An Overview of Deepwater Reservoir Elements in the Eastern - - PowerPoint PPT Presentation

An Overview of Deepwater Reservoir Elements in the Eastern Mediterranean

Seafloor characteristics: lobate patterns

Pirmez et al., 2000 Modern slope of Nigeria

Friedmann et al., 2000

Shelf-Margin Delta

Levees Channel Depositional lobe (sheet) Depositional lobe (sheet)

Best analogs: Base-of-slope turbidite systems Unconfined area (no major bathymetric highs creating sediment traps) Modern oceanic depths Fed by updip area with large drainage systems Sediments are delivered by submarine canyon (possibly) Best producing analogs: northern Gulf of Mexico (unconfined area), Miocene, Paleogene Okay analogs: intraslope basins (GOM, Angola); Cenozoic-Brazil; Base-of slope unconfined, limited drainage and water depths (Lower Cretaceous, NW Shelf of Australia) North Sea (Upper Jurassic through Eocene). Good published examples for production: Thunder Horse, Mars, Augur (high porosity and permeability values, little diagenesis)

Choosing the best depositional analogs for the Levant

Northern Gulf of Mexico Lowstand Paleogeography

Kendrick (1998)

Unconfined deepwater systems: Seafloor image

Sinuous channel Depositional lobes 1 2 3 4 5 6 7 Wen et al., 1995

False-color image derived from the GLORIA II side-scan sonar image of the Mississippi Fan surface. Brighter colors: sand-rich, depositional lobes (red and yellow colors) at the termini of the channels. Blue areas: finer-grained, overbank sediments..

Slope settings: erosional channels and their fill

Unconfined settings: depositional lobes

Gardosh, 2012

Unconfined settings: depositional lobes

Gardosh, 2012

Lobe (Sheet) sands and sandstones: some of the best high-rate, high-ultimate-recovery (HRHU) reservoirs in deep water. Characteristic sedimentary features in cores/outcrops: massive to graded beds with non-erosive bases that have conformable, non-erosive bed contacts Simplest reservoir geometries: good lateral continuity, potentially good vertical connectivity, high aspect ratio (> 500:1), narrow range in grain size (and thus greater porosity and permeability), and few erosional features. Deepwater reservoir elements: lobe reservoirs

Unlike other deepwater reservoir elements, lobe (sheet) sands commonly have an areal extent that exceeds the area of the trap Sealing capacity of interbedded shales is potentially important Diagenesis generally not a problem in “younger” reservoirs, i. e. Miocene or younger, or those without significant burial. Commonly certain layers will be more permeable than

• thers; sometimes this is related sorting

Deepwater reservoir elements: lobe reservoirs

Northern Gulf of Mexico Lowstand Paleogeography

Kendrick (1998)

Green Knoll Frampton K2/Timon Shenzi Neptune Atlantis Mad Dog Puma

Northern Gulf of Mexico: Unconfined lobes now in Foldbelt

OBN WAZ & NATS Merge, TTI RTM -2010

’ ’

OBN WAZ & NATS Merge, TTI RTM -2010

’ ’

Walker et al, 2012

Green Knoll Puma Mad Dog Shenzi Komodo K2 Atlantis GC AV WR L 10 Miles Fan System Salt near seafloor in early Miocene ? ?

lower Miocene lobes

Dendara Frampton

Walker et al, 2012

Green Knoll Puma Mad Dog Shenzi Komodo 13 Miles 15 Miles 8 Miles 12 Miles

Regional correlation of lower Miocene depositional lobes Walker et al, 2012

200 feet

13 Miles 15 Miles 8 Miles 12 Miles

DD EE

lower FF upper FF

Green Knoll Puma Mad Dog Shenzi Komodo

Regional correlation of lower Miocene depositional lobes Walker et al, 2012

200 feet

Depositional lobes: reservoir architecture

Mander et al, 2012

Depositional lobes: reservoir architecture

7 Miles 7 Miles

Mander et al, 2012

3 Miles 200 feet

Mander et al, 2012

Depositional lobes: reservoir architecture

200 feet

bed lobe element lobe lobe complex ( or fan) 27 km x 13km x 5 m 0.1 km x 0.1 km x 0.5 m 44 km x 29 km x 50 m 5 km x 3.5 km x 2 m DD fan lower FF fan fan complex 95 km x 80 km x 170 m Expected dimensions of architectural elements

(this study) (from Karoo basin analog: Prelat, and

• thers, 2010)

upper FF fan EE fan

Depositional lobes: details in reservoir architecture

Mander et al, 2012

Mander et al, 2012 Much of this detail is below seismic resolution

Depositional lobes: details in reservoir architecture

Although lobe (sheet) sands and sandstones are considered to be some of the best deepwater reservoirs, each field has its own set

• f characteristics that make it a challenge to produce.

Several case studies of fields with lobe (sheet) reservoirs indicate that the initial reservoir models were overly simplistic, and the actual complexity of the reservoir was only discovered with field production. Shales at various scales are important because they, too, are laterally extensive and offer the potential for isolating individual sheet sands and sandstones and packages of sheet sands and sandstones. In some reservoirs, this results in multiple fluid contacts and depletion rates. Development scenarios should make use of the sealing capacity of shales for selective water flooding and horizontal drilling.

Summary: reservoir lessons learned

Channel-fill reservoirs: have proven to be great reservoirs in some deepwater settings (Angola (> 4 Bbbls), Nile (> 50 Tcf), Nigeria, Gulf of Mexico, North Sea). Channels have relatively low aspect ratios (30:1 to 300:1) and are considerably longer than they are wide. Channels vary from erosional to erosional/aggradational to purely aggradational (channel-levee) types. On seismic-reflection data, channel fills show a variety of geometries, including shingled reflections (laterally migrated packages), offset patterns with aggradational fill, and entirely aggradational fill. Lithofacies and grain-size distribution are also highly variable in channel-fill deposits and create many baffles and barriers to pressure and fluid communication.

Deepwater reservoir elements: channel-fill reservoirs

Slope settings: erosional channels and their fill

Treacle (D) Polaris (C) Giza North (B) Giza South (A)

10km

Subregional Strike Line

150km

Butterworth, 2012

Mid Pliocene-Pleistocene WND Strike Section

Giza Channel Complex Set P80 MFS

2 km 200m

P78 MFS Leveed channels Lobes

SW NE

Slide blocks MTD MTD slide

Butterworth, 2012

distal

• A. Giza South

~ 35km from shelf edge

100ms 100ms 100ms

• B. Giza North

~ 50km from shelf

100ms 100ms 100ms

• C. Polaris

~ 75km from shelf

100ms 100ms 100ms

• D. Treacle

~100km from shelf

750m 750m 750m 750m 100ms 750m 750m 100ms 100ms 750m 750m 750m 750m 750m 750m

proximal Butterworth, 2012

Stage I Stage II Stage 0 Stage IV Stage IV III

Sandy channel element Sandy channel element - axis Sandy channel - margin Abandonment levee Abandonment levee – along axis Levee (internal) Muddy channel Levee (external) Lobe

400m

flattened time slice

Butterworth, 2012

flattened time slice flattened time slice + 20ms flattened time slice + 40ms flattened time slice + 60ms flattened time slice + 80ms flattened time slice + 100ms

GIZA NORTH-1 NAB-1 GIZA NORTH-1 NAB-1 GIZA NORTH-1 NAB-1 GIZA NORTH-1 NAB-1 GIZA NORTH-1 NAB-1 GIZA NORTH-1 NAB-1

Butterworth, 2012

GN-1 GS-1

10m

SST TB TB TB

Giza South-1-P80-Levee A B C D E F G H

SLT TB TB SLT MST

Giza North-1-P80-Channel Complex A B C D E F G H

TB SST SLT SLT MST SST SLT MST

• Downdip of Structure:

Preservation of Channel Axis

• Updip of Structure:

Preservation of channel margin and levee

Butterworth, 2012

Turbidite Silts Amalgamated Lobes & Levees Abandonment Levees & “Terminal Lobes”

Thin Bedded, Laminated Thick Bedded, Graded, Massive

1.5 km 145 m “channel complex set”

• I. Erosion & Bypass
• II. Aggradational

Phase

• IV. Constructional

Phase Muddy Debrites

15m incision “channel element”

Channel axis Margin

40-50m incision “channel complex”

• III. Switchoff

Injected Sand

Butterworth, 2012

Summary: reservoir lessons learned

Although channel fills are internally complex, the complexity is arranged in a hierarchical pattern, which is recognizable at outcrop (large) and seismic scales. It may be more difficult, but not impossible, to identify the hierarchy in wellbores and cores. Because of the extreme complexity of channel fills, reservoir performance can vary laterally within a reservoir. Proper well spacing and orientation are imperative for effectively draining hydrocarbons from channel fills. Proper well placement requires a knowledge of the nature of the fill that can only be determined with sufficient data early in the life of the field. Collect as much static data during drilling (e.g. cores, wireline and image logs, biostratigraphy) and collect dynamic data frequently to monitor. Spectacular failures: Mauritania example

Unconfined settings: deeper targets

Gardosh, 2012

Additional potential reservoirs? Large volumes of reserves have been found in the Mesozoic strata in many deepwater margins in the world Need good 3D seismic resolution to accomplish Deeper targets: although largely fine-grained, potential for good sands to develop Local build-ups Possibly fractured Lessons from the Santos Basin, Brazil

: Microbialite carbonates

Finis