石油与天然气地质 ›› 2020, Vol. 41 ›› Issue (4): 696-709.doi: 10.11743/ogg20200404

• 油气地质 • 上一篇    下一篇

渤海海域页岩油气地质条件与勘探前景

薛永安(), 王飞龙, 汤国民, 李新琦   

  1. 中海石油(中国)有限公司 天津分公司, 天津 300452
  • 收稿日期:2020-03-16 出版日期:2020-08-01 发布日期:2020-08-11
  • 第一作者简介:薛永安(1963-),男,博士、教授级高级工程师,矿产普查与勘探。E-mail:xueya@cnooc.com.cn
  • 基金项目:
    国家科技重大专项(2016ZX05024-003)

Geological condition and exploration prospect of shale oil and gas in the Bohai Sea

Yong'an Xue(), Feilong Wang, Guomin Tang, Xinqi Li   

  1. Tianjin Branch, CNOOC, Tianjin 300452, China
  • Received:2020-03-16 Online:2020-08-01 Published:2020-08-11

摘要:

渤海海域是渤海湾盆地新生代的沉降中心,在古近系发育了东营组三段、沙河街组一段-二段(沙一二段)和沙河街组三段3套主力烃源岩,具有丰富常规和非常规石油资源,页岩油气作为重要的非常规资源在渤海海域具有巨大的勘探潜力。基于渤海海域勘探开发实际情况,通过与国内外典型页岩油气盆地石油地质条件对比,综合烃源岩地球化学参数、测井资料、镜下薄片观察及X射线衍射全岩矿物分析等,并结合盆地模拟手段,明确了渤海海域页岩油气的资源潜力,并指明了勘探方向及有利目标。研究结果表明:1)渤海海域4个富烃凹陷主力烃源岩品质好,都有利于形成页岩油气,其中渤中凹陷烃源岩成熟度高,形成页岩气可能性更大,黄河口凹陷和辽中凹陷成熟度相对较低,更易形成页岩油,歧口凹陷东三段和沙一二段成熟度低,易形成页岩油,其沙三段成熟高,易形成页岩气;2)3套主力烃源岩脆性矿物平均含量超过63.5%,粘土矿物平均含量低于34.7%,具有良好的可改造性,在3 200 m以深泥页岩进入中成岩B期,伊蒙混层中的蒙脱石大量向伊利石转换,增加了页岩储层的可改造性,结合国内外勘探实践认为3 200~4 200 m是渤海海域页岩油气勘探开发的有利深度范围;3)渤中凹陷是渤海海域页岩油气资源潜力最大的凹陷,总资源量高达95.8×108 t,占据渤海页岩油气资源的45.2%,主力烃源岩整体处于超压状态,结合渤海勘探开发的经济成本,渤中凹陷东三段和沙一二段烃源岩埋深适中、成熟度高,是目前渤海海域页岩气勘探最有利层位;4)渤中凹陷西斜坡处于凹陷边缘,3套烃源岩整体处于异常高压且埋深适中,平均TOC值超过3.04%,页岩层段气测全量达到99%,X衍射矿物显示该区页岩储层中粘土矿物含量较渤海其他区域最低,具备更好的可压性,可作为渤海现阶段最有利目标区。

关键词: 烃源岩特征, 储集特征, 异常高压, 资源潜力, 页岩油气, 渤海海域

Abstract:

The Bohai Sea is the Cenozoic subsidence center of the Bohai Bay Basin.Three sets of hydrocarbon source rocks (i.e., Ed3, Es1+2, Es3) developed in the Paleogene of the Basin indicate significant exploration potentials of conventional and unconventional oil and gas resources, especially the shale oil and gas.To further determine the shale oil and gas potential of the area, the exploration and development activities in the Bohai Sea were investigated and the comparison of the petrogeological conditions in the Basin with those in typical shale basins both in China and other countries, was combined with analyses of geochemical parameters and logging data, microscopic observation of thin sections and X-ray diffraction results of whole rock mineral of samples from the Basin, as well as basin simulation, to carry out an in-depth study.It comes out with four conclusions.(1) There are four high-quality hydrocarbon-rich sags in the Bohai Sea.Of which the Bozhong sag has the highest potential of harboring shale gas with gas-prone and highly matured source rocks.The Huanghekou and Liaozhong sags are more oil-prone with relatively low maturity.And the Qikou sag is both oil and gas prone with its low matured Ed3 and Es1+2 source rocks more likely generating oil and highly matured Es3 producing gas.(2) The three sets of source rocks have good reformability with an average brittle mineral content of more than 63.5% and an average clay mineral content of less than 34.7%.The mud shale below 3 200 m was once at the stage B of middle diagenesis, during which the montmorillonite in the montmorillonite-illite mixture was largely converted to illite, thus increasing the plasticity of the shale reservoir.Considering exploration activities in other areas with similar conditions, layers buried between 3 200 m and 4 200 m are suggested to be the targets for shale oil and gas exploration and development in the Bohai Sea.(3) The Bozhong sag has the greatest potential of shale oil and gas resources with an estimated resource of up to 95.8 billion tons, accounting for 45.2% of shale oil and gas resources in the Bohai Sea.The major source rocks in the sag are under overpressure as a whole.Given the economic cost of shale gas and oil exploration and development in the Bohai Sea, the Ed3 and Es1+2 source rocks of the Bozhong sag that are characterized by moderate burial depth and high maturity, are the most promising shale gas exploration targets in the Bohai Sea.(4) The west slope (at the edge) of the Bozhong sag is considered to be the most promising part in the area for current exploration stage as the three sets of source rocks with an average TOC value of more than 3.04% in the slope are under abnormally high pressure and have relatively shallow burial depth.Furthermore, gas logging shows a total gas content as high as 99% and X-ray diffraction results indicate that the clay mineral content in the shale reservoirs is the lowest compared with that of other areas in the Bohai Sea, making them ideal candidates for future fracturing.

Key words: source rock characteristics, reservoir characteristics, abnormally high pressure, resource potential, shale oil and gas, Bohai Sea

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