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LD-MKT simulator
Reservoir numerical simulator

 

Reservoir Numerical Simulation System

LD-MKT simulator (MKT simulator, for brevity) is an advanced hydrodynamic simulation system designed by LandOcean as part of the next generation of tools for simulating and developing oil and gas fields. МКТ simulator uses the latest computer and engineering science and technology available to provide a robust, efficient, accurate, and fast modeling system for simulation. System features include corner point geometry, the extended Black-Oil mode (3D), three-phase flow including the effects of gas dissolved in the oil phase and volatile oil vaporized in the gas phase. MKT simulator incorporates the best modern methods and approaches to generate approximate solutions to differential equations, yielding accurate results for even very complex grids. The system uses the support operator method, developed under the guidance of the academician Samarsky, for the approximation.

 

Irregular up-scaling technology
Currently popular packages use an upscaling technology that we call regular upscaling. Indeed, this is not hydrodynamically correct because it cannot retain the heterogeneity of geological bodies after upscaling. The flow direction shown in the following figure might be changed (to left, to right, up or down) while the flow direction might be different for cells 1 and 4. The quantitative criterion of up-scaling quality is the “topology” coefficient, which is calculated as the ratio of the sum of permeable cell thicknesses to the package thickness. For the case of regular upscaling, this ratio is normally much less than unity.

 

Alternatively, in the process of irregular upscaling,the upscaling of geological models begins in vertical columns, either with respect to a user specified number of layers in the coarse grid, or automatically.The same method spreads laterally. This “lumping” algorithm minimizes the changes in geometry and the connectivity of layers. In this case, the “topology” coefficient can commonly reach unity, or 1. The differences between the results of the two upscaling techniques are very obvious (see the above figure).This technology can retain the heterogeneity of geological bodies by introducing hydrodynamic equivalents (pseudo functions of relative permeability and critical saturations) into the model.  The algorithm for up-scaling grid properties solves a second task – the flow process simulated on the coarse grid has to be equal to the simulation on the fine grid with respect to minimal deviation of dynamic characteristics (current oil and water saturations of cells) and final quantities (cumulative oil, water and gas productions and their vertical distribution). For this purpose, the module calculates additional cell parameters: residual oil saturation, vertical connectivity multipliers, modified relative permeability and saturation function regions.

 

                                 Vertical shape of regular grid         Vertical shape of irregular grid                                            

 

Unique predictor-corrector method
Apart from the problem of space approximation precision there is the problem of time approximation. The belief that the use of fully-implicit schemes allows the simulation of any model with arbitrary large time steps is inaccurate. In the presence of physical instability with a certain specific evolution time, it is impossible to detect this instability when using fully-implicit schemes with large time steps. Implicit schemes guarantee the stability but not the precision. An explicit-implicit scheme with proper choice of time steps is preferable.

Implicit-explicit difference schemes are used in MKT simulator. These schemes are based on Godunovs predictor-corrector method. Compared with the common implicit pressure and explicit saturation method, MKT simulator uses predictor methods for solving for time step, pressure and saturation. MKT simulator avoids the problem of “time-chopping” because it has a special algorithm which precisely determines each time step. This reduces memory requirements and allows faster simulations. This method consists of the following steps

1. Implicit calculation of the pressure equation using known saturation values
2. Explicit calculation of saturation using a process splitting method
3. A thermodynamic adjustment of the saturation solution


In addition, it should be noted that non-linear iterations and the matrix inversion are the most time consuming procedures. Thus, it is much better to use the divergent closure which provides the local thermodynamic equilibrium instead of converging non-linear iterations, since that avoids the inversion of a large-dimension matrix. Fully dynamic memory allocation is also supported in MKT simulator.

 

The support-operators method

This method replaces the finite difference method used in common practice to minimize the error due to non-orthogonal flow, which occurs in every form of grid geometry—except rectangular grids. This error is inevitable in formations with a large obliquity since they require non-orthogonal grids in the vertical section. The support operators method uses a successful approach to get a high precision solution in the non-orthogonal grid. For comparison, the shape of a flooding front edge is very different when generated by the support operators method and the finite difference method—the later method is obviously influenced by non-orthogonal grids.

                               

Elliptical flooding front edge from finite difference                            Circle flooding front edge from MKT 

 

3D modeling of the near wellbore region
If there is flow near a borehole along the wellbore, it is necessary to change Peacemans formula since a source of fluid appears in cells without perforations. This is seen in the direct calculations of 3D flow near the borehole through a vertical set of cells. As a result, it is possible to include the structure of the near-well region and the zone around the bottom of the well. We believe this feature is unique to MKT among all common and commercially available simulators.

                      

                                           Peaceman method sketch map                                           MKT 3D modeling sketch map

 

Full tensor permeability
A fractured volume of rock can be considered as an anisotropic continuum in terms of flow. The permeability for this volume is a tensor quantity, and can be described by the coefficients of the anisotropic tensor. MKT simulator uses a special method, developed by LandOcean for determining these coefficients. This method recognizes that flow in fractured cells is not, in general, cylindrical and cannot be fully described simply by a vertical and radially symmetric permeability. For that reason, the MKT technique substitutes Peacemans formula with a direct calculation of the non-cylindrical flow from (or to) fracture cells. This method takes into account the dependence of the flow rate in fractured cells on the direction of the flow in the horizontal plane.

 

Hydraulic racturing
Common simulators (for example Eclipse 100) does not have the capability for hydraulic fracture modeling, except for skin-factor modification or LGR. There is the option FWELLS in Eclipse 300, but it only allows for vertical fractures in two directions (X or Y), thus it is not possible to determine fracture and proppant properties. When modeling hydraulic fracturing, MKT simulator takes into account the fracture azimuth, the length, the width and the height, and the proppant permeability. Dynamic fracturing is also supported.

 

        

 

Representation of full permeability

 

   

Full permeability application in hydrodynamic measure

 

 

 

 

Particular function for pre- and post-processing

MKT simulator has a function specifically designed for the visualization of model characterization and simulation results and. This feature can render a local model in the perspective best for viewing, and allows the user to modify the model as well as how the data are visualized. MKT simulator allows for several multiple windows to be viewed simultaneously—for example, the user can view flux profiles and well production history and calculation process at the same time. MKT simulator can handle very large models with more than tens of millions of cells.

 

             

 

Multiple windows show results simultaneously                     Dual medium viewing and modifying

 

Grid downscaling technology
During upscaling, some protocol files are reserved. When the simulation is complete, some flux files, saturation files, and pressure files are produced. Using these files, a downscaling process can show the distribution of oil, water and gas in the original geological model. This is a unique technique in this field.

             

Rough resolution in common simulator                      Sharp resolution in MKT

 

Critical pressure
Darcys law is valid only for Newtonian fluids over a specific velocity range. Further, it has been shown in experiments that in the case of small pressure gradients, i.e. less than a critical gradient, fluid remains stagnant. Other simulators ignore the presence of critical pressure gradients. This leads to overestimating the conformance efficiency. MKT simulator includes critical pressure gradients in its simulation—generating more accurate results that become very important when dealing with heavy oil fields.


For high filtration velocities, it is necessary to apply Forchheimers law which states that at high gas velocities there is a detrimental effect due to turbulence. MKT simulator has an option to include Forcheimers law in its simulations, unlike other commercial packages.

 

 

          

Not accounting for critical pressure                         Accounting for critical pressure

 

Optimal partitioning in parallel calculation
For multiprocessor systems, parallel processing achieves the highest efficiency and speed by using a partitioning that automatically balances the load across all processors. MKT simulator uses parallel processing that maintains high efficiency for an increasing number of processors.

 

  

                                                    The relation between CPU time and the number of processors in a massive simulation

 

 

Module Descriptions

 

AutoLink
 
Autolink is an upscaling module that converts the geological model into a grid of cells that can be simulated—the properties of each cell are derived from the geological data in the cell volume.
Upscaling steps
●   Project description
●   Specify fine grid dimensions and input files
●   Specify relative permeabilities and fluid viscosities            
●   Specify correlations for residual saturation, with respect to porosity, permeability, or initial oil saturation 
●   Specify dimensions of the coarse grid
●   Control up-scaling in the X,Y, and Z-directions
 
 
Conversion steps
●  Read input data
●  Convert model
 
MKT
MKTTM simulator is a modern reservoir simulator for oil and gas field development. MKT simulator uses the extended 3D Black-Oil model—three phase flow, including the effects of the gas dissolved in the oil phase and the volatile oil vaporized in the gas phase. MKT simulator is based on investigations made by scientists of the Keldysh Institute for Applied Mathematics of the Russian Academy of Sciences.
MKT simulator uses corner point geometry. Using the best available modern methods and approaches to the approximation of differential equations leads to accurate results, even for very complex grids. The support operator method and the predictor–corrector method developed under the guidance of the academician Samarsky is used for the approximation. To increase the accuracy, a 15-point schema is used that gives MKT simulator significant advantages in calculation power over other analogous simulators.
 
Key advantages
● High speed and accuracy of simulations
● High resolution of fluid movement fronts
● Wide class of grids, including non-orthogonal and unstructured grids
● Minimal orientation error for highly deformed grids
● The predictor-corrector algorithm allows decreasing the implicit matrix size
● Special algorithm for choosing the time-step allows faster calculations with high accuracy
● Special algorithm for critical pressure grads.
 
 
MKT office
MKT office is used to edit and visualize the model in 3D and in 3 phases. Features include editing and modifying the parameters of a model, starting the simulation calculations, reading and analyzing the calculation results, and visualizing and modifying portions of the model from various perspectives.
 
Project creation and definition
●Create new projects
●Modify existing projects
 
Data input
● Import geological and reservoir simulation models, the results of simulation and observations, and PVT properties. 
● Allow the input of data in VIP and eclipse formats.
● Allow the modification of well parameters and history data.
 
Data visualization
● Allow 3D and 2D visualization of the parameters of a model.
● Allow visualization of a portion of the model and the parameters for that portion.
● Allow local visualization in detail.
● View and exporting graphical output of simulation results.
● Visualize various kinds of data and compare windows side by side—wells, regions, full field comparison maps of calculation vs. observed data, etc.
 
Data processing
● Modify model parameters as needed
● Modify or define the PVT and relative permeability data
● Modify or define well data
●Check and modify well history data
 
Other functions
● Automatically or manually correct the model files as needed
● Create a fully gridded model for calculation
● Submit the reservoir model as input for simulation
● Keep record of all processes and modifications of the data

 

Delink

This module uses protocol files generated during the upscaling process in Autolink and dynamic field fluid data to essentially reverse the simulation and get the original fluid saturation distribution in the geological model. Functions include

● Read data
● Perform the downscaling calculations
● Output the results of downscaling for viewing.

  

Software Technology and Requirements

 Version——This is the first version of MKT, called MKT

Licensing——One software dongle for each MKT package purchased.

 

Software and hardware requirements

Operating system——Microsoft® Windows XP Professional (Sp2),   Microsoft® Windows 2000  (Sp4)

Office application——Microsoft® Office 2003,   Microsoft® Office XP

Whats in the box?——Software setup disk, a software dongle, a printed manual. 

 

 

 

assemble

elemental

best

1

processor

Inter Pentium4 1.5GHz

Inter Pentium processor4cores3.0GHZ and up

2

EMS

256MB

4GB or more

3

Hard disk

40GB

500GB or more

4

video card

64MB graphical

512MB with  NVIDIA or ATI

5

monitor

17inches

19inches

 

 
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