wheatstone deep-1 exploration drilling

Chevron Australia is planning to conduct exploration drilling within the Northern Carnarvon Basin off the northwest coast of Western Australia between 2023 and 2025.

The proposed exploration well, Wheatstone Deep-1, is targeting a gas reservoir within production licence WA-47-L in Commonwealth waters to search for and confirm new gas resources.

Chevron Australia has submitted this Environment Plan to NOPSEMA, which has been made available for a 30-day public comment period. To view the Wheatstone Deep-1 Exploration Drilling Environment Plan or to submit a comment, visit info.nopsema.gov.au

Drilling is scheduled to commence between 2023 and 2025, subject to approvals and drill rig availability. Activities will be conducted 24/7 for up to approximately 50 days.

A mobile offshore drilling unit will drill a well below the seabed. It may be supported by up to three vessels.

The well will be drilled and a casing will be cemented into the ocean floor. The well is then drilled deeper from inside the casing. Following the shallow hole drilling a wellhead is installed on the seabed to support the deeper casings.

A blow-out preventer will be installed on top of the wellhead to enable control and monitoring of the well during drilling operations and to prevent an uncontrolled water, oil or gas flow out of the well.

A marine riser will be installed to provide a physical connection between the well and the MODU.

The process of drilling and casing the hole continues until the target gas reservoir of the well is reached.

Upon reaching the target gas reservoir, experts will evaluate the geological formation.

Once these activities are completed, the well will be plugged with cement at various depths and the wellhead will be removed to below the seabed.

Drilling activities will have the potential for environment interactions, known as ‘aspects’.

All planned aspects can result in environmental impacts and changes to the environment and may present environmental risks within the operational area, with the exception of underwater sound emission, which could extend approximately 13 kilometres from the source.

Unplanned releases and events may occur while conducting activities. 

The size of the ‘environment that may be affected’, also known as an ‘EMBA’ is based on an emergency condition’s worst case environmental scenario, which in this case is an unplanned spill event from a loss of well control.

The EMBA has been defined through combining 300 simulations of loss of well control under three different hydrological and meteorological conditions. Figure 2 shows the EMBA.

Control measures to prevent this event are in place, but Chevron Australia is required to assess this highly unlikely scenario.

In this scenario, cultural, ecological and social values and sensitivities may be exposed to hydrocarbons. These are considered environmental risks because they are not planned to occur.

Table 1 lists the potential environmental impacts, risks and control measures.

A 500-metre safety exclusion zone will be requested around the drilling unit for the duration of the exploration drilling activities.

Petroleum activities in Commonwealth waters are regulated by the National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA). Before petroleum activities can take place, Chevron Australia must develop an Environment Plan which will be assessed by NOPSEMA in accordance with the requirements of the Offshore Petroleum and Greenhouse Gas Storage (Environment) Regulations (2009). These regulations require Chevron Australia to consult with relevant persons whose functions, interests and activities may be affected by the petroleum activity.

The Environment Plan will describe the environment in which the petroleum activity takes place, provide an assessment of the potential environmental impacts and risks arising from the activity, and identify control measures to manage environmental impacts and risks to acceptable levels that are as low as reasonably practicable.

The environment plans outline how Chevron Australia has engaged with ‘relevant persons’, whose interests, functions, and activities may be affected and how their feedback has been considered and addressed.

Exploratory drilling environment plans must be submitted to NOPSEMA and published on its website for a 30-day public comment period.

Chevron Australia welcomes feedback from relevant persons prior to the public comment period to ensure feedback is incorporated into the draft environment plan before it is submitted to NOPSEMA and published on NOPSEMA’s website.

Summary of impacts/risks and key proposed controls – view Table 1.

We are committed to engaging with Traditional Owners and Custodians, commercial fishers, recreational groups and other relevant individuals and organisations, as required by regulation.

We are seeking your feedback if you consider your functions, interests or activities may be affected based on the information outlined in table 1.

Let us know if you consider there are any control measures we could implement to eliminate, reduce or avoid an effect.

You can contact us tollfree at 1800 225 195 or leave feedback online below.

If a relevant person asks that their feedback be treated as confidential, Chevron Australia will make this known to NOPSEMA and the information will be kept confidential.

 

Your feedback during the consultation period will be considered and incorporated into the environment plan.

We commit to keeping you informed and providing responses to any relevant person who so requests.

If you choose to provide feedback on this proposal, Chevron Australia will collect your name and contact details, in addition to your comments, for the purposes of maintaining contact with you and inclusion of your feedback in our submission to NOPSEMA. Provision of this information is purely voluntary, however if you choose not to provide it, we may not be able to contact you in the future regarding your submission.  Chevron may transfer your information to NOPSEMA, if required and if you do not identify it as sensitive, and to other Chevron affiliates including our head office based in the United States. For further information regarding how we protect your personal information, and your rights, please refer to our privacy notice.