Geoffrey Thyne Science Based Solutions LLC

Geoffrey Thyne Science Based Solutions LLC

 Introduction  Observations  Chemistry and Physics

 Predictions  Future Work

160°C

Late Diagenesis

120°C

Diagenetic Window

80°C

Diagenetic reactions

Physical Effects

Pedogenic processes Early carbonate cements Quartz cementation Clay coats Dolomitization

Clay infiltration Bioturbation Compaction

Silica diagenesis (opal A to CT) Clay diagenesis (ordering of smectite) Carbonate dissolution Feldspar dissolution Kaolinite formation Hydrocarbon generation Albitization Chlorite precipitation Ferroan carbonate precipitation Quartz overgrowths

Only Five Common Styles Zone of intense diagenesis

Early Diagenesis

20°C

Carbonate dissolution Thermal degradation of hydrocarbons

"Terminal mineral assemblage" = Alb./Qtz./Cal./Chlor./Ill.

 Quartz (with clay and late Fe

  

carbonate cements) Clay (with quartz and late carbonate) Early grain-coating clay Early carbonate or evaporite (often localized) Zeolites (late non-Fe carbonates) Primmer et al., 1997

 Carbonate cements can reduce porosity to zero.  Often stratigraphically-controlled = lithologic contacts .  Distinctive geophysical expressions (bulk density, resistivity,    

sonic travel time, neutron porosity ). Cementation in all depositional environments. Cementation can be, but is not always related to depositional environment. Variety of modes – disseminated, massive, concretions, laterally continuous beds. Local sources predominate (intra and inter-formational).

 Por/perm loss or gain may be spatially restricted

 Scales range from cm’s to km’s  Difficult to predict Calcite Cement

Dolomite Cement

Tensleep Sandstone 4208 feet

Uncompacted sample from outcrop, showing approximately 25-30% porosity. Sample CD2-8 from outcrop channel facies, (Org. M=Organic Matter), (P=Porosity – Blue Areas), (F=Feldspar), (C=Carbonate Grain), Q=Quartz).

Early Cementation

Poikilotopic carbonate cement (PC) from outcrop (sheet) sample #SD2-1. (Org. M=Organic Matter), (F=Feldspar).

Early Cementation

Grain-rimming siderite and pore-filling Calcite 5265 feet Pembina Field, Canada

Well Bore SP

Vertical Scale (feet) 0 10

sample points

"A" Sand

20

1 2 3 4 5 6 7 8 9 10

% acid soluble

Later Carbonate Cement 0 2000

y = 30696e-0.1331x

Depth (ft)

4000

R2 = 0.8369

6000 8000 10000 12000 14000 16000 0

5

10

15 20 Porosity (%)

CSM #61 CEPO PMt. Desert Springs Crestone Hay Reservoir Hay-hydrostatic Great Divide Strike Unit Series1 25 all data 30 35 40

Replacement

Cb-D Cb-c

P

Cb-R A

0.1mm

Replacement textures and other authigenic components in the Dad Member of the Lewis Shale. (A) Carbonate replacing (Cb-R); plagioclase (P); detrital carbonate (Cb-D) and cement (Cb-c). Clays altering cherty grain (arrows); (XPL). Well 10-Triton 13321 ft (20x).

Poikilotrophic Ferroan (Fe-rich) calcite fills most porosity (18-25%) creating flow barriers

Later Cementation

North Sea, Oseberg - Well 30/9 –B40

Abundance (%) 0 1 2 3 4 5 6 7 8 9 10

3180 3200

Shale

3220 3240 3260 3280 3300 3320 3340 3360 3380

Sandstone 22%

 Thick to thin beds, lateral extent is highly variable.  Both early and later carbonates can form laterally-extensive

zones of cement.  Later cements are often co-located with early cements.  Temperature Zones    

Early (15-30°C) Eogenetic/Mesogenetic boundary (50-70°C) Associated with oil generation (80-120°C) Post-generation (120+°C)

 Most temperatures come from IGV and isotopic data which

have some uncertainty.  Geologically rapid, short-term events

Carbonate Cemented Zones

Machent et al 2000 Van Der Bril and Swennen 2008 Al-Ramadan et al 2005 Girard 1998 Beckner and Mozley 1998 Dutton 2008 Ali 1995 Mansurbeg et al. 2008 Taylor and Machent 2011 Taylor et al. 2004 Molenaar 1998 Gierlowski-Kordesch 1998

Timing E, L E, L E, L L E E E to L E, L E, L E E E

Lateral extent 100-1000's m 10-100 m 10's m 100's m 100's m 100's m km's ? 100's m km' s 100-1000's m 50-100 m

thickness cm to m cm to m cm to m 1-2 m 0.2-0.3 m 0.3 m ? 30-100 cm 1.5 m 0.5-2 m 2-60 cm 30 cm

Local Sources yes yes yes no no yes yes yes no yes yes yes

Hammer et al. 2010

E, L

100's m

0.2-2 m

yes

 Tidal Pumping (seawater-freshwater mixing)

 Evaporative pumping (cretes)  Sulfate reduction and methanogenesis

 Aragonite to Calcite  Chemical Compaction

 Plagioclase Dissolution  Smectite to Illite (clay reactions)

 Decarboxylation  Oil Generation/Kerogen Maturation

 Deep Fluids

Carbonate Cementation Reactions

Carbonate Cemented Zones •

Most of the wells with cemented zones (68%) have one to three zones with a few having more than three.

•

•

Multiple cemented zones are best developed in the southern area near the major fault zone. Location of the cemented zones is not well correlated to any sedimentary/deltaic structures such as depositional surfaces, lag deposits, edges of lobes or channel bases.

Calcite cemented zones in vertical wells not including ankerite zones near basal contact

Carbonate Cemented Zones

7 Thickness of Carbonate Zones in the Oseberg Field (Oseberg Formation)

6 5 Thickness (m)

26 vertical and 7 horizontal wells have carbonate cemented zones. Carbonate forms relatively thin bands,