Biogenic Gas in Central Sumatra Basin

Biogenic gas is a distinct and uncommon type of natural gas that differs from conventional natural gas produced through the thermogenic process. Thermogenic gas forms deep within the Earth’s crust, where the heat from the mantle breaks down organic matter to create methane. In contrast, biogenic gas is the product of microbial decomposition of organic matter that occurs in relatively shallow, low-temperature environments, such as shallow sediments and swampy regions.

Biogenic Gas compared to Thermogenic Gas and Oil

How is biogenic gas special you may ask? because it generally has very high methane content, up to 98% and has low H2S and CO2 content, thus making it a high quality dry gas with relatively uncomplicated processing. This of course, may vary depending on the specific conditions of its formation. Typically, biogenic gas accumulates in small pockets scattered across formation, making it difficult to extract economically. Moreover, these pockets of gas are also a common drilling hazard that sometimes may trigger an unexpected kick during drilling operation.

However, Bentu, Segat, and North-Segat are three adjacent gas fields situated in the Central Sumatra Basin that are quite different. These fields contain a massive accumulation of shallow biogenic gas in a continuous reservoir, trapped within the Late Miocene to Early Pliocene Binio Formation (Lower Petani). The presence of biogenic gas in this area is attributed to the extensive deposition of organic-rich sediments in the region. The accumulation of gas in the reservoir is due to the unique geological and structural features of the field, which have created favorable conditions for gas trapping.

Central Sumatra Basin Chronostratigraphy

The Bentu PSC is a highly coveted resource for the national energy resilience. Its gas is currently utilized by various industries and also supplies gas to around 15,300 households in the Pekanbaru and Dumai City Gas Network. This field provides an excellent example of how careful geological analysis and exploration can uncover valuable gas resources in unexpected places.

Central Sumatra Regional Structure

Sources: US Energy Information Administration and Journal of Petroleum Geology

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