Biwai & Turama (PPL 366 & 367)

These licences are located in the highly prospective onshore Papuan Basin close to oil and gas discoveries and production infrastructure.  Three prospective leads have been identified – Turama, East Turama and Gamma River.  Seismic acquisition in 2013-14 will determine if any can be promoted to drillable status.

Onshore PPL 366 and 367 are located only 16km south of the Barikewa gas discovery (Figure 2). The structural geological ‘grain’ in PPL 367 parallels that in the oil & gas producing Papuan Foldbelt which extends into the northern portion of the license.

Common Risk Segment by South Pacific Resources Ltd or ‘CRS’ mapping shows that PPL 366 and 367 are located in areas of high probability that effective Cretaceous age reservoirs, source and cap rocks are all present. In other words that Toro reservoir targets carry low play risk and the critical risk lies in the detailed imaging and definition of trap geometry.

Figure 1 is an example of a Composite CRS Map for the Toro reservoir combining reservoir, source and cap rock play risk maps for the Toro petroleum system. Similar maps have been produced for additional Cretaceous age reservoirs and for the Tertiary Petroleum Systems that dominate the offshore areas (including PPL 356 and 357). 

Figure 1   Composite CRS Map for the Toro Play (PPL 366 and 367). 

Turama & East Turama Leads (PPL 367)

South Pacific Resources Ltd has evaluated all available existing seismic and well data, and in particular Strontium data obtained from surface Darai limestone outcrop samples collected in PPL 367 (Figure 2). Integration of all these data suggests a possible structural trap, known as the Turama Lead, at Toro and deeper reservoir levels up-dip from the Turama-1 well penetration to the north of the license.

A second, similar yet apparently smaller East Turama Lead has also been identified to the east, entirely within PPL 367 (Figure 2).

Mapping of the surface strontium data values suggests that the surface crest of a four-way-dip-closed component of the Turama feature is located within PPL 367 (evident from the closed orange contour in Figure 3). No seismic data have yet been acquired over the Turama Lead to constrain the subsurface geometry at Toro and deeper reservoir levels. Further it is evident from the nearby Omati-1, Turama-1, Darai-1 & Barikewa-1 wells that the surface carapace of Darai limestone thins north-wards across PPL 367 (Figure 3).

The implication is that the subsurface structure of the Turama Lead may not exactly match its surface expression and that seismic data and fine-scale structural modelling will be required to further reduce uncertainty and risk prior to making a decision whether or not drilling is justified.

These initial observations are cautiously encouraging given that the surface expression of the Turama Lead based on the Strontium data has a similar size, shape and trend to the nearby Barikewa Gas discovery (Figures 2 & 3).

 Figure 2   Turama & East Turama Leads in PPL 367 (Evident from strontium data contours

Figure 3   Turama Lead to Barikewa Field Geological Cross Section (highlighted in Figure 2)

Gamma River Lead (PPL 367)

A complex fault-related feature, the Gamma River Lead has been identified mostly within and along the boundary of PPL 366 and 367 (Figure 4). The feature is located in the elevated footwall of an east-west trending extensional fault associated with a local convex jog in the regional Komewu Fault Zone (Figures 4 & 5).

The structural dip in the footwall panel south of the bounding fault is consistent with the strong regional south-eastward dip down into the Omati Trough. The Omati Trough is interpreted to be the local source kitchen for hydrocarbons migrating up regional dip into PPL 366 and 367. The presence of the Biwai Oil Seep supports oil migration towards the Gamma River Lead (Figure 4).

The structural geometry at the west end of the Gamma River Lead is very poorly imaged due to a paucity of seismic lines. It is therefore unclear given the current seismic grid whether or not the Gamma River feature closes in the west and therefore constitutes a petroleum trap.

Additional seismic data are required to better image the Gamma River Lead, especially at its western end. Seismic imaging will then either reduce the trap presence & effectiveness risks and promote the Gamma River Lead to potentially drillable status, or remove it from the lead inventory.

Figure 4   Top Toro Seismic Structure Map showing the Gamma River Lead (circled red)

Figure 5   Seismic line across the Gamma River Lead (Line A-B in Figure 6)