大巴山山前带油气成藏条件与勘探方向
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摘要
位于四川盆地边缘的大巴山山前带由于构造变形较为强烈,地表地震地质情况复杂,给地震资料采集和处理带来诸多困难,目前该区勘探程度还较低。为预测其油气勘探前景,从生储盖组合、烃源岩条件、储层条件、盖层条件等几个方面分析了该区油气成藏条件,发现其原始成藏条件优越,存在3套成藏组合和多种类型的勘探目的层。古油藏解剖结果表明,山前带二、三叠系油气主力烃源岩为上二叠统,油气成藏分为3个阶段:①晚三叠世—早侏罗世开始变形,形成宽缓背斜,形成古油藏;②中侏罗世—早白垩世进一步变形,圈闭构造定型,部分古油藏裂解,形成油气藏;③古近纪喜山运动对先期构造进行了强烈的改造,造成古油气藏的调整与破坏。综合评价该区构造变形样式、储层分布和油气显示特征后认为:南大巴山西北部镇巴断裂至铁溪—巫溪隐伏断裂是油气勘探有利区,应以二叠系长兴组和三叠系飞仙关组礁滩相储层勘探为主展开工作;东南部鸡鸣寺断裂至铁溪—巫溪断裂为二、三叠系出露区,应以落实寒武系膏盐岩下伏地层的保存条件为主进行勘探部署。
Seismic acquisition and processing are challenging in the foothill belt of the Dabashan Mountain in the marginal area of the Sichuan Basin due to strong tectonic deformation and complex surface seismic geologic conditions,so the exploration maturity is still very low in the study area at present.In order to predict the potential of petroleum exploration,we analyzed the hydrocarbon pooling conditions in this area in respect of source-reservoir-seal combination,source rocks,reservoir and sealing conditions.The original hydrocarbon pooling conditions are favorable and there are 3 plays and various types of exploration pay zones.The analysis of the paleo-reservoir in this study area shows that the major source rocks contributing hydrocarbons to the Permian and Triassic reservoirs in the foothill belt are mainly in the Upper Permian formations,where the hydrocarbon pooling is divided into 3 stages.The first stage is at the Late Triassic-Early Jurassic,when tectonic deformation initiated and paleo-pools were formed in wide and gentle anticlines.The second stage is at the Middle-Jurassic-Early-Cretaceous,when tectonic deformation continued,traps finalized,and crude oil in some palaeo-pools cracked to form oil/gas reservoirs.The third stage is at the Paleogene,when the Himalayan movement strongly transformed the existing traps,which resulted in the adjustment and destruction of the palaeo-pools.The comprehensive analysis of tectonic deformation style,reservoir distribution and oil/gas displaying characteristics reveals that the favorable exploration area is from the Zhenba Fault to the Tiexi-Wuxi buried fault in the northwestern part of South Dabashan Mountain,where the major targets are the Permian Changxing Formation and the Triassic Feixianguan Formation reservoirs of reef-bank facies.In addition,it indicates that preservation conditions of the presalt Cambrian reservoirs should be the focus of research in the southeastern part of South Dabashan Mountain,where the Permian and Triassic are outcropped from the Jimingshi Fault to the Tiexi-Wuxi Fault.
Seismic acquisition and processing are challenging in the foothill belt of the Dabashan Mountain in the marginal area of the Sichuan Basin due to strong tectonic deformation and complex surface seismic geologic conditions,so the exploration maturity is still very low in the study area at present.In order to predict the potential of petroleum exploration,we analyzed the hydrocarbon pooling conditions in this area in respect of source-reservoir-seal combination,source rocks,reservoir and sealing conditions.The original hydrocarbon pooling conditions are favorable and there are 3 plays and various types of exploration pay zones.The analysis of the paleo-reservoir in this study area shows that the major source rocks contributing hydrocarbons to the Permian and Triassic reservoirs in the foothill belt are mainly in the Upper Permian formations,where the hydrocarbon pooling is divided into 3 stages.The first stage is at the Late Triassic-Early Jurassic,when tectonic deformation initiated and paleo-pools were formed in wide and gentle anticlines.The second stage is at the Middle-Jurassic-Early-Cretaceous,when tectonic deformation continued,traps finalized,and crude oil in some palaeo-pools cracked to form oil/gas reservoirs.The third stage is at the Paleogene,when the Himalayan movement strongly transformed the existing traps,which resulted in the adjustment and destruction of the palaeo-pools.The comprehensive analysis of tectonic deformation style,reservoir distribution and oil/gas displaying characteristics reveals that the favorable exploration area is from the Zhenba Fault to the Tiexi-Wuxi buried fault in the northwestern part of South Dabashan Mountain,where the major targets are the Permian Changxing Formation and the Triassic Feixianguan Formation reservoirs of reef-bank facies.In addition,it indicates that preservation conditions of the presalt Cambrian reservoirs should be the focus of research in the southeastern part of South Dabashan Mountain,where the Permian and Triassic are outcropped from the Jimingshi Fault to the Tiexi-Wuxi Fault.
引文
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[13]汤济广,梅廉夫,周旭,等.扬子陆块差异构造变形对海相地层成烃演化的控制[J].天然气工业,2011,31(10):36-41.
[14]沈传波,梅廉夫,郭彤楼.川东北地区中、新生代热历史的裂变径迹分析[J].天然气工业,2007,27(7):24-26.
[2]马永生.普光气田天然气地球化学特征及气源探讨[J].天然气地球科学,2008,19(1):1-7.
[3]郭旭升,胡东风.川东北礁滩天然气勘探新进展及关键技术[J].天然气工业,2011,31(10):6-11.
[4]郭彤楼.川东北地区台地边缘礁、滩气藏沉积与储层特征[J].地学前缘,2011,18(4):201-211.
[5]马永生,牟传龙,谭钦银,等.达县—宣汉地区长兴组—飞仙关组礁滩相特征及其对储层的制约[J].地学前缘,2007,14(1):182-192.
[6]牟传龙,谭钦银,王立全,等.四川宣汉盘龙洞晚二叠世生物礁古油藏的发现及其重要意义[J].地质论评,2003,49(3):315.
[7]蔡立国,饶丹,潘文蕾,等.川东北地区普光气田成藏模式研究[J].石油实验地质,2005,27(5):462-467.
[8]MA Yongsheng,GUO Xusheng,GUO Tonglou,et al.ThePuguang gas field:new giant discovery in the mature Si-chuan Basin,southwest China[J].AAPG Bulletin,2007,91(5):627-643.
[9]胡东风.普光气田与元坝气田礁滩储层特征的差异性及其成因[J].天然气工业,2011,31(10):17-21.
[10]李智武,刘树根,罗玉宏,等.南大巴山前陆冲断带构造样式及变形机制分析[J].大地构造与成矿学,2006,30(3):294-304.
[11]许志琴,卢一伦,汤耀庆,等.东秦岭造山带的变形特征及构造演化[J].地质学报,1986,60(3):237-247.
[12]胡明,陈蓉,陈华生,等.南大巴山造山带构造特征及油气勘探方向[J].天然气工业,2008,28(11):26-28.
[13]汤济广,梅廉夫,周旭,等.扬子陆块差异构造变形对海相地层成烃演化的控制[J].天然气工业,2011,31(10):36-41.
[14]沈传波,梅廉夫,郭彤楼.川东北地区中、新生代热历史的裂变径迹分析[J].天然气工业,2007,27(7):24-26.
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