Vertical discretization should be fine enough for accurate accounting of gas percolation and migration and/or gravity over-ride or under-ride. It is usually a trial-and-error process to find the appropriate grid block sizes. and they may be dependent on operating conditions of wells in the simulation.
The 1st step in the workflow involves the reduction of noise in your seismic data and the creation of anedge-enhancing attribute (i.e. variance, chaos, dip deviation), highlighting special discontinuities.During the 2nd step, the Ant Track cube is created. The Ant Tracking algorithm follows an analogy ofants finding the shortest path between their nest and their food source by communicating usingpheromones, a chemical substance that attracts other ants. The shortest path will be marked with morepheromones than the longest path and so the next ant is more likely to choose the shortest route, and soon.The idea is to distribute a large number of these electronic "ants" in a seismic volume; and let each antmove along what appears to be a fault surface while emitting "pheromone." Ants deployed along a faultshould be able to trace the fault surface for some distance before being terminated. Surfaces meetingexpectations will be strongly marked by "pheromone." Surfaces unlikely to be faults will be unmarked orweakly marked. The Ant Tracking algorithm creates a new fault attribute highlighting the correspondingfault-surface features having orientations within some pre-determined settings. The algorithm thenautomatically extracts the result as a set of fault-patches, a highly detailed mapping of discontinuities.Manual interaction is provided in the 3rd step. The extracted fault patches must be evaluated, editedand filtered in order to obtain the final interpretation.This is done using an innovative approach applyingan interactive stereo-net and histogram filter tool.In the final step, the fault patches are used for further seismic interpretation or as input to the faultmodeling directly.
Let us see how can we do correlation with the help of petrel. Using flexible 2D visualization module available in petrel we can simultaneously view the log files of different adjacent wells side by side
SEDIMENTOLOGICAL MODEL: Also known as depositional model. It describes the type of depositional environment of the sediments (fluvial, deltaic, marine, etc.)CLASSIFICATION OF FACIES: Facies can be classified by setting the cut-off values in the log. i.e. simple sands-clays classification may be realizedby identifying a cut-off value in the gamma ray log. Once they are classified, they are compared with the available core data. In these way the accuracy of the characterization is maximized.3-DDISTRIBUTION OF FACIES: The 3-dimensional distribution of facies is usually obtained by applying stochastic algorithms.These algorithm when applied will help you to create the realistic model(fig. given on next slide).Thesemodel has a large #of cells (of order of millions), later on upon simplification and by reducing the #of cells these it would behave as the input for the dynamic model to simulate the production behavior of the reservoir.
Moving avg: a set of data is divided into several subsets and their mean avg value is computed. Then after again the mean avg value of new subset (preceding) is found out and so on. This is usually done to filter out noise, remove fluctuations to make it smooth.
Static model development
Static Model Development
Static model development |Section 1Section 2 .Section 3Section 4Section 5
Static model development |Section 1 Introduction to static reservoir modelingSection 2 For decision making and improving the estimation of reserves; a computer model of a reservoir is constructedSection 3 which we call as “The Reservoir Model”.Section 4Section 5
Building the model Real Model Computer Model ……How ?? CLICK HERE FOR MORE INFO
Introduction to static reservoir modeling Geocellular modeling It is a way to describe the subsurface in 3D space (mathematically), which is constrained by a structural and stratigraphic framework. In a layman’s language, it is the process of generating the model/prototype of the subsurface. This model will resemble the real reservoir model. The physical properties of the reservoir are stored at the grid points or at the centers of gravity (3D voxels). So the first thing is to define the GRID
Introduction to static reservoir modeling Grid The simulation grid is the definition of how we divide, or discretize, space in order to solve the differential equations numerically. Common grid co-ordinate system includes Cartesian Cylindrical Corner Point Curvilinear
Grid Simulation |Selection of proper GRIDIt is necessary that the grid that is defined should have desired level of accuracy inthe solution of the flow equations; properly represents the reservoir geology;locations of wells, boundaries, faults, etc. and has the lowest computer memoryand time requirements to solve the problem.Common rules of constructing GRID In case of cylindrical grid system, the grid spacing is at logarithmic scaledifference. The grid spacing should be such that the adjacent block size should notincrease by the factor more that 3. Even the pressure drop between the blocks should not decrease by 30-20 %. Reservoir flow units should be separated by grid block boundaries. Vertical discretization should be fine enough for accurate accounting of gaspercolation and migration and/or gravity over-ride or under-ride
Grid Simulation | using CMG simulator (version 2007.1) GRID type (Cartesian, corner or cylindrical) # of grid blocks in x, y and z direction respectivelyHere, 10 is width of the block and 3 is the # of blocks in each direction
Grid Simulation | using CMG simulator (version 2007.1) Date @ which simulation starts A block withwidth 10m each in x, y & z direction
Static model development |Section 1Section 2 .Section 3Section 4Section 5
Static model development |Section 1 Structural modelingSection 2 .Section 3Section 4Section 5
Structural Modeling |Using Petrel 2009 Seismic Simulator Identifying structural top Structural top identification means recognizing the geometric structure of hydrocarbon trap. The workflow(in petrel) for the same would be : Load SEG-Y format data. Interpret it manually. Full range of tools allows us to take a traditional line-by-line approach combined with the latest algorithms and tools including amplitude & waveform based tracking for best interpretation, allowing us to achieve rapid results
Structural Modeling |Using Petrel 2009 Seismic Simulator Interpreting set of faults Since the presence of fault/set of faults directly makes a huge difference to the field development plan and production characteristics…we need to carefully investigate it’s presence. Fault can be interpreted in the same way (as we seen the workflow in case of structural top). But consider only Sealing faults !!! BUT STILL … THERE CAN BE NUMEROUS FAULTS SO, MANUAL INTERPRETATION BECOMES TEDIOUS !
Structural Modeling |Using Petrel 2009 Seismic Simulator So many faults Can we do it automatically ???..
Structural Modeling |Using Petrel 2009 Seismic SimulatorThe Petrel Automated Structural All u need is ANTInterpretation module uses an TRACKING moduleadvanced computing algorithm "AntTracking" to overcome the tedious task.Benefits : Increases structural accuracy and detail & thus provides unbiased, repeatable & highly detailed mapping of discontinuities. Significantly reduces tedious manual interpretation time.
Structural Modeling |Using Petrel 2009 Seismic Simulator The Ant Tracking workflow consists of four independent steps: Enhance the spatial discontinuities in your seismic data using any edge detection algorithm (i.e. variance, chaos, edge Step 1 detection) and optionally, pre-condition your seismic data by reducing noise. Generate the Ant Track Cube and extract the fault patches. Step 2 Validate and edit the fault patches. Step 3 Create final fault interpretation model. Step 4
Static model development |Section 1 Stratigraphic modelingSection 2 .Section 3Section 4Section 5
Stratigraphic Modeling |Analytical approach Analytically the best technique to establish the correlation between thegeological units is by using the sequence stratigraphic method. As per this technique the deposition of sedimentary bodies is governed by thecombined effects of changes in sea-level, sedimentation, subsidence and tectonics. On this basis, we can identify sequences of different hierarchical order within a geological unit that are separated bysequence boundaries which representUnconformities or maximum floodingsurfaces.
Stratigraphic Modeling |Analytical approach Biostratigraphy Production data (density, GOR etc.)
Stratigraphic Modeling |Petrel v2009 Simulator In Petrel we can display and organize your logs in a flexible 2D visualization environment.
Stratigraphic Modeling |Petrel v2009 Simulator A flexible 2D canvas allows simultaneous display of logs, seismic, 3D grid, and simulation results.
Stratigraphic Modeling | Petrel v2009 Simulator The workflow for correlation can be given as follows :  Import well log las-file data : By importing well trajectories, well deviations and logs(las file) you can pick/select any horizon top and analysis it.  Create cross sections : Under “window” option select “new well section window”. Then you can select the #of wells (to display their cross section) Then after you can carry out other secondary operations (colorfill, thickness etc.)
Stratigraphic Modeling | Petrel v2009 Simulator Revise formation top picks &compare: Pick horizon tops in the well panel andsee the effects directly in 3D, or viceversa.Now you can compare the requiredsection of the well log to other sectionsby using “ghost curve” option in the righthand side bar of petrel.Using ghost curve you can clip out a smallsection of your seismic and drag it over toother parts to correlate acrossfaults.(refer to next slide)
Stratigraphic Modeling | Petrel v2009 SimulatorNow after selecting the portion, you candrag it to the other portion of the log tofigure out the similarity between them.(see the yellow curves in box)This operation is called ghosting. Evaluate real-time updated picks in2D and 3D interpretation windows :You can view the real time updated picksby turning ON (simply click on it) the wellsection fence.
Static model development |Section 1 Lithological modelingSection 2 .Section 3Section 4Section 5
Lithological Modeling | As a rule, facies Modeling can be performed using appropriate deterministic orstochastic functions which allow us to generate 2 or 3 dimensional spatialdistributions of significant characteristics, such as porosity and permeability, directlyfrom well data. The idea behind this procedure is that the petrophysical characteristics of thereservoir can be considered intimately linked to the lithological facies. In practical terms, the lithological model of a reservoir is constructed byintegrating an ideal representation of the reservoir (sedimentological model), aclassification stage (definition of facies) and a spatial distribution stage (three-dimensional model).
Lithological Modeling |. Classification of facies Sedimentological Model 3D distribution of facies Lithological Modeling
Lithological Modeling |. Example of a stochastic model of facies
Static model development |Section 1 Petrophysical modelingSection 2 .Section 3Section 4Section 5
Petrophysical Modeling |using Petrel v2004.The values between the cells are interpolated by various techniques. Two • Select the Moving average as the of the important techniques are: . Method; leave all other settings as • Deterministic Model default. • Stochastic Model • Click on OK; display the model in 3D window and it would appear like : Deterministic ModelIt uses moving average method, based oninverse distance weighting.• Open the petrophysical process optionfrom the menu.(this will open a dialogbox)• From the dialog box, select Use ExistingProperty and select the Porosity propertyas the property to be modeled from thedrop down menu.
Petrophysical Modeling |using Petrel v2004. Stochastic Model . Stochastic method : userThis method uses Sequential Gaussian defined variogram and range.Simulation method. To create stochasticModeling follow the given steps:• Open the Petrophysical Modelingprocess. Go to the Use Existingproperty and select Porosity from thedrop-down list.• Activate the required zone by clickingon the zone tab.• Select Sequential Gaussian Simulationas the method to use.• In variogram tab, select the Variogramtype. In it select the MajorRange, Minor Range, Vertical Range andAzimuth. Then after click on OK andcreate the property model.
References |Journal article, organization as author :ESSCA Group, LESSCA, la Grande Ecole directement Petrel 2009 Seismic to Simulation Software,2009.Petrel-A Schlumberger product group, Release notes; Petrel™ Workflow Tools 2004, November2004. .Encyclopaedia on the Internet : Portale Treccani. Lenciclopedia Italiana; Oil Field Characteristics and Relevant Studies [Internet], Italy Inc.; 2008, Available from : http://www.treccani.it/enciclopedia/oil-field-characteristics-and-relevant-studies_(altro)/Part of an Internet website :West Virginia University, Department of Geology and Geography [Homepage on Internet], WestVirginia : The University; c2008, Available from : http://www.geo.wvu.edu/~wilson/casi/