Reservoirs Stability Evaluation through Analysis of Rock Mechanical Parameters and Stresses in "Beta" Field, Offshore Niger Delta, Nigeria.

The geomechanical characterization of the reservoirs of "Beta Field" was carried out to predict the stability of hydrocarbon reservoir rocks and hence, mitigate drilling and exploitation challenges within offshore Niger Delta. Gamma ray, sonic, and density logs from four wells within the field, including core data and 3D reflection seismic volume from the area, were integrated to determine rock mechanical and petrophysical properties from empirical equations, and generate 3D geomechanical models using Petrel and Ms-Excel software. Principal stresses operating within the reservoirs and pore pressure were also estimated from empirical models. Cross plots of these rock parameters were obtained to ascertain the relationship between them and obtain model equations. Results show that the rock mechanical properties have lower values in sand units than shale units with petrophysical parameters having lower values in shale. Average values of 13.70GPa, 0.33, 13.30GPa, 32.32GPa, 5.12GPa, 0.07, and 0.022mD were obtained in shale; while 0.30, 10.94GPa, 0.30, 12.76GPa, 25.19GPa, 4.11GPa, 0.19, and 192.00mD were recorded in sand for Young's modulus, Poisson ratio, bulk modulus, uniaxial compressive strength, shear modulus, effective porosity, and permeability respectively. Mean pore pressures observed in sand and shale units are 13,683psi and 15,662psi while mean total vertical stress, maximum and minimum horizontal stresses recorded in the reservoirs are 28,392psi, 25,537psi and 20,781psi respectively. Comparative analysis of obtained rock mechanical and strength parameters with the principal stresses operating within the reservoirs show that the studied reservoirs and by extension reservoirs of this petroleum play are stable. [ABSTRACT FROM AUTHOR]