摘要
四川盆地蕴藏着丰富天然气资源,其中筇竹寺组页岩对盆地中下组合天然气聚集作出巨大贡献。通过对川西和川中震旦系—寒武系及上覆志留系—三叠系多层系储集层中天然气特征精细对比发现,以筇竹寺组页岩为主要烃源的油气资源极为丰富、类型多样:(1)既有典型原油裂解气,甲烷碳同位素较轻(<35‰),分布在资阳地区震旦系、太合地区寒武系沧浪铺组(角探1井)及川西北河湾场/吴家坝的茅口组。它们成藏时间早,在岩性圈闭或岩性-构造圈闭得以长期保存;(2)页岩超晚期释放气,分布广泛,高石梯—磨溪、太合、威远等地区下组合震旦系—寒武系均以该类天然气补充成藏为主,甲烷碳同位素较重(>35‰),如未遭受过硫酸盐热化学还原作用(TSR)的改造则具典型甲、乙烷碳同位素倒转(δ^(13)C_(1)>δ^(13)C_(2))特征,该类气藏具多期次复杂成藏过程,但超晚期页岩来源天然气的持续补充控制着聚集丰度;(3)中组合泥盆系—三叠系(须家河组之下)天然气以断层沟通的页岩超晚期释放天然气成藏为主。综合分析可见,筇竹寺组页岩(与页岩气)保存较好区域是形成关联大气藏的关键。勘探最为现实的领域是围绕绵阳—长宁拉张槽开展多层系立体勘探,尤其是考察拉张槽内及周缘震旦系—寒武系及上覆中组合是否存在好的成藏条件。同时对其他区域筇竹寺组页岩保存状况进行评估,可在高效保存区开展多层系立体勘探部署。本项研究可为该区及其他同类地区天然气勘探带来启发和借鉴。
Benefitting from numerous sets of source rocks,a huge amount of natural gas resources have been proven in the Sichuan basin.Here we conducted detailed correlation and comprehensive analysis of geochemical and geological characteristics of natural gases from the underneath reservoirs of the Sinian-Cambrian systems and the overlying gas reservoirs of the Silurian-Triassic systems.The results suggested that the Early Cambrian Qiongzhusi Formation shales were the most important hydrocarbon source for natural gas accumulations in the central and western Sichuan basin.Typical paleo oil-cracked gases were found in the Sinian gas reservoir in the Ziyang area,in the Cambrian Canglang Formation(well Jiaotan-1)in the Taihe area,and in the Permian Maokou Formation in the Hejiawan area.The high replenishment of released shale gas is a key factor for the other Sinian-Cambrian reservoirs found so far in Gao-Mo,Taihe,and Weiyuan areas.Similarly,the Silurian-Triassic reservoirs in western and central Sichuan basin are dominated by gas released from the Qiongzhusi Formation shale in very-late period-Himalayan phase through the faults.The limited distribution of paleo oil cracked gas is inconsistent with the wide distribution of the marine source rocks of the Qiongshusi Formation.The organic matter in the Qiongshusi Formation shale is Type II.Normally,Type II kerogen is prone to generate oil with a little gas.Therefore,oil-cracking gas from paleo oil reservoirs should be dominant in such geological units.Abundant paleo oil-cracking gases had been filled in earlier in the Sinian-Cambrian reservoirs of Leshan-Longnvsi paleo-uplift but had been released quickly during the Himalayan phase.There were limited oil-cracking gas residuals trapped in the lithological and/or lithological-tectonic reservoirs.The reason could be strong tectonic movement during the Himalayan tectonic period(contraction).The accumulation mechanisms for various gas reservoirs were finalised by comparing and correlating their geological characteristics,reservoir fo
作者
帅燕华
李剑
田兴旺
陈竹新
张斌
魏彩云
Shuai Yanhua;Li Jian;Tian Xingwang;Chen Zhuxin;Zhang Bin;Wei Caiyun(Research Institute of Petroleum Exploration and Development(PetroChina),Beijing 100083,China;Research Institute of Westsouth Oil Field Branch Company,Chengdu,Sichuan 610041,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2023年第5期1526-1543,共18页
Acta Geologica Sinica
基金
国家自然科学基金项目(编号42272139)
中石油项目(编号2021DJ0604,YGJ2019-04-02)联合资助的成果。
