Rock Mechanical Properties The Most Critical For Stimulation Stress & Strain F F Observations Length will decrease Radius will increase L1 L2 F Stress A r2 r1 Stress & Strain F Strain is the change in the shape It can be positive or negative Strain in length is (-) L L F L L r2 Strain in radius is (+) r r r1 Poisson’s Ratio It is the ratio between the two strains F F r r L L L L r r ORTHOGONAL - NORMAL L L r2 r1 Young’s Modulus F Stress A It is the ratio between stress and strains in the longitudinal direction F Stress E A L Strain L F F L L L L r r r2 r1 Relationship between Acoustic Velocity and Elastic Moduli Particle Motion Particle Motion Wave Direction Wave Direction Compressional Velocity (P- Wave) Shear Velocity (S- Wave) Computation of Elastic Properties from Logs Three log inputs are used: ts, tc, and b t s v p 2 R 2 2 t c v s 2 2 b G 13,474 2 t s R 2 2R 2 G 3R 4 E R 1 2 2 2 2 Three log inputs are used: ts, tc, and b FORMATION STRESSES z = Po Z H = h + t + ( * P p )* (1 ) h = Po * 1- 1- h H Parameters Needed for Stress Calculations Overburden Po POBW *Wdepth POBR * (TVD Wdepth ) Biot Constant Biot A B * t Pore Pressure Worldwide Experience A= 0.64 B = 0.854 Pp Pgrad current * Pgrad Original * (1 ) * TVD max max Deviated wells r=( x + y =( 2 4 2 x - y )(1 - R2 ) + ( )(1+ 3 R4 - 4 R2 ) cos 2 2 2 r r r 4 2 2 + xy (1+ 3 R4 - 4 R2 ) sin 2 + P w R2 r r r x + y x - y )(1+ R2 ) - ( )(1+ 3 R4 ) cos 2 2 2 r r 4 2 - xy (1+ 3 R4 ) sin 2 - P w R2 r r 2 zz y 4 2 r 2 R R z = z - [2( x - y ) 2 cos 2 + 4 xy 2 sin 2 ] r r x Poisson’s Ratio Varies With Lithology 0.45 Poisson's Ratio 0.40 0.35 0.30 PR qtz 0.25 PR clay 0.20 PR dolo 0.15 0.10 50 PR lime PR coal 60 70 80 90 100 110 120 130 Compressional T (sec/ft) For Internal Use Only 107 140 150 160 Young’s Modulus Estimates Multiply E/Dens by Rock Density (g/cc) 6.00 E qtz E clay 5.00 E dolo E lime E/Dens 4.00 E coal 3.00 2.00 1.00 0.00 50 60 70 80 90 100 110 120 Compressional t (sec/ft) For Internal Use Only 108 130 140 150 160 Thank You