Rock Mechanical Testing and Petrologic Analysis in Support of Well ...

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Table 3. Summary of Triaxial Compression Tests for Selected Samples - Desert Peak 35-13 Depth and General Lithotype 2286 ft devitrified rhyolite 2437 ft siliceous rhyolite Sample ID As- Received Bulk Density (g/cm 3 ) Effective Confining Pressure 1 (MPa) Effective Compressive Strength (MPa) Residual Effective Compressive Strength (MPa) Quasi- Static Young’s Modulus (MPa) Quasi- Static Poisson’s Ratio ODP1-2 2.120 1 52.28 17.1 8510 0.15 ODP1-5 2.086 4 55.43 26.7 6538 0.14 ODP1-1 2.107 10 78.85 51.4 7819 0.17 ODP1-4 2.106 20 105.04 81.3 8216 0.21 ODP4-3 2.406 1 108.17 16.4 22,100 0.13 ODP4-2 2.407 4 138.15 36.7 25,410 0.18 ODP4-1 2.410 10 170.83 56.3 25,970 0.18 ODP4-5 2.419 20 227.29 104.8 26,490 0.19 2624 ft illitic/siliceous ODP13-2 2.711 4 132.31 47.6 30,340 0.40 metamudstone ODP13-1 2.719 20 213.68 127.9 38,090 0.17 1 Pore pressure = 0 psi in all tests Table 4. Calculated Unconfined Compressive Strength (UCS) and Mohr-Coulomb Properties Well 35- 13 Test Sample and Average Depth ODP1 2286 ft ODP2 2376 ft ODP3 2392 ft ODP4 2437 ft ODP5 2483 ft ODP6 2579 ft ODP12 2591ft ODP13 2624ft ODP7 2741 ft General Lithotype devitrified rhyolite argillic rhyolite siliceous rhyolite illitic/siliceous metamudstone siliceous metamudstone Average UCS (as calculated from TSI tests) (psi) (MPa) Internal Friction Angle (degrees) Internal Linear Cohesion (MPa) Mohr-Coulomb Properties Residual Linear Cohesion (MPa) Residual Friction Angle (degrees) Coefficient of Sliding Friction (µ) 12,000 82.8 29.3 13.84 3.82 33.3 0.655 16,000 110.3 35.4 10.02 3.63 35.2 0.704 15,000 103.4 32.5 12.85 4.38 33.0 0.650 26,000 179.3 45.9 21.86 3.31 39.6 0.827 19,000 131.0 38.2 24.02 1.74 40.5 0.855 17,000 117.2 47.6 19.23 0 43.9 0.962 21,100 144.8 44.4 12.75 1.93 50.5 1.215 27,000 186.2 42.2 24.83 6.13 41.9 0.898 26,000 179.3 33.8 34.89 13.27 33.6 0.664
Axial Stress Difference, MPa 120 100 80 60 40 Effective Compressive Strength ODP1-2 (Vert), C o' = 52.28 MPa ODP1-5 (Vert), C o' = 55.43 MPa ODP1-1 (Vert), C o' = 78.85 MPa ODP1-4 (Vert), C o' = 105.04 MPa Pc = 20 MPa Pc = 10 MPa Pc = 4 MPa Axial Stress Difference, MPa 240 200 160 120 80 Effective Compressive Strength ODP4-3 (Vert), C o' = 108.17 MPa ODP4-2 (Vert), C o' = 138.15 MPa ODP4-1 (Vert), C o' = 170.83 MPa ODP4-5 (Vert), C o' = 227.29 MPa Pc = 20 MPa Pc = 10 MPa Pc = 4 MPa Pc = 1 MPa Pc = 1 MPa 20 40 0 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 (Radial) Strain (Axial) 0 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 (Radial) Strain (Axial) Coulomb Failure Envelope - Ormat Desert Peak 35-13 Depth 2285 ft Coulomb Failure Envelope - Ormat Desert Peak 35-13 Depth 2437 ft 80 140 Shear Stress, MPa 70 60 50 40 30 20 Effective Compressive Strength Friction Angle = 29.3 o Linear Cohesion = 13.84 MPa Effective Residual Compressive Strength Friction Angle = 33.2 o Linear Cohesion = 3.82 MPa Shear Stress, MPa 120 100 80 60 40 Effective Compressive Strength Friction Angle = 45.9 o Linear Cohesion = 21.86 MPa Effective Residual Compressive Strength Friction Angle = 39.6 o Linear Cohesion = 3.31 MPa 10 20 0 0 20 40 60 80 100 120 140 Effective Normal Stress, MPa 0 0 50 100 150 200 250 Effective Normal Stress, MPa Figure 4. Comparison of failure behavior between devitrified, less stiff rhyolite at 2285 ft (left), and stonger, more siliceous rhyolite at 2437 ft (right). The upper plots show the results of triaxial compressive tests and the stressstrain response for four vertical samples under confining pressures of 1, 4, 10 and 20 MPa. The effective compressive strength is indicated for each test. The lower plots present Coulomb failure envelopes for the four vertical samples from each depth. Coulomb criteria (friction angle and linear cohesion) were determined for two ranges – peak effective compressive strength (red) and effective residual compressive strength (green) for the entire test group. High residual cohesions are likely an effect of the plastic jackets on the fractured core plugs.
Page 1 and 2: PROCEEDINGS, Thirty-Fifth Workshop
Page 3 and 4: Rock Mechanical Testing Mechanical
Page 5 and 6: and dramatic changes in foliation o
Page 7: Based on the results of compression
Page 11: CONCLUSIONS Most of the rocks in th

Rock Mechanical Testing and Petrologic Analysis in Support of Well ...

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