A combined workflow using geology, petrophysics, and geomechanics to locate productive zones and ideal fracture networks

Abstract

A complete reservoir evaluation requires studying both petrophysical and mechanical rock properties. Accordingly, Well logs are widely used in the oil industry to determine key parameters and locate high-production zones. This study presents an integrated workflow using Formation MicroImager logs. The objectives are to analyze borehole stability, identify productive zones, determine the optimal drilling direction, classify porosity types, and perform a mechanical analysis of fractures in the Sarvak Formation. First, a petrophysical evaluation of the Formation was carried out using the multi-mineral method in Geolog software. This step calculated essential reservoir properties and identified high-production intervals. A neutron-density crossplot indicated that the reservoir mainly consists of limestone with minor shale content. Next, interpretation of high-resolution FMI image logs showed vuggy, fracture and secondary porosities. Then, one-dimensional geomechanical model was built for the reservoir using the Mohr–Coulomb failure criterion to calculate geomechanical parameters. It also predicted outcomes such as mud loss, fluid inflow, borehole collapse and fracture zones. The results show that the implemented drilling mud weight was suitable for most of the reservoirs; however, in the lower sections, the high concentration of vuggy porosity made the borehole wall at the collapse threshold. A sensitivity analysis revealed that the optimal drilling direction is close to 90°, representing a horizontal well path. Finally, by combining results from the petrophysical evaluation, geomechanical model, fracture density, and vug density, the main productive zone of the reservoir was obtained between 2685 and 2755 m and is characterized by a high density of natural fractures.