Graduation Semester and Year

2010

Language

English

Document Type

Thesis

Degree Name

Master of Science in Earth and Environmental Science

Department

Earth and Environmental Sciences

First Advisor

John Holbrook

Abstract

The Northwest Shelf of Australia contains many producing world class gas reservoirs with large areas remaining unexplored. The fluvio-deltaic Mungaroo Formation of Rankin Trend on the Northwest Shelf is the site of many producing fields on the Northwest Shelf and data collected from these sites is invaluable in understanding the architecture and geometry of the fluvial strata that house these reservoirs. The Mungaroo Formation contains alternating sections of low accommodation amalgamated sand bodies, and high accommodation shale prone sections that record architecturally complex floodplain deposits. The study sections were broken down into eight architectural elements; thalweg fill, unit bar, abandonment phase, floodplain mudflat, crevasse splay, splay delta, open lake, and swamp. This work presents architectural and geometrical interpretations of the high and low accommodation sections of the Mungaroo Formation on the Rankin Trend using core.The low accommodation Lower E amalgamated sands are multiple channel belts thick and display internal architectural complexity that implies internal higher order surfaces up to the sequence boundary level and the buffers and buttresses model is employed to gain a better understanding of their regional context. The channel/channel belt geometries can be divided into three size populations that can be reconciled by using the modern Pilbara as an analog.The Middle E and Upper F high accommodation sections are complex mud and silt dominated floodplain deposits. This study suggests that floodplain deposits may have a better reservoir potential than current thinking implies due the complexity of the sand bodies and the tendency of splay deltas to form ribbon channels, not lobes as current thinking implies, that connect channel belts, thus, creating larger reservoirs consisting of multiple channel belts. A better understanding of the areas complicated sedimentology will enhance current fields production, and assist in ongoing exploration efforts.

Disciplines

Earth Sciences | Physical Sciences and Mathematics

Comments

Degree granted by The University of Texas at Arlington

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