Reservoir simulation

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A simulated Top of Structure, depth map from geological data in a full field model. (GSI MERLIN simulator) Reservoirdepth.PNG
A simulated Top of Structure, depth map from geological data in a full field model. (GSI MERLIN simulator)

Reservoir simulation is an area of reservoir engineering in which computer models are used to predict the flow of fluids (typically, oil, water, and gas) through porous media.

Contents

The creation of models of oil fields and the implementation of calculations of field development on their basis is one of the main areas of activity of engineers and oil researchers. On the basis of geological and physical information about the properties of an oil, gas or gas condensate field, consideration of the capabilities of the systems and technologies for its development create quantitative ideas about the development of the field as a whole. A system of interrelated quantitative ideas about the development of a field is a model of its development, which consists of a reservoir model and a model of a field development process. Layer models and processes for extracting oil and gas from them are always clothed in a mathematical form, i.e. characterized by certain mathematical relationships. The main task of the engineer engaged in the calculation of the development of an oil field is to draw up a calculation model based on individual concepts derived from a geological-geophysical study of the field, as well as hydrodynamic studies of wells. Generally speaking, any combination of reservoir models and development process can be used in an oil field development model, as long as this combination most accurately reflects reservoir properties and processes. At the same time, the choice of a particular reservoir model may entail taking into account any additional features of the process model and vice versa.

The reservoir model should be distinguished from its design scheme, which takes into account only the geometric shape of the reservoir. For example, a reservoir model may be a stratified heterogeneous reservoir. In the design scheme, the reservoir with the same model of it can be represented as a reservoir of a circular shape, a rectilinear reservoir, etc.

Fundamentals

Representation of an underground fault by a structure map generated by Contour map software for an 8500ft deep gas & Oil reservoir in the Erath field, Vermilion Parish, Erath, Louisiana. The left-to-right gap, near the top of the contour map, indicates a Fault line. This fault line is between the blue/green contour lines and the purple/red/yellow contour lines. The thin red circular contour line in the middle of the map indicates the top of the oil reservoir. Because gas floats above oil, the thin red contour line marks the gas/oil contact zone. Contour map software screen snapshot of isopach map for 8500ft deep OIL reservoir with a Fault line.jpg
Representation of an underground fault by a structure map generated by Contour map software for an 8500ft deep gas & Oil reservoir in the Erath field, Vermilion Parish, Erath, Louisiana. The left-to-right gap, near the top of the contour map, indicates a Fault line. This fault line is between the blue/green contour lines and the purple/red/yellow contour lines. The thin red circular contour line in the middle of the map indicates the top of the oil reservoir. Because gas floats above oil, the thin red contour line marks the gas/oil contact zone.

Traditional finite difference simulators dominate both theoretical and practical work in reservoir simulation. Conventional FD simulation is underpinned by three physical concepts: conservation of mass, isothermal fluid phase behavior, and the Darcy approximation of fluid flow through porous media. Thermal simulators (most commonly used for heavy crude oil applications) add conservation of energy to this list, allowing temperatures to change within the reservoir.

Numerical techniques and approaches that are common in modern simulators:

Correlating relative permeability KrData Correlation.PNG
Correlating relative permeability

The simulation model computes the saturation change of three phases (oil, water and gas) and the pressure of each phase in each cell at each time step. As a result of declining pressure as in a reservoir depletion study, gas will be liberated from the oil. If pressures increase as a result of water or gas injection, the gas is re-dissolved into the oil phase.

A simulation project of a developed field usually requires "history matching" where historical field production and pressures are compared to calculated values. It was realised at an early stage that this was essentially an optimisation process, corresponding to Maximum Likelihood. As such, it can be automated, and there are multiple commercial and software packages designed to accomplish just that. The model's parameters are adjusted until a reasonable match is achieved on a field basis and usually for all wells. Commonly, producing water cuts or water-oil ratios and gas-oil ratios are matched.

Other engineering approaches

Without FD models, recovery estimates and oil rates can also be calculated using numerous analytical techniques which include material balance equations (including Havlena–Odeh and Tarner method), fractional flow curve methods (such as the Buckley–Leverett one-dimensional displacement method, the Deitz method for inclined structures, or coning models), and sweep efficiency estimation techniques for water floods and decline curve analysis. These methods were developed and used prior to traditional or "conventional" simulations tools as computationally inexpensive models based on simple homogeneous reservoir description. Analytical methods generally cannot capture all the details of the given reservoir or process, but are typically numerically fast and at times, sufficiently reliable. In modern reservoir engineering, they are generally used as screening or preliminary evaluation tools. Analytical methods are especially suitable for potential assets evaluation when the data are limited and the time is critical, or for broad studies as a pre-screening tool if a large number of processes and / or technologies are to be evaluated. The analytical methods are often developed and promoted in the academia or in-house, however commercial packages also exist.

Software

Many programs are available for reservoir simulation. The most well known (in alphabetical order) are:

Open source:

Commercial:

Application

Reservoir simulation is ultimately used for forecasting future oil production, decision making, and reservoir management. The state of the art framework for reservoir management is closed-loop field development (CLFD) optimization which utilizes reservoir simulation (together with geostatistics, data assimilation, and selection of representative models) for optimal reservoir operations.

Notable people

See also

Related Research Articles

<span class="mw-page-title-main">Petroleum engineering</span> Extracting crude oil and natural gas

Petroleum engineering is a field of engineering concerned with the activities related to the production of hydrocarbons, which can be either crude oil or natural gas. Exploration and production are deemed to fall within the upstream sector of the oil and gas industry. Exploration, by earth scientists, and petroleum engineering are the oil and gas industry's two main subsurface disciplines, which focus on maximizing economic recovery of hydrocarbons from subsurface reservoirs. Petroleum geology and geophysics focus on provision of a static description of the hydrocarbon reservoir rock, while petroleum engineering focuses on estimation of the recoverable volume of this resource using a detailed understanding of the physical behavior of oil, water and gas within porous rock at very high pressure.

<span class="mw-page-title-main">Computational fluid dynamics</span> Analysis and solving of problems that involve fluid flows

Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyze and solve problems that involve fluid flows. Computers are used to perform the calculations required to simulate the free-stream flow of the fluid, and the interaction of the fluid with surfaces defined by boundary conditions. With high-speed supercomputers, better solutions can be achieved, and are often required to solve the largest and most complex problems. Ongoing research yields software that improves the accuracy and speed of complex simulation scenarios such as transonic or turbulent flows. Initial validation of such software is typically performed using experimental apparatus such as wind tunnels. In addition, previously performed analytical or empirical analysis of a particular problem can be used for comparison. A final validation is often performed using full-scale testing, such as flight tests.

<span class="mw-page-title-main">Hydrogeology</span> Study of the distribution and movement of groundwater

Hydrogeology is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust. The terms groundwater hydrology, geohydrology, and hydrogeology are often used interchangeably, though hydrogeology is the most commonly used.

Permeability in fluid mechanics, materials science and Earth sciences is a measure of the ability of a porous material to allow fluids to pass through it.

Darcy's law is an equation that describes the flow of a fluid through a porous medium. The law was formulated by Henry Darcy based on results of experiments on the flow of water through beds of sand, forming the basis of hydrogeology, a branch of earth sciences. It is analogous to Ohm's law in electrostatics, linearly relating the volume flow rate of the fluid to the hydraulic head difference via the hydraulic conductivity. In fact, the Darcy's law is a special case of the Stokes equation for the momentum flux, in turn deriving from the momentum Navier-Stokes equation.

In fluid statics, capillary pressure is the pressure between two immiscible fluids in a thin tube, resulting from the interactions of forces between the fluids and solid walls of the tube. Capillary pressure can serve as both an opposing or driving force for fluid transport and is a significant property for research and industrial purposes. It is also observed in natural phenomena.

<span class="mw-page-title-main">Multiphase flow</span> Simultaneous flow of materials with two or more thermodynamic phases

In fluid mechanics, multiphase flow is the simultaneous flow of materials with two or more thermodynamic phases. Virtually all processing technologies from cavitating pumps and turbines to paper-making and the construction of plastics involve some form of multiphase flow. It is also prevalent in many natural phenomena.

<span class="mw-page-title-main">Tecplot</span>

Tecplot is the name of a family of visualization & analysis software tools developed by American company Tecplot, Inc., which is headquartered in Bellevue, Washington. The firm was formerly operated as Amtec Engineering. In 2016, the firm was acquired by Vela Software, an operating group of Constellation Software, Inc. (TSX:CSU).

<span class="mw-page-title-main">Reservoir engineering</span>

Reservoir engineering is a branch of petroleum engineering that applies scientific principles to the fluid flow through a porous medium during the development and production of oil and gas reservoirs so as to obtain a high economic recovery. The working tools of the reservoir engineer are subsurface geology, applied mathematics, and the basic laws of physics and chemistry governing the behavior of liquid and vapor phases of crude oil, natural gas, and water in reservoir rock. Of particular interest to reservoir engineers is generating accurate reserves estimates for use in financial reporting to the SEC and other regulatory bodies. Other job responsibilities include numerical reservoir modeling, production forecasting, well testing, well drilling and workover planning, economic modeling, and PVT analysis of reservoir fluids. Reservoir engineers also play a central role in field development planning, recommending appropriate and cost-effective reservoir depletion schemes such as waterflooding or gas injection to maximize hydrocarbon recovery. Due to legislative changes in many hydrocarbon-producing countries, they are also involved in the design and implementation of carbon sequestration projects in order to minimise the emission of greenhouse gases.

<span class="mw-page-title-main">SimulationX</span> Software application

SimulationX is a CAE software application running on Microsoft Windows for the physical simulation of technical systems. It is developed and sold by ESI Group.

<span class="mw-page-title-main">Reservoir modeling</span>

In the oil and gas industry, reservoir modeling involves the construction of a computer model of a petroleum reservoir, for the purposes of improving estimation of reserves and making decisions regarding the development of the field, predicting future production, placing additional wells and evaluating alternative reservoir management scenarios.

The black-oil equations are a set of partial differential equations that describe fluid flow in a petroleum reservoir, constituting the mathematical framework for a black-oil reservoir simulator. The term black-oil refers to the fluid model, in which water is modeled explicitly together with two hydrocarbon components, one (pseudo) oil phase and one (pseudo-)gas phase. This is in contrast with a compositional formulation, in which each hydrocarbon component is handled separately.

Computer Modelling Group Ltd., abbreviated as CMG, is a software company that produces reservoir simulation software for the oil and gas industry. It is based in Calgary, Alberta, Canada with branch offices in Houston, Dubai, Bogota, Rio de Janeiro, London and Kuala Lumpur. The company is traded on the Toronto Stock Exchange under the symbol CMG.

Worst Case Discharge (WCD) is a calculation used by the Bureau of Ocean Energy Management, Regulation and Enforcement to determine the maximum flow rate for an offshore oil well in the event of an oil spill. WCD first came to prominence in the aftermath of the Deepwater Horizon Oil Spill to determine potential liability if another oil spill were to occur.

Integrated asset modelling (IAM) is the generic term used in the oil industry for computer modelling of both the subsurface and the surface elements of a field development. Historically the reservoir has always been modelled separately from the surface network and the facilities. In order to capture the interaction between those two or more standalone models, several time-consuming iterations were required. For example, a change in the water breakthrough leads to a change in the deliverability of the surface network which in turn leads to a production acceleration or deceleration in the reservoir. In order to go through this lengthy process more quickly, the industry has slowly been adopting a more integrated approach which captures the constraints imposed by the infrastructure on the network immediately.

<span class="mw-page-title-main">MOOSE (software)</span> Finite element framework software

MOOSE is an object-oriented C++ finite element framework for the development of tightly coupled multiphysics solvers from Idaho National Laboratory. MOOSE makes use of the PETSc non-linear solver package and libmesh to provide the finite element discretization.

<span class="mw-page-title-main">Baghir A. Suleimanov</span>

Baghir A. Suleimanov — Petroleum Scientist, Doctor of Technical Sciences, Professor, Corresponding Member of Azerbaijan National Academy of Sciences

<span class="mw-page-title-main">Morris Muskat</span> American petroleum engineer

Morris Muskat was an American petroleum engineer. Muskat refined Darcy's equation for single phase flow, and this change made it suitable for the petroleum industry. Based on experimental results worked out by his colleagues, Muskat and Milan W. Meres also generalized Darcy's law to cover multiphase flow of water, oil and gas in the porous medium of a petroleum reservoir. The generalized flow equation provides the analytical foundation for reservoir engineering that exists to this day.

Morris Muskat et al. developed the governing equations for multiphase flow in porous media as a generalisation of Darcy's equation for water flow in porous media. The porous media are usually sedimentary rocks such as clastic rocks or carbonate rocks.

References

Other references

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