Method and system for determination of horizontal stresses from shear radial variation profiles

摘要

Described is method and system of determining horizontal stress from radial profiles of dipole shear together with the far-field estimate of the Stoneley shear modulus. The system and method include selecting an optimal number of regression points on measured radial profiles for obtaining reliable estimation of maximum and minimum horizontal stress magnitudes in the presence of noisy data, where measured radial profiles of dipole shear moduli might exhibit a small amount of random fluctuations.

主权项

1. A method for structural modeling formation stresses, comprising:
selecting an interval of the formation having stress induced anisotropy within a borehole; computing model parameters m1 and m3 by linear regression of radial profiles of shear moduli C44 and C55 using a computer wherein the model parameters m1 and m3 are obtained using a model; computing and outputting a maximum horizontal stress σH and minimum horizontal stress σh using the computer wherein the maximum horizontal stress σH and minimum horizontal stress σh are determined from a series of equations:σH-σh+C55∞-C44∞AE-1,⁢σh≈σv-C55∞-C66∞AE-1,⁢AE=-A2+A22-4⁢A1⁢A32⁢A1,⁢where,⁢A1-2⁢(-Pw+σv)⁢⁢A2=-(C44∞+C55∞-2⁢C66∞-m1-m3-2⁢Pw+2⁢σv),⁢A3=C44∞+C55∞-2⁢C66∞.(3) PW=(Pmud−Pp) Pmud represents mud pressure in the borehole, Pp represents pore pressure in the borehole, σv represents vertical stress of the formation, AE represents an acoustical parameter, C44∞ represents a far field slow shear modulus defined as r/a=7, where r represents a distance to the center of the borehole, a represents a radius of the borehole C55∞ represents a far field fast shear modulus defined as r/a=7, and C66∞ represents a far field Stonely shear modulus.