Potential Proterozoic Petroleum System 20 July 2011

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AAPG International Conference & ExhibitionMilan, 23-26 October 2011

Siwalik Group (Mio-Pliocene)

Murree Group (Lr. Miocene)

Subathu Formation (Eocene)

Volcanic Rocks & Slates

Cambro-Triassic and Panjal Traps

Sirban Formation (Prote rozoic)

PUNCH

REASI

MUTHALJAMMU

Jhelum R.

1

2

34

L E G E N D

Inliers of Sirban Formation in the Jammu area

1. Dandili . Devigarh Inlier

2. Kalakot - Mahogala Inlier

3. Reasi Inlier

4. Dhansal - Sawalkot (Lop ri) Inlier

0 50 100 Km

I N D I A

Jammu and KashmirArea of Map

KATRAHAZARA

ISLAMABADSRINAGAR

Control ID: 1077114Potential Proterozoic Petroleum System, Northwest Himalayan Thrust Belt,Jammu (India)

Naveen Hakhoo1

, G. M. Bhat1*

, Sumita Koul1

, Jonathan Craig2

and Bindra Thusu3

1. Institute of Energy Research and Training (IERT), University of Jammu (India)

2. Eni, exploration and production division, Milan, Italy

3. MPRG, Department of Earth Sciences, University College London, UK

*e-mail:[email protected]

Introduction

The Proterozoic Sirban Formation is an allochthonous unit which crops out in detached inliers within the Himalayan

region of north India and as far west as the oil producing Potwar Basin in northeast Pakistan (Figure 1). The Reasi

Inlier, at 40 Km long and 12 Km wide, is the largest in the Jammu region.

Fig. 1. Regional geological map with location of the Sirban Formation inliers and generalized stratigraphy.(Map modified after Gansser, 1964)

The Sirban Formation comprises thick bedded, highly jointed, hard, dark grey, reservoir quality dolomite/limestone,

interbedded with seal horizons of chert and organic rich shale. The dolomite/limestone has vuggy, inter- and intra-

granular, fracture, and inter- and intra-layer porosity. The shale, with up to 10% TOC, has oil/gas generating

potential. The carbonate and shale horizons yield cyanobacterial trichomes, branching filaments, and a

Neoproterozoic microflora, including Synsphaeridium sp., Leiosphaeridiaspp., comparable with that reported from

North African Neoproterozoic shales and from Late Proterozoic carbonate reservoirs in the giant oil/gas fields of the

Siberian Platform. The presence of this microfloral assemblage, the microbial mats, stromatolitic biostromes (see

also Raha, 1984), and samples with TOC values of ca. 2.5% from the Muthal area (Reasi Inlier succession, Fig. 2)

suggest that the carbonates of the Sirban Fm. also have good hydrocarbon source potential.
mailto:[email protected]:[email protected]:[email protected]:[email protected]


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Gilgit

Srinagar Leh

Reasi

Jammu

AkasaiChin

Study Area

Kalakot

Triyath

Barakh

Chapparwari

Chakkar Coal Field

Pauni

Reasi

KatraMuttal

Kalimitti

Ans

Bidda

Dhyangarh

Kanthan

R. Chenab

Rad

Anji

Reasi Inlier

Lopri Inlier

3315N

33N

7 5 E7430 E

Sukhwal

GaliSiwalik Group

Murree Group

Subathu Fm.

L E G E N D

0 50 100

Sirban Fm.

Biostrome

Section Line

Fig. 2. Geological map of the Reasi Inlier and adjoining areas showing key localities and thrust contacts

Structure and Hydrocarbon Potential

The Sirban Formation is juxtaposed against the Tertiary sedimentary successions of the Subathu Formation (coal,

carbonaceous shale, nummulitic limestone) and the Murree Group (sandstone and mudstone) in the northern part

of the Reasi Inlier, and against the Siwalik Group (mudstone, sandstone and conglomerate) in the south. The

southern contact is the Reasi Thrust, a subsidiary of the Himalayan Main Boundary Thrust (Fig. 1 & 2). The

northern contact has conventionally been considered as a major regional unconformity, but recent study has

revealed that this contact is a back thrust, which may act as a hydrocarbon trap. The Subathu Formation and the

Sirban Formation are separated by a complex thrust zone at Muthal and the thrusted contact between these two

units has also been established along the central and terminal portions of the Reasi Inlier. The Sirban Formation,

Sabathu Formation, Murree Group and Siwalik Group sediments are all involved in a north directed re-entrant (the

structural embayment of Dasarathi, 1968). There is a Triangle Zone within the Reasi Inlier in the Anji Valley, east

of the Reasi town, and the Sirban Formation succession in the Reasi Inlier exhibits multiple generations of folds.

The Sirban Basin has experienced at least four different tectonic episodes (Raha, 1984). The TriangleZone may

be an important potential exploration target. To the north of the Reasi Inlier, the Chenab River veers abruptly from

west to south, forming a loop. This drainage anomaly suggests the presence of a subsurface tectonic structure

(Bhat et. al., 2009b), which is also a potential target for hydrocarbon exploration.


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Geochemical Analysis

Gas sampled from seeps in the Chenab River bed along the back thrust at Kanthan village has been analysed for

bulk chemical and isotopic composition (CH4, CO2, N2). The preliminary results suggest that the gas mainly consists

of CH4, is very dry and has 13

C

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Potential Proterozoic Petroleum System 20 July 2011