Production Block B8/38 lies within the larger surrounding exploration Block G4-50 in the central part of the Western Basin geological province.

The Gulf of Thailand consists of four main Tertiary basins – Chumphon, Western, Kra and Pattani. The earliest date of basin development is Oligocene and movement along major faults initially resulted in N-S oriented grabens /half grabens. The basins are results of the collision of India with Central Asia in Eocene time which caused asymmetrical grabens and strike-slip faults with right-lateral movements, as well as en-echelon normal faults trending generally north-south. The grabens filled with non-marine to marginal marine Tertiary sediments. Underlying the graben sediments are a variety of Palaeozoic marine carbonates, granitic intrusive rocks and meta sediments. The Stratigraphy of the Western Basin comprises three main sequences: a pre-Tertiary sequence, a syn-rift sequence and a post-rift sequence.

The T2 and T3 oil bearing sands are within the syn-rift sequence. This sequence consists of Late Oligocene to Early Miocene fluvial-deltaic sands and shale. The T4 sand which is the primary producing zone in Bualuang oil field and the T5 unit which is also oil bearing are part of the post-rift sequence. This sequence consists of Mid Miocene fluvial clastics with minor marginal marine mudstone and sandstone.

The proved and probable (“2P”) reserves booked against the Bualuang oil field as at 31 December 2013 stood at 30.1 MMbo.  The field was initially thought to contain only 14 MMbo of 2P reserves and has undergone six reserves upgrades to date to take it to the 30.1 MMbo currently booked. In addition, over 17 MMbo have been produced since the field went on-stream in August 2008.

Production to date has mainly been from the T4 reservoir and this is where the majority of the 2P reserves sit. Further reserve and resource upside has been indentifed in the field following the drilling programme in 2013 and this resulted in 129% increase in contingent resources as at 31.12.13 to 27.8 MMbo.

In addtion to the main T4 reservoir which has been the focus of the majority of development activity to date, reserves or resources are now booked in the shallower T5 reservoir, the deeper T2 and T3 reservoirs and in the East Terrace.

Production on the Bualuang field has historically been range bound between 7,000 and 8,000 bopd as a result of there being only one well-head platform, Alpha, with ten producing well slots. In November 2012 the Group installed the Bravo platform, which contained 16 well slots, and embarked on an on-going development drilling programme that will drive annual production up to between 11,000 and 14,000 bopd.

The main producing reservoir is the T4 Miocene sandstone reservoir. It is characterised by excellent porosity and permeability which means that water will be produced through the reservoir if the wells are pulled too hard. To counter this we drill horizontal wells into the attic of the reservoir to maximise the stand-off from the oil-water contact.  There is strong aquifer support which helps to sweep the reservoir and we also have Electric Submersible Pumps (“ESP’s”) downhole that we set to the lowest possible level.

The majority of wells are brought on-stream at c. 1,500 bopd however in 2013, two development wells were completed in the deeper T2 reservoir, the first time this reservoir had been brought on-stream. These wells were expected to come on-stream at a lower rate than the T4 wells but both of the T2 wells actually went on-stream at over 2,000 bopd. The T2 reservoir appears to have an edge water drive, as opposed to the bottom water drive in the T4, which means there is a greater stand off from the oil-water contact so the wells can be pulled harder without water coning. As a result an extra two T2 wells have been added to the Bravo programme

The initial phase of development drilling from the Bravo platform is expected to complete in 1H 2014. Additonal slots will be added to the Bravo platform in 2014 and for the first time a number of new wells will be drilled with with dual lateral completions.

Scoping work is being carried out for additional infrastructure to develop the contingent resource. Construction of additonal facilities is expected to take place during 2015 with first oil from the facilities expected in 2016.

Exploration activities in the Gulf of Thailand are centred on the G4/50 concession. G4/50 covers 5,800 sq km and surrounds the B8/38 licence (that contains the Bualuang oil field).

The Gulf of Thailand is underlain by a series of rift basins and there are five sub-basins defined within G4/50: the Western Central; Bualuang; Western South; Kra Central; and Kra South sub-basins.  There is comprehensive 3D seismic coverage on the licence and from this data over 60 leads and prospects have been identified.  The majority of the preferred leads and prospects lie within the Bualuang and Western South sub-basins.

An Environmental Impact Assessment for 20 drilling locations in the Bualuang and Western South sub-basins is going through the approval process.  

On receiving the EIA approval, an extensive exploration programme is planned with the initial targets likely to include the following prospects:

Exploration wells in G4/50 are both quick and cheap to drill, taking around 10 days and costing c. $4MM*.  Any discoveries can be brought on-stream in around 18-24 months.

^{*Post tax offset}