Elastic rock properties

The main reservoir strata of Olituoz area was originally formed at the surface or near surface (less than 1km, Gu, et al., 2002) during Es3, Which later on were overlaid by Dongying Formation and the up-layers. Thus the up-layers were peeled in order to obtain the corrected depth for these strata till the end of Dongying Formation time with normal temperature conditions. After depth calculation, rock samples collected from the intact well cores are subjected to tri-axial compression tests to gain the mechanical parameters of these rocks (Table 1 and Table 2) for the simulation of stress field and prediction of fractures.

Table 1. Rock Mechanic Parameters Obtained Through Triaxial Compression Tests

Sample Number Lithology Depth (m) Diameter (mm) Height (mm) Confining Pressure σ3(Mpa) Axial Crack Stress σ1(Mpa) Young's Modulus E (GPa) Poisson's Ratio ν Form of Crack
O11-1 Basalt 2411.4 25 50 31.52 244.34 28.73 0.232 Tension
O15-1 Trachyte 2303.7 25 50 26.1 167.52 18.78 0.252 Shear
O15-4 Trachyte 2313.1 25 50 26.33 176 41.09 0.189 Shear
O15-8 Trachyte 2405.6 25 50 28.6 302.51 37.17 0.33 Shear
O19-4 Trachy-breccia 2369.1 25 50 25.95 141.28 15.58 0.143 Tension
O27-1 Trachyte 2401.1 25 50 28.2 153.83 20.58 0.206 Shear
O27-4 Trachyte 2525.3 25 50 31.24 233.76 37.47 0.253 Shear
O28-2 Tuff 2341.2 25 50 26 93.82 10.41 0.232 Shear
O29-4 Trachy-breccia 2218.5 25 50 23.48 115.47 16.88 0.268 Shear
O29-5 Trachy-breccia 2223 25 50 23.52 151.9 20.35 0.23 Shear
O30-1 Basalt 2515.4 25 50 29.41 111.79 45.57 0.179 Tension

Table 2. Evaluation of Shear Strength Parameters Based on Triaxial Compression Tests

Number Sample Number Lithology σ0(MPa) K C(MPa) φ(°)
1 O11-1 Basalt 92.83 4.807 21.17 40.96
2 O15-1 Trachyte 67.61 3.828 17.28 35.86
3 O15-4 Trachyte 81.56 3.587 21.53 34.33
4 O15-8 Trachyte 61.91 8.413 10.67 51.95
5 O19-4 Trachybreccia 68.22 2.815 20.33 28.41
6 O27-1 Trachyte 66.37 3.101 18.84 30.82
7 O27-4 Trachyte 38.1 6.263 7.61 46.44
8 O28-2 Tuff 24.95 2.649 7.67 26.86
9 O29-4 Trachybreccia 49.1 2.827 14.6 28.51
10 O29-5 Trachybreccia 38.9 4.804 8.87 40.95
11 O30-1 Basalt 72.17 1.347 31.09 8.51