Field Overview of West Seno
Authors: Chudanov Donald A. , Terry Albert , Partono Yoseph , Inaray Jossy 
Published: October 2008

The West Seno Field is located in the Makassar Strait PSC offshore East Kalimantan, Indonesia (figure 1). The field sits in 2,400 - 3,400 feet of water on the continental slope of the northern Mahakam Delta making it Indonesia's first deepwater development. The development concept uses two Tension Leg Platforms (TLP), one Floating Production Unit (FPU), and two export pipelines tied back to existing onshore infrastructure (figure 2). A staged approach is being used to fully develop the field. TLPA was installed in February 2003. Development drilling of 28 wells on TLPA commenced March 19, 2003 and will be completed by the end of 2004. TLP-B is scheduled to be installed during the last quarter of 2005 and development drilling of 20 wells on this platform should be completed during the first quarter 2006. Phase 2 production is scheduled to commence in the 1st quarter of 2006.

The field development follows up a successful exploration and appraisal program in the West Seno Field from mid-year 1998 through first quarter 1999. A total of eight exploration/appraisal wells were drilled in the West Seno structure. An extensive collection of subsurface data was obtained during the program which includes 3D seismic data, well log data, formation tester pressure data and fluid samples, drill stem tests, and conventional cores. Evaluation of the well data along with seismic interpretation and reservoir simulation provides the basis for the recoverable reserve assessment.

Reservoir sands in the West Seno Field are interpreted to have been deposited in a deepwater, intraslope basin setting during the Miocene period. The reservoir sands are a series of amalgamated channel and channel-levee deposits, which have both structural and stratigraphic trapping elements. The nature of these reservoir bodies is discontinuous and, sometimes with the available seismic and well data, the areal extent of the sands is difficult to predict. Relatively close well spacing is required to effectively recover reserves in the field.

Typical production wells are expected to need frequent well intervention to allow multiple recompletions during the life of the well. This led to the need for a dry tree solution for field development.

First production from the West Seno Field began on August 5th, 2003. As the Phase 1 drilling program continues, production from Phase 1 is scheduled to ramp up to rates of 30,000 to 40,000 BOE per day. The peak average daily production from the field is expected to reach 60,000 to 80,000 BOE per day after completion of Phase 2 of the field development. Designing for a lower sustained peak oil and gas rates with staged TLP's significantly reduces the up-front commercial risk. In addition, it reduces the total investment required for topsides processing facilities and deepwater pipelines.

Exploration and Appraisal History

Seismic Surveys

The acquisition of exploration 3-D seismic data in Unocal's East Kalimantan PSC outboard of the Serang Field in 1995 was initiated due to the encouraging results of the 1994 well, Berukang-1, which encountered in excess of 350 feet of reservoir quality Miocene sands with minor accumulations of oil and gas.