Browsing by Author "Agoha, Chidiebere Charles"

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    3D geomechanical characterization of reservoirs of "BETA" and "FUJA" fields, offshore Niger Delta, Nigeria, using an integrated approach
    (Federal University of Technology, Owerri, 2021) Agoha, Chidiebere Charles
    The geomechanical characterization of the reservoirs of ‘‘Beta’’ and ‘‘Fuja’’ Fields, offshore Niger Delta has been carried out to mitigate well drilling and hydrocarbon exploitation challenges encountered in this environment. Well log data from 8 wells within the fields in addition to 3D reflection seismic data and core data from the fields were integrated to calculate rock elastic, inelastic and petrophysical properties, pore pressure, total vertical stress, as well as maximum and minimum horizontal stresses within the reservoirs from empirical equations, and generate 3D geomechanical models using Petrel and Microsoft Excel software. Cross plots between these rock properties were also obtained to ascertain the relationship between them in both fields. Using Matlab 2015 software, empirical linear and non-linear models and artificial neural network (ANN) model were used to model 4 parameter relationships and establish their prediction performances. Results revealed that all the rock elastic and inelastic properties have higher values in shale units than sand units within the reservoirs, while the petrophysical properties showed higher values in sand. In ‘‘Beta’’ Field, the average values of these properties in shale are 0.33, 13.70GPa, 13.30GPa, 5.12GPa, 0.07𝐺𝑃𝑎ିଵ , 32.32GPa, 0.09, 0.07, and 0.022 mD; while in sand they are 0.30, 10.94GPa, 12.76GPa, 4.11GPa, 0.10𝐺𝑃𝑎ିଵ , 25.19GPa, 0.25, 0.19, and 192.00mD. In ‘‘Fuja’’ Field, the average values of these properties in shale are 0.42, 6.08GPa, , 6.09Gpa, 2.84GPa, 0.016𝐺𝑃𝑎ିଵ , 42.3GPa, 0.06, 0.04, and 0.110 mD; while in sand they are 0.39, 5.11GPa, 5.10GPa, 2.39GPa, 0.023𝐺𝑃𝑎ିଵ , 39.0GPa, 0.16, 0.13 and 44.10mD for Poisson’s ratio, Young’s modulus, bulk modulus, shear modulus, bulk compressibility, unconfined compressive strength (UCS), total porosity, effective porosity, and permeability respectively. This implies larger vertical stress would be required to achieve deformation in the compacted shale than the unconsolidated highly porous sand. The cross plots reveal a definite relationship between these rock properties as shown by the increase in UCS with rock elastic properties and depth; and a decrease with total and effective porosity in both fields. From the generated geomechanical models, there will be lower mechanical rock failure around the NNE part of ‘‘Beta’’ Field and around the northeastern and parts of the eastern and western portions of ‘‘Fuja’’ Field due to the high values of elastic moduli and UCS observed in these areas. Stress estimations within the reservoirs in relation to the obtained elastic and rock strength parameters show that the reservoirs are stable. Also, results of parameter relationships modeling with ANN revealed that ANN can be utilized in the analysis and modeling of UCS versus bulk density, UCS versus sonic, and shear wave velocity versus sonic due to their high prediction performances (0.93214, 0.99953 and 0.69854 respectively). However, it cannot be used in the modeling and analysis of permeability versus bulk density due to its low prediction performance (0.13817). It is hoped that these findings will be invaluable in mitigating drilling and exploitation challenges within these fields