Surfaces and surface attributes

This section offers an overview of the different functions and properties available for the Petrel Surface object subcategories.

Surfaces

Check out the API documentation to view a detailed description of all the functions and properties available for working with surfaces.

from cegalprizm.pythontool import PetrelConnection
petrel = PetrelConnection()

The .surface property returns all the surfaces as a dictionary where the keys represent the path of the surface within the Petrel input tree and the values represent the name of each surface:

petrel.surfaces

Surfaces({'Input/Depth surfaces/Top Etive (Depth 1)': Surface(petrel_name="Top Etive (Depth 1)"), 'Input/Velocity Data/Top Ness [Final]': Surface(petrel_name="Top Ness [Final]"), 'Input/Surfaces (Time)/Top Etive': Surface(petrel_name="Top Etive"), 'Input/Surfaces (Time)/Base Cretaceous': Surface(petrel_name="Base Cretaceous"), 'Input/Isochores (depth)/Ness/Ness-2': Surface(petrel_name="Ness-2"), 'Input/Depth surfaces/Top Tarbert (Depth 1)': Surface(petrel_name="Top Tarbert (Depth 1)"), 'Input/AOI Model': Surface(petrel_name="AOI Model"), 'Input/Depth surfaces/Base Cretaceous (Depth 1)': Surface(petrel_name="Base Cretaceous (Depth 1)"), 'Input/Surfaces (Time)/Seabed': Surface(petrel_name="Seabed"), 'Input/Velocity Data/Top Tarbert [Final]': Surface(petrel_name="Top Tarbert [Final]"), 'Input/Depth surfaces/Top Ness (Depth 1)': Surface(petrel_name="Top Ness (Depth 1)"), 'Input/Surfaces (Time)/Top Ness': Surface(petrel_name="Top Ness"), 'Input/Isochores (depth)/Tarbert/Tarbert-1': Surface(petrel_name="Tarbert-1"), 'Input/Velocity Data/Base Cretaceous [Final]': Surface(petrel_name="Base Cretaceous [Final]"), 'Input/Surfaces (Time)/Top Tarbert': Surface(petrel_name="Top Tarbert"), 'Input/Velocity Data/Top Etive [Final]': Surface(petrel_name="Top Etive [Final]")})

We can iterate over all the surfaces within the dictionary and print out their names:

for s in petrel.surfaces:
    print(s.petrel_name)

Top Etive (Depth 1)
Top Ness [Final]
Top Etive
Base Cretaceous
Ness-2
Top Tarbert (Depth 1)
AOI Model
Base Cretaceous (Depth 1)
Seabed
Top Tarbert [Final]
Top Ness (Depth 1)
Top Ness
Tarbert-1
Base Cretaceous [Final]
Top Tarbert
Top Etive [Final]

To select the Top Etive surface, we can create a list of paths for all of the surfaces and then use list slicing to access the surface we want. The argument paths[2], selects the third item from the list you get from paths = list(all_surfaces.keys()):

all_surfaces = petrel.surfaces
paths = list(all_surfaces.keys())
Top_Etive = petrel.surfaces[paths[2]]
print(Top_Etive)

Surface(petrel_name="Top Etive")

To determine the size of the surface we can use the .extent property, which returns the number of surface nodes in the i and j directions:

extent = Top_Etive.extent
print(extent)

Extent(i=236, j=268, k=1)

The .coords_extent returns the extent of the surface in world-coordinates (Xmin, Xmax, Ymin, Ymax, Zmin, Zmax):

coord_extent = Top_Etive.coords_extent
print(coord_extent, '\n')
print(f'x: {coord_extent.x_axis}')
print(f'y: {coord_extent.y_axis}')
print(f'z: {coord_extent.z_axis}')
print()

CoordinatesExtent(x_axis=AxisExtent(min=450800.000000, max=459080.000000), y_axis=AxisExtent(min=6780240.000000, max=6790240.000000), z_axis=AxisExtent(min=-2278.070000, max=-1643.700000))

x: AxisExtent(min=450800.000000, max=459080.000000)
y: AxisExtent(min=6780240.000000, max=6790240.000000)
z: AxisExtent(min=-2278.070000, max=-1643.700000)

The returned results of the .extent and .coords_extent properties can also be visualized in Petrel by accessing the Statistics of the selected surface:

Using the .position() function we can retrieve the x,y,z position of the surface node by specifying the i and j-index of the surface node:

i = 11
j = 20
pos = Top_Etive.position(i, j)
print(f' {i}, {j}: {pos}')

 11, 20: Point(x=451000.00, y=6781040.00, z=nan)

Similarly, using the .indices() function we can retrieve the indices of the surface node nearest the specified point. Note that the node indices are 0-based, but in the Petrel UI they are 1-based:

inds = Top_Etive.indices(pos.x, pos.y)
print(f'{pos}: {inds.i}, {inds.j}')

Point(x=451000.00, y=6781040.00, z=nan): 11, 20

The .parent_collection property will return the selected surface and all its siblings in the Petrel Input Tree:

sibling_surfaces = Top_Etive.parent_collection
for Top_Etive in sibling_surfaces:
    print(f'\t{Top_Etive.extent}\t{Top_Etive.petrel_name}')

        Extent(i=286, j=180, k=1)       Seabed
        Extent(i=238, j=291, k=1)       Base Cretaceous
        Extent(i=237, j=269, k=1)       Top Tarbert
        Extent(i=235, j=269, k=1)       Top Ness
        Extent(i=236, j=268, k=1)       Top Etive

To check the available surface attributes for the selected surface we can use the .surface_attributes property:

for atr in Top_Etive.surface_attributes:
    print(atr)

SurfaceAttribute(petrel_name="TWT")
SurfaceAttribute(petrel_name="Depth 1")

Surface attributes

Check out the API documentation to view a detailed description of all the functions and properties available for working with surface attributes:

• Continuous attributes

• Discrete attributes

The .surface_attributes property returns all the continuous surface attributes as a dictionary where the keys represent the path of the surface attribute within the Petrel input tree and the value represents its name:

petrel.surface_attributes

SurfaceAttributes({'Input/Surfaces (Time)/Base Cretaceous/Depth 1': SurfaceAttribute(petrel_name="Depth 1"), 'Input/Surfaces (Time)/Top Tarbert/TWT': SurfaceAttribute(petrel_name="TWT"), 'Input/Surfaces (Time)/Top Ness/Depth 1': SurfaceAttribute(petrel_name="Depth 1"), 'Input/Surfaces (Time)/Top Etive/TWT': SurfaceAttribute(petrel_name="TWT"), 'Input/Surfaces (Time)/Top Tarbert/Depth 1': SurfaceAttribute(petrel_name="Depth 1"), 'Input/Surfaces (Time)/Top Etive/Depth 1': SurfaceAttribute(petrel_name="Depth 1"), 'Input/Surfaces (Time)/Top Ness/TWT': SurfaceAttribute(petrel_name="TWT"), 'Input/Surfaces (Time)/Base Cretaceous/TWT': SurfaceAttribute(petrel_name="TWT")})

Similarly, we can retrieve a dictionary of all the discrete surface attributes by using the .surface_discrete_attributes property:

petrel.surface_discrete_attributes

SurfaceDiscreteAttributes({'Input/Surfaces (Time)/Top Etive/Facies': SurfaceDiscreteAttribute(petrel_name="Facies")})

We can iterate over all the surface attributes and return their names:

print('Continuous surface attributes:', '\n')
for sa in petrel.surface_attributes:
    print(sa.petrel_name)
print('\n','Discrete surface attributes:', '\n')
for sa in petrel.surface_discrete_attributes:
    print(sa.petrel_name)

Continous surface attributes

Depth 1
TWT
Depth 1
TWT
Depth 1
Depth 1
TWT
TWT

 Discrete surface attributes

Facies

Let’s select the depth surface attribute which belongs to the Top Etive surface:

all_surfaces_atr = petrel.surface_attributes
paths = list(all_surfaces_atr.keys())
Top_Etive_Depth = petrel.surface_attributes[paths[5]]
print(Top_Etive_Depth)

SurfaceAttribute(petrel_name="Depth 1")

We can check if the selected attribute belongs to the Top Etive surface using the .surface property:

parent_surf = Top_Etive_Depth.surface
print(parent_surf)

Surface(petrel_name="Top Etive")

To check what other attributes the selected surface has we can use the .surface_attributes property:

for attr in parent_surf.surface_attributes:
    print(f'{attr}')

SurfaceAttribute(petrel_name="TWT")
SurfaceAttribute(petrel_name="Depth 1")
SurfaceDiscreteAttribute(petrel_name="Facies")

Petrel represents some undefined values by MAX_INT, and others by NaN. The undef value of the surface attribute can be returned using the .undef_value property:

print(Top_Etive_Depth.undef_value)

nan

The .template property returns the Petrel template for the surface as a string. If no template is available, it will return an empty string. Similarly, using the .unit_symbol property, we can access the unit for any object associated with a certain template. In Petrel, you can access this data by opening the global settings for the selected property template.

print('Template:', Top_Etive_Depth.template)
print('\n')
print('Unit:',Top_Etive_Depth.unit_symbol)

Template: Elevation depth


Unit: m

The .has_same_parent() function checks if two attributes belong to the same parent surface. In the example, below we assign two different surface attributes to the variables attr0 and attr1. The .has_same_parent() checks if the two belong to the Top Etive surface and returns a boolean value:

attr0 = petrel.surface_attributes[paths[0]]
attr1 = petrel.surface_attributes[paths[3]]
print(f'{attr1} and {Top_Etive} has same parent: {attr1.has_same_parent(Top_Etive_Depth)}')
print(f'{attr0} and {Top_Etive} has same parent: {attr0.has_same_parent(Top_Etive_Depth)}')

SurfaceAttribute(petrel_name="TWT") and Surface(petrel_name="Top Etive") has same parent: True
SurfaceAttribute(petrel_name="Depth 1") and Surface(petrel_name="Top Etive") has same parent: False

We can create a chunk that contains all the values for the attribute by using the .all() function. To learn more about chunks please view the Working with chunks subchapter of the User Guide.

Top_Etive_Depth.all()

<cegalprizm.pythontool.chunk.Chunk at 0x1fc8683f040>

Alternatively, using the .chunk() function, we can select only a range of the surface attribute that we want to convert into a chunk:

i = (11, 25)
j = (20, 40)
Top_Etive_Depth.chunk(i,j)

<cegalprizm.pythontool.chunk.Chunk at 0x1fc7a0d4070>

For the discrete surface attributes, we can return a dictionary of the discrete codes and values using the .discrete_codes property:

all_surfaces_atr = petrel.surface_discrete_attributes
paths = list(all_surfaces_atr.keys())
Top_Etive_Facies = petrel.surface_discrete_attributes[paths[0]]

Top_Etive_Facies.discrete_codes

{0: 'Clay', 1: 'Sand', 2: 'Silt', 3: 'Fine Silt'}