Numerical Simulation of the In-Situ Upgrading of Oil Shale

Fan, Yiran; Durlofsky, Louis J.; Tchelepi, Hamdi A.

doi:10.2118/118958-pa

“…Mineral grains of the Mahogany zone in the Green River formation are mainly composed of dolomite, calcite, and quartz (Baughman 1978), and naturalfracture systems may exist in such calcareous shales (Dyni 2006). Shell has been actively studying the Green River formation, which is the largest oil-shale formation in the US, and there also exist natural-fracture systems in the Green River formation (Fowler and Vinegar 2009). …”

Section: Simulator Developmentmentioning

confidence: 99%

“…Because the analytical method used in their study was developed by assuming for simplicity that the reaction rate was not affected by temperature, their numerical simulator was also built on this limitation. Fan et al (2010) developed their own simulator for oil-shale in-situ upgrading with Stanford's General Purpose Research Simulator. They conducted sensitivity analyses of the Shell ICP to the diverse temperature, spacing, and patterns of vertical heaters.…”

Section: Introductionmentioning

confidence: 99%

A Comprehensive Simulation Model of Kerogen Pyrolysis for the In-situ Upgrading of Oil Shales

Lee

¹

,

Moridis

²

,

Ehlig-Economides

³

2016

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Oil shale, which is composed of abundant organic matter called kerogen, is a vast energy source. Pyrolysis of kerogen in oil shales releases recoverable hydrocarbons. Here, we describe the pyrolysis of kerogen with an in-situ upgrading process, which is applicable to the majority of oil shales. The pyrolysis is represented by six kinetic reactions resulting in 10 components and four phases. Expanding the Texas A&M Flow and Transport Simulator (FTSim), which is a variant of the TOUGH þ simulator (Moridis 2014), we develop a fully functional capability that describes kerogen pyrolysis and accompanying system changes.The simulator describes the coupled process of mass transport and heat flow through porous and fractured media and includes physical and chemical phenomena of reservoir systems. The simulator involves a total of 15 thermophysical states and all transitions between them and computes a simultaneous solution of 11 mass-and energy-balance equations per element. The simulator solves the equations in a fully implicit manner by solving Jacobian matrix equations with the Newton-Raphson iteration method. To conduct a realistic simulation, we account for geological structure of oil-shale reservoirs and physical properties of bulk-oil shale rocks by considering phases and components in the pores. In addition, we involve interaction between fluids and porous media, diverse equations of state (EOSs) for computation of fluid properties, and numerical modeling of fractured media.We intensively reproduce the field-production data of Shell Insitu Conversion Process (ICP) implemented in the Green River formation by conducting sensitivity analyses for the diverse reservoir parameters, such as initial effective porosity of the matrix, oil-shale grade, and the spacing of the natural-fracture network. We analyze the effect of each reservoir parameter on the hydrocarbon productivity and product selectivity. The simulator provides a powerful tool to quantitatively evaluate production behavior and dynamic-system changes during in-situ upgrading of oil shales and subsequent fluid production by thoroughly describing a reservoir model, phases and components, phase behavior, phase properties, and evolution of porosity and permeability.

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“…Upscaling of the initial permeability and initial thermal conductivity in the fine-scale model to computationally more-efficient coarse-grid representations is performed by use of an extended local fluid/heat flow-based transmissibility (interface property) upscaling method (e.g., White and Horne 1987;Durlofsky 1991;Pickup et al 1994;Romeu and Noetinger 1995;Farmer 2002;Wen et al 2003). Upscaling of the initial porosity field relies on the conventional net-volume averaging stencil.…”

Section: Global Coarse-scale Model Through Flow-based Upscalingmentioning

confidence: 99%

Adaptive Local-Global Multiscale Simulation of the In-situ Conversion Process

Alpak

¹

,

Vink

²

2016

SPE Journal

10

0

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Numerical modeling of the in-situ conversion process (ICP) is a challenging endeavor involving thermal multiphase flow, compositional pressure/volume/temperature (PVT) behavior, and chemical reactions that convert solid kerogen into light hydrocarbons and are tightly coupled to temperature propagation. Our investigations of grid-resolution effects on the accuracy and performance of ICP simulations demonstrated that ICP-simulation outcomes (e.g., oil/gas production rates and cumulative volumes) may exhibit relatively large errors on coarse grids, where "coarse" means a gridblock size of more than 3 to 5 m. On the other hand, coarsescale models are attractive because they deliver favorable computational performance, especially for optimization and uncertainty quantification workflows that demand a large number of simulations. Furthermore, field-scale models become unmanageably large if gridblock sizes of 3 to 5 m or less have to be used. Therefore, there is a clear business need to accelerate the ICP simulations with minimal compromise of accuracy.We developed a novel multiscale-modeling method for ICP that reduces numerical-modeling errors and approximates the fine-scale simulation results on relatively coarse grids. The method uses a two-scale adaptive local-global solution technique. One global coarse-scale and multiple local fine-scale near-heater models are timestepped in a sequentially coupled fashion. At a given global timestep, the global-model solution provides accurate boundary conditions to the local near-heater models. These boundary conditions account for the global characteristics of the thermal-reactive flow and transport phenomena. In turn, fine-scale information about heater responses is upscaled from the local models, and used in the global coarse-scale model. These flowbased effective properties correct the thermal-reactive flow and transport in the global model either explicitly, by updating relevant coarse-grid properties for the next timestep, or implicitly, by repeatedly updating the properties through a convergent iterative scheme. Upon convergence, global coarse-scale and local finescale solutions are compatible with each other.We demonstrate the much-improved accuracy and efficiency delivered by the multiscale method by use of a 2D cross-section pattern-scale ICP simulation problem. The following conclusions are reached through numerical testing: (1) The multiscale method significantly improves the accuracy of the simulation results over conventionally upscaled models. The method is particularly effective in correcting the global coarse-scale model through the use of the fine-scale information about heater temperatures to regulate the heat-injection rate into the formation more accurately. The effective coarse-grid properties computed by the multiscale method at every timestep also enhance the accuracy of the ICP simulations, as demonstrated in a dedicated test case, in which a constant heat-injection rate is enforced across models of all investigated resolutions. (2) Multiscale ICP models...

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“…Shell's ICP uses tightly spaced electrical heaters to heat the insitu oil-shale resources to temperatures of approximately 350 C. Long-chain kerogen molecules within the oil shale are thermally cracked into smaller oil and gas molecules at pyrolysis conditions (Fowler and Vinegar 2009;Shen 2009). High liquid-recovery efficiencies were attributed to relatively uniform heating and vaporphase transport under reservoir conditions (Shen et al 2010).…”

Section: Introductionmentioning

confidence: 99%

“…ICP circumvents fundamental difficulties associated with direct rockextraction-driven recovery techniques, such as mining/retort, especially for deeply located oil-shale deposits. A historical perspective for ICP and associated pilot projects is documented by Fowler and Vinegar (2009).…”

Section: Introductionmentioning

confidence: 99%

An Efficient Multiscale Method for the Simulation of In-situ Conversion Processes

Li

¹

,

Vink

²

,

Alpak

³

2015

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Numerical modeling of the in-situ conversion process (ICP) is a challenging endeavor involving thermal multiphase flow, compositional pressure/volume/temperature (PVT) behavior, and chemical reactions that convert solid kerogen into light hydrocarbons, which are tightly coupled to temperature propagation. Our investigations of grid-resolution effects on the accuracy and performance of ICP simulations have demonstrated that ICP-simulation outcomes-specifically, chemical-reaction rates, kerogen-accumulation profiles, and oil-/gas-production rates, may exhibit relatively large errors on coarse grids. Coarse grids are attractive because they deliver favorable computational performance. We have developed a novel multiscale modeling method for simulating ICP that reduces numericalmodeling errors and reproduces fine-scale-simulation results on relatively coarse grids. The method uses a two-scale solution method, in which the reaction kinetics of the solids is solved locally on a fine-scale grid, with interpolated temperatures obtained from coarse-grid simulations of thermal flow and fluid transport.We demonstrate the accuracy and efficiency of our multiscale method with representative 1D models. It is shown that the method delivers accurate solutions for key ICP performance indicators with very little computational overhead compared with corresponding coarse-scale models. The robustness of the multiscale method has been verified over a number of physical-parameter ranges with a limited-scope sensitivity study. Numerical results show that the multiscale method consistently improves the simulation results and matches the fine-scale reference results closely.Governing Equations. The mass-conservation equation for the ICP problem is written for each component by combining the

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Numerical Simulation of the In-Situ Upgrading of Oil Shale

Cited by 108 publications

References 12 publications

A Comprehensive Simulation Model of Kerogen Pyrolysis for the In-situ Upgrading of Oil Shales

A Comprehensive Simulation Model of Kerogen Pyrolysis for the In-situ Upgrading of Oil Shales

Adaptive Local-Global Multiscale Simulation of the In-situ Conversion Process

An Efficient Multiscale Method for the Simulation of In-situ Conversion Processes

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