地都处于隆升状态,整体隆升幅度大,速率一般大于40m/Ma,隆升幅度超过1000m:第三阶段:快速隆升阶段,全盆地的隆升速率除川西外均大于100m/Ma,隆升幅度超过1500m。晚白垩世以来,总体隆升幅度大,一般大于3000m。喜马拉雅期如此大规模的隆升作用,时间短,速率快,一方面控制了现今构造的形成,另一方面引起能量场调整(压力和温度效应),促使地层势能的转换,油气的再运聚,对油气最终运聚起重要作用。隆升前四川盆地下组合存在深埋作用,由于深埋致使高地温,四川盆地下组合天然气均为油裂解气,烃类经历古油藏→古气藏的演化过程;由于原油裂解天然气产生异常高压,致使天然气(甲烷)在较高的压力和温度下至少有一部分天然气曾以水溶气的形式存在。第二,论文通过威远-资阳地区构造和丁山构造两个地区详细剖析了四川盆地下组合天然气成藏特征和机理。资阳含气区的成藏过程为:(资阳--威远)古油藏→原油裂解→气顶天然气→隆升调整→现今(残留)含气区,其天然气藏是隆升调整成藏,是在原古气藏的基础上改造残留而成。威远地区的成藏过程则是:(资阳--威远)古油藏→原油裂解→天然气大量溶于水中→隆升使得带有大量天然气的水向威远运移和天然气脱溶→现今(新生)气藏,属天然气的脱溶成藏。丁山构造的成藏破坏过程是:古油藏→古油藏破坏→二期古油藏→古油藏裂解形成古气藏→隆升、断裂活动破坏保存条件,使得天然气逸散。最后,论文概括与总结了四川盆地下组合油气成藏的特点。四川盆地下组合是老的储层+老的烃源岩+多期成藏,演化时间长,因此也决定了油气成藏条件的苛刻性,成藏过程的复杂性和成藏模式的多样性。油气早期成藏过程中最显著的特征是,以液态烃为主,成烃高峰期参差不齐,供烃时间长,供烃中心具迁移性;乐山--龙女寺古隆起对油气的运移、聚集和分布具有明显的控制作用;三叠纪末是早期成藏的主要时期。发生于中侏罗世及以前的原油热裂解产生天然气、沥青和异常高压过程,导致天然气中期成藏,其主要特征是深埋高温、油气转化。晚白垩世喜马拉雅期开始的隆升过程,造成了圈闭的改造、隆升脱气、天然气的重新分配等一系列效应,致使天然气晚期成藏或破坏,其主要特征是隆升剥蚀、晚期调整成藏。这决定了叠合盆地深层天然气成藏的苛刻性。更多还原

【Abstract】 The thesis summarizes the exploration conditions and results of Proterozoic-Low Paleozoic Erathem in Sichuan basin. Petroleum exploration in Sichuan basin has lasted forty years and drilled more than fifty wild cat wells. These wells distributed at Leshan-Longnvsi paleouplift and orogenic belts around Sichuan basin. Till now, there is a gas field (Weyuan gas field) with proved reserves of 408.6×10~8m~3(2000), a gas-brone area (Ziyang gas-brone area) with probable reserves 102×10~8m~3 in upper Sinian system, and five gas wells(Wei42, Wei52, Wei78, Wei92 and Shui 2) in Cambrian sytem in Weiyuan gas field. In the other area of the basin, there are six gas show wells. Except Weiyuan gas field there are only five industrial wells (Zi 3, Dongshen 1, Heshen 1, Wuke 1 and Tai 13). The success rate for the petroleum exploration in Sichuan basin is no more than 10%.Therefore the present thesis has firstly studied the evolution of energy field and change process of hydrocarbon phase state in the Sinian to Low Paleozoic natural gas pools in Sichuan basin. Before the whole uplift of Sichuan basin by Himalayan movement, the Sinian to Low Paleozoic Erathem in Sichuan basin had suffered deep bury and high temperature stage. The paper has quantitatively simulated the buried and geothermal histories of the Sinian to Low Paleozoic Erathem by apatite fission track and fluid inclusion data.There was strong uplift at Himalaya movement period in Sichuan basin and its peripheral orogenic zones. The main uplift stage was Neogene. The rise rates exceeded 100m/ma, and the rise height exceeded 4200m. The uplift stage can be divided into three stages: the first stage, differential uplift stage, late Cretaceous to Paleogene; the second stage, whole basin uplift stage with the rise rates of more than 40m/Ma and the rise height of more than 1000m; the third stage, fast uplift stage with the rise rate of more than 100m/Ma and the rise height of more than 1500m exceped the west Sichuan. The uplift history in the peripheral orogenic zones of Sichuan basin can also be divided into three stages, the first stage(120Ma-65Ma) with the rise rate of 15-93m/Ma and the rise height of 1000m; the second stage(65-25Ma) with the rise rate of 5-47m/Ma and the rise height of 250-1800m; the third stage (25Ma-) with the rise rate of 60-300m/Ma and the rise height of 1300 to more than 3000m.The paleo-geopressure was overpressure by deep buried. But it is normal pressure now. It showed that the geopressure field suffered the process of overpressure to normal pressure. The gas in Sinian-Low Paleozoic Erathem are thermal cracked gas by high temperature. Hydrocarbon pools suffered evolutional process from paleo-oil pool to paleo-gas pool. Because of the overpressure by thermal cracked gas, some gas (CH4) dissolved in water by overpressure and high temperature.Based on the studying above, the present thesis has analyzed the gas reservoir characteristics and formation mechanism in the Sinian to Low Paleozoic Erathem, taking Weiyuan-Ziyang and Dingshan as examples.The formation process of Ziyang Sinian gas-borne area is: (Ziyang—Weiyuan) palaeo-oil pool→oil thermal crack→oil-cracked gas pool→gas pool modified by uplift→present gas borne area.The formation process of Weiyuan Sinian gas field is: (Ziyang--Weiyuan) palaeo-oil pool→oil thermal crack→the gas largely dissolved in water→the water with dissolved gas migrated to Weiyuan area by uplift and escaped from water in Weiyuan→present gas field.The destroy process of Dingshan structure is: palaeo-oil pool→plaeo-oil pool destroyed→palaeo-oil pool→oil thermal cracked and formed paleo-gas pool→gas escape by uplift and fault actionThe thesis has summarized the characteristics of petroleum pools in the Sinian to Low Paleozoic Erathem in Sichuan basin:(1) The process, generating and exhausting hydrocarbon from mature organic matter, happened before Triassic Period and made the petroleum pool multi-formation in early time. The main characters of this process are difference of hydrocarbon generation and exhaustion, multi-migration and accumulation;(2) the process of oil cracking to gas before middle Jurassic Epoch produced gas and bitumen and made the gas pool formation in middle period. The main characters of the process are deep buried and oil cracking gas;(3) the process of structural trap formation and uplifting denuation led to the gas pool formation in late period. The main characters of the process are uplifting denuation and late period gas pool formation.更多还原