四川宣汉盘龙洞生物礁古油气藏油气源分析

THE OIL-GAS SOURCES OF THE LATE PERMIAN ORGANIC REEFAL OIL-GAS POOLS IN THE PANLONGDONG, XUANHAN, SICHUAN

牟传龙 马永生 余谦 郭彤楼 谭钦银 王立全

Mou Chuanlong Ma Yongsheng Yu Qian Guo Tonglou Tan Qinyin Wang Liquan

成都地质矿产研究所 成都610082 2. 中国石化南方勘探开发分公司 昆明650200

Chengdu Institute of Geology and Mineral Resources, Chengdu, Sichuan 610082, China 2. Southern Oil and Gas Exploration Branch Company, SINOPEC, Kunming, Yunnan 650200, China

盘龙洞生物礁古油气藏位于四川省宣汉县鸡唱乡盘龙洞,是一个海绵礁古油气藏;大地构造位置上位于四川盆地东北边缘,属米仓山—大巴山前缘地带。地层层位为上二叠统长兴组,厚度约80 m。岩性主要为浅灰色块状海绵障积岩和海绵骨架岩;造礁生物主要为房室海绵、水螅、苔藓虫等。生物礁及其上下地层中均含有大量的沥青,主要分布于礁核的骨架岩、障积岩和礁盖的白云岩中。通过对盘龙洞生物礁古油气藏的实地考察,结合测试结果和室内综合分析,推断该古油气藏先期为原油充填,后来一部分裂解为天然气,一部分氧化形成沥青;油气源来自于长兴组本身烃源岩的可能性较大,不排除混源的可能。

The present paper propose a newly discovered sponge-reef fossil oil-gas pool in the ChangxingFormationin the Panlongdong,Xuanhan,Sichuan.The organic reefs are developedin the middle and upper parts of the Upper Permian Changxing Formation,with a thickness of about 80 m.The rock typeswithin the Panlongdong organic reefs consist significantly of bafflestone and skeletal li mestone.Theorganic reefs are made fromsponge,hydra and polyzoa et al.The occurrence of abundant asphalt in the organic reefs and the strata above and belowthemhas disclosed the migration of oil and gas.The asphalt often fills into pore spaces,fissures and cracks,as well as into brachiopods and sponges.Macroscopically,three phases may be identified for the filling processes of the asphalt :the one is the filling into organicframeworks,intergranular pores,sponges and other organic coelomata such as brachiopods,asindicatedinthe field sections.In this phase,the asphalt occurs chiefly in the organic reefs and reef caps;the secondphase is the fillinginto paulopost fissures(the diameter of the fissures>2mm).In this phase,the asphaltis widespreadin the organic reefs and their cap rocks(including spararenite and dolostone) and secondarypores.The other is the fillinginto paulopost fissures(the diameter of the fissures<2 mm).Onthe basis ofcomparative analysis of δ13C,saturated hydrocarbon chromatogram and biomarkers,the authors contendthat the oil-gas sources vary probably fromthe source rocks of the Changxing Formation.

四川省学术和技术带头人培养资金资助项目(1200308)

https://doi.org/10.11781/sysydz200506570