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Darwin gas condensate discovery

A 3D animation of the Darwin Field
The top Darwin reservoir amplitude surface is locked within the 3D depth cube. As the animation plays the seismic date in the horizontal plane is stripped back from shallow to deep (analogous to draining water from a bathtub). As the layers are peeled back firstly the crest of Darwin West is revealed in the foreground closely followed by the crest of Darwin East located behind at to the East of Darwin West. The animation stops at the approximate location of the hydrocarbon water contacts. The axes of the cube are orientated North to South (north being to the left) and West to East (East being the far edge of the cube). As a scale reference the distance from the western edge of Darwin West (image foreground) to the eastern end of Darwin East is approximately 17 km.

Top Reservoir Amplitude Map (click image to expand)

Seismic sections through Darwin West and East (click image to expand)

Sub-regional Aptian surface amplitude map (click image to expand)

Darwin East phased development (click image to expand)

Darwin discovery

Darwin’s Evolution

The Darwin field is located in 2000m of water and is approximately 2.6 km below the seabed. Darwin comprises two adjacent tilted fault blocks, Darwin East and Darwin West. The discovery well, drilled in 2012, is situated on Darwin East structure. The 3D seismic acquired in 2008 significantly de-risked the objective.  Pre-drill, the target was supported by a class 3 AVO response, flat spots and excellent amplitude conformance to structure on both fault blocks. The flat spots and conformance to structure are indicative of fluid contacts. Prior to drilling it was anticipated that fluid contacts represent the hydrocarbon water contact. The well was designed to target an Aptian aged shallow marine sandstone reservoir deposited on a broad marine shelf. Regional interpretation suggested the presence of the ubiquitous Early Cretaceous source rocks that would provide sufficient hydrocarbon charge to the field.

At the target depth the well penetrated a gross reservoir interval thickness of 84.5m, with a net pay of 67.8m. The average porosity across the reservoir interval is 22% and average permeability is 337 Md. The reservoir is a relatively immature, quartz-rich, shallow marine sandstone. The likely provenance of the reservoir sands is through erosion of the extensive Devonian quartzites that form the rugged hills and mountains on the present day Falkland Islands.

The reservoir was charged with a rich gas condensate. At reservoir pressure and temperature, the liquid hydrocarbons present are in a gas phase. As the pressure and temperature drops the liquids drop out, or condense, similar to how water droplets entrained in air will ‘condense’ out on a cold window pain. At surface temperature and pressure conditions the fluid separates into a gas and liquid phase. The liquid has properties of a light crude oil, 46 to 49 API. The initial liquid yield is relatively rich, 123–140 stb/MMscf.

A gas has a higher mobility in a reservoir compared to a liquid meaning that it will travel through the pores of that reservoir with relative ease compared to a liquid. Therefore, our expected hydrocarbon recovery rate is high due to the mobility of the hydrocarbon in the reservoir and the excellent reservoir quality.

Based on an independent resource assessment of the combined Darwin East and Darwin West fault blocks, the estimated un-risked (P5O) recoverable resource is 462 million barrels of liquids (the liquids comprise of 296 MMbbs of liquid condensate and 166 MMbbls of LPG)

A number of development scenarios have been considered, including the full development of Darwin East and Darwin West or a phased development. Engineering studies have demonstrated that the discovery, if successfully appraised, could be commercialised by a straightforward FPSO development, utilising proven, off-the-shelf technology. The liquids would be produced and the dry gas re-injected back into the reservoir.

Falkland islands

The Falkland Islands are a United Kingdom Overseas Territory. Supreme authority is vested in His Majesty The King and exercised by a Governor on his behalf, with the advice and assistance of the Executive Council and Legislative Assembly.
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Technical summary

Borders & Southern’s acreage is located in the South Falkland Basin, a frontier basin extending to the south and east of the Falkland Islands. Six wells have been drilled in the basin. In 2012 Borders & Southern made the first significant hydrocarbon discovery with exploration well 61/17-1.
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Darwin discovery

Darwin comprises two adjacent tilted fault blocks, Darwin East and Darwin West. The discovery well is situated on Darwin East. A clear flat spot and amplitude conformance to structure help define the hydrocarbon charged reservoir.
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