石油与天然气地质 ›› 2008, Vol. 29 ›› Issue (6): 733-739,747.doi: 10.11743/ogg20080605

• 油气地质理论 • 上一篇    下一篇

碳酸盐岩成岩史及其对储层的控制作用—以普光气田为例

高林1,2   

  1. 1. 成都理工大学,四川 成都 610059;
    2. 中国石油化工股份有限公司 勘探南方分公司,四川 成都 610041
  • 收稿日期:2008-07-15 出版日期:2008-12-24 发布日期:2012-01-16

Diagenesis of carbonate rocks and their control over reservoirs—an example from the Puguang gas field

Gao Lin1,2   

  1. 1. Chengdu University of Technology, Chengdu, Sichuan 610059, China;
    2. South Exploration Company of Sinopec, Chengdu, Sichuan 610059, China
  • Received:2008-07-15 Online:2008-12-24 Published:2012-01-16

摘要:

碳酸盐岩成岩作用贯穿沉积物从堆积到埋藏直至抬升的整个历史,碳酸盐矿物对成岩环境的高度敏感性使得岩石原始组构及其物性在长期的成岩作用过程中不断被改造,川东北普光大气田长兴组礁滩云岩和飞仙关组鲕滩云岩储层复杂的成岩史即是例证。综合运用高精度三维地震和岩心资料对储层的准同生成岩环境进行分析,利用普光气田重点探井薄片资料对埋藏成岩进行研究。上二叠统长兴组至下三叠统飞仙关组沉积时期,普光气田主体位于(镶边)台地,长兴组台地镶边礁、飞仙关组台缘滩和台内滩构成该气田的储层相,礁滩后和鲕潍间的局限环境提供了渗透-回流准同生白云石化条件。薄片研究表明普光气田长兴组和飞仙关组经历了大范围白云石化、多期胶结作用、压实、多期溶解、裂缝等成岩作用。白云石化作用产生了晶间孔并提高储层渗透率,早期方解石胶结物可使岩石原始孔隙度免遭压实作用破坏,鲕粒的选择性溶解形成溶模孔,埋藏期非组构选择性溶解产生溶蚀扩大孔或溶洞,构造裂缝不仅大大提高了储层渗透率而且作为埋藏溶蚀性流体运移通道形成溶蚀扩大缝。尽管多种成岩事件的叠加以及沉积组构的复杂性决定了礁滩储层物性的非均质性,但鲕滩和礁滩岩相的原始沉积组构控制着潜在储层分布。

关键词: 成岩作用, 准同生成岩, 白云石化, 碳酸盐岩, 普光气田, 四川盆地

Abstract:

The diagenesis of carbonate rocks underwent through the entire period from the accumulation,burial to the uplifting of sediments.Because carbonate rocks were sensitive to the rock-forming environment,primary petrofabric and physical properties of rocks were constantly modified during the long time of diagenesis.Exam-ples are the complex diagenesis processes of the Changxing reef shoal dolomite and the Feixianguan oolitic beach dolomite in the Puguang gas field in northwest Sichuan.This paper focuses on the burial diagenesis through thin-sections of key wells in the Puguang gas field,and high precision 3D seism and cores data have been used to analyse the penecontemporaneous diagenesis environment.From the sedimentation of the Changxing Formation of the Upper Permian to the Feixianguan Formation of the Lower Triassic,most part of the Puguang gas field was lo-cated on the platform margin.Reef on the Changxing Formation platform margin,marginal beach and intraplat-form beach on the Feixianguan Formation platform composed the reservoir facies of the Puguang gas field.Limi-ted environment after and between reef beach has provided penetration-reflux conditions for penecontemporane-ous dolomitization.The study on thin-sections shows that the Permian Changxing Formation and the Triassic Feixianguan Formation underwent large-scale diagenesis processes like dolomitization,multistage cementation, compaction,multistage dissolution and fissure.The dolomitization generated intracrystalline pores and improved reservoir permeability.Early calcite cementing materials protected the original porosity from compaction.The se-lective dissolution of oolite formed moldic pores.The selective dissolution of non-fabric materials created en-larged pores or caverns.Tectonic fracture not only improved reservoir permeability but also served as the liquid migration channels to enlarge the dissolved fissure.Despite the heterogeneity of reef beach facies reservoirs, which was determined by various diagenesis processes and the complexity of depositional fabric,the original dep-ositional fabric of oolitic beach and reef beach facies controlled the distribution of potential reservoirs.

Key words: diagenesis, penecontemporaneous, dolomitization, carbonate rock, Puguang gas field, Sichuan Basin

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