GNS Science1 Fairway DriveAvalonLower Hutt 5010PO Box 30368Lower Hutt 5040New ZealandT +64-4-570 1444F +64-4-570 4600

3400

3500

3600

3700

3800

3900

MH

2

MH

2 M

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MH

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4

PM

3a

3100

3200

3300

3400

Dm

-Dh

Dw

MH

1P

M3

3600

3700

3800

3900

4000

4100

MH

1P

M3

4650

4700

4750

4800

4850

4900

4950

5000

5050

MH

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Dm

-Dh

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-Dh

MH

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MH

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4

Pukeko-1 Maui B-8(P) Kapuni-13 Cardiff-1

Depth

(m

)

Depth

(m

)

Depth

(m

)

Depth

(m

)

GR GR GR GRF/D

Age

F/D

Age

F/D

Age

F/D

Age

M Z

one

M Z

one

M Z

one

M Z

one

Sett

ing

Sett

ing

Sett

ing

Sett

ing

QE

M

QE

M

QE

M

QE

M

Core

Core

Core

Core

TS

TS

TS

TS

MH2/MH1 boundary: OmataMember/D-shale equivalent

upper part of MH1 zone (Dm-Dh): K3E Sandstone in KapuniField and D-sands in Maui Field

Intraformational mudstonesand coals

lower part of MH1 zone andPMb zone (Dw)

Eocene

Paleocene

3. Well Correlation

Well correlations have been made both perpendicular and parallel to the paleoshorelineusing wireline logs constrained by biostratigraphy (e.g., Fig. 2). More detailed correlationis planned following targeted biostratigraphic analyses and full facies interpretations.

The top of the Kaimiro Formation is taken as the base of a widely developed marinemudstone (Omata Member/D-shale) of Heretaungan age (Dh), equivalent to the upperMH1 miospore zone. The base of the study interval (Paleocene/Eocene boundary) istaken at the top of the PM3a miospore zone.

Figure 2. ENE-WSW oriented cross section through the coastal plain/marginal marine environment from

Cardiff-1 to Pukeko-1, approx. parallel to the depositional paleoslope. Biostratigraphic sample depths

(F/D, foraminifera/dinoflagellate; M, miospore), cored intervals, thin section (TS) and QEMSCAN (QEM)

sample depths are shown. Setting is the broad depositional environment with the key presented in Fig. 1.

These data suggest that much of the producing K3E reservoir of the Kapuni Field (estuarine channel

facies) may be time-equivalents to the producing D-Sands of the Maui Field (tidal channel facies).

wsw ENE

Reservoir Quality Prediction for the KaimiroFormation, Taranaki Basin

1. Introduction and Methods

The Early to Middle Eocene Kaimiro Formationrepresents an attractive reservoir play in TaranakiBasin. Hydrocarbons were discovered in theformation in the late 1960's, and are still beingproduced from the Maui and Kapuni fields today.However, the formation remains under-explored,partly due to burial depths, which are >4,500 mover much of the Taranaki Peninsula.

Preliminary results are presented from a newKaimiro Formation reservoir study beingundertaken at GNS Science. The main objectivesare facies interpretation, correlation, petrographyand reservoir assessment, ultimately with the aimof developing a better understanding of thecontrols on reservoir quality, and in order todiscriminate regions where the Kaimiro Formationis likely to have the most favourable reservoirproperties.

The study area extends along the length of theENE-WSW trending reservoir fairway, andincludes many newly released offshore wells (Fig.1). Open-file biostratigraphic data, core data, andpetrographic data has been used. New analysesare planned which will target data gaps andthereby better illustrate reasons for reservoirvariability within the formation.

ReferencesCore Laboratories,

Flores, R.M.,

Higgs, K.E., Strogen, D., Griffin, A., Ilg, B., Arnot, M.,

King, P.R. and Thrasher, G.P.,

Strogen, D.P.,

2007:

2004:

2012:

1996:

2010:

Detailed petrographic evaluation of sidewall core samplesfrom Hector No.1 well. PR report 3806.

Coal buildup in tide-influenced coastal plains in the Eocene KapuniGroup, Taranaki Basin, New Zealand. AAPG Studies in Geology, v.51, p.45-70.

Reservoirs of theTaranaki Basin, New Zealand. GNS Science Data Series No. 2012/13a.

Cretaceous-Cenozoic geology and petroleumsystems of the Taranaki Basin, New Zealand. IGNS monograph 13.

Updated paleogeography maps for the Taranaki Basin andsurrounds. GNS Science Report 2010/53.

AcknowledgmentsThis project is supported by public research funding from the Government of NewZealand; we also acknowledge NZ Petroleum and Minerals for funding the PEGIinitiative, which has provided a source of petrographic data (Higgs et al., 2012).

Authors: Karen Higgs and Ian Raine; Email Contact: k.higgs@gns.cri.nz

6. Summary

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The Early to Middle Eocene Kaimiro Formation is considered to be a good reservoir target along most of the coastal plain to shallow marine reservoirfairway due to 1) common occurrence of fine-, medium- and coarse-grained sandstones, and 2) a consistently quartz-rich, lithic-poor composition.

Excellent reservoir properties have been proven in marginal marine channel facies at Maui and Kapuni; slightly poorer reservoir properties occur incoastal plain facies at Toru-1.

There is little available data for shallow marine facies, but these deposits are likely to contain some of the best reservoir properties due to: dominantmedium grain size with moderate-good sorting; high energy facies with little detrital matrix; good lateral sandbody connectivity; good vertical stackingof sandstone beds (i.e., less heterolithic than sandstones within the coastal/marginal marine environment).

Relatively poor reservoir properties occur in the deeply buried parts of the stratigraphy (>4.5 km) due to severe compaction, and relatively abundantquartz cement and illitic clay minerals.

Preliminary results indicate that the best reservoir quality is likely to be developed in the high energy facies of marginal to shallow marineenvironments, where present-day burial depths are < 4 km.

4. Petrography

Sandstone grain size and mineralogy has been determined bythin section analysis of core and SWC samples. Most samplesare from fluvial or tidal/estuarine channel facies, with a few SWCsamples from the shallow marine facies (wells Tui-1, Hector-1,Hochstetter-1). QEMSCAN data is available for some cuttingssamples and this allows grain size and mineralogicalassessment through uncored parts of the Kaimiro Formation.

Grain size data show the Kaimiro Formation to comprise veryfine- through to very coarse-grained sandstones (Fig. 3). Fine(upper) through to coarse (lower) sandstones predominate, withoverall more coarse-grained facies in the relatively proximalsettings (fluvial/estuarine channel facies); these coarsersandstones are generally associated with moderate to poorsorting (Higgs et al., 2012). Medium-grained sandstonespredominate in the shallow marine depositional environment,and are often characterised by moderate to good sorting.

Point-count data suggest the mineralogy of sandstones is fairlylimited, with most samples plotting as feldsarenites orsubfeldsarenites (Fig. 4). These results are consistent withQEMSCAN data of cuttings, which illustrate the quartzosenature of the samples, both stratigraphically and geographically(e.g., Fig. 5). The formation is lithic-poor, feldspar is typicallyminor, and K-feldspar is the dominant feldspar type. Feldspar isparticularly scarce at Cardiff-1, which we interpret to be relatedto the deep burial depth and advanced diagenesis at thiswellsite.

Clay minerals are variably abundant in the Kaimiro Formation.Detrital clay is common in the relatively fine-grainedsandstones (low energy facies), and mica is locally common intidally influenced facies. Authigenic clay minerals are locallyabundant (e.g., at Pukeko-1, Kapuni-13, Cardiff-1). However,the dominant clay differs (Fig. 6), which we interpret to be due todifferent burial and fluid histories. Other authigenic mineralscomprise locally pervasive carbonate cements and generallyminor quartz cement; abundant quartz overgrowths have onlybeen identified in deeply buried wells.

Figure 4. Ternary diagram showing the quartz-

feldspar-lithic composition (Q-F-L) for the Kaimiro

Formation based on thin section data. Hector-1 data

from Core Laboratories (2007).

Figure 3. Histogram summarising the mean grain

size for Lower-Middle Eocene sandstones based on

thin section petrography and QEMSCAN. Data has

been grouped into relatively proximal to relatively

distal wells.

Background

Quartz

Fe-infiltrated Muscovite

Chlorite

Biotite/Phlogopite

K-Feldspar

Plagioclase Feldspar

Illite/Muscovite

Glauconite

Smectite

Kaolinite

Pyrite

Calcite

Ferroan Calcite

Dolomite

Ferroan Dolomite

Fe-Oxides

Siderite

CaFeCO3/Ankerite

Heavy Minerals

Porosity

Figure 5. QEMSCAN image maps for selected Early to Middle Eocene cuttings showing

dominant quartz and subordinate/minor feldspar grains. Lithified sandstones occur over

parts of the Taranaki Peninsula where strata are deeply buried. Loose grains are dominant

elsewhere and may be indicative of better quality sandstones.

Kiwa-1, 3481 m: Loose grains are

dominant and may be indicative

of poorly consolidated

sandstones. Quartz dominant,

subordinate feldspar.

Tui-1, 3470 m: Loose grains are

dominant, mostly quartz,

suggesting presence of poorly

consolidated, quartzose

sandstones.

Pukeko-1, 3585 m: Sandstone

with quartz and remnant feldspar;

abundant kaolinite interpreted as

a diagenetic alteration phase

related to acidic flux.

Te Whatu-2, 3453 m: Common

loose and coarse quartz grains;

finer lithologies including kaolinite

and carbonate cemented

sandstones.

Kaimiro-1, 4750 m: Common

sandstone cuttings suggesting

the presence of relatively lithified

deposits. Quartz dominant,

subordinate feldspar, illitic clay.

Cardiff-1, 4845 m: Common

sandstone cuttings, predominantly

composed of detrital quartz and

authigenic illite; rare feldspar due

to advanced feldspar reactions.0

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vfL vfU fL fU mL mU cL cU vcL

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Grain Size (class)

020406080100

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FMaui Field Kapuni Field Cardiff-1Toru-1 Pukeko-1 Maui-4Tui-1 Hector-1 Hochstetter-1

Sublitharenite

Subfeldsarenite

Quartz Arenite

LithareniteFeldspathicLitharenite

LithicFeldsarenite

Feldsarenite

Note

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ldsp

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Proximalwells

Distal wells

Clays dominated by illite

Clays dominated by kaolinite

Illite/muscovite

Depths are present-day, along-hole (AH).

Plots are in stratigraphic order with the left-handplot representing the shallowest sample.

Fe-muscovite/biotite

Chlorite

Kaolinite

Smectite

Glauconite

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Hochstetter-1c. 3 km

Kiwa-13.2-3.6 km

Pukeko-13.5-3.7 km

Rahi-13.1-3.3 km Toru-1

3.8-3.9 km

Kapuni-133.7-3.9 km

Cardiff-1c. 4.8 km

Kaimiro-14.5-4.8 km

Maui-2c. 3.3 km

Tui-13.4-3.5 km

Maui-7c. 3.1 km

Maui B-8(P)c. 3.4 km

Te Whatu-2c. 3.4 km

Maui-42.2-2.3 km

Max extent of E

arly to

Middle Eocene shoreface

Min extent of Early

to Middle Eocene shoreface

N

Max extent of deposition orpreservation of the KaimiroFormation. From Strogen (2010).

Figure 6. Pie charts showing clay mineral composition based on QEMSCAN, plotted by sample and well. Clays include kaolinite,

illite/mica, chlorite, smectite, glauconite. Note locally dominant kaolinite (Pukeko-1, Te Whatu-2, Maui-4) interpreted as a diagenetic

alteration of feldspar and other unstable minerals during circulation of acidic fluids. Illite is dominant in deeply buried wells (Cardiff-1,

Kaimiro-1). Clay mineralogy in wells from the shallow marine environment (Hochstetter-1, Kiwa-1, Tui-1; <4 km depth) is generally

comparable (illite/kaolinite co-dominant). Note variable chlorite and glauconite, generally more common in marine-influenced settings.

5. Reservoir Quality

Conventional core analysis data are used here as a proxy forreservoir quality. Most data is from the Maui and Kapuni fields(Fig. 7A, 7B), which display similar ranges of porosity-permeability and illustrate the locally excellent reservoirproperties of marginal marine channel sandstones. Variability inreservoir properties is largely due to facies heterogeneities.

The cored sections at Toru-1 and Cardiff-1 do not contain thesame excellent quality sandstones as seen at Maui/Kapuni (>1Dpermeability; Fig.7C); slightly poorer quality at Toru-1 could berelated to the relatively proximal sedimentary environment,whilst poor reservoir quality at Cardiff-1 is a result of deep burial,advanced compaction and diagenesis (quartz/illite cements).

Conventional core analysis data from the shorefaceenvironment is limited to a few rotary SWC (Hector-1, Taranui-1). However, these data suggest that excellent qualitysandstones do occur in the shallow marine facies (Fig. 7D).

Figure 7. Measured

helium porosity versus

air permeability for all

conventional core and

rotary SWC samples,

Kaimiro Formation,

Taranaki Basin; data

from well completion

reports.

0.01

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Hector-1

Taranui-1

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Kapuni-14

Kapuni-3

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Maui A-1(G)

Maui-7

Maui B-P(8)

A) B) C) D)

Figure 1. Paleogeographic maps showing study well locations, the ENE-WSW trending

shoreline belt, and overall transgression from the Early to Middle Eocene (Dw to Dh). Maps are

modified from Strogen (2010).

2. Core Facies and Paleogeography

Conventional cores have been cut through the Kaimiro Formation in the Maui andKapuni fields (D-Sands/K3E reservoir respectively), with short cores also atCardiff-1 and Toru-1 (Fig. 1). Cored lithologies are vertically heterolithic,composed primarily of sandstone, siltstone, mudstone and, less commonly, coal(King & Thrasher, 1996; Flores, 2004). They represent a range of coastal plainand marginal marine facies, with fluvial and tidal/estuarine channels as the primereservoir facies. Conventional cores are not available for the more seaward,shallow marine depositional environment.

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Kapuni-3

Kapuni-8

Taranui-1

Kupe South-4

Fresne-1?

?

?

North Tasman-1

pene

plain

Hochstetter-1

Kiwa-1

Hector-1

Pukeko-1

Rahi-1Toru-1

Kupe South-4

Kapuni-13

Kapuni-14

Cardiff-1Te Kiri-1

Kaimiro-1

Inglewood-1

Maui-1

Maui-2Maui-5

Maui-3Maui-6Tieke-1

Tui-1Kiwi-1

West Cape-1 Amokura-1

Pateke-2

Kopuwai-1

Maui-7Maui B-8(P)

Moki-1

Maui-4

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pene

plain

Hochstetter-1

Kiwa-1Hector-1

Pukeko-1

Rahi-1Toru-1

Kupe South-4

Kapuni-13Kapuni-3

Kapuni-14 Kapuni-8

Cardiff-1

Stratford-1Te Kiri-1

New Plymouth-2

Kaimiro-1

Inglewood-1

Maui-1

Maui-2Maui-5

Maui-3Maui-6Tieke-1

Tui-1Kiwi-1

West Cape-1 Amokura-1

Pateke-2

Kopuwai-1 Taranui-1

Maui-7Maui B-8(P)

Te Whatu-2

Moki-1

Maui-4

Fresne-1?

?

?

North Tasman-1

Dw-Dm (c. 54 Ma) Dm-Dh (c. 49 Ma)

Shelf

Shoreface

Marginal marine

Coastal plain

Fan (from seismic)

Study well

Other well with Early-Middle Eocene

Other well, no Early-Middle Eocene

MauiField

N

KapuniField

50 km