Mehdi Teymouri


Mehdi Teymouri, Ph.D.

Postdoctoral Scholar

Office Address: EERC.7.610

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Mobile Phone Number: 979-676-7419

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Project A:

Impact of Spatial Distribution of Fluids and Minerals and Their Interaction on Effective Mechanical Response and Fracture Propagation in Complex Rock-Fluid Systems

Understanding the dynamic mechanical behavior of rock-fluid systems under high pressure and high temperature in formations with complex mineralogy and pore structure requires advanced methods for quantifying the impacts of spatial distribution of rock components, pore structure, and pore pressure on mechanical properties. However, the existing methods for assessment of mechanical properties such effective medium modeling or numerical methods for assessment of fracture propagation and strain/stress distribution either (a) neglect coupled hydraulic and mechanical (HM) processes and pore pressure, (b) neglect realistic rock-fluid morphology, (c) contain oversimplified assumptions, or (d) require extensive calibration efforts. Either case leads to significant uncertainties in geomechanical evaluation. Fundamental understanding of the impact of rock-fluid spatial distribution and properties (e.g., fluid pressure, mechanical properties) on spatial distribution of mechanical properties in multiple scales enables reliable and real-time geomechanical characterization in complex formations, which enhances real-time production planning.

The main objectives of this project are to fundamentally investigate spatial distribution of strain and stress profile in porous media in the presence of complex mineralogy and rock fabric (i.e., spatial distribution of rock and fluid components). This objective is achieved by developing advanced numerical techniques to determine how strain and stress profiles are affected by pore structure, solid-fluid interfacial interactions, rock fabric, pore pressure, dynamic fluid flow, and spatial distribution of minerals. The outcomes of this project can potentially lead to a reliable, real-time, and safe method for assessment of effective mechanical properties and natural/induced fracture propagation in spatially heterogeneous and anisotropic formations.

The outcomes of the developed numerical framework enable quantifying the effects of rock-fluid dynamic properties, petrophysical properties, and their spatial distribution, on fracture propagation and the evolution of effective stress/strain in complex spatially heterogeneous formations, which is invaluable for completion decisions. They are also promising to reduce the uncertainties in geomechanical evaluation to improve production in tight and anisotropic reservoirs where mechanical properties of rocks are important to be taken into account for designing production strategies.


Project B

Coupled Thermal, Hydraulic, Chemical and Mechanical (THCM) Modeling of Gas Hydrate Bearing Sediments: from Laboratory to Field-Scale Analyses

Recently, geotechnical engineering has expanded its domain into the field of Energy Geotechnics. This has led to study the behavior of soils and rocks under complex and extreme conditions involving mechanical, hydraulic, thermal, and geochemical coupled actions. Constitutive modeling of gas production from methane hydrates, as the largest source of hydrocarbons on Earth, is one of the challenging topics in this field. Methane hydrates are solid compounds made of water molecules clustered around methane gas molecules. The ice shaped methane hydrates form under specific conditions of high pressure and low temperature that are common in sub-permafrost layers and in deep marine sediments. Methane hydrate gas is produced from hydrate bearing sediments (HBS) as a valuable energy resource based on releasing the molecules of gas from lattice components of hydrate with the aid of depressurization, heat and/or chemical stimulation. Coupled thermal, hydraulic, chemical and mechanical (THCM) analyses are necessary for realistic simulation of this complex phenomenon since hydrate dissociation comes with interrelated THCM processes.

The primary goals of this research effort are to develop a truly coupled numerical model that addresses the complex THCM phenomena in hydrate-bearing sediments through incorporation of proven constitutive relationships that also satisfy fundamental conservation principles (conservation of mass, energy, and momentum) and apply that model to analyze available data and further enhance understanding of the behavior of HBS in the context of field production experiments and the development of hydrate production approaches and technology. This fully coupled formulation incorporates the different phases existing in HBS (including hydrate and ice).

We adopted published results involving hydrate dissociation to develop a novel model formulated in the pressure-temperature (P-T) plane that assumes a rate of hydrate dissociation proportional to the distant between the current state and the phase boundary, accounting implicitly for the time dependency associated with this chemical reaction. The model is simple to implement in numerical simulators and consists of only one parameter, which is clear advantage respect to previous attempts in this area that generally require the definition of multiple constants. We adopted the same pseudo-kinetic concept to model gas hydrate formation, as well as, ice formation/thawing.

An analytical solution is also proposed for the steady state condition involving fluid flow in a cylindrical geometry and accounting for the presence of two zones of different permeability coefficients. This solution can be very useful in problems encompassing HBS since it can predict the ultimate radius of depressurization induced dissociation front in HBS based on reservoir initial conditions; hydrate morphology and its pertinent effect on sediment properties; induced pressure at vertical well; and the most important of all, the boundary conditions, geometries and properties of reservoir confining layers. The suggested analytical solution can also determine the influence zone of depressurization, which paves the path to define realistic boundary conditions in the numerical simulation. In addition, the effect of crucial parameters on hydrate dissociation, induced by depressurization, are investigated by both constitutive modeling and analytical solution.