Development Characteristics and Formation Mechanism of Intra-Organic Reservoir Space in Lacustrine Shales
Zhang Linye
Li Juyuan
Li Zheng
Zhu Rifang
Zhang Shouchun
Liu Qing
Zhang Jingong
Chen Zhonghong
Abstract：Organic reservoir is one of the important reservoir types in shale.The development of organic reservoir space in la-custrine shales within oil window is lack of research work.In view of this,lacustrine shale samples with different maturities in oil window were selected and prepared by argon ion-milling techniques.Joint Quanta200 scanning electron microscope and EDAX energy spectrometer,and JSM-6700f field emission scanning electron microscope were employed to observe the micro-structure and analyze the composition of lacustrine shales.Both back scattered images and secondary electronic images show that abundant mixtures of dark banded organic matter (OM)-clay-carbonate and OM-clay-sulfate were developed in shales. Pores were easily developed in the mixtures.From 2 500 m to 4 000 m,the pores continuously exist.At the depths less than 3 600 m,the pore size generally occurs on micron scale.With the continued evolution,nano pores increase and are densely dis-tributed.The intra-pores in the mixtures are synchronous with the rapid increasing of oil saturation and the rising of free organ-ic acids in shales,respectively.The development of the pores not only depends on the hydrocarbon generation,but also on the interaction of hydrocarbon conversion and the organic acid dissolution.The results indicate that in lacustrine shales within oil window,organic matter and inorganic minerals undergo evolution as a whole and interact with each other.The combination of hydrocarbon generation and dissolution form abundant reservoir space in the hybrid of organic matter and minerals,which has important significance to the occurrence of oil and gas in continental shales.
Keywords：lacustrine shaleoil windoworganic reservoir spaceorganic acidformation mechanismpetroleum geology
Publication Date：2015-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：10( 1824-1833 )