Finding Petroleum Conference London: January 2010 Low pressures to high pressures - how regional overpressure mapping helps find trapped hydrocarbons Richard Swarbrick & Stephen O Connor GeoPressure Technology
Principal Messages Overpressure mapping is an underutilised technology Low overpressure can be highly significant for reserves determination and unrecognised potential High overpressure controls exploration risk for breached traps Regional overpressure mapping projects have now been completed in NW Europe and in progress elsewhere
RELATIONSHIPS ARE KEY TO PRESSURE PRESSURE STRESS
Depth Lateral drainage and pressure regressions Pressure Near Normally Pressured Shale O/P gradient (rapid loading) Water Gas Water Overpressure RESERVOIR PRESSURE > SHALE PRESSURE Overpressured Reservoirs
Low Pressure Relationships Interpret reservoir pressure data Assign overpressure values for each reservoir Map overpressures for each reservoir If reservoir continuous contour values Establish possible hydrodynamic flow directions Examine well field data Establish tilt on hydrocarbon-water contact Revise reserves
Distribution Map of Overpressures Forties Forties Formation 20 2 353 15 19 27 Update of CNS (2003) Map Contours of overpressure in psi Nelson Field 13 Depleted HC in wells 38 61 73 68 93 540 17 Cat 4 19 Cat 3 13 Cat 2 60 57 80 83 51 48 107 282 27 54 332 222 No Palaeocene Data Channel Axis 58 59 119 165 151 243 183 336
Central Graben Pressure Study O/P < O/P 50 psi < 50 psi Andrew Sandstone limit Hydrodynamic flow directions Distribution Map of Overpressures Andrew Formation Contours of overpressure in psi O/P > 2000 psi Close to shale pressures?
EXPLORATION SIGNIFICANCE
Potential to fill to structural spill point Hydrostatic OWC/ FWL Simple Anticline: Pressure- Depth plot for oil accumulation
Well A Oil Down To Upside potential to spill point Proven Reserves 30 MMBO Possible Reserves + 30 MMBO
Appraisal Well B Well A OWC/FWL DRY HOLE Proven Reserves 40 MMBO
DECISION TIME! Assess reserves not enough to justify development Relinquish acreage? Farm out/sell assets to smaller/leaner company? Examine other possibilities and look at regional pressure distribution?
Well B Well A DRY HOLE Regional overpressure distribution suggests lateral drainage, with outflow to right
Well B Well A Well C OWC/FWL OIL & WATER
Hydrodynamic Model o o o Common Oil Leg o x Well A Well B x + + x + x + Well C Variable water legs Minimum pressure data to define reserves
Well B Well A Well C Proven Reserves 70 MMBO OIL & WATER
Implications Hydrodynamic model influences reserves distribution, volumes and reservoir connectivity Hydrodynamic reservoirs are to be found in many overpressured basins we just have not properly looked yet. GeoPressure Technology, an Ikon Science company, specialises in identifying hydrodynamic aquifers (lateral drainage)
High Pressure Relationships Interpret well pressure data Assign overpressure values for each reservoir Map overpressures for each reservoir Similar values are in same pressure cell Define pressure cell boundaries (not trivial) Map aquifer seal capacity/effective stress Identify trap leak points and protected traps Establish seal breach risk and exploration strategy
LEAKING TRAP PROTECTED TRAP after Seldon & Flemings,
LEAKING TRAP PROTECTED TRAP Overpressure after Seldon & Flemings, 2005
AQUIFER SEAL CAPACITY Structural Crest Aquifer Seal Capacity Hydrostatic Gradient Aquifer Gradient Minimum Stress Hydrocarbon seal capacity Determined from RFTs, etc Determined from 2 algorithms
22/30a-1 22/29-6s2 23/26a- 21 22/30b-4 22/24b-8 30/1c-2A 22/21-4 22/21-7 30/01f- 8 22/30b- 15Z 23/26b- 8 23/26-3 23/26b-15 22/29-7 23/26b- 14 22/07a-2 21/20a-1 22/30b- 11 22/28a-1 23/26-7 23/16d- 6 29/5a-3 22/08a-3 15/30-12 NO1/6-7 22/27a- 1 30/1c-4 29/4a-2 22/25b- 2 29/05b- 4Z NO7/7-2 22/23b-6 29/5a-5 29/08b- 5 22/30a-2 22/22b- 4 21/25-12 30/01c- 3 22/28a- 4 29/10a-2 22/24d- 10 29/2a-2 29/10-3 sti 22/24a-A1Z 22/30c-10 29/09c- 4 29/05a- 1Z 23/26-2 29/08a- 3 15/23a-12 22/30a- 6 22/24-7 22/24a-2 30/7a-7 29/05b-F1 21/30-3 30/11b-3 22/24b-9 23/22b-4 30/07a-P1 30/07a- 8 39/02-2Z 21/30-19 22/8a-4 21/25-10 30/7a-12 22/30c-13 29/07a- 7 21/01a- 21 15/22-16 30/07a- 6 29/08a- 4 23/11-4 NO3/4-1 22/18-6 29/07a-4 15/22-D1A 29/07a- 5 21/25-8 23/27-6 30/11b- 4 22/30a- 16 29/07-8 29/07-11 15/27-10 Top Reservoir Seal Capacity (psi) 3000 Aquifer Seal Top Reservoir Capacity Seal Top Capacity Reservoir (85 wells) 2500 2000 Offers a risking strategy 1500 1400 psi 1000 500 0-500 High Risk Low Risk Well
Primary Eruption: 29 th May + secondary eruption 2nd June 2006 17 June 2006 Courtesy of Bakrie Media Centre
Concluding Remarks Overpressure mapping is a valuable exploration tool Hydrodynamic systems are not well recognised worldwide exploration opportunity High overpressure represents an exploration and drilling challenge Integration of pressure data into the finding petroleum workflow is key to success
Finding Petroleum Conference London: January 2010 QUESTIONS