Quick question. Deviated 12–1/4" through interbedded shale/sand at 67° inclination: breakouts show on images at 2,940–3,020 m MD with 1.20 sg, but we trigger DIFs above 1.28 sg; my Mohr–Coulomb model (UCS 22–32 MPa, Biot 0.8) points to 1.24–1.27 sg as the sweet spot. Has anyone widened the margin here by incorporating transverse isotropy or bedding-parallel weakness, or is this more likely pore-pressure uncertainty tied to depletion?
But > margin here by incorporating transverse isotropy or bedding-parallel weakness, or is this more likely pore-pressure uncertainty tied I’ve widened it about 0.03 sg by switching to weak‑plane MC with bedding cohesion about 0–1 MPa and φ∥ about 18–20° calibrated off dipole sonic anisotropy. Caveat: our DIF trigger didn’t budge until we corrected cuttings‑loaded ECD and re‑anchored PP with a couple mini‑LOTs — do you have dipole and at least one LOT in that interval?
I’ve had almost the same window, and the only way we widened it was to add a bedding‑parallel weak‑plane MC (cohesion about 0.4×UCS, φ≈20° on planes within ±15° of bedding) constrained by cross‑dipole sonic; “bedding‑parallel shear was the first to go.” Small caveat: if PP is off by >0.05 sg the gain disappears, so confirm with a quick DFIT/step‑down before dialing mud weight.