地学前缘 ›› 2016, Vol. 23 ›› Issue (2): 48-54.DOI: 10.13745/j.esf.2016.02.006

• 页岩气富集规律与分布 • 上一篇    下一篇

中国南方海相页岩气超压机制及选区指标研究

刘洪林, 王红岩, 方朝合, 郭为, 孙莎莎   

  1. 1. 中国石油勘探开发科学研究院 廊坊分院, 河北 廊坊 065007
    2. 国家能源页岩气研发(实验)中心, 河北 廊坊 065007
    3. 中国石油非常规油气重点实验室, 河北 廊坊 065007
  • 收稿日期:2015-09-11 修回日期:2015-11-19 出版日期:2016-03-15 发布日期:2016-03-15
  • 作者简介:刘洪林(1973—),男,硕士,高级工程师,主要从事非常规天然气地质评价工作。E-mail:liuhonglin69@petrochina.com.cn
  • 基金资助:

    国家油气重大专项“页岩气勘探开发关键技术研究项目”(2011ZX05018);国家重点基础研究发展计划“973”项目“中国南方海相页岩气高效开发的基础研究”(2013CB228001)

The formation mechanism of overpressure reservoir and target screening index of the marine shale in the South China.

  • Received:2015-09-11 Revised:2015-11-19 Online:2016-03-15 Published:2016-03-15

摘要:

在页岩气勘探开发选区的过程中,首先要寻找含气量较高的地区作为开发区块,含气量高的地区其资源丰度高,在同样的增产改造规模下单井EUR也较高,经济性也好。由于页岩含气量等于吸附气加上游离气,再加上溶解气,游离气、吸附气和溶解气都与压力系数关系密切。在美国开展页岩气地质选区过程中,由于地质条件稳定,认为超压对于页岩气田没有那么重要,正常压力、甚至欠压都可以实现开发,因此美国页岩气地质选区指标中没有压力系数的概念,并没有将超压作为一个关键指标。但是由于中国与北美地质成藏背景不同,北美页岩气主要位于环加拿大克拉通盆地,背景非常稳定,而我国是由多个地块拼接而成,构造复杂,同时页岩形成的时代较久,因此,我国与北美地质条件最大的差别为页岩成熟度高低和构造运动的强弱。因为我国海相成熟度高,导致孔隙压实,孔隙度降低;我国构造运动相对活跃,断裂发育,保存条件相对差。对于高成熟、低孔隙度的页岩,要达到同样的含气量需要较大的地层压力系数,这样单井最终可采储量才能达到经济极限,才能实现商业开发。我国南方分布有丰富的海相页岩气,具有厚度大、分布稳定的特点,普遍经历了高成熟演化和强烈地质构造运动。在油气生成过程中由于排烃作用的发生形成了广泛发育超低含水饱和度的特征,超低含水饱和度存在为形成超压富集区创造了条件,这种超压核心区是南方海相页岩气近期主要的勘探目标。扬子地区已经发现的超压页岩气田的增压机制主要包括构造抬升型增压、水热型增压、黏土矿物脱水型增压、生烃型增压。焦石坝海相页岩气田主要为构造型增压所形成的超压页岩气田,长宁页岩气田主要为生烃增压型页岩气田。页岩气选区指标应该是核心区/富集区优选指标,指标取值依据必须与超压气田地质特征参数匹配才有意义。北美地区页岩气地质选区需要考虑埋深、页岩厚度、TOC含量、含气量、硅质矿物含量。由于北美地质条件简单、成熟度适中,在低压、欠压条件下可实现商业化,但在高成熟、断裂发育背景下,地层压力系数尤其重要,应该考虑地层层压力系数。因此,本文认为页岩气地质选区中,除了考虑页岩埋深(1 500~4 500 m)、页岩厚度(>30 m)、总有机碳含量(>2%)、硅质矿物含量(>30%)等基本参数外,应把地层压力系数大于1.3以上作为我国南方海相页岩气选区的重要指标之一,才能体现我国南方海相页岩气特点,同时提高页岩气选区的准确性和科学性。

关键词: 海相页岩, 超压核心区, 超低含水饱和度, 地层压力系数

Abstract:

In the process of exploration and development of shale gas, we find some areas as Development Zone, with high gas content and high resource abundance. The EUR of a single well is also high, and the economy is good. Since shale gas content equals to the adsorbed gas and free gas, in addition to dissolved gas, free gas, adsorbed gas and dissolved gas are closely correlated with pressure coefficient. In the United States, due to stable geological conditions, it is easy to carry out shale gas geological screening. The overpressure is not so important for shale gas field, normal pressure, even underpressure can be achieved commercially. So, In the United States shale gas geological screening index has no concept of pressure coefficient, or it is not a key indicator. However, due to the different geological formations in China and North America, the North American shale gas is mainly located in the basin of central Canada, and the background is very stable. In contrast, China consists of many blocks with complex structure and long time. Because of the high maturity of marine shale, the porosity is low and decreases. The tectonic movement is active with developed faults, and the preservation condition is relatively poor. For the shale with high maturity and low porosity, it is necessary to reach the same pressure coefficient of gasbearing formation, so that the ultimate recoverable reserves of single well can reach the economic limits, and the commercial development can be realized. South China has abundant marine shale gas, which is characterized by large thickness and stable distribution. The formation of low water saturation often occurs in the process of hydrocarbon generation. Pressure mechanism of the overpressure shale gas field in the Yangtze region mainly consists of uplifting construction, water pressure, the type of clay mineral dehydration, and hydrocarbon generation. The marine shale gas field is mainly resulting from the formation of super pressure. Changning shale gas field is a main hydrocarbongenerating pressurization field. Screening index of favorable area should include core area/enrichment area optimization index. Index value based on the geological characteristics of the super pressure gas field must match the significance of the parameters. Geological areas of North American shale gas need to consider the burial depth, shale thickness, TOC content, and the content of silica. Due to the simple geological conditions and moderate maturity of the North American shale, it can be realized under the condition of low pressure and under pressure, but in the background of high maturity and fault development, the formation pressure coefficient is especially important. Therefore, this paper considers that the basic parameters, such as depth (15004500 m), thickness (>30 m), total organic carbon content (>2%), and silica mineral content (>30%), should be considered as an important index to reflect the characteristics of marine shale gas in southern China.

Key words: South China marine shale, overpressure core area, ultralow saturation, strata pressure coefficient

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