神狐海域气源特征及其对天然气水合物成藏的指示意义
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摘要
为了了解神狐海域天然气水合物成藏的气体来源及聚集特征,根据过SH2井区高分辨率地震剖面构建了该区地质模型,并进行了天然气水合物成藏模拟。在恢复SH2井区地史和热演化史的基础上,利用EASY%Ro模型计算了SH2井区烃源岩的成熟度演化史,结合探区采样成果对水合物的气源特征进行了初步探讨。结果表明:深部发育的2套烃源岩(古近系文昌组和恩平组)演化程度均较高(Ro>2%),处于产干气阶段,热解生气潜力巨大;浅部新近系珠江组、韩江组、粤海组和万山组基本处于未成熟—低成熟阶段(Ro<0.7%),有机质丰度较高,是生物气的烃源岩,具有生物生气的巨大潜力。同时,神狐海域地质构造复杂,断层与底辟发育,这些断裂和底劈构造成为连接浅部水合物稳定域和气源的桥梁,为生物成因气和深部热解气的运移提供了良好的通道。当气源和天然气水合物稳定域的时空匹配得当,在适当的地质条件下便可形成天然气水合物。初步预测该区天然气水合物资源潜力巨大,是勘探远景区。
In order to recognize gas sources and accumulation patterns of gas hydrate in the waters of Shenhu,we built a geologic model based on the high-resolution seismic profile tied to the SH2 well and simulated the accumulation of gas hydrate.The geologic history and thermal evolution history of the SH2 wellblock were restored,the EASY% Ro model was used to define the thermal evolution history of source rocks in the SH2 well,and the characteristics of gas source were preliminarily discussed in combination with the sampling results in the exploratory area.The following conclusions were obtained.Sources rocks in both the deep Palaeogene Wenchang and Enping formations have high thermal maturity(Ro>2%),and are in dry gas generating stage with a huge potential of pyrolysis gas.In contrast,source rocks in the shallow Neogene Zhujiang,Hanjiang,Yuehai and Wanshan formations are basically immature and/or low mature(Ro<0.7%),are relatively high in organic abundance,and have a huge potential of biogas.In addition,faults and diapires are highly developed in Shenhu waters.They act as the bridges connecting the shallow gas hydrate stable zones with the gas sources,and are pathways for the migration of the shallow biogas and deep pyrolysis gas.When the temporal and special combination of gas sources and gas hydrate stable zones is favorable,gas hydrate can accumulate in suitable geologic conditions.Preliminary prediction results show that the study area has huge gas hydrate resource potentials,thus it is a prospect for future gas hydrate exploration.
In order to recognize gas sources and accumulation patterns of gas hydrate in the waters of Shenhu,we built a geologic model based on the high-resolution seismic profile tied to the SH2 well and simulated the accumulation of gas hydrate.The geologic history and thermal evolution history of the SH2 wellblock were restored,the EASY% Ro model was used to define the thermal evolution history of source rocks in the SH2 well,and the characteristics of gas source were preliminarily discussed in combination with the sampling results in the exploratory area.The following conclusions were obtained.Sources rocks in both the deep Palaeogene Wenchang and Enping formations have high thermal maturity(Ro>2%),and are in dry gas generating stage with a huge potential of pyrolysis gas.In contrast,source rocks in the shallow Neogene Zhujiang,Hanjiang,Yuehai and Wanshan formations are basically immature and/or low mature(Ro<0.7%),are relatively high in organic abundance,and have a huge potential of biogas.In addition,faults and diapires are highly developed in Shenhu waters.They act as the bridges connecting the shallow gas hydrate stable zones with the gas sources,and are pathways for the migration of the shallow biogas and deep pyrolysis gas.When the temporal and special combination of gas sources and gas hydrate stable zones is favorable,gas hydrate can accumulate in suitable geologic conditions.Preliminary prediction results show that the study area has huge gas hydrate resource potentials,thus it is a prospect for future gas hydrate exploration.
引文
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[16]龚跃华,杨胜雄,王宏斌,等.南海北部神狐海域天然气水合物成藏特征[J].现代地质,2009,23(2):210-216.
[17]龚建明,曹志敏,陈建文,等.天然气水合物发现区沉积物生气量的模拟实验[J].中国科学:D辑地球科学,2009,39(2):204-211.
[2]付少英.烃类成因对天然气水合物成藏的控制[J].地学前缘,2005,12(3):263-267.
[3]坚润堂,李峰,王造成.青藏高原冻土区活动带天然气水合物异常特征[J].西南石油大学学报:自然科学版,2009,31(2):13-17.
[4]夏新宇,戴金星,宋岩.海底天然气水合物气源及资源评价问题[J].天然气地球科学,2001,12(1/2):11-15.
[5]张光学,祝有海,梁金强,等.构造控制型天然气水合物矿藏及其特征[J].现代地质,2006,20(4):605-612.
[6]雷新民,张光学,郑艳.南海北部神狐海域天然气水合物形成及分布的地质因素[J].海洋地质动态,2009,25(5):1-5,9.
[7]王建桥,祝有海,吴必豪,等.南海ODP1146站位烃类气体地球化学特征及其意义[J].海洋地质与第四纪地质,2005,25(3):53-60.
[8]何家雄,夏斌,刘宝明,等.莺歌海盆地中深层天然气运聚成藏特征及勘探前景[J].石油勘探与开发,2005,32(1):37-42.
[9]于兴河,张志杰,苏新,等.中国南海天然气水合物沉积成藏条件初探及其分布[J].地学前缘,2004,11(1):311-315.
[10]吴能友,张海啟,杨胜雄,等.南海神狐海域天然气水合物成藏系统初探[J].天然气工业,2007,27(9):1-6.
[11]何家雄,姚永坚,刘海龄,等.南海北部边缘盆地天然气成因类型及气源构成特点[J].中国地质,2008,35(5):1007-1016.
[12]张树林,陈多福,黄君权.白云凹陷天然气水合物成藏条件[J].天然气工业,2007,27(9):7-10.
[13]张树林.中国海域天然气水合物勘探研究新进展[J].天然气工业,2008,28(1):154-158.
[14]王家豪,庞雄,王存武,等.珠江口盆地白云凹陷中央底辟带的发现及识别[J].地球科学:中国地质大学学报,2006,31(2):209-213.
[15]蔡周荣,夏斌,万志峰,等.珠江口盆地与莺琼盆地油气运聚特征的差异性[J].天然气工业,2009,29(11):9-12.
[16]龚跃华,杨胜雄,王宏斌,等.南海北部神狐海域天然气水合物成藏特征[J].现代地质,2009,23(2):210-216.
[17]龚建明,曹志敏,陈建文,等.天然气水合物发现区沉积物生气量的模拟实验[J].中国科学:D辑地球科学,2009,39(2):204-211.
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