Acta Petrolei Sinica ›› 2022, Vol. 43 ›› Issue (9): 1236-1252.DOI: 10.7623/syxb202209004

• PETROLEUM EXPLORATION • Previous Articles     Next Articles

Karst characteristics at early diagenetic stage and their enlightenment for the origin of ancient deep carbonate reservoirs: a case study of the Member 4 of Dengying Formation in Moxi 8 well area, central Sichuan

Zhao Dongfang1,2, Tan Xiucheng1,2, Luo Wenjun3, Wang Xiaofang4, Xu Wei3, Luo Sicong5, Tang Dahai1,3, Luo Yao1,2, Zeng Wei1,2   

  1. 1. State Key Laboratory of Oil and Gas Geology and Exploitation, Southwest Petroleum University, Sichuan Chengdu 610500, China;
    2. CNPC Key Laboratory of Carbonate Reservoirs, Southwest Petroleum University Division, Sichuan Chengdu 610500, China;
    3. Research Institute of Exploration and Development, PetroChina Southwest Oil & Gasfield Company, Sichuan Chengdu 610041, China;
    4. PetroChina Hangzhou Research Institute of Geology, Zhejiang Hangzhou 310023, China;
    5. Exploration and Production Research Institute, Sinopec Southwest Oil and Gas Company, Sichuan Chengdu 610041, China
  • Received:2021-09-21 Revised:2022-02-19 Published:2022-10-08

早成岩期岩溶特征及其对古老深层碳酸盐岩储层的成因启示——以川中地区磨溪8井区灯影组四段为例

赵东方1,2, 谭秀成1,2, 罗文军3, 王小芳4, 徐伟3, 罗思聪5, 唐大海1,3, 罗垚1,2, 曾伟1,2   

  1. 1. 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;
    2. 中国石油天然气集团有限公司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;
    3. 中国石油西南油气田公司勘探开发研究院 四川成都 610041;
    4. 中国石油杭州地质研究院 浙江杭州 310023;
    5. 中国石油化工股份有限公司西南油气分公司勘探开发研究院 四川成都 610041
  • 通讯作者: 谭秀成,男,1970年3月生,2007年获成都理工大学博士学位,现在为西南石油大学教授、博士生导师,主要从事沉积学及碳酸盐岩储层地质研究,Email:tanxiucheng70@163.com
  • 作者简介:赵东方,男,1992年9月生,2021年获西南石油大学博士学位,现为西南石油大学助理研究员,主要从事沉积学及碳酸盐岩储层地质研究,Email:zdf5757@163.com
  • 基金资助:
    国家科技重大专项(2016ZX05004-002-001)和中国石油-西南石油大学创新联合体科技合作项目(2020CX010300)资助。

Abstract: To further enrich and deepen the generation theory of ancient and deep dolomite reservoirs,a case study of the Member 4 of Dengying Formation in Moxi 8 well rea,central Sichuan Basin was conducted.Based on the data of cores,rock slices,logging and physical properties of reservoir,this paper analyzes the karst characteristics and evolution law of the Member 4 of Dengying Formation and discusses its significance for reservoir development and preservation.The results show that the Member 4 of Dengying Formation is dominated by a porous-type reservoir,the reservoir lithology is dominated by microbial dolomite,karst breccia and granular dolomite,and the karstification shows typical early corrosion characteristics such as fabric-selective corrosion,graniphyric corrosion and semi-discrete zone.The reservoirs of the Member 4 of Dengying Formation are mainly found in the middle and upper part of the upward shallowing sequence,and multiple sets of thin-layered reservoirs are frequently overlapped and rhythmically distributed in the longitudinal direction.The development of high-quality reservoirs in the Member 4 of Dengying Formation is closely related to early diagenetic karstification driven by frequent rising and falling of the relative sea level,and the reservoir quality is related to exposure time and corrosion intensity.The reservoir of the Member 4 of Dengying Formation experienced three stages of karst evolution:selective corrosion,karst zoning and overall brecciation.Appropriate exposure reformation is beneficial to the corrosion expansion of primary residual pores and plays an important and constructive role in reservoir reformation.If the exposure time is too long or the corrosion strength is too high,the early relatively isolated holes connect with each other.Most of them collapse or are damaged by filling,shown as the overall brecciation.On the whole,the effective reservoirs of the Member 4 of Dengying Formation are characterized by "preservation in small pore (hole) and filling in large pore (hole)".With the evolution of reservoirs in the karst stage,the reservoiring performance is first optimized and then getting worse.

Key words: frequent exposure, corrosion strength, porous-type reservoir, microbial dolomite, Dengying Formation, Sichuan Basin

摘要: 为进一步丰富和深化古老深层白云岩储层的成因理论,以四川盆地中部磨溪8井区灯影组四段(灯四段)为例,基于岩心、岩石薄片、测井、储集物性等资料,分析灯四段岩溶特征及演化规律,并探讨了其对储层发育和保存的意义。结果表明,灯四段发育孔洞型储层,储集岩性以微生物白云岩类、岩溶角砾岩和颗粒白云岩为主,岩溶作用具有组构选择性溶蚀、花斑状溶蚀和半离解带等典型早期溶蚀特征。灯四段储层主要集中在向上变浅序列的中—上部,纵向上呈多套薄层状储层频繁叠置、韵律性分布。灯四段优质储层的发育与相对海平面频繁升降驱动的早成岩期岩溶作用密切相关,储层品质与暴露时间和溶蚀强度有关。灯四段储层主要经历了3期岩溶演化阶段:选择性溶蚀阶段、岩溶分带阶段和整体角砾化阶段。适宜的暴露改造有利于原生残余孔隙的溶蚀扩大,对储层改造具有重要的建设性作用;暴露时间过长或溶蚀强度过大导致早期相对孤立的孔洞彼此连接,但大多垮塌或被充填破坏,表现为整体角砾化。整体上,灯四段有效储层具有"小孔(洞)保存,大孔(洞)充填"的特征,随着岩溶阶段的演化,储集性能先优化后变差。

关键词: 高频暴露, 溶蚀强度, 孔洞型储层, 微生物白云岩, 灯影组, 四川盆地

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