Oil & Gas Geology ›› 2021, Vol. 42 ›› Issue (3): 615-626.doi: 10.11743/ogg20210308

• Petroleum Geology • Previous Articles     Next Articles

Distribution of paleo-karst reservoirs in Ma 4 Member, Hangjinqi area, northern Ordos Basin

Wei Zhang1,2(), Xiaoqi Ding3,*(), Chuntang Li2, Zhuangzhuang Qi3   

  1. 1. Faculty of Earth Resource, China University of Geosciences (Wuhan), Wuhan, Hubei 430000, China
    2. Huabei Oil & Gas Branch, SINOPEC, Zhengzhou, Henan 450000, China
    3. College of Energy, Chengdu University of Technology, Chengdu, Sichuan 610000, China
  • Received:2021-01-07 Online:2021-06-28 Published:2021-06-23
  • Contact: Xiaoqi Ding E-mail:cupzhangwei@126.com;xiaoqiding@qq.com

Abstract:

Karst limestone reservoir, a newly recognized reservoir type with hydrocarbon potential in recent years, is also present in the northern Ordos Basin.Its forming mechanism and distribution pattern are of great significance for future gas exploration in the area.Studies were carried out on samples from the area on the relationship between cavern facies and the reservoir through cavern anatomy, on the paleotopography of weathering crust and vertical pattern of the multiple cave layers through cavity logging and levelling interpretation to explain the relationship between multi-layers of caverns and structural uplift, and on the distribution pattern of caverns based on seismic data.The results show that vugs occurring below the unconformity are mostly filled with clay and fine-grained debris, thus incapable of storing.However, those far away from the unconformity are dominant reservoirs.Cave roof and unfilled cavities are also dominant reservoir space.Three layers of caverns, a result of periodic uplifting in northern part of the study area during the Caledonian, are developed in Ma 4 Member in a steady distribution and good well-to-well correlation.The cavities are more developed in the west of study area compared with the east part.The prediction of cavity distribution by well-seismic correlation indicates that sink holes mostly occur in the north, and underground channels mostly occur in the south.Cavities show a network-shaped distribution in plane view, implying a minor controlling effect by faults.Paleo-water table serves to control the stratification of cavities.The discovery of three layers of cavities in Ma 4 Member broadens the horizon of gas exploration in the northern Ordos Basin.

Key words: karst, cavity, reservoir, Majiagou Formation, Ordos Basin

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