Fault Facies modeling

Fault Facies

Tveranger, J.1) , Cardozo, N.1) , Kjeldaas, G.C.1) , Nøttveit, H.1) and Røe, P.2) + Fault Facies Facies project team

Volumetric fault zone modeling using fault facies

1) 2)

Center for Integrated Petroleum Research, University of Bergen, Norway The Norwegian Computing Center

Department of Earth Science Department of Mathematics

Impressions „

Descriptions of deformed rock volumes

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Uncertainty?

Business end of structural geology

Very uncertain fault zone properties

Fault impact on reservoirs „

Displacement of stratigraphy (seismic/subseismic scale)

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Modification of the initial properties and structures inside a volumetrically expressed fault envelope „ „ „

Zonation (e.g. core, damage zone) Recurring structural features (fractures, lenses, membranes) Changes in petrophysical properties

Hangingwall damage zone

Fault core

Footwall damage zone

Background fracturing

Fossen et al.

Fault modeling practice „

Seismic interpretation – fault plane/fault sticks „

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Grid displacement (except sub-seismic faults)

Impact on fluid flow is included in the simulation model using transmissibility coefficients across grid splits. These can be derived from: „ „

History matching of model using production data Specialized software applications (HAVANA™, Juxtaposition™, TransGen™, a.o.) calculating permeability across fault planes as a function of lithology and displacement

Problematic features „

Petrophysical modelling

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Communication between nonnonjuxtaposed cells

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3D fluid flow inside fault envelope

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Drilling hazards

Severe limitations for explicit representation of the geology of the fault zone!

Shortcomings Observations

Model representation

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Seismic scale faults exhibit complex architectures

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Faults as planes with displacements of model grid

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Fault related changes in rock properties occur throughout a volume of host rock (fault envelope)

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Fault related spatial property changes in volume surrounding faults commonly not included

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Flow through faults is a result of how these petrophysical changes are distributed in the fault affected rock volume

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Fluid flow through faults approximated as 2D effect. Flow along faults and between reservoir zones with no juxtaposition can only be modeled deterministically (i.e. ”best guess” guess”)

Consequences for simulation model • Actual 3D flow inside and through fault zones is not captured • In-place volumes may be overestimated • Fault sealing is simplified by handling fault zones as homogenized at any given position along the fault plane • Communication along faults can not be forecast as the fault description does not include a Perm Z description. It can only be set ad hoc using history matching (no predictive value) •Discrepancy between observed well behavior and modeled behavior is often assigned to fault impact (makes it impossible to distinguish between effects caused by the sedimentary model and the structural model) – contribution of model components (sedimentological and structural) to overall model uncertainty can not be properly evaluated

Model scales & modeled elements Tectonic features

Sedimentary features Vertical scale (m)

Vertical scale (m) 1000

1000

100

100

Interpreted fault displacements from seismics

Seismic scale

1

Geological model

0.1

beds

0.1

0.01

0.01 laminae 0.001 0.001

0.01

0.1

1 10 100 Horizontal scale (m)

Adapted from Pickup & Hern (2002) „ „ „

1000

10000

Sim.model Fault zone elements

0.001 0.001

FF

Geological model

lenses

1

10

membranes

paraSim.sequences model

Sub-seismic scale

fractures/slip surfaces

10

Fault zone widths

0.01

0.1

1

10 100 1000 10000 Horizontal scale (m) (Read as thickness for fault zone elements)

Reservoir model scale is not inherently adapted for fault zone modeling; Current practice skips scales. Present fault modeling is largely dictated by software limitations Using facies as building blocks for fault zone architectures may be a means to bridge the gap and enable industrial reservoir models to incorporate more detailed geological descriptions of fault zone properties FF=Fault Facies: Informally defined as any feature or body of rock with properties derived from tectonic deformation

The Fault Facies project; aims „

Develop a method for explicit representation of fault structure in reservoir models „

Concept and technical solution „

Feasibility/compatibility

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Test methodology and identify performance critical elements in model setup

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Identify strengths and limitations of the method

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R&D cooperation CIPR, NR, Roxar, University of Bergen, the University Centre on Svalbard and industry

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30 senior researchers post docs and PhD students + 8 master students

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Sub-projects comprising basic and applied research in „ „ „ „ „ „

structural geology reservoir engineering mathematics software development rock physics reservoir modelling

Fault Facies

Fault zone models Required elements „

Volumetric representation of fault envelope (i.e. FZ grid) in reservoir model

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Description and classification system for elements occurring inside fault envelope and their petrophysical properties under given sets of boundary conditions

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Conditioning factors for position and distribution of fault facies inside the fault envelope; room for complex displacement trends

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UpUp-scaling methods

Sedimentary facies

Fault Facies with petrophysics

Deformation boundary conditions

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As for sedimentary facies, fault facies can be applied on any model scale defined by the user; facies definitions can be adapted to the available data and purpose of the model

Approach „

Develop an improved method for fault modeling within the framework of existing industrial modeling tools in order to ensure an easy incorporation of the new method into standard industrial modeling workflows and practices

Grid design and Software adaptation

Fault rock properties

TECHNICAL FRAMEWORK

FAULT FACIES DATABASE

Geo-modeling and simulation

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Scope of study limited to normal faults in siliciclastic rocks

Strain modeling

CONDITIONING PARAMETERS

Grid design IRAP-RMSTM, HAVANATM, ECLIPSETM

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HAVANA

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Conventional grid

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Define and extract fault zone Perform stretching Refine grid (optional) Merge with original

Fault Facies Grid

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Can be used as integral part of or add-on to any RMS model

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Fault facies grids are XY regularized corner point grids: no need to adapt grid stringently to interpreted fault planes „ No/few deformed cells in grid „

Deterministic element of interpreted fault plane position eliminated; position of maximum displacement inside fault zone determined by strain modelling

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Moves uncertainty from position of max displacement to margin of fault zone

Fault facies in geo-modelling „

All techniques used for modeling of sedimentary facies can be applied to the FF grid Indicator simulation Object based modeling Petrophysical properties Trend functions Conditioning parameters

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Modelling of fault facies can be performed at any scale and any level of detail as defined by user and available data

PermZ

PermX

PermY

“Grey matter” model with anisotropic permeability field in fault zone

Differentiated properties for fault rocks from surrounding formations

Highly detailed FF model with fault rock lenses

Geological input Outcrop analogues Empirical databases

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Stochastic modelling approach „

Define case specific elements „ „

Statistic models

FF types FF properties „ „ „ „

Strain modelling tools

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Geometry Dimensions Frequency distribution Petrophysical properties

Trends and conditioning parameters „ „ „

Displacement distribution inside fault envelope Strain distribution Intra-facies petrophysical property trends

Adapted from Fredman et al submitted

Geological input Fault facies petrophysical props

Petrophysical trend patterns

100 000,00

10 000,00

Tveranger et al in prep 10 000,00

Chile Tayieba mines

Tinyperm

1 000,00

Wadi Kahboba Wadi Isaila Bartlett fault 100,00

Permeability

1 000,00

Horizontal Perm

100,00

Vertical perm

Navajo SST

10,00

10,00

1,00 0,0

1,0

Host rock

2,0

3,0

4,0 Category

5,0

Fault facies

6,0

1,00 0,00

7,0

5,00

10,00

15,00

20,00

25,00

Distance from fault

1 000,00

100,00

Even very simplified input and data with high variability help to constrain the model

10,00

Permeability

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V/H 1,00 0,00

Distance between DB's 5,00

10,00

15,00

0,10

0,01

0,00 Distance from fault

20,00

25,00

DBdist/(V/H) (V/H)/DBdist

Strain modeling using HavanaTM

Cardozo et al submitted

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Used as tool for testing conditioning methodology + Operates on structured corner point grids User defined width of fault zone Yields comparable results to more advanced tools FAST Displacement formula can be easily modified Restrictions as to mechanical layering

Conditioning the distribution of fault facies

Original model with FF grid

Database derived or user defined functions

Strain modelling tool

Displacement function

Strain distribution

Sedimentary facies F1

User defined facies and properties

Fault facies intensities

F1

F12

F11

F2

F22

F21

F2

X

Adapted from Fredman et al submitted

Fault Facies vs. Strain distribution

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FF model workflow Conventional geo modelling

Gridding

Fault facies modelling loop Fault zone

FF-Gridding

Facies

FF-Facies

Petrophysics

Petrophysics

FF intensity parameters

Fault trans.calc. Combine grids

Flow simulation

Conventional rendering

Fault zone with fault facies

Simulation „

Host rock Facies Sand Shale

Log(Kx) Log(Ky) Log(Kz) Poro 5.0 ± 0.5 5.0 ± 0.5 2.0 ± 0.5 0.20 ± 0.02 1.5 ± 0.7 1.5 ± 0.7 0.5 ± 0.3 0.05 ± 0.03

For details see Soleng et al. 2007

Fault Facies Sand 1 Sand 2 Sand 3 Sand 4 Shale 1 Shale 2 Shale 3 Shale 4

Illustration case „ Synthetic model „ 2200m x 2200mX 300 m „ Cell dimensions 20 X 20 X 20 „ Single fault 0-100 m displacement „ One injector in HW one producer in FW „ Rate controlled prod. and inj. „ Simulation time 5600 days „ FF grid 120 m wide „ Two Host rock facies „ Eight fault facies „ 100 model realizations

Log(Kx) 5.0 ± 0.7 4.3 ± 0.5 3.2 ± 0.5 2.0 ± 0.5 1.5 ± 0.7 1.4 ± 0.5 0.0 ± 0.5 -1.4 ± 0.5

Log(Ky) 5.0 ± 0.7 2.5 ± 0.5 1.5 ± 0.5 0.8 ± 0.5 1.5 ± 0.7 0.5 ± 0.5 -0.8 ± 0.5 -2.0 ± 0.5

Log(Kz) 2.0 ± 0.3 4.1 ± 0.5 3.0 ± 0.5 1.8 ± 0.5 0.5 ± 0.3 1.2 ± 0.5 -0.1 ± 0.5 -1.6 ± 0.5

Poro 0.20 ± 0.03 0.20 ± 0.05 0.15 ± 0.04 0.10 ± 0.03 0.05 ± 0.03 0.03 ± 0.012 0.02 ± 0.008 0.01 ± 0.007

Water cut vs. time

FF model Fault zone 12 cells wide 30 cells high

Upscaled FF model 1 Fault zone 6 cells wide 15 cells high

Upscaled FF model 2 Fault zone 1 cell wide 15 cells high

Conventional model With trans. mult. No fault zone For details see Soleng et al. 2007

Oil production rate vs. time

GOR vs. time

Strengths and limitations of FF modeling; status „

Strengths „ Geo-realistic rendering of structural elements in fault zone in geo and simulation models „ Method integrated into standard reservoir modeling workflows „ Flexible - Can be used on any scale and adapted to available data and user requirements „ Allows well conditioning of model „ Uncertainty handling using standard stochastic facies modeling methods „ Potential for modeling and forecasting fluid flow inside fault envelope „ Provides a clear separation between deformed and undeformed parts of the reservoir „ Potential for Improved uncertainty evaluation „ Improved risk assessment when drilling faults

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Current limitations „ Incomplete databases on fault facies descriptions and properties „ Systematic empirical links between strain distribution and fault facies need to be established „ Insufficient knowledge about up-scaling methods to be used on volumetrically rendered fault rocks „ Sensitivity mapping of parameters and assessment of artifacts in FF type models still incomplete „ CPU cost for large, high detailed models

Upcoming activities „

Geophysical conditioning and seismic signature of fault facies models models (pilot study)

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Fault zone properties (continued from FF I) „ Expand existing FF databases through lab and field studies „ Characterization of Fault Facies of different reservoir rocks

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Fault process studies „ Strain modelling Havana, Trishear, (DEM), „ Fault zone evolution, „ Stress modelling „ Deformation impact on porosity and permeability

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Reservoir modelling and simulation „ Workflows and software development „ Virtual reality „ Analogue models, case studies and synthetic tests „ Strain & fluid flow „ MPFA „ Adaptive gridding vs regular cornerpoint grids – impact on fluid flow „ CO2/leakage (case studies?)

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UpUp-scaling techniques for FF

Full field test model

Emerald Resolution 75X75X3 m Stratigraphic thickness 129 m Model 6.2 X 9.5 km

Thank you for your attention SEE ALSO: Fachri et al. Poster, this conference : Sensitivity of fluid flow to faulted siliciclastic reservoir configurations & Presentations by Braathen, Nøttveit and Schueller, This conference

Department of Earth Science Department of Mathematics