Abstract: This paper analyzes the regional tectonic stress field characteristics in Ordos basin, develops the reasonable geological and mechanical model of its Su-10 block based on the finite element basic theory, and presents the maximum horizontal principal stress, minimum horizontal principal stress, maximum shear stress, mean stress and deformation energy contour distribution diagram of the target zone by numerical simulation of the earth stress field. The evaluation indices such as "3-D equivalent tensile stress (σ_T)", "crack value (I)" and " strain energy per volume (u)" are applied to get composite assessment factor (R_c) for quantitative description of the fracture development. It is indicated that the zones with developed structural fractures are more accordant with the results of the high-yield gas wells and the drilled core fracture description.

Key words: Ordos basin, Su-10 block, stress field, reservoir fracture, 3-D finite element