Nautec Energy Solutions (Nautec) supported Korea Gas Corporation (KOGAS) for the review of four New Zealand Offshore Petroleum Exploration Permits (12TAR8, 12CB1, 12CB2, 12EC2) on offer as part of the 2012 Block Offer. The 4 blocks are located in 3 different New Zealand offshore basins.
The review included interpretation of available seismic data and ties to wells in the area. The petroleum system review evaluated the reservoir, seal and source potential of the permits. Based on these evaluations play concepts were developed and an inventory of prospect and leads generated, risked and resources calculated. Engineering considerations for well design, development and facilities planning was reviewed and economics estimated. Based on these results recommendations were provided for bid parameters.
Data for the project was supplied from the New Zealand Petroleum and Minerals Department, Block Offer 2012 Data Pack and other readily available and relevant material.
The Kapuni is deep and also spills however, there are some relatively flat areas that may develop into broad low relief closures. Forward work includes the delineation of the potential closure in the Kapuni. Detail the size and extent of the “Moki” submarine slope and fan deposits and further interpretation in the north-west region to see if fault related closures exists.
Some key risks identified within the basin which need to be considered while exploring 12TAR8 include:
- Kapuni Group is deep – expensive to drill within 12TAR8
- Sand against sand juxtaposition along fault bounded traps which could result in the structure leaking (ie North Tasman 1)
- Structuring post-dates peak oil migration or does not lie on a current migration pathway (ie North Tasman 1)
- Significant source rock maturity and volume in the area around identified trap. Kea 1 (SE of 12TAR8) and Te Kiri-1 (Nth of 12TAR8) have immature source rock and lack of significant fetch area to mature source rock
- Difficulties producing a high wax content crude such as the Maari oil
Further risks may become apparent as work progresses.
The offshore East Coast Basin is highly structured and difficult to interpret due to sparse well control and would require a longer time frame to evaluate it thoroughly. This is beyond the scope of this initial evaluation. Horizons have currently been interpreted as a first pass, with no fault interpretation; this was in an attempt to create a grid of data that could be tied over the area. This has been completed for the primary horizon, the approximate Mid-Miocene, this will now be further detailed and more accurately interpreted with mapping to be attempted in the final phase of this project.
Potential prospects are within or below the Miocene and are on basement highs, these key targets are:
- Structural leads
- Onlap/Fault plays
Other possible plays were identified and mapped as further seismic interpretation is undertaken, however will be time dependant and the primary focus will be on the mapping of potential leads. The Canterbury Basin tender area seems to not be greatly deformed, there is minor structural inversion and faulting along the northern and western margins of the basin. At this stage the prospectivity of 12CB1 is lacking with small drape structure mapped, however it should be noted that depth maps obtained from previous exploration in the area indicates that these structures are at a depth of approximately 6,000m in deep water (+1,000m).
Due to water depth (greater than 1000m), conventional wellhead platform is not a viable option. If the major produced fluid phase is gas condensate, potential options include (in order of increasing amount of reserves required):
- Subsea well(s) tied back to a subsea manifold, then fed by pipeline to shore based facility.
- Subsea wells tied back to Spar Production Buoy/Tension Leg Platform (TLP), then fed by pipeline to shore based facility.
- Subsea wells tied back to a floating LNG facility
The economics would improve dramatically if it could tie into a major development e.g. Carrack/Caravel. The option would then be to either sell the resource, or develop and tie in to their production facilities. Potential for sharing drilling rigs would also be there, saving on mob/demob.