DEEP STRESS MEASUPEMENTS IN TANGSHAN AREA

11 hydraulic fracturing in-situ stress measurements have been successfully performed in upper 300m deep borehole at Huangtuo nursery, East Mine Region, 20Km east of Tangshan city.Variations of magnitude and direction of in-situ stresses with depth were obtained.The results indicate that the horizontal principal stresses are very low presently in Tangshan area, the maximum horizontal principal stress is only 7.8 Mpa near depth of 300m, and the maximum horizontal shear stress is 1 Mpa.The direction of maximum stress varies apparently in upper 180m depth, the results of three measurements are considerably consistent below the depth of 180m, the directions of the maximum principal stresses are N81°W to N86°W and consist with the general direction of in-situ stress measurements in North China.This paper also presents comparison of hydrofracturing stress measurements with the results obtained using overcoring and acoustic emission Kaiser effect methodes.