Three-Dimensional Modeling of Geomechanical Units Using Acoustic Impedance in One of the Gas Fields in South of Iran

Adabnezhad, P. (University of Tehran) | Aghighi, M. A. (University of Tehran) | Kadkhodaie, A. (Curtin University of Technology) | Rostami, A. (Pars Oil and Gas Company)


ABSTRACT: Geomechanical modeling of a reservoir has a very important role in all parts of a field lifecycle. In this paper, we demonstrate a new method for modeling the distribution of elastic properties in the whole reservoir using the concept of geomechanical units (GMUs). In this study, a GMU is a cluster of Young’s, Bulk and shear modulus, Poisson’s Ratio and unconfined uniaxial strength. To establish these GMUs we used eight wells and the Post-stack seismic data in the field of interest. Dynamic elastic parameters were computed from logging data of mentioned wells. To convert these dynamic parameters to static values, empirical equations were determined in a neighboring field of Salman, in the interval of Kangan and Dalan formations. In the next step, Multi-resolution graph-based clustering was applied to these static elastic parameters to construct five distinct GMUs. For three-dimensional modeling of GMUs, the 3D acoustic impedance model of the field was made by genetic inversion and used as a secondary parameter of Co-kriging. The amounts of elastic parameters of each GMU at the location of well number six in the final 3D model are found to be in good agreement with the known values of this well.


Geomechanics is a petroleum engineering sub-discipline developed to address the mechanical behavior of the reservoir and bounding rocks during exploration and production activities (Zoback, 2010; Aadnoy and Looyeh, 2011). In this regard, Three-dimensional modeling of geomechanical parameters plays a significant role in whole life of a reservoir. These models are used for seismic modeling, interpretation, hydraulic fracture design, assessing borehole stability and stress calculations in geological studies. Therefore, any improvement in one of these momentous applications could lead to better and more sufficient field development plans, at the same time save the considerable amount of money and operation time.

This study employs an efficient approach to construct a 3D reservoir geomechanical model based on the concept of Geomechanical Units (GMUs). A GMU is a single unit for design and modeling purposes. A GMU can be selected from logs, cores, or judgment (Dusseault, 2011). The advantages of GMU use in engineering studies have been discussed by a number of authors including Uwiera et al. (2011) and Nygaard (2010). In this work, a GMU is a set of rock mechanical properties, such as: Young’s modulus, bulk modulus, shear modulus, Poisson’s ratio, and uniaxial compressive strength. These elastic parameters are clustered by using different clustering methods to establish the best GMU. The purpose of using this method is to determine the distribution of elastic parameters in whole parts of the field of study. The Kangan and Dalan formations are the reservoir layers in the field of study. These formations are consisted of carbonate and dolomite (Figure 1).