石油学报 ›› 2012, Vol. 33 ›› Issue (5): 772-780.DOI: 10.7623/syxb201205005

• 地质勘探 • 上一篇    下一篇

南堡凹陷深层火山岩天然气成因与成藏模式

王政军 马 乾 赵忠新 夏景生 张永超 刘永昌 王建伟   

  1. 中国石油冀东油田公司勘探开发研究院 河北唐山 063004
  • 收稿日期:2012-03-26 修回日期:2012-07-04 出版日期:2012-09-25 发布日期:2012-11-27
  • 通讯作者: 王政军
  • 作者简介:王政军,男,1979年10月生,2007年获中国石油大学(华东)硕士学位,现为中国石油冀东油田公司勘探开发研究院工程师,主要从事石油地质、油气地球化学研究与勘探工作。
  • 基金资助:

    国家重大科技专项(2011ZX05006-006)和中国石油天然气股份有限公司科技攻关项目(2011D-0704)资助。

Natural gas origin and gas accumulation model for deep volcanic rocks in Nanpu sag, Bohai Bay Basin

WANG Zhengjun MA Qian ZHAO Zhongxin XIA Jingsheng ZHANG Yongchao LIU Yongchang WANG Jianwei   

  • Received:2012-03-26 Revised:2012-07-04 Online:2012-09-25 Published:2012-11-27

摘要:

南堡凹陷深层火山岩油气藏具有较大勘探潜力,其天然气以烃类气体为主,甲烷含量主要在70%~90%,重烃含量在4%~27%,为湿气;非烃含量较低。天然气中甲烷碳同位素主要分布在−35‰~−43‰,乙烷碳同位素主要分布在−28‰~−24‰。这些天然气相当于有机质在镜质体反射率 Ro为 1.0%~1.5%阶段形成的天然气,为烃源岩在成熟—高成熟阶段生成的油型气,与凝析油或原油伴生,因此天然气碳同位素偏重。南堡凹陷深层火山岩天然气以凝析气为主,结合单体烃碳同位素,对天然气和伴生凝析油的成因与来源进行了分析,结果表明,南堡凹陷深层火山岩油气同源,沙河街组一段(简称沙一段)以下天然气主力源岩主要为沙河街组三段(简称沙三段)烃源岩,以凝析气为主;沙一段及以浅地层天然气主力源岩主要为沙一段烃源岩,以油为主。沙一段厚层泥岩是一套优质烃源岩,处于生烃高峰,同时形成烃浓度封闭,又是区域优质盖层。这些来自于凹陷深部烃源岩生成的高成熟油气,主要通过继承性发育的深大断裂运移到火山岩复合岩性圈闭中聚集成藏,火山岩油气成藏受火山岩单体和火山岩相双重控制。

关键词: 深层火山岩, 稳定碳同位素, 成熟度, 气源对比, 单体烃碳同位素, 成藏模式

Abstract:

A breakthrough has been made recently in natural gas exploration of deep volcanic rocks in Nanpu sag of Bohai Bay Basin, East China, indicating a very high potential in natural gas exploration of deep volcanic rocks in Nanpu sag. Therefore, it is quite important to study the origin and hydrocarbon accumulation model of natural gases for the future exploration. Natural gases accumulate mainly in deep volcanic rock reservoirs within the Paleogene Shahejie Formation. They are dominated by hydrocarbon gases in chemical composition, of which the methane content varies from 70% to 90%, ethane and heavy hydrocarbons are relatively high, ranging between 4%~27%, the dry coefficient varies from 0.71 to 0.96, indicating mainly a wet gas. Carbon isotopes of natural gases are relatively heavy, with δ13C1 mainly varying from −35‰ to −43‰ and δ13C2 mainly from −24‰ to −28‰. According to plots of C1/(C2+C3) versus δ13C1 and δ13C1 versus δD, the natural gas in deep volcanic rock reservoirs belongs to an oil-type condensate gas. The calculated thermal maturity of the gas ranges between 1.00%~1.50% by the δ13C−Ro method, it matches the thermal evolution of typeⅡ1 source rocks in the Es3 member. In addition, Pr/Ph ratios of associated condensates, light hydrocarbon parameters and hydrocarbon isotopes also show that the deep volcanic rock gas is an oil-type gas and it is dominated by a condensate gas. Carbon isotopes of individual hydrocarbons of associated condensates show that the gas in deep volcanic rocks is generated from source rocks of the Es3 and Es1 members, namely the natural gas below the Es1 stratum is mainly derived from source rocks of the Es3 member and composed of mainly a condensate gas, while the natural gas above the Es1 stratum is mainly derived from source rocks of the Es1 member, which generate chiefly oils. Thick mudstones of the Es1 member serve as not only a high-quality cap rock but also a good source rock. The highmaturity oil and gas generated from deep source rocks in the sag migrate laterally through inherited abysmal faults to and accumulate in deep volcanic rock traps, hydrocarbon accumulations are controlled both by volcanic individuals and by volcanic phases.

Key words: deep volcanic rock, stable carbon isotope, maturity, gas-source correlation, carbon isotope of individual hydrocarbon, model of hydrocarbon accumulation