The Majiang paleo-reservoir of hydrocarbon formed in the Majiang area

Guizhou Province

is one of the large-scale paleo-reservoirs in the residual units of marine strata in southern China.Affected by multi-stages of tectonic movements and experiencing complicated tectonic evolution processes

a large amount of joints were developed in the strata in the area.Joints are the final representation of surface rocks being reshaped and re-formed by multi-stages of tectonic evolution and stress fields

and can be used to reconstruct stress field status and evolution(transformation) processes as indicators for tracing the stress fields.Actual measurements of joints in different strata in the Majiang area are gathered for a statistical analysis on characteristics

occurrence

and geometries of the joints.The regional geological background as well as the intersecting relationship of joints and their crosscutting relationship with faults indicate that there are five stages of joints developed in the Majiang area. They are

from the oldest to the youngest

the planar X-shaped conjugated shear joints of early stage

X-shaped conjugated shear joints of SEE-NNE orientation

joints of NE

SSE

and near EW orientations

which are the products of the Duyun Movement

early Guangxi Movement

Indo-China Movement

and Yanshang Movement re-spectively.The tectonic stress field of each stage is reconstructed through inversion with joint occurrence.The calculation shows that the principle stress field in the Majiang area had shifted clockwise from SEE to SE

SSE

and finally EW.