Cooper makes new gas field discovery in Otway basin

Cooper Energy has made a new gas field discovery with the exploration well Annie-1 in the Otway basin offshore Victoria.

Ocean Monarch; Source: Quadrant Energy

The well is located in VIC/P44 where Cooper Energy is the operator and 50% interest holder and Mitsui E & P Australia also holds a 50% interest.

The Diamond Offshore-operated semi-submersible rig Ocean Monarch started mobilization from the Gippsland basin to the Otway basin offshore Australia to drill two offshore gas exploration wells for Cooper in late July. The rig started drilling the Annie-1 gas exploration well in early August.

In a statement on Friday, Cooper said that the well had reached total depth (TD) of 2,442 meters measured depth rotary table (MDRT) at 9:00 am AEST on September 4, 2019.

Within the Annie-1 borehole, the Waarre C and Waarre A Formation sandstones productive in the Otway basin were penetrated. The Waarre C primary target was encountered at 2,241 meters MDRT, comprising a gross gas column of 70 meters with gas-on-rock at its base. The net pay thickness is 62 meters.

The deeper Waarre A sandstone was encountered at 2,341 meters MDRT and was water wet. The analysis was carried out using Logging While Drilling (LWD) data. Wireline logging operations to collect pressure and sample data required to inform resource volume estimates and to determine gas composition have been completed. Data collected in Annie-1 is consistent with adjacent analogue producing fields. Laboratory analysis to confirm gas composition is to be conducted.

Cooper Energy Managing Director David Maxwell described the Annie gas discovery as a solid and promising result from the first well in the program.

“Annie-1 is the first offshore gas exploration well Cooper Energy has drilled in Australia and the first of an $80 million drill campaign by the Joint Venture this year to find new gas supply for south-east Australia.

“We are very pleased with the success at Annie. It is very encouraging for future exploration in the offshore Otway basin and for our strategy to build gas production around the hub of the existing Minerva Gas Plant.

“Preliminary analysis of the geological data from Annie-1 is consistent with the mid-range of our pre-drill estimates. In the coming months, we will complete the subsurface assessments and analysis of data to refine our estimates of field size and to inform decisions regarding field development,” said Maxwell.

The Annie gas discovery is the first by an offshore well in the Otway basin in 11 years, with the most recent being the nearby Netherby gas field in 2008. Annie-1 is located approximately 9 km offshore Victoria in a water depth of 58 meters. The field is located between the producing Henry (15 km west) and depleted Minerva (11 km east) gas fields.

Cooper Energy and Mitsui E & P Australia currently produce gas from the nearby Casino, Henry and Netherby fields. The presence of subsea infrastructure and future access to the existing Minerva Gas Plant enables the development economics for field discoveries in the region. The timing of any development will depend on rig scheduling for the drilling of a development well. With this proviso, a favorable decision on field development could result in the commencement of production from the Annie gas field in the latter half of calendar 2021.

The Diamond Offshore Ocean Monarch drilling rig is about to start preparations to plug and abandon Annie-1. Following this, the rig is scheduled to move to drill the second well in the two well program, Elanora-1 in VIC/L24, 23 km southwest of Annie-1.

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