OFFSHORE EASTERN ALGERIA CASE STUDY: 3D PETROLEUM

SYSTEM MODELLING AND HYDROCARBON OCCURRENCE

Dr Mohamed ARAB

Co-authors: François roure, Marina Rabineau, Arezki Lassal, Didier Granjeon, Rabah

Bracene and Jacques Déverchère.

04/04/2017 1

OUTLINES

INTRODUCTION

GEOLOGICAL SETTING

INTEGRATED BASIN MODELING PROCESS

3D CONCEPTUAL GEOLOGICAL MODEL • Stratigraphy, Structure and geological maps (from seismic)

PETROLEUM SYSTEM ELEMENTSSource rock, Reservoir and Seals

THERMAL AND PETROLEUM SYSTEM MODELING • Thermicity, pressure prediction, timing of HC generation/

charge and hydrocarbon accumulations

CONCLUSION & RECOMMANDATIONS

The eastern Algerian offshore, as a frontier basin, is becoming a well studied basin in terms of

exploration geology, thanks to a large volume of G&G data and integrated research projects (e.g.

SPIRAL) initiated between SONATRACH and international scientific research organisations.

Regarding the favorable geological indications and the existing analogs of Mio-Pliocene PS in W.

Mediterranean, numerical basin modeling has been conducted for the needs of hydrocarbon potential

prediction.

3D conceptual geological model is needed before basin modeling process, using geophysical and

geological field data.

INTRODUCTION

Mihoubi et al. 2014

Offshore Jijel

Zone of interest

Back-arc basin of Oligo-Miocene and PQ Deposits, inverted at Quaternary.

Faccena et al. (2004)

GEOLOGICAL SETTING

Stratigraphic units

Facies type(field data, Seismic and by analogy)

Stratigraphic modeling

Sequences Evolution ‘T/R events

Facies and subsidence maps

3D Geological model

Geodynamics(Basin evolution)

Thermal modeling

Heat flow model

3D Petroleum system modeling

Petroleum systems(SR, Reservoir and Seal)

Geochemical data (Source rocks)

Pressure, temperatures, hydrocarbon accumulation and

resources

Crustal acrchitecture

Basin architecture

Inp

ut

fro

m g

eolo

gica

l stu

die

s

Blo

ck B

uild

ing

3D

Bas

in

mo

del

ing

Ou

tpu

t

BASIN MODELING WORKFLOW, TEMIS-FLOW SOFTWARE (IFPEN)

(1)

(2)

(3)

(4)

(5)

(6)

04/04/2017 6

3D CONCEPTUAL GEOLOGICAL MODEL

Stratigraphy and basin structure

(Block Building)

3D CONCEPTUAL GEOLOGICAL MODEL

Messinian

Pre-Messinian

P1: Seismic profil

Morphostructure and seismic facies

Off

sho

re d

eep

bas

in

Mar

gin

Cong.& Sand

Sandstone

Sandy shale

Shaly marl

Siliciclatis

Anhydrite

Salt

Marl

3D Geological Block

Time/Depthmaps

(2)

(3)

(4)

M. Arab et al. (2016a, MPG journal)

Stratigraphic onshore- offshore extrapolation

(1)

04/04/2017 8

PEROLEUM SYSTEM ELEMENTS

Geochemical data used for source rocks haracterization.

Identified Source rocks:Flysch shale (Cretaceous),Langhian shale and Burdigalian(Miocene).

The Messinian SR is defined by analogy.

Reservoirs (from onshoredomain):

Basal Langhien (within the TST and HST wedges.

PETROLEUM SYSTEM ELEMENTS (Reservoirs and source rocks)

Langhian reservoir, Littoral chanels,central margin.

Langhian reservoir(2), turbidites, central margin.

Langhian reservoir, (3) turbidites), central margin.

Langhian reservoir, (4) Shelf type,eastern margin.

Langhian reservoir(5) turbidites, eastern margin.

(1) (2) (3) (4) (5)

M. Arab , PhD. Thesis (2016)

SCHEMATIC REPRESENTATION OF THE PETROLEUM SYSTEM ELEMENTS

Possible source rocks Possible reservoirs,

Probable petroleum systems: Late Oligocene (R)/Burdigalian (SR); Burdigalian (SR)/Lower

Langhian (R), Langhian (SR)/ Late Serravallian (R), Langhian(SR)/Lower Messinian and Lower Messinian(SR)/Pliocene (R).

P3 section: interpreted from seismic

Potential trap

P3

04/04/2017 11

THERMAL AND PETROLEUM SYSTEM MODELING

THERMAL MODELLING RESULTS

The GG ranges from 50 to 70 °C/km, the surface HF= 65 to 85 mw/m² and the temp. varying from 100 to 200°C in the pre-salt series.

2D Temperatures

Thermal gradients

Surface heat flow

M. Arab et al. (2016b)

PRESSURE PREDICTION

Pressures at Lower Langhian (pre-salt layer) Vary from 7000 to 14000 psi (deep troughs)

M. Arab et al. (2016b)

(a) Oil generation period: 7 Ma- 0Ma,Gas generation at PQ period

(b) Occurring of gas accumulation (C1- C5) in the Serravallian reservoir (stratigraphic trap).

The MSC induced HC loss av. 6 Ma in the same reservoir.

TIMING OF HYDROCARBON GENERATION, 1D MODELING (VERTUAL WELL)

The rate of conversion to hydrocarbons is defined by a first-order rate equation known as the Arrhenius

equation. Kinetic parameters of the organic matter are involved in the cracking simulation.

M. Arab et al. (2016b)

3D HC MIGRATION, GAS AND OIL SATURATION,PROSPECTIVE ZONES FOR EXPLORATION

1st SCENARIO: SYSTEM WITH

CLOSED FAULTS

2nd SCENARIO: OPEN SYSTEM

Langhian playStructural traps

(Gas)

Serravallian playStratigraphic traps

(Oil)

Lower Messinian playSlope fans

(Oil)

The HC saturation maps are taken from 3D block.

M. Arab etal. (2016b)

2D PETROLEUM SYSTEM (PS) MODELLING RESULTSTHERMAL MATURITY OF THE SR, AND HYDROCARBON SATURATION WITHIN RESERVOIRS

(1) N-S Section of TR, indicating moderate to high thermal maturity of the main possible source rocks (Late Burdigalian, Late Langhian and Lower Messinian).

(2) 2D PS model: oil saturation in the OMK and Serravallian reservoir.

(3) Gas saturation in the OMK and Serravallianreservoir.

(4) Oil saturation in the OMK (Oligo-Miocene), Serravallian reservoir and Lower Messinian (at the upper margin).

(1)

(2)

(3)

(4)

In TemisFlow, whole hydrocarbon migration is governed by triphasic Darcy lawM. Arab et al. (2016b)

• THE THICKNESS (3000- +5000 M) OF THE SEDIMENTARY SERIES AND VARIETY OF FACIES ARE INDICATIONS OF PETROLEUM SYSTEMS

EFFICIENCY. • MESSINIAN (ANALOGY) AND LANGHIAN (LAB DATA) SOURCE ROCKS ARE THE MAIN SOURCE ROCKS WHICH MAY EXISTED IN THE DEEP

OFFSHORE BASIN.

• SEISMIC INTERPRETATION INDICATES EXISTENCE OF BOTH STRUCTURAL AND STRATIGRAPHIC TRAPS (REEFS, DSF AND CHANNELS).

• THE TIMING (7- 0 MY) OF OIL AND GAS GENERATION IS FAVORABLE FOR ENTRAPMENT IN STRUCTURAL AND STRATIGRAPHIC TRAPS .

• BASIN MODELING SHOWS HIGHER HEAT FLOW (70 TO 90 MW/M²) AND OVERPRESSURES IN THE PRE-SALT SERIES.

• PETROLEUM SYSTEM MODELING REVEALS HYDROCARBON CHARGE IN THE RAMP ANTICLINES ALONG THE UPPER MARGIN AND IN

STRATIGRAPHIC/STRUCTURAL TRAPS IN THE DEEP BASIN.

• THE AREAS EXTENDING BETWEEN 10-12 KM TO AVERAGE 65 KM (ZONE OF CONTINENTAL CRUST) ARE THE MOST PROLIFIC IN TERMS OF

HYDROCARBON ACCUMULATION.

• IN SUCH AN ACTIVE MARGIN, GEOHAZARDS STUDIES SHOULD BE UNDERTAKEN BEFORE ANY DRILLING ACTIVITY.

CONCLUSION

Algerian offshore

Thank You For Your Attention