西南石油大学学报(自然科学版)

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Hydration Experiment of Hard Brittle Shale of the Longmaxi Formation

LIU Xiangjun1,2*, XIONG Jian2, LIANG Lixi1   

  1. 1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu,Sichuan 610500,China
    2. School of Geosciences and Technology,Southwest Petroleum University,Chengdu,Sichuan 610500,China
  • Online:2016-06-01 Published:2016-06-01

Abstract:

The hydration of hard brittle shale has an important influence on the borehole stability. Therefore,the hydration
experiments was done for different types of shale from the Longmaxi formation in the south region of Sichuan Basin,observations
were made to mineral composition,microstructure,hydration swelling stress,water absorption by self-priming and core
immersion. And based on observations,the paper discusses the hard brittle shale hydration process and hydration mechanism.
The result shows that the main clay mineral of shale is illite,the shape of the clay mineral particles is flake and directional
alignment. There are lots of bedding and micro-crack in the shale,which provide the operation-space and flow channel for
the hydration of shale. The hydration swelling stress and water absorption by self-priming of shale tend to ascent first before
becoming stable. The fabric of the shale has an important influence on the ascend velocity or extent. The fractures in the
surface of sample are parallel plane of bedding in the process of immersion. With the increase of immersion time,the sample
would keep its integrality or spall to pieces. The fabric and cementation type of the shale have an important influence on the
hydration swelling. The hydration of the shale is a result of coupling of physical-chemical action and mechanical action,the
former decreasing the rock fracture toughness,and the later increasing the stress intensity factor for mode-I fracture. When the
stress intensity factor is greater than the rock fracture toughness,the crack will extend or broaden.

Key words: hard brittle shale, Longmaxi Formation shale, hydration swelling, spontaneous imbibition rate of water, physicalchemical
action,
mechanical action

CLC Number: