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古地理学报 ›› 2023, Vol. 25 ›› Issue (1): 226-244. doi: 10.7605/gdlxb.2023.01.015

• 古地理学及矿产资源 • 上一篇    下一篇

碳酸盐岩早期差异成储路径及其对储集性能的影响:以滨里海盆地N油田石炭系KT-Ⅰ与KT-Ⅱ层系为例*

卢家希1,2,3, 谭秀成1,2,3, 金值民1,2,3, 陈烨菲4, 王淑琴4, 赵文琪4, 李长海4,5   

  1. 1 中国石油碳酸盐岩储层重点实验室西南石油大学研究分室,四川成都 610500;
    2 西南石油大学油气藏地质及开发工程国家重点实验室,四川成都 610500;
    3 西南石油大学天然气地质四川省重点实验室,四川成都 610500;
    4 中国石油勘探开发研究院,北京 100083;
    5 北京大学地球与空间科学学院,北京 100871
  • 收稿日期:2022-07-18 修回日期:2022-08-05 出版日期:2023-02-01 发布日期:2023-02-17
  • 通讯作者: 谭秀成,男,1970年生,教授、博士生导师,研究方向为碳酸盐岩沉积与储层。E-mail: tanxiucheng70@163.com。
  • 作者简介:卢家希,男,1998年生,硕士研究生,研究方向为储层地质学。E-mail: lujiaxi199801@163.com。
  • 基金资助:

    *中国石油集团公司十四五前瞻性基础性科技项目(编号: 2022DJ3209)资助

Differential reservoir formation paths of carbonate rocks in early stage and impacts on reservoir properties: a case study of KT-Ⅰ and KT-Ⅱ layers in N Oilfield,Pre-Caspian Basin

LU Jiaxi1,2,3, TAN Xiucheng1,2,3, JIN Zhimin1,2,3, CHEN Yefei4, WANG Shuqin4, ZHAO Wenqi4, LI Changhai4,5   

  1. 1 Research Branch of Southwest Petroleum University,Key Laboratory of Carbonate Reservoirs,CNPC,Chengdu 610500,China;
    2 State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu 610500,China;
    3 Sichuan Natural Gas Geology Key Laboratory,Southwest Petroleum University,Chengdu 610500,China;
    4 PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China;
    5 School of Earth and Space Sciences,Peking University,Beijing 100871,China
  • Received:2022-07-18 Revised:2022-08-05 Online:2023-02-01 Published:2023-02-17
  • Contact: TAN Xiucheng,born in 1970,is a professor in Southwest Petroleum University. He is engaged in sedimentology and reservoir geology. E-mail: tanxiucheng70@163.com.
  • About author:LU Jiaxi,born in 1998,is a master's degree candidate in Southwest Petroleum University. He is mainly focus on reservoir geology research. E-mail: lujiaxi199801@163.com.
  • Supported by:

    Financially supported by the Fourteenth Five-Year Plan Forward-looking Basic Science and Technology Project of CNPC(No.2022DJ3209)

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摘要：

以滨里海盆地N油田石炭系KT-Ⅰ与KT-Ⅱ层系碳酸盐岩储集层为例,综合岩心、薄片、扫描电镜、高压压汞、常规物性分析以及各类测试资料,对碳酸盐岩储集层特征以及早期成储路径展开系统研究,并进一步探讨成储路径与储集层孔喉结构和质量的关系。结果表明,KT-Ⅰ层系以云岩类储集层为主,颗粒灰岩次之,其中云岩类储集层以晶间(溶)孔、小型溶洞为主,孔喉连通性好,为高孔—高渗的孔洞型储集层, 而颗粒灰岩类储集层以粒内溶孔、铸模孔及生物体腔孔发育为特征,孔喉连通性差,属中孔—低渗的孔隙型储集层。KT-Ⅱ层系以粒间(溶)孔和生物体腔孔发育的颗粒灰岩为特征,为中高孔—高渗的孔隙型储集层。进一步分析表明,KT-Ⅰ层系云岩与灰岩储集层单旋回厚度小,皆受高频海平面升降变化驱动的早成岩期岩溶的控制, 而KT-Ⅱ层系单旋回厚度大,颗粒滩未经历早期岩溶的改造。 3类储集层的成储路径分别为: (1)KT-Ⅰ云岩类储集层,准同生期白云石化作用导致矿物相转变并使得部分矿物更易遭受溶蚀→早成岩期岩溶作用控制储集层的形成→云岩抗压溶岩石骨架有利于储集层的保护; (2)KT-Ⅰ颗粒灰岩储集层,早成岩期岩溶作用优化储集层→初期压实控制胶结流体通道进而控制胶结作用—粒间孔与粒内孔差异胶结控制储集层的保护; (3)KT-Ⅱ颗粒灰岩储集层,原始沉积环境控制储集层的形成→初期压实与早期胶结作用控制储集层的保护。成储路径差异控制了不同的孔渗特征与孔喉结构,而孔喉结构进一步控制了早期岩溶型云岩、早期岩溶型颗粒灰岩、原生孔保存型颗粒灰岩3种储集层的质量。研究结果将为具类似特征的碳酸盐岩储集层成因分析提供参考,也因发现了云岩较灰岩更易早期溶蚀的现象而具有较为重要的岩溶地质学意义。

关键词: 碳酸盐岩, 储集性能, 成储路径, 早成岩期岩溶, 石炭系, 滨里海盆地

Abstract:

Taking Carboniferous KT-I and KT-II carbonate reservoirs in N oilfield in Pre-Caspian Basin as an example,the characteristics of carbonate reservoirs and evolution of reservoir properties at the early stage are systematically studied based on the core analysis,thin section,scanning electron microscopy,high-pressure mercury invasion,conventional physical property analysis and various tests. In addition,the relationship among the evolution of reservoir properties,pore throat structure and quality is further discussed. The results show that KT-I reservoir is dominated by dolomite with intergranular dissolved pores and small karst caves with good pore-throat connectivity,which belongs to high porosity-high permeability pore-cavity reservoir,followed by grainstone with intragranular dissolved pores,mold pores and biologic cavity pores that have the poor pore-throat connectivity,which belongs to the pore-type reservoir with the medium porosity and low permeability. KT-II reservoir is characterized as grainstone with intergranular dissolved pores and biologic cavities,belonging to the porous reservoir with medium-high porosity and high permeability. Further analysis shows that the thickness of single cycle layer of KT-I dolomite and limestone reservoirs is small,which is controlled by the early diagenetic karst driven by high frequency sea-level fluctuation. The thickness of KT-II layer is large,and there is no early karstification of the grain beach. There are mainly three types of reservoirs: (1)Penecontemporaneous dolomitization with stable transformation of minerals results in the dissolution of some minerals,followed by the formation of reservoirs controlled by the karstification at early diagenetic stage,and the pressure dissolution-resistance rock skeleton helps the protection of reservoir;(2)The early diagenesis karstification promoted the reservoir property→the early compaction controls the chemical fluid migration that can induce the cementation→differential cementation controls the preservation of intergranular pore and intragranular pore;(3)Primary sedimentary environment controls the formation of reservoir→early compaction and cementation control preservation of reservoir. Different reservoir formation mechanisms lead to different porosity,permeability and pore throat structure,which controls the quality of reservoirs including the dolomite and grainstone after early karstification,and the limestone that owns the primary pores. The results will provide a reference for the genetic analysis of carbonate reservoirs with similar characteristics. It also has significant karst geology meaning based on the discovery that dolomite is much easier to dissolve than limestone during the early diagenetic stage.

Key words: carbonate rock, reservoir performance, reservoir formation pathway, eogenetic karstification, Carboniferous, Pre-Caspian Basin

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