Cornea – Appraisal
Greater Cornea Fields, Browse Basin, Australia
18.75% interest, Operated by Cornea Resources Pty Ltd
The Greater Cornea Fields (being the Cornea, Focus and Sparkle Oil Fields and the Cornea North (Tear) Gas Field) are located in the Browse Basin, offshore from Western Australia and held via a Retention Lease (WA- 54-R).
The Greater Cornea Fields present a large in place oil resource contained in a challenging reservoir. At the time the Retention Lease was applied for and granted, production uncertainty was identified as the primary constraint to the development of the Greater Cornea Fields. A successful production test well designed to demonstrate threshold productivity for development initiation is required to commercialise Cornea. A production test well must be placed and constructed in the same manner as intended for field development in order to prove up viable well construction methodologies and technologies, ensure representative threshold oil production is achieved and control of gas and water ingress.
Given the favourable prevailing oil price when the Retention Lease was applied for and granted, numerous field development concepts were then considered to be economic (subject to achieving threshold production volumes).
The current?environment presents a further significant challenge to the field’s commerciality, having rendered as non-viable the field development concepts previously considered as potentially viable.
Reflecting the changed oil price environment, new development concept screening has been undertaken with the objective of identifying a field development concept with the potential to be commercial at current oil prices.
Following this screening, a field development concept predicated on the use of a Mobile Offshore Production Unit (MOPU) with a subsea holding tank and single point mooring has been selected for further investigation. This concept is significantly different to earlier concepts with significant cost reduction implications.
Integrated reservoir modelling and facilities work has been commenced to support design of a production test well capable of delivering threshold productivity using this development concept.
The Cornea oil and gas accumulation was discovered by Shell within the early exploration wells Cornea-1, 1B and 2. The wells are considered to have established the presence of a 25m gas column and a 22.2m oil column in the Albian sandstones of the Jamieson Formation. The field is a large drape feature. It accumulated 22 to 24 degree API oil derived from Early Cretaceous, Echuca Shoals Formation and possibly Late Jurassic source rocks in the Heywood Graben, located over 60km to the west. The field is split into three main structural components Cornea South and Cornea Central, both with gas and oil, and Cornea North with gas and no underlying oil presence.
In December 2009, Octanex participated in the Cornea-3 well which was drilled into the known oil and gas accumulation by the Songa Venus semi-submersible rig. The objectives of the Cornea-3 well were to define the location of hydrocarbon contacts and obtain data on the potential reservoir qualities of the Middle Albian and Lower Jamieson Formation.
The well penetrated the targeted Middle Albian and Lower Jamieson Formation B and C sand reservoir interval (2.2 metres deeper than predicted) but, as planned, just below the predicted gas oil contact.
The well was then deepened to penetrate exploration targets in the Early Albian and Aptian of the Lower Heywood Formation, before terminating at a total depth of 910.6m MDRT. The data obtained while drilling indicated the intersection of a hydrocarbon bearing column in the Middle Albian, Lower Jamieson Formation. The secondary exploration targets in the Lower Heywood Formation did not contain hydrocarbons.