case study: establishing, predicting and modelling the...
TRANSCRIPT
Basement Reservoir Specialists
Case study:
Lancaster development –
making fractured basement
reserves viable
November 2017
Establishing, predicting and modelling the hydrodynamic fracture network of basement reservoirs during the exploration and early appraisal phase:
A case study from the
West of Shetland
Finding Petroleum Understanding Fractured Reservoirs & Rock January 23rd
Hurricane | Dubai Site Visit | December 2017 2
Presentation
1 The Lancaster reservoir
2 Relative magnitude of fluid pressure and lithostatic pressure
3 Magnitude and orientation of mean stress gradient
4 Fracture connectivity
5 Horizontal well results
6 Planned data acquisition
7 QA
Hurricane | Dubai Site Visit | December 2017 3
Presentation
1 The Lancaster reservoir
2 Relative magnitude of fluid pressure and lithostatic pressure
3 Magnitude and orientation of mean stress gradient
4 Fracture connectivity
5 Horizontal well results
6 Planned data acquisition
7 QA
Hurricane | Dubai Site Visit | December 2017 4
0 10 20 30 40 50 km
Typhoon
Schiehallion
Foinaven
Shetland
Strathmore
Shetland Islands
Orkney Islands
SCOTLAND
Isle of Lewis
Isle of Skye
Aberdeen
Solan
Clair
410000 420000 430000 440000 450000 460000 470000 480000
6650000
6660000
6670000
6680000
6690000
6700000
410000 420000 430000 440000 450000 460000 470000 480000X/Y:
Meters
6650000
6660000
6670000
6680000
6690000
6700000
Warwick
Whirlwind
Lancaster
Halifax
Lincoln
Hurricane licences
Rona Ridge basement play
HEX-COR-BDV-PRS-0001-0 16
Hurricane | Dubai Site Visit | December 2017 6
Lancaster well schematic prior to the 7Z well
205/21a-6
205/21a-4 205/21a-4Z
205/21-1A
P1
36
8 B
lock B
ou
nd
ary
Max ESP rate 9,800 stb/d 205/21a-6 (2014)
Mobile oil swabbed 205/21a-4 1,597m TVDSS
597m TVT (2017 CPR 1C OWC)
678m TVT (2017 CPR 3C OWC)
Oil Column Heights
653m TVT (2017 CPR 2C OWC)
205/21a-7
Wireline oil samples 205/21a-7 Deepest at 1,669m TVDSS
Hurricane | Dubai Site Visit | December 2017
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0 0.5 1 1.5 2km
Exploration well 205/21a-4
Appraisal well 205/21a-4Z
Development well 205/21a-6
Top hole location Top basement penetration
205/21a-7Z (2016) Horizontal Well
•Hurricane’s second horizontal well planned as a producer
•Average well porosity expected to be :
- between 3.6% – 4.4 %
•Objective to repeat success of the 205/21a-6 horizontal well (2014) :
PI of 160 stb/psi
Maximum flow rate of 9,800 stb/d
Shell well 205/21-1A
Development well 205/21a-7Z
Appraisal well 205/21a-7
Hurricane | Dubai Site Visit | December 2017 8
The case study - what did we need to know? •Confident that the reservoir would have similar performance to that previously
experienced
•Confidence that we understood what was making the reservoir work
•Key controls on fluid flow in Type 1 fractured reservoirs
– Relative magnitude of fluid pressure and lithostatic pressure
– Magnitude and orientation of mean stress gradient
– Connectivity of the fracture network
Hurricane | Dubai Site Visit | December 2017 9
Presentation
1 The Lancaster reservoir
2 Relative magnitude of fluid pressure and lithostatic pressure
3 Magnitude and orientation of mean stress gradient
4 Fracture connectivity
5 Horizontal well results
6 Planned data acquisition
7 QA
Hurricane | Dubai Site Visit | December 2017 10
Lancaster - normally pressured environment
•All wells planned and drilled assuming a normal hydrostatic gradient
•No evidence of “over pressure” in either the basement or overlying clastic successions
•4Z drilled on balance
•Primary drive mechanism is therefore :
–Expansion of reservoir fluids
–Expansion of the aquifer
Hurricane | Dubai Site Visit | December 2017 11
Presentation
1 The Lancaster reservoir
2 Relative magnitude of fluid pressure and lithostatic pressure
3 Magnitude and orientation of mean stress gradient
4 Fracture connectivity
5 Horizontal well results
6 Planned data acquisition
7 QA
Hurricane | Dubai Site Visit | December 2017 12
Limited borehole indicators 205/21a-7
Hurricane | Dubai Site Visit | December 2017 13
Stress ratio = (2- 3)/(1- 3)
All fracture sets
H orientation
Stress ratio = (2- 3)/(1- 3) Stress ratio = (2- 3)/(1- 3)
Normal Strike-slip Reverse Normal Strike-slip Reverse Normal Strike-slip Reverse
Stress ratio = (2- 3)/(1- 3)
Regional Joints Cross Cutting Joints Large Open Fractures
Cost maps showing the predicted maximum horizontal stress orientation and structural regime. The top image shows all fracture run together, and the bottom three show the results split into joint types. The ~45 stress orientation of the regional joints corresponds to Hurricane’s understanding that SHMax is orientated to the northeast.
Stress Regime
Hurricane | Dubai Site Visit | December 2017 14
•Limited core measurements and sonic waveform analysis indicate that preferential production is not associated with critically stressed or shear fractures
• Geophysical mapping and structural modelling indicate that the most likely model to constrain the current stress regime is a north easterly maximum horizontal stress resulting in a pervasive open (dilationary) joint system
• Ongoing work program to challenge this model and to develop a structural/stress model for the surrounding basement prospectivity
Stress Regime – working model
Hurricane | Dubai Site Visit | December 2017 15
Presentation
1 The Lancaster reservoir
2 Relative magnitude of fluid pressure and lithostatic pressure
3 Magnitude and orientation of mean stress gradient
4 Fracture connectivity
5 Horizontal well results
6 Planned data acquisition
7 QA
Hurricane | Dubai Site Visit | December 2017 16
Fracture characteristics at different scales
Note: [x]
Core plug
Borehole
Dynamic well test 3D seismic survey
0 250 500 750 1,000 m
Microfractures
Joints Faults
Hurricane | Dubai Site Visit | December 2017 17
1. 2009. Manual picking of high confidence faults for placement of initial exploration well
2. 2010. Post-drill. Lower confidence coherency faults confirmed by 205/21a-4. Combination of manual and FaultX coherency picked faults
3. 2014. Horizontal well confirms Ant Tracking results. Manual picking, FaultX coherency and Ant Tracking all combined
Fault map evolution
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1. 2. 3.
Hurricane | Dubai Site Visit | December 2017 18
Ant Tracking matched to Wells •Ant Tracking extracted at top basement
surface correlates well with log-interpreted Fault Zones
• Indication that faults are generally vertical or near vertical
•Good confidence that Ant Tracking response is representing faulting
•Note that the Ant Tracking gives no indication of width of Fault Zones
Overburden Victory Fractured Basement Fault Zone Jurassic sand
Hurricane | Dubai Site Visit | December 2017 19
Example of a single joint picked from electrical and acoustic image logs
Joints
Hurricane | Dubai Site Visit | December 2017
205/21a-6 Joint Analysis by Facies Fractured Basement
Regional Joints Cross Joints >60° Cross Joints >20°,<60° Cross Joints <20° Large Aperture Joints
Mean dip/strike: 76⁰ NESW Mean dip/strike: 74.5⁰ EW and a
secondary trend NS Mean dip/strike: 47.9⁰ NESW
Mean dip/strike: 14.7⁰ NESW and a minor trend NWSE
Mean dip/strike: 61.9⁰ NESW
Fault Zones
Regional Joints Cross Joints >60° Cross Joints >20°,<60° Cross Joints <20° Large Aperture Joints
Mean dip/strike: 75.5⁰ NESW Mean dip/strike: 73.6⁰ EW and a secondary trend NNW/SSE
Mean dip/strike: 48.2⁰ NESW Mean dip/strike: 15⁰ NESW, NS and EW
Mean dip/strike: 66.5⁰ NESW
Hurricane | Dubai Site Visit | December 2017 21
• Separation between the deep and shallow resistivity curves indicates invasion and demonstrates the reservoir is permeable
• NMR and density neutron porosity logs show clear responses to fractures
• High-resolution Platform Express density and resistivity illustrate how the standard resolution curves relate to the highest resolution image data
Sequential log analysis corroborates permeability
Hurricane | Dubai Site Visit | December 2017 22
205/21a-4Z formation evaluation
•Comprehensive, high-quality log suite (LWD and wireline) acquired
• Integrated with well test and PLT data
70
m
11
0 m
Hurricane | Dubai Site Visit | December 2017 23
Large Aperture Fracture Example (205/21a-4Z)
PLT
Hurricane | Dubai Site Visit | December 2017 24
Picking SWC locations
Hurricane | Dubai Site Visit | December 2017 25
Microfractures “captured” by sidewall core
Hurricane | Dubai Site Visit | December 2017
Microfracture Porosity
Relics of calcite occlude vuggy/channel porosity. The porosity is readily interpreted as secondary porosity created by extensive dissolution of the calcite. Sidewall core porosity estimated to 4.1%.
Hurricane | Dubai Site Visit | December 2017 27
Final PBU derivative match
205/21a-6 pressure build up analysis
Hurricane | Dubai Site Visit | December 2017 28
DFN modelling
•History and PLT matched DFN models require there to be a hydrodynamically effective:
–A) fault network
–B) regional joint system
•No match achieved using regional joints in isolation and or faults in isolation
Hurricane | Dubai Site Visit | December 2017 29
Conceptual reservoir model
Fractured Basement The intervening host rock is pervasively fractured and also contributes to fluid flow
Fault Zones Represent pervasively fractured volumes of rock that include preferentially enhanced aperture fractures and therefore improved reservoir characteristics. Fault Zones are associated with seismically-resolvable faults
Micro fractures and joints are present throughout the Fractured Basement and Fault Zones
Hurricane | Dubai Site Visit | December 2017 30
Presentation
1 The Lancaster reservoir
2 Relative magnitude of fluid pressure and lithostatic pressure
3 Magnitude and orientation of mean stress gradient
4 Fracture connectivity
5 Horizontal well results
6 Planned data acquisition
7 QA
Hurricane | Dubai Site Visit | December 2017 31
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Exploration well 205/21a-4
Appraisal well 205/21a-4Z
Development well 205/21a-6
Top hole location Top basement penetration
205/21a-7Z (2016) Horizontal Well
•7Z Expected to encounter:
eleven fault zones
ne-sw striking permeable regional joints
Produce at rates similar or greater rates than 205/21a-6
PI of 160 stb/psi and maximum flow rate of 9,800 stb/d
Shell well 205/21-1A
Development well 205/21a-7Z
Appraisal well 205/21a-7
Hurricane | Dubai Site Visit | December 2017
Seismic section through 205/21a-7Z
Top Victory
Top Kyrre
Top Basement
205/21a-7 NW SE 205/21a-7Z
ll
Well Facies Bateman Konen
Porosity (%)
Well Facies Bateman Konen
Porosity (%)
205/21a-4 FZ1 2.3 205/21a-7 FZ1 8.4
FB1 3.1 FB1 2.8
FZ2 7.2 FZ2 3.4
FB2 2.8 FB2 2.2
FZ3 4.4 FZ3 3.1
FB3 3.2 FB3 1.9
FZ4 4.1 All 3.6
All 3.9 205/21a-7Z FB1 4.0
205/21a-4Z FB1 6.7 FZ1 6.2
FZ1 3.4 FB2 2.6
FB2 4.8 FZ2 3.6
FZ2 4.4 FB3 3.0
All 4.4 FZ3 5.0
205/21a-6 FB1 3.7 FB4 2.6
FZ1 4.2 FZ4 5.4
FB2 3.5 FB5 3.4
FZ2 4.5 FZ5 5.4
FB3 3.3 FB6 4.0
FZ3 4.3 FZ6 5.4
FB4 4.4 FZ7 4.2
FZ4 5.5 FB7 2.6
FB5 3.2 FZ8 5.7
FZ5 5.3 FB8 3.0
FB6 3.7 FZ9 4.1
FZ6 3.4 FB9 2.8
FB7 2.6 FZ10 2.9
FZ7 6.7 FB10 2.1
FB8 4.5 FZ11 4.3
FZ8 5.1 FB11 3.0
FB9 3.3 FZ12 3.6
FZ9 8.5 FB12 1.6
FB10 3.8 All 3.8
FZ10 5.3 Lancaster (all wells)
FB 3.2
All 4.4 FZ 4.8
All 4.0
Porosity and Fault Zone summary
Field average
Fault Zone widths (MD)
7Z average
Hurricane | Dubai Site Visit | December 2017 35
Regional joint distribution per well
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-2120
-2120
-1820
-1820
-1820
-1820
-1820
-1820
-182
0
-18
20
-1820
-1820
-1820
-1820-1820
-1820
-1820
-1220
-1220
-1220
-1220
-1620
-1120
-1020
-232
0
-2320
-2320
-2320
-1320
-1320
-1320
-13
20
-132
0
-1320
-1320-142
0
-1320
-1320
-1320
-1420
-142
0
-1420
-1420
-1420
-1420
-1420
-1420
-1420
-1420
-1420
-1220
-1220
-1520
-1520
-1520
-1520
-1520
-152
0
-1520
-1520
-152
0
-1520
-1520
-1520
-1520
-1520
-2420
-2420
-2420
-2420
-1620
-1620
-1620
-1620
-1620
-1620
-1620
-162
0
-1620
-1620
-1620
-162
0
-1620
-1620
-2320
-252
0
-1720
-1720
-1720
-1720
-1720
-172
0
-1720
-17
20
-1720
-172
0
-1720
-1720
-1720
-172
0
-1720
-2820
-2120
-2520
-2520
-2520
-2220
-2320
-2420-2620
-2620
-2720
-2720
-2820
-2920
0 0.5 1 1.5 2km
205/21a-7
205/21a-7Z
205/21a-4
205/21a-4Z
205/21a-6
Hurricane | Dubai Site Visit | December 2017 36
205/21a-7Z PBU Interpretation
Complex storage response – combination of wellbore and well connected fractures
Dual porosity dip
Late time drop
Tidally corrected derivative plot
P.I. 147 stb/d/psi Maximum ESP flow rate of 15,375 stb/d (constrained by flare boom) Stable natural flow rate of 6,520 stb/d achieved (constrained by critical flow through separator) No formation water produced
Hurricane | Dubai Site Visit | December 2017 37
Summary of well results
•The 7Z well static and dynamic data corroborated the:
– conceptual reservoir model
– pre drill seismic fault interpretation (12 faults instead of 11)
–zonal properties (Fault Zone thickness and porosity) within expected ranges
•The high flow rates and associated high PI were consistent with the expectations from the 6 well
•The well was suspended as a future producer
Hurricane | Dubai Site Visit | December 2017 38
Connectivity summarised •Fracture intensity does not appear to be controlled by
-Distance to fault zones
-Distance to fault zone boundaries
-Elevation (reservoir depth)
-Relative distance to top basement
•The above observations support the concept of early pervasive joint development which has been subsequently exploited by faulting
•Connectivity induced by the geometric disposition of joints is interpreted as being further enhanced by hydrothermal and epithermal processes
Hurricane | Dubai Site Visit | December 2017 39
Lancaster geological history
Preserved Stratigraphy Eon Era Period Epoch
Ph
aner
ozo
ic
Cen
ozo
ic
Neogene Miocene
Palaeogene
Oligocene
Eocene
Palaeocene
Mes
ozo
ic
Cretaceous Upper
Lower
Jurassic
Upper
Middle
Lower
Triassic
Pal
aeo
zoic
Permian
Carboniferous
Devonian
Silurian
Ordivician
Cambrian
Proterozoic
Archean
Basement at Lancaster dated as a minimum of 2.3Ga
Hot fluid pulses enhance fracture network (hydrothermal processes)
Epithermal enhancement of fracture system
Oil charge (biodegraded)
Oil charge (undegraded)
Period of burial / deposition
Period of uplift / erosion
Key
? ?
Variscan Inversion
Caledonian Orogeny
Alpine Orogeny
Emplacement of plutonic TTG (tonalite-trondhjemite-granodiorite) gneisses. Resulting cooling creates joint system
Laxfordian compression results in extensive NW-SE shear faults
Brittle deformation along pre-existing planes of weakness – i.e. cooling joints – creating fault network. Repeated burial and uplift of basement reactivates faults
Regional ENE-WSW extension
Rona Ridge comprised of a series of island surrounded by a shallow sea, enhancing the fracture network through subareal exposure
Marine transgression. Deposition of Kimmeridge Clay source rock
Atlantic Rifting NE-SW extension
Pasteurisation of basement through burial (temperatures >80oC)
Lancaster basement uplifted by 1 – 1.5km, relaxation of pre-existing fracture network. Uplift coeval with charge (undegraded due to previous pasteurisation)
Renewed subsidence. Lancaster still receiving charge today
Hurricane | Dubai Site Visit | December 2017 40
Presentation
1 The Lancaster reservoir
2 Relative magnitude of fluid pressure and lithostatic pressure
3 Magnitude and orientation of mean stress gradient
4 Fracture connectivity
5 Planned data acquisition
6 Q&A
Hurricane | Dubai Site Visit | December 2017 41
EPS Field Development •2 existing wells (205/21a-6, 205/21a-7Z)
•Base case initial production 20,000 bopd to avoid reservoir damage
Hurricane | Dubai Site Visit | December 2017 42
RPS Energy CPR production forecasts
EPS production forecasts
Note: Chart data based on RPS Energy May-17 reserve cases which assume an EPS duration of 6 years. Under the scenario where the EPS is extended to 10 years, additional volumes would qualify as reserves
-
5,000
10,000
15,000
20,000
25,000
30,000
2019 2020 2021 2022 2023 2024
Dai
ly O
il P
rod
uct
ion
Rat
e (m
stb
/d)
3P 2P 1P
EPS Low Case EPS Base Case EPS High Case
Basement assumptions
OWC 1,597m TVDSS
(swab depth from 205/21a-4 well)
1,653m TVDSS (MDT oil gradient
intercept)
1,678m TVDSS (resistivity log, oil sample collected
lower)
Porosity 2.0% 4.0% 7.1%
Operational efficiency (/uptime)
80% 85% 90%
Plateau production rate
Gross (peak run-rate)
20,000 bbl/d falling to 14,000 bbl/d
20,000 bbl/d 20,000 bbl/d rising
to 30,000 bbl/d
Net (adjusted for operational efficiency)
16,000 bbl/d falling to 11,200 bbl/d
17,000 bbl/d 18,000 bbl/d rising
to 27,000 bbl/d
RPS Energy CPR Cases
Hurricane | Dubai Site Visit | December 2017 43
Summary
•The effective fracture network at Lancaster has predictable static properties in the currently drilled GRV:
– a persistent ne-sw striking joint population
– pervasive hydrodynamic fracture network comprising microfractures, joints and fault zones
•Dynamic data supports the static observations:
–dual porosity response
–no identified permeability barriers
–high initial productivity index
•Long term data gathering and further modelling work is required to evaluate:
–dynamic properties of the reservoir in the vicinity of the current wells
–potential static and dynamic properties of the fracture network away from well control
Hurricane | Dubai Site Visit | December 2017
Thank You