10 - Petrophysical applications.ppt
- 1. Petrophysical applications/1 Image log & dipmeter analysis course Petrophysical applications of borehole images
- 2. Petrophysical applications/2 Sedimentology - Facies analysis - Ichnofabric analysis - Depositional environment - Palaeocurrents - Sandbody geometry - Sequence stratigraphy Petrophysics - Porosity typing - Permeability heterogeneity - Flow baffles / barriers - Diagenetic effects - Net sand & thin beds - Input to reservoir models Structure - Structural dip - Fault detection - Fracture description - In situ stress - Correlation - Integration with seismic Borehole image applications
- 3. Petrophysical applications/3 Abundant dark conductive patches interpreted as vuggy porosity. There is likely to be good connectivity in this example. The bright, resistive patches are probably bioclasts. Porosity typing
- 4. Petrophysical applications/4 Alternating relatively resistive and conductive horizons corresponding to fining-upward units. Conductive horizons are the coarser, more porous packstone-grainstone facies. Resistive horizons are finer grained packstone to wackestone facies. Permeability heterogeneity Well laminated horizon
- 5. Petrophysical applications/5 Sandstone 2600 psi Sandstone 3600 psi Borehole Flow baffles/barriers
- 6. Petrophysical applications/6 Static & dynamically normalised UBI images of thin bedded marine sands Baffles and thin beds
- 7. Petrophysical applications/7 Static amplitude Dynamic amplitude 0.4” resolution Thin beds and net/gross
- 8. Petrophysical applications/8 Static and dynamic UBI images of deep marine sandstones Non-planar feature - this represents sandstone remobilised during dewatering Net sand
- 9. Petrophysical applications/10 • What is thick and thin? • Thin beds & their effect on open hole logs … or lack of … • Considerations such as the earth model where images and core can help Thin beds
- 10. Petrophysical applications/11 • What is thick or thin? • “something that is thinner than the measurement resolution.” What is resolution? Depends who asks? Geophysicist, geologist, petrophysicist? Definitions
- 11. Petrophysical applications/12 Scales of data Borehole images and dipmeters 15 m 1 cm Core 10000 100 1 0.01 3D seismic 0.01 1 100 10000 Fault throw (m) Cumulative fault density (faults per km) Walsh, Watterson & Yielding 1991
- 12. Petrophysical applications/13 • Vertical resolution - logging tool “Thinnest bed in which a true reading can be obtained.” - bit vague? Log resolution • Intrinsic vertical resolution (IVR) “Width of the tool response function at half its maximum value.” “thinnest average bed that can be distinguished from its neighbours and responds to >90% true bed value”
- 13. Petrophysical applications/14 Vertical resolution reported on a log: • combination of tool IVR • sampling rate • data filtering/averaging during acquisition Vertical resolution
- 14. Petrophysical applications/15 0.1 cm 0.3 cm 1 cm 3 cm (1.2”) 10 cm (4”) 30 cm (1 ft) 1m (3 ft) Log scale 0.4” 4” 3’ Log resolution and scale
- 15. Petrophysical applications/16 • Do Standard log measurements underestimate net pay? Wireline logs This is a resolution problem 100 sw 0 The problem
- 16. Petrophysical applications/17 • Bypassed pay estimation STOIIP or gas equivalent? • More accurate reservoir delineation & producibility perm/thickness (kh)? • More accurate perforation & testing? YES! Does it matter?
- 17. Petrophysical applications/18 • Do cuttings show pay? • ‘Spiky’ open hole logs that repeat? • Vertical facies associations? • May require tools below standard log resolution to answer. – core, image logs, dipmeters Do we realise we have thin beds?
- 18. Petrophysical applications/19 • Understand the Geology ( the ‘earth model’) • Enhance logs using the earth model Use forward & inverse modelling to better predict log responses Adjust Porosity, Rt, Rxo, Sw, Vsh => STOIIP Addressing the problem
- 19. Petrophysical applications/20 Forward model Real & synthetic log Tool response function ‘earth model’ Modelling
- 20. Petrophysical applications/21 Thin beds – earth model from images
- 22. Petrophysical applications/23 – vertical facies associations – depositional environments likely to give rise to thin beds.. – Submarine fan, lacustrine, deltaic, fluvial, shelf (tempestites) – bed resolution & TST – post depositional features – injected sands, carbonate cements Understand the geological environment..? The earth model
- 23. Petrophysical applications/24 Core • highest resolution (mm) • facies associations • TST Borehole image & dipmeter data • resistive images (>5mm) • acoustic images (>2 cm) • dip information (2d earth model) Log data • resolution enhanced (0.5ft) Defining the earth model
- 26. Petrophysical applications/27 1 ft Static Dynamic 0.4” res Acoustic amplitude images
- 27. Petrophysical applications/28 Lawrence 2002 Lofts et al 2002
- 28. Petrophysical applications/29 1 ft 0.3” res. water/oil based Dipmeter data
- 29. Petrophysical applications/30 Horizontal or dipping? Layer cake or injected sands? Permeability - invasion? Can lead to complex 2d/3d earth models. Geological considerations
- 36. Petrophysical applications/37 With a model
- 37. Petrophysical applications/38 • Bad hole • Log physics • Depth matching • Lateral Continuity • Inventing logs! Reserves don’t always increase Pitfalls
- 38. Petrophysical applications/39 Benefits • By passed pay estimation STOIIP? • Reservoir delineation & producibility perm/thickness (Kh) • Accurate perforation & testing
- 39. Petrophysical applications/40 High resolution images help us to build the all important earth model, leading to: – By passed pay estimation STOIIP? – Reservoir delineation & producibility permeability/thickness (Kh) – Accurate perforation & testing improved Looking at thin beds
- 40. Petrophysical applications/41 • Data Acquisition • Existing tools • High resolution tools • Resolution Enhancement • deconvolution, dual detector, squaring • Formation Evaluation • should be same as normal evaluation Looking at thin beds
- 41. Petrophysical applications/42 Always better to acquire at high resolution than to try to enhance low resolution data Data acquisition
- 42. Petrophysical applications/44 GR Sw Por GR Sw Por Lith Lith Increase net pay
- 43. Petrophysical applications/45 Acquire High Resolution data Enhance Resolution Processing Methodology
- 45. Petrophysical applications/47 + = Tool Response Function Deconvolution
- 46. Petrophysical applications/48 GR Low Res Lith High Res Sw 10ft Increased STOIIP
- 47. Petrophysical applications/49 • Acquire High Resolution data • Enhance Resolution Processing + Earth Model :- • 1D Modelling • 2D Modelling • 3D Modelling Methodology
- 48. Petrophysical applications/50 Forward model Real & synthetic log Tool response function ‘earth model’ Modelling
- 50. Petrophysical applications/52 No Yes Start “Forward Model” Compare synthetic with original log Stop Make initial estimate Adjust parameters Match? Inversion
- 52. Petrophysical applications/54 InversionResultfor Rtand Rxo 0.2 200 Ohm-m X300 X320 X340 X360 X380 DPIL DLL Rxo Rt Rm Rt n-1 BHD Rxo n-1 Rt n-1 Rt n+1 Rt n Rxo n Lxo n borehole Lxo n-1 Rt n Rt n+1 Rxo n+1 Lxo n+1 2D
- 53. Petrophysical applications/55 20 ft thick 0° dip 20 ft thick 50° dip Dipping beds
- 54. Petrophysical applications/56 STAR Image Rt + Rxo Raw data North Sea 2D example
- 55. Petrophysical applications/57 Sw Gain Porosity GR Thick reservoir, North Sea
- 60. Petrophysical applications/62 • Level by level analysis • Depths of investigation • Compare back to core Formation evaluation
- 61. Petrophysical applications/63 • <2.5 ft Rt and Sw • <1 ft porosity and lithology • <3” shaliness • Use core/image to calibrate at early stage With thin bed modelling
- 62. Petrophysical applications/64 Thick or thin? It ALWAYS matters!