Geomechanics Without Sonic In Tight Gas Reservoirs In The North Of Oman

摘要

Barik and Miqrat are the main two deep tight gas clastic reservoirs in several fields of Oman.In the area of the current Study,these reservoirs are encountered at depth 4500-5200 m and contain rich gas/ condensate.Average permeability for different units ranges from 0.02 to 4 mD,porosity up to 14%with averages values within the range 5-10%.In order to produce economically,hydraulic fracturing is applied in these reservoirs.Geomechanics calculations are essential for the fracturing design.One of the particular challenges is fracture containment within the gas zone because in view of low stress contrast between different lithologies.Sonic data are normally used for these calculations.However,based on the analysis of the Sonic data available,a simple workflow was developed for Geomechanics calculations which don’t require Sonic.A good restoration of compressional Sonic was achieved using the total porosity and the rock volumetrics as the input data.The analysis reveals good correlation between the complex rock constituents and the Poisson’s ratio.These findings resulted in good Shear Sonic restoration and fir for purpose calculations of Geomechanics parameters.The Minimum horizontal stress data obtained based on actual Sonic data matches very well with the Minimum horizontal stress derived without Sonic resulting in practically the same hydraulic fracturing design. The normalization of Gamma Ray and Neutron and rigorous multimineral analysis was a key to success for this methodology.A fit for purpose methodology was developed which enabled to perform identifi- cation of 3 key rock constituents even from the basic Triple Combo. The methodology for Geomechanics without Sonic was used for frac design in several wells.The proposed model is found to be very robust.