Temana: Old Field, New Ideas and New Insights

Temana Field is located approximately 30km offshore from Bintulu in water depth of about 90 feet and was discovered in 1962 by exploration well TE-1. Development commenced following commercial volume confirmation by appraisal wells TE-9 and TE-10 in 1972. The field is divided into three areas; Temana West, Central and East. For more than 35 years, the development concept in Temana has been driven by the presence of structural plays. Well locations being placed mostly in the crest of anticlines. Even though there was a belief that a stratigraphic component was involved in the trapping mechanism, the bold move to test this concept was deferred until recently. Approximately 90% of the field’s production is from the H and I series which are characterized by<br>Miocene aged fluvial sands. The I60/I65 series in particular are said to have been deposited in a lower coastal plain environment with tidal influence. Developing the Temana fields entails several challenges, mostly due to the field’s rather intricate structure, consisting of over 80 structurally and stratigraphically isolated reservoir compartments. Furthermore, the channelised I60/I65 sands results in several pinch-outs, limiting the sand distribution across the field and resulting in relatively thin reservoirs. A new appraisal well TE-72 was drilled in 2004 in the Temana Saddle area to test the seismic anomaly on a plunging anticline for the presence of a combination stratigraphic and structural play. This appraisal well was motivated by encouraging results from wells TE-54ST1 and TE-71 for the I60 reservoir, in which a similar amplitude anomaly response was proven as oil bearing (Figure 1). Although the amplitude anomaly was not conformable with the structure at TE-72 well location, the well penetrated 58ft of thick<br>blocky I65 sands, confirmed as hydrocarbon bearing. The sand is observed to be shaled-out in the up-dip offset wells (Figure 2). This pinching-out of the I65 sands towards the northeastern direction gives the reservoir the stratigraphic play needed to act as a trapping mechanism for the hydrocarbon accumulation. Following the success of TE-72, several geological and geophysical studies were undertaken including a fluid substitution study and a reservoir characterization study on acoustics impedance inversion<br>volumes (Figure 3 & 4). This led to the drilling of three development wells (TE-73ST1, TE-74ST2 and TE- 51ST2) in the Temana Saddle area in 2006/07 to delineate fluid contacts and provide drainage points for I65 reservoir. The success of the drilling campaign is reflected in the production figure whereby production from a single well could reach as high as 3600 bopd. The producing wells confirmed the geological model and further established the integrity of the trapping mechanism. The accomplishment of the Temana Drilling campaign triggered more interest to further dissect the field. Existing seismic cube was reprocessed and subsequently an AVO study was embarked to further delineate the hydrocarbon bearing sands. The discovery from the appraisal well and the success of the recent development campaign inspire a new paradigm in exploring the Temana Field and opening a new chapter of stratigraphic and structural play concept, hence giving a new direction of exploration towards the flank of the structure.