Fault modelling software from Badleys: TrapTester & TransGen

TrapTester is a structural analysis toolkit Suite of advanced functionality in one environment for fault trap integrity analysis & risking Tools for … Visualizing, interpreting and analyzing fault & horizon data Building faulted framework models with stratigraphic & property infill Predicting fault trap integrity with pressure, stress & mechanical data (fault seal analysis, column height prediction, fracture stability …) What is TrapTester? …the software formerly known as FAPS

Horizon & Fault interpretation Well data* (paths, curves, well-based picks) Seismic data* (SeisWorks, IESX, Charisma) (* import only) Interpretation Data – Direct links IESX & Charisma GF3.8, 4.0 Two-way link (import/export) One-way link (import only) OpenWorks R2003, Also extensive ascii I/O e.g. Fault & horizon surfaces as tri-mesh / grids, inc. RMS, Petrel formats Faults and horizons on vertical & horizontal sections Fault surfaces & framework polygons as XYZ data Wells, well picks, attribute logs

Framework model using intersecting faults Create intersecting faults (with automatic functions) and analyse all faults at same time Result: 3D geometric tie of horizons & fault polygons across all faults and modelling of displacement across branchlines Displacement is partitioned across branchlines

Fault-displacement mapping to quality-check interpretation Problem: Discrepancy in fault polygon due to anomaly in horizon interpretation that may be due to mis-picks, absence of other faults, etc Solution: Interpret new structure or edit horizons on sections or in 3D Edit fault polygons directly on fault surface

Solution: Generate well-based horizon picks (markers) and populate model with 3D isochore in-fill surfaces that properly honour the faulting Result: A structurally-valid framework model, with detailed reservoir-scale stratigraphy at fault surface Allan fault-plane diagrams Problems: Seismic horizons too widely spaced to depict detailed reservoir stratigraphy required for fault-seal analysis.

Stratigraphic in-fill Reservoir intervals on fault Infill to volume Reservoir intervals and horizon surfaces are then populated with Vshale from wells for use in the SGR algorithm

Allan diagram – shows areas of juxtaposition seal and areas of potential cross-fault leakage Downthrown Red juxtaposed against Upthrown Yellow Yellow reservoir zones self- juxtaposed across fault Areas of reservoir non-overlap = juxtaposition seal at fault. Grey = non-reservoir sealing lithology on both sides of fault plane. up down Downthrown Yellow juxtaposed against Upthrown Green

Determination of potential leak points in the trap complex Faults with only the potential leak points highlighted Fault zone composition (SGR) calculated using well model (or acoustic impedance volume) 15%30%50% SGR Shale Gouge Ratio painted onto reservoir juxtaposition areas (leak points on Allan diagram) Green = low SGR = high risk of cross-fault leakage Red = high SGR = low risk of cross-fault leakage

Seismic fault slicing Seismic slices are extracted from the 3D volume, on either side of the fault Up to 5 slices from each side (e.g. 25m, 50m, 75m, etc) Displayed on the fault plane Excellent for visualisation of reflection pattern on each side of the fault, for QC of modelled juxtaposition relationships Footwall (upthrown) seismicHangingwall (downthrown) seismic

Fault seal analysis using fault slices from inverted seismic volumes Result : Seal potential for all faults derived directly from volume properties (green low, red high seal potential) Seismic volume inverted to Vshale Problem: Very difficult to predict reservoir-scale layering and variation in interval properties in areas of complex stratigraphy, such as channel systems etc. Solution: Use inverted seismic data (calibrated to lithology, e.g. Vshale) and integrate volume property with displacement fields on faults

Length vs Throw Lateral extent of fault traces in areas of poor or sparse data quality and can be used as an aid to correlating fault segments in 2D data sets Frequency Plots Predict the number of faults with throws of a certain value less then the limit of seismic resolution Array summation & fault related strain Examine partitioning of displacement between different elements of a fault array and calculate the fault-related strain in a particular area Fault statistics and analysis – based on sampling the faulted horizon framework

Likelihood of fault reactivation Methodology developed in collaboration with National Centre for Petroleum Geology & Geophysics (NCPGG), University of Adelaide. Assessment of fault reactivation likelihood by looking at how far the stresses acting on a fault plane are from tensile and/or shear failure. Leakage of hydrocarbons along the fault zone is more likely when the “slip tendency” is high (i.e. the elevation in pore pressure required to induce failure is low). Input data: Pore pressure data points (gradients, depths, pressures) In situ stress data points (gradients, depths, magnitudes) Mechanical properties (coefficient of friction, cohesive strength) Slip tendency

E-D model of seismically-mapped fault Fracture planes predicted from calculated stress tensor Horizon colour-coded by calculated shear stress ~= fracture intensity red = normal faulting, cyan/magenta = strike-slip FaultED - A new add-on module for TrapTester-5 Algorithms for Elastic Dislocation (E-D) modelling have been implemented within TrapTester to predict the 3D strain and stress tensors in the rock volume surrounding seismically-mapped faults. This allows us to predict small-scale fracture patterns.

TrapTester bridges the gap between geometric framework models and geological analysis & prediction During interpretation, fault plane analysis can help to identify problems with the data, to determine fault linkage and to derive more complete analysis of juxtaposed reservoir intervals Having built a framework model, predictors for column height and fault reactivation can be derived to quantify fault trap integrity and assess risk Provides all the tools for trap integrity risking and analysis in one seamless environment for exploration and appraisal TrapTester - Summary

after TrapTester……. …. TransGen : getting fault properties into reservoir simulators

TransGen – A tool for generating geologically meaningful fault transmissibility multipliers for ECLIPSE simulation models, and for examining the influence of faults on flow Fault transmissibility multipliers Grid-block Net:Gross ratio

Summary of TransGen methodology: Geologically derived transmissibility multipliers Shale content Transmissibility multiplier SGR Displacement Thickness Permeability After Manzocchi et al Fault-rock permeability is a user-defined function of SGR, displacement, depth

Scott Field TransGen analysis TransGen view showing net-to-gross of cells Shale-prone cells Sand-prone cells TransGen view showing SGR on faults High SGR Low SGR Low SGR in regions of sand- prone cells High SGR in regions of shale-prone cells TransGen view showing transmissibility multipliers (T) on faults High T Low T Low T in regions of high SGR High T in regions of low SGR    dZ dZVs SGR permeability (mD) SGR The Scott Field ECLIPSE model achieved a close history match when the SGR methodology was used to calculate transmissibility multipliers for faults.

4Further refinement and calibration of algorithms against reservoir production data Future developments (funded by Shell UK, Statoil & Petrobras) Breached relay Unbreached relay Doubly-Breached relay 2Routine inclusion of sub-resolution fault-zone structure (relays, normal drag, damage zones) 1Additional fault-rock properties (SSF, CSP, etc) via a macro language With the relay incorporated explicitly With no relay With the relay incorporated using the proposed methodology Pressure distribution in a layer 3Routine inclusion of two-phase fault-rock properties (Manzocchi et al, 2002) to acknowledge the changing relative permeabilities as oil saturation in the fault zone changes through time during production Relative Permeability Water saturation Capillary Pressure With the fault rock included as discrete grid- blocks. With no two- phase fault properties (Conventional representation). With the two-phase fault-rock incorporated using the proposed methodology. Increasing oil saturation.

TransGen summary Calculate transmissibility multipliers at all faulted cellular connections in an ECLIPSE model. Visualise and QC ECLIPSE faulted reservoir connections and compare with seismically- mapped fault juxtaposition relationships. A visualisation environment for engineers and geologists to help understand and discuss faulted reservoir models. Import ECLIPSE re-start file to visualise the impact of fault properties on flow simulations.

TrapTester – testing faulted trap integrity in exploration and appraisal TransGen – transmissibility multipliers for production simulation