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Dong Y.,Kunming University of Science and Technology | Dong Y.,Zhejiang University | Dong Y.,Research Center for the Structures in Oil and Gas Bearing Basin | Xiao A.,Zhejiang University | And 4 more authors.
Journal of Earth Science | Year: 2014

Field observations of the crossing relationships of fractures have been used to explain the sequence of fractures. Based on field observations from Fuyang-Lin’an anticline, located near Hangzhou, Zhejiang Province, this paper proposes that the formation of synfolding fractures was influenced dominantly by one fracture set, which developed prior to folding and the orientation was nearly parallel to the bedding. The length of the prefolding fractures is longer than the synfolding fractures. These prefolding fractures cut thicker strata into small pieces and form a dense network of fractures in thicker strata. Most synfolding fractures, which are oblique to the bedding, are truncated by prefolding fractures in thicker strata. The synfolding fractures, which result from local stress, are inferred to form during folding. Here, the mechanism of truncation was analyzed using finite-element models. The approach was based on the idea that natural fractures can be interpreted or inferred from stress distribution. The presence or absence of prefolding fractures is shown to strongly control the distribution of stress, and this control has an important implication for interpreting the fracture truncation mechanism from geomechanical models. © China University of Geosciences and Springer-Verlag Berlin Heidelberg 2014.

Dong Y.-P.,Kunming University of Science and Technology | Dong Y.-P.,Zhejiang University | Dong Y.-P.,Research Center for the Structures in Oil and Gas Bearing Basin | Xiao A.-C.,Zhejiang University | And 7 more authors.
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | Year: 2013

To explore the relationship between the formation of fractures and the deformation of strata, fractures data from outcrops in the Upper Jurassic strata of Lin'an are integrated with geometry modeling in this study. It is found that two main type fractures are secondary structures to the fold, which are referred to as fold accommodation fractures in this paper, and named as D and D' fractures respectively. An angle ranging 44°-80° exists between fractures and stratum layers, with D' fracture directing the motion of local layer and D fracture directing the motion of adjacent layer. The fractures formed primarily because of an increase in bed curvature within fold cores. The relationship between fracture density and layer thickness is established on the basis of geometrical analysis of the fold and we find that fractures density is proportional to the layer thickness.

LIN X.,Zhejiang University | LIN X.,Research Center for the Structures in Oil and Gas Bearing Basin | CHEN H.,Zhejiang University | CHEN H.,Research Center for the Structures in Oil and Gas Bearing Basin | And 8 more authors.
Mining Science and Technology | Year: 2010

Fault related folds and fractures, which always improve reservoirs and trap capacity, especially in the oil and gas fields in western China, are of extreme importance for oil and gas exploration. Based on four assumptions and fault related fold theory, we propose four conceptual models for fracturing in fault related folds, i.e., a simple-step parallel fault bend anticline, a simple-step parallel fault propagation anticline, a multiple-bend fault-bend fold and a break-forward imbricate. Fracture conditions depend on structural evolution and specific site conditions. A case study of the Kulongshan Anticline in the Jiuquan Basin shows that our conceptual models match reality data very well. © 2010 China University of Mining and Technology.

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