1 - Late charge problems in the K5 area
Late Charge problems in the K5 area
1
Bernard GeissTEP Nederland, 5th June 2008TNO/EBN Workshop Utrecht
2 - Late charge problems in the K5 area
Agenda
Regional context
K5-13 results and Post Mortem
Structural Setting K4-K5 area
Conclusions
3 - Late charge problems in the K5 area
SW NE
Top ChalkBase ChalkTop SaltTop RotliegendesHercynian UnconformityTop Westphalian A
Chalk
Salt
5 km
Chalk
Salt
Stratigraphic Column and HC Play in core area
D2
R
HU
E
D1
C2
R
HU
E
D1
C2
TWA
D4
DT
K5-2
4 - Late charge problems in the K5 area
K5-1
K5-12
K5-2
K5-5
K5-6
K5-4
K5-3
K5-7
K5-8
K5-9
K5-11
K4-8
K5-13
K6-8
K6-1
K6-6
K6-5
K6-4K6-2
K6-3
K6-7
K6-9
K3-2
K5-F2 K6-11
K6-10
100%1111K6
100%1212K5
50%12K3
100%22K2
Exploration wells and success rate
10 km
5 - Late charge problems in the K5 area
Westphalian B Coal Measures
K2-2K2-1 K5-11E17-1E17-2E16-1
Miocene Unconf.
Top Chalk
Top SaltBase Chalk
Top RotliegendesHU
Top Westph. A
Top Westph. B
NE SW
T
W
T
1 -
3 -GDT GDT
K5-13
WUT
Regional seismic line
K5bK5-13
K2
E16/17
K5-11
6 - Late charge problems in the K5 area
Random tie line K5bTop ChalkBase ChalkTop SaltTop RotliegendesHUTop Westphalian A
K5-13K5-12K1-5NW ESE
RHU
Top Salt
Fairly similar context with K5-12
m
Top West A
7 - Late charge problems in the K5 area
Well correlation flattened at MFS2K5-12 K5-13
RSWC
Pressure tests
10 m
Sand box concept confirmed
Seq. 212.3 m
39m Seq. 3-3856 mss
-3841 mss
-3834 mss
Seq. 1
Additional sands not predicted
8 - Late charge problems in the K5 area
Seismic Interpretation: K5b Top Westphalian B Depth Structure
Outline of erosion at HU
Westphalian ABC
S N
HU
K5-13K5-12
9 - Late charge problems in the K5 area
Fluvial to aeolian depositional processes: Back stepping of LS system (F16-3) The main NE-SW wrench trend possibly
constrains fluvial sediment supply K6 Block located within the main fluvial belt
axe with an impact on the reservoir properties
L7-2K4-9
K5-12 K1-5
K4-12
L4-2
K5-9
L1.7
F16-3
E-18
K4-K5 : Aeolian dominated, Sand box conceptStrong impact of HU geometry
West.D
West. Upper CWest. Lower CWest. B
West. A
Stephanian
K6-10
Regional Depositional environment sketch - confirmed
Sand deposits on Westphalian B subcrop
K5-13
N
10 - Late charge problems in the K5 area
K5-13: What did go wrong?
Intra Westph. B coalbed
Base Chalk
Top Salt
Zechstein CarbonatesTop Rotliegend
Hercynian Unconformity
2.5 km
K5-13
K5-13
Top Rotliegend Depth Structure Map
SENW
Reservoir
Juxtaposition?
Low saturations of gas in fluid inclusions
11 - Late charge problems in the K5 area
The dilemma to explain the failure of K5-13 Leakage ? Gas found in fluid inclusion but only low
saturations More sands drilled. Sand juxtaposition
across faults still unlikely but possible If such a juxtaposition is present then
the spill point is below the well. However no attic gas found.
Leakage through faults very unlikely as the surrounding formations are supposed to be highly sealing: Silverpit shales laterally and vertically, Zechstein evaporites as ultimate vertical seal.
Lack of HC Charge ? Gas in fluid inclusions where has it
gone? Never observed in K4-K5 area Westphalian SR within the K5-13 horst
block not mature enough to expellsufficient amounts of gas
Presence of N45 oriented faults, separating kitchen area from K5-13 panel
Shales
Evaporites
Reservoir
What is so peculiar about these N45 oriented faults?
12 - Late charge problems in the K5 area
Fault pattern K4/K5 area on NW-SE gradient map
K5-13
Gradient at Top Rotliegendes
13 - Late charge problems in the K5 area
K4-K5 Structural Pattern at Top RotliegendesBlack = Normal faultsRed = Inverted faultsWhite = Transfer Faults
N40
N150
Close-up areaTop Rotliegendes Depth Structure and Dip
14 - Late charge problems in the K5 area
K4-K5 Close-Up Structural Pattern at Top Rotliegendes
N40
N150
K4-A4
K4-7
K5-A2
K5-A4
K5-A1
K8-12
K5-4
K5-10
K4-A3 Black = Normal faultsRed = Inverted faultsWhite = Transfer Faults
Top Rotliegendes Depth Structure and Dip
Xline 1875
15 - Late charge problems in the K5 area
Subtle Transfer faults on Xline 1875
K5-A1
K5-A2
K5-A4
2.5 km (1:4)
K8-12
K5-4
200 m
NW SE
Hercynian Unconformity
Top Salt
Top Rotliegend
Near Top Westphalian B
K5-A1 K5-A4K5-A2 K5-4
Faults with hardly any throw within the Rotliegendes
Reservoirjuxtapositioning
16 - Late charge problems in the K5 area
K5A Pressure History on Well correlationK5K5--A4A4 K5K5--44K5K5--A1 (ex. K5A1 (ex. K5--3)3)K5K5--A2A2
HU
Seq. 6
Seq. 3-4
Seq. 6
Seq. 3-4
1999 236 bar 198 bar 401 bar2006 126 bar 96 bar 221 bar
1988 409 bar 409 bar Not yet drilled 409 barBHP Lower Slochteren Reservoir Sequences 3-4
1994 Production start-up K5-A1 & A2 Not yet drilled 409 bar
K5-A1
K5-A2
K5-A4
K5-4
Transfer Fault Transfer Fault
17 - Late charge problems in the K5 area
Small scale: Graben alike structures along transfer faults
The observed vertical throws are little but may be underestimated as they are often resembling conjugate fault systems.
When evaluating juxtaposition and SGR, we are constantly hurdling against the lack of vertical resolution. Therefore deterministic evaluations are uncertain.
Further uncertainties are the horizontal throw and fault cementation
More throw
18 - Late charge problems in the K5 area
Large scale: Separation of K5-13 from kitchen by
~ 10 km
K5-13
N
Producing Areas (sketched) andno expulsion from SR expected
Kitchen Areas
Kitchen Areas
19 - Late charge problems in the K5 area
NW-SE Striking Normal and Inverted Faults
Top ChalkBase ChalkTop SaltTop RotliegendesHUTop Westphalian BTop Westphalian A
2.5 km
500 m
SWNE
K5-12
Strong throws on the NW-SE (N120-150) faults no reservoir juxtapositionDecoupling between Pre- and Post salt. Salt cored buckle folds above Rotliegend Highs
20 - Late charge problems in the K5 area
Top Rotliegendes Depth MapBase Chalk Depth MapTop Chalk Depth Map
Late Cretaceous to Tertiary Inversion
Late Cretaceous Tertiary inversion axis around N45
21 - Late charge problems in the K5 area
Present day maximum horizontal stress oriented N135
The N135 direction of the present day maximum stress is also confirmed by borehole induced fracturing.
The N45 transfer faults are therefore very likely to be closed
Total data
22 - Late charge problems in the K5 area
Leveille et al. 1997Sealing N40 trending faults
SGR predicts clay smear is not sealing
Leveille argues for cementation, on the basis of cemented fractures from cores
23 - Late charge problems in the K5 area
Conclusions
Confirmation of the geological model for sand deposits above Westphalian B subcrop (Sand box concept)
Fluid inclusions can not conclude on the reason of the failure
Migration from northern kitchen may be deflected by closed N45 faults
These transfer faults have hardly any vertical throw but may form significant barriers to fluid flow. This is not fully understood today
Beware of certainties even in a mature area
24 - Late charge problems in the K5 area
3D View of K5b area
K5-13
The N45 faults appear as distinct corridors on this view. They are not just a thin lineament but a graben system probably composed of helicoidal en echelon faults.
25 - Late charge problems in the K5 area
Throw variation along fault
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