Publications

Indonesia’s growing gas market has turned shallow gas, previously considered a drilling hazard, to become a commercial opportunity. Since 2007, EMP Bentu Ltd, operator of the Bentu PSC has been producing shallow gas from the Binio Formation. Over recent years, several blow-outs have occurred in the shallow gas zones making this a hazardous operation. Now on its fourth shallow gas project, EMP Bentu has been continuously refining its development strategy. We present a case study of the Seng and Segat shallow gas field developments, in terms of both sub-surface studies and engineering practices. The Binio Formation sandstones are encountered at depths between 300 m and 700 m below mean sea level (MSL). Reservoir thicknesses vary from 1.5 m to 14 m, with porosities around 30% and permeabilities ranging from a hundred millidarcies to one darcy. The gas composition is more than 98% methane, with a carbon-isotope value range from –61 to –67%. Seismic bright-spots can be reliably used as indicators of the presence of gas. Given the shallow depths and minimal time to react, drilling hazards are a major concern. Reliable pore pressure prediction is critical to avoid drilling problems and ensure safe operations. To attain this, a three-dimensional pore pressure model and advanced arithmetic time-depth (T-D) conversion has been applied to the drilling program and operation. As a result, the drilling campaign in 2013 has been completed successfully without any major well control issues. Since Seng and Segat gas production began in early 2011, sales rates have increased to more than 35 MMSCFD. Drill stem test and production tests show that each well in the field could produce up to 10 MMSCFD with a wellhead pressure around 700 psia, avoiding the need for compression until future years. This demonstrates that shallow gas reservoirs can be economically attractive and effective in terms of production cost. A good exploration-development strategy, along with good reservoir management has been applied and is still being developed by the operator. Keywords: Biogenic Gas, Hazard, Seng and Segat Fields, Development.