﻿ Visualization tutorial

## MRST - MATLAB Reservoir Simulation Toolbox

Visualization tutorial

# Visualizing in MRST

MRST contains a suite of visualization routines which make it easy to create visualizations of grids and results. This tutorial shows how to visualize grids, subsets of grids and details the different routines included in MRST.

## We define a simple two phase example

The following is only meant as an example for the visualization and will not be covered thourougly. Create a simple 3D Cartesian grid

```G = cartGrid([10, 10, 3]);
G = computeGeometry(G);
% Disable gravity
gravity off
% Set up uniform permeability and constant porosity
rock.perm = repmat(100*milli*darcy, [G.cells.num, 1]);
rock.poro = repmat(0.5            , [G.cells.num, 1]);
% A simple two phase system.
fluid = initSimpleFluid('mu' , [   1,  10]*centi*poise     , ...
'rho', [1014, 859]*kilogram/meter^3, ...
'n'  , [   2,   2]);
% Two wells, an injector at 1 bar and a producer at 0 bar.
W = verticalWell([], G, rock, 1, 1, [], ...
'Type', 'bhp' , 'Val', 1*barsa(), ...
'Comp_i', [0, 1]);

W = verticalWell(W, G, rock, 10, 10, [], ...
'Type', 'bhp' , 'Val', 0*barsa(), ...
'Comp_i', [1, 0]);

% Create a initialized state and set initial saturation to phase 1.
sol = initState(G, [], 0, [1, 0]);

% Find transmissibility.
T = computeTrans(G, rock);

% Reference TPFA
psolve = @(state) incompTPFA(state, G, T, fluid, 'wells', W);

% Implicit transport solver
tsolve   = @(state, dT) implicitTransport(state, G, dT, rock, ...
fluid, 'wells', W);
```

## PlotGrid

PlotGrid is an essential part of MRST's visualization routines. It simply draws a grid to a figure with a reversed z axis.

```clf;
plotGrid(G)
view(30,50)
```

## MRST and patch

All grid plotting routines are based on MATLAB's patch routine which enables plotting of general polygons. Any keyword arguments will be passed on to patch, which makes it possible to alter many attributes. For instance, we can replot the grid with partially transparent edges and faces in another color:

```clf;
plotGrid(G, 'EdgeAlpha', 0.1, 'FaceColor', 'blue')
view(30,50)
```

## plotGrid and subsets

plotGrid's second argument corresonds to a list of cells to be plotted. This can be either logical indices (a logical vector of length G.cells.num will plot Cell i if the ith element of the vector is true) or an explicit list of indices, i.e. the cell numbers to be plotted. To demonstrate this, we will plot all indices with equal values in a different color. Note that the plotting routines do not reset the figure between plots, making it easy to create compositions of different plots.

```clf;
equal_index = mod(1:G.cells.num,2) == 0;
plotGrid(G,  equal_index, 'FaceColor', 'red')
plotGrid(G, ~equal_index, 'FaceColor', 'blue')
view(30,50)
```

## plotCellData

Generally seeing only the grid is not that interesting. If we want to show actual values, we need to use plotCellData. Let us solve the reservoir pressure and plot it:

```sol= psolve(sol);
clf;
plotCellData(G, sol.pressure)
colorbar
view(30,50)
```

## plotCellData with subsets and plotWell

plotCellData is closely related to plotGrid. We can observe that the pressure has its largest values in the wells, which makes it seem that the pressure is almost homogeneous inside the domain. Let us then plot pressure values for the middle of the domain. We also plot an empty grid to see where we are actually plotting.

```[i j k] = ind2sub(G.cartDims, 1:G.cells.num);
clf;
plotGrid(G, 'FaceAlpha', 0, 'EdgeAlpha', .1)
plotCellData(G, sol.pressure, j == round(G.cartDims(2)/2))
% Plot the wells
plotWell(G, W);
view(30,50)
```

## plotFaces

Some data is given at a per face basis instead of cells. For this purpose we have plotFaces and plotFaceData which are analogous to plotGrid and plotCellData respectively.

```% Plot Faces with positive normals in z direction
clf;
plotFaces(G, find(G.faces.normals(:,3)>0));
view(30,50);
```

## plotFaceData

plotFaceData lets us plot face values, for instance when dealing with fluxes and faults. For an example, let us plot the faces colored by the z values of the face centroids.

```clf;
plotFaceData(G, G.faces.centroids(:,3));
view(30,50);
```

## Animated example

We will now simulate a simple transport problem between the wells. We will plot the empty grid and the wells, and in each time step we will visualize the saturation in the cells where the inejcted phase is above a threshold, here 0.05.

```dT = 10*day;
for i = 1:20
sol = tsolve(sol, dT);
sol = psolve(sol);
clf;
plotCellData(G, sol.s(:,2), sol.s(:,2)>0.05)
plotGrid(G, 'FaceAlpha', 0, 'EdgeAlpha', .1)
plotWell(G, W);
view(30,50);
pause(.5)
end
```

Published October 2, 2012