Petrel Structural Modeling Best practices to tackle complex geometries and engineering requirements
11th January 2007
S c h l u m b e r g e r P r i v a t e
Petrel Structural Modelin Modeling g Objectives Review fault modeling best practices Examine Petrel complex modeling possibilities Discuss the issues and constraints around modeling radial geological structures Discuss optimization and enhanced complexity of the client’s model Present a methodology to build more flow complexity without wit hout affecting the cell geometry
Petrel Structural Modelin Modeling g Objectives Review fault modeling best practices Examine Petrel complex modeling possibilities Discuss the issues and constraints around modeling radial geological structures Discuss optimization and enhanced complexity of the client’s model Present a methodology to build more flow complexity without wit hout affecting the cell geometry
Grid building in Petrel: The concept 1. Fault model building Key pillars extending to top and base of reservoir Input : fault and horizon interpretations
2. Pillar gridding Fitting of a regular structured grid on the faults Interpolation of the grid to the top and base
3. Vertical layering Horizons and layers building Input : horizon interpretations and well data
Fault modeling best practices Creating the fault model
Prepare your fault input data: – Cut the fault fault sticks at at reservoir reservoir level – Organize faults faults in folder by areas – Re-name faults faults with short short names(+ names(+ name of affected horizons) horizons)
Adjust workflow to quality of input – Use automated automated conversion conversion whenever whenever possible – Use manual conversion when low quality quality input
Use simple pillar geometry initially (linear (linear )
Fault modeling best practices Editing the fault model
Keep a finger on the Esc key to swap quickly between manipulation and select/pick mode. Use the Target zoom to centre the 3D View on the part of the model on which you are working.
Use the smoothing tools – Smooth XYZ XYZ – Smooth Z values only – Space pillars evenly
Fault modeling best practices Connecting the faults
Connect faults by areas (Right-click on a fault \ Show connected faults) Use auto-connection only on small simple models! Review modeled faults against: – Fault sticks inputs
AND – Horizon inputs (Gridded surfaces, seismic interpretations)
Vertical truncations How to create a vertical truncation 1. Detect the truncating and truncated faults in the fault model 2. Make truncating fault active 3. Select two key pillars you want to truncate 4. Press ”truncate pillar” icon 5. Truncate the rest of the key pillars
Complex antithetic X faults can be modeled in Petrel Two faults truncated at the top and bottom by a third one Necessity to align the truncated pillars
No particular rule to model reverse faults in Petrel At the Make Horizons stage: – Input surfaces cannot have double Z values – Different input used for each fault compartment – Fault compartments must be isolated segments
Take into account at the fault modeling and Pillar Gridding stage (Use trends to isolate segments)
Petrel structural modeling and radial geological events How to combine radial fault pattern and structured grid in Petrel? – Gridding and Engineering constraints – Zig-Zag faults
How complex can the model be? – Vertical truncations – X-faults
A work-around to build more complexity in the simulation grid
Gridding constraints Directions assigned to faults – Force cell edges along fault – Distort the grid in the direction of the fault – Prevent triangular cells on fault
Trends – Force cell edges between faults or away from faults – Used to solve local issues or constrain cell number
Real field model Radial fault network 29 faults simplified to 25 without vertical truncations 50*50 Grid 100 layers : average cell thickness 2.2 metres Average theoretical cell volume Ca. 5000 m3 Four segments
Model No Trends Coarse 100x100 Grid Zig-Zag faults Good cell geometry 471 triangular cells GRV difference with 50x50 non ZZ grid between 0.7 and 2% depending on segment and due mainly to the model edges.
Flow path, flight time (particles displacement time) and simulation time similar in original Client model (Red) and in simple 50x50 model. Potentially faster and more stable ECLIPSE simulation as better cell geometry in the 50x50 Zig-Zag model
Model with added complexity Fault model modifications
Replacement of “jumping” truncation by two independent truncations Replacement of simple approximation by Truncated – Truncating combination Add of X-fault and extra vertical truncation
Flow path, flight time (particles displacement time) and simulation time similar to original simplified Client model Directions on truncated faults result in more distorted cells locally.
Model with added complexity A workflow using RE faults
Objective : Replace complex faults by equivalent RE faults Method : – Digitizing of RE faults – Assignment of variable transmissibility vertically – Creation of permeability barriers
