Geomechanics and Geoenergy Journal

Geomechanics and Geoenergy Journal

Evaluation of the quality of Gachsaran Formation cap rock using petrophysical, geomechanical and rock mechanics parameters in a field in southwest Iran

Document Type : Original Article

Authors
Hassan Sadr 1
Ali Misaghi 2
Mohammad Reza Asef 2
Ahmad Reza Lakzaie 3
1 Department of Geology, Faculty of Earth Sciences, Kharazmi University, Tehran, Iran
2 Applied Geology Department, Faculty of Earth Sciences, Kharazmi University
3 National Iranian South Oil Company (NISOC)
10.22107/ggj.2026.589715.1266
Abstract
The cap rock of an oil reservoir plays a fundamental role in preserving hydrocarbons over geological time, against the stresses imposed. An integrated effective cap rock must be thick and have sufficient lateral continuity at the field scale, so that there are no leakage windows. Otherwise, the entire hydrocarbon reserve will be lost. For this reason, it is of great importance to study the cap rock to assess its integrity, type of geomechanical behavior, degree of permeability, its relationship to subsurface faults and drilling hazards.
In this research, using 3D seismic data and inversion, as well as well logs, various information layers related to petrophysical, rock mechanics, and geomechanical parameters of the caprock of the Gachsaran Formation in one of the fields in southwestern Iran were generated and examined as a three-dimensional model for the field volume and mapped across the geographical area. These parameters were analyzed both individually and in combination, and the strengths and weaknesses of the caprock were reported. These layers include acoustic impedance, seismic wave velocity, density, porosity, effective Young's modulus, shear modulus, bulk modulus, Poisson's ratio, brittleness, and closure stress ratio. Finally, the investigation revealed that most areas of the caprock exhibit suitable ductility and resistance to stress due to minimal variations in these parameters. However, certain areas with higher strength and competence can be identified for drilling and field development programs.
Keywords
Cap rock
Integrity
Geomechanics
Rockmechanics
Petrophysics
Gachsaran
Subjects
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Geomechanics and Geoenergy Journal
Volume 8, Issue 3
Autumn 2025
Pages 31-43