石油学报 ›› 2012, Vol. 33 ›› Issue (6): 978-986.DOI: 10.7623/syxb201206008

• 地质勘探 • 上一篇    下一篇

歧口凹陷缓坡区湖泊碳酸盐岩优质储层特征及成因

杨有星 金振奎 高白水   

  1. 中国石油大学地球科学学院油气资源与探测国家重点实验室 北京 102249
  • 收稿日期:2012-06-17 修回日期:2012-10-03 出版日期:2012-11-25 发布日期:2012-12-07
  • 通讯作者: 杨有星
  • 作者简介:杨有星,男,1985年2月生,2008年获中国石油大学(北京)学士学位,现为中国石油大学(北京)博士研究生,主要从事沉积学与开发地质学等方面的研究工作。
  • 基金资助:

    国家重大科技专项(2009ZX05009-002)资助。

Characteristics and origin of lacustrine carbonate high-quality reservoirs in the slope area of Qikou sag

YANG Youxing JIN Zhenkui GAO Baishui   

  • Received:2012-06-17 Revised:2012-10-03 Online:2012-11-25 Published:2012-12-07

摘要:

针对歧口凹陷缓坡区湖泊碳酸盐岩储层非均质性强、优质储层特征及分布规律认识不清的问题,综合利用薄片观察、岩性测井响应、物性实验数据和压汞曲线等资料对储层进行综合研究。研究表明,研究区沙河街组一段下部颗粒灰岩储层是一类具有高-中孔隙度、中渗透率、低排驱压力和大喉道为主等特征的优质储层。岩石类型以亮晶生物碎屑灰岩和亮晶鲕粒灰岩为主,储集空间主要为次生的粒间溶孔和裂缝。水动力条件控制了储层的分布,强水动力条件下形成的灰岩颗粒之间以亮晶方解石胶结物充填为主,成为后期溶蚀作用的易溶物质,是次生孔隙发育的直接原因之一。鲕粒滩与生屑滩水动力条件最强,储层物性最好;滩坝边缘为间歇动荡的高能环境,储层物性中等;湖湾与潮上带为安静低能环境,储层物性较差。晚成岩期泥页岩释放出大量的有机酸和弱酸性水沿沙河街组三段顶部不整合面运移,导致碳酸盐岩储层产生了大量的次生溶蚀孔隙,是研究区优质储层形成的主要原因。同时,烃类的早期充注抑制了自生矿物的形成和方解石的交代,使溶蚀孔隙很好地保存下来。

关键词: 歧口凹陷, 湖泊碳酸盐岩, 储集空间, 优质储层, 不整合面, 成因机理

Abstract:

Grain-limestone reservoirs in the lower 1st Member of Shahejie Formation in the slope area of Qikou sag are high-quality reservoirs characterized by high-medium porosity, medium permeability, low discharge pressure, large throat and good connectivity. These reservoirs, lithologically, are composed mainly of bioclastic sparite, oolitic sparite and dolomicrite, and their major accumulation capacity consists of secondary intergranular pores and fractures characteristic of the combination of pore type and pore-fracture type. Generally speaking, hydrodynamic conditions control the distributional pattern of these reservoirs, for limestone grains filled intergranularly with sparry calcite cement are formed under strong hydrodynamic conditions, providing late dissolution with abundant soluble substances, which is one of the direct causes that result in well-developed secondary pores. Oolitic beach and bioclastic beach are under a highly-hydrodynamic condition environment and have best physical properties. Margin of beach bars is usually under an intermittent highly-hydrodynamic environment, and has medium physical properties. However, hydrodynamic conditions in lake bays and supratidal zones are low-energy and still, under which rocks are formed with bad physical properties. Well-developed oolitic beach and bioclastic beach as well as large quantities of organic acid and slightly acidic water released from surrounding shale in late diagenesis, which migrated along the top unconformity of the third Member of Shahejie Formation, resulted in the formation of large-scale secondary dissolution pores in these reservoirs. In addition, early charging of hydrocarbons restrained the occurrence of authigenic minerals and replacement of calcite, having kept dissolved pores well preserved.

Key words: Qikou sag, lacustrine carbonate, accumulation capacity, high-quality reservoir, unconformity, genetic mechanism