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The future of large very mature oilfields relies upon the successful application of EOR techniques. This paper discusses from the Handil field case, the more useful concept and practices that are applicable to optimize oil recovery in a multi-layer, multi reservoir waterflooded field. The Handil field, discovered in 1974, is a giant mature oilfield located in the Mahakam Delta, Indonesia. The field was developed using conventional oil recovery methods: natural depletion and peripheral water injection and produced a maximum of 200,000 BOPD in the late seventies. Currently, the oil recovery is around 50% with a 15,000 BOPD production at high watercut. The Handil EOR lean gas injection project was started in November 1995 on five reservoirs and following its positive result was extended with six reservoirs in 2000. In 2003, an integrated study on the largest EOR reservoir was performed to assess the projects' performance. This included 3D geomodeling, reservoir simulation and chemical tracer injection. The study permitted to track the main effects of the gas injection, to identify "bypassed oil" areas and to define reservoir management guidelines for the other lean gas injection reservoirs. As field scale application of the gas injection technique is not sustainable since the gas is exportable, two other techniques are currently being evaluated as an alternative. Second Contact Water Displacement (SCWD) is planned to be introduced on the maturest lean gas injection reservoirs. Simulation studies forecast potential for this technique which also allows decreasing the volumes of injected gas. An Air injection pilot on a waterflooded reservoir was started in 2001. First results are encouraging but the injection was temporary suspended due to injector well problems after 6 months of injection. The project was comprehensively studied by compositional and thermal simulation and intends to restart early 2005. Integrated studies of the Handil reservoirs provided in-depth understanding of EOR mechanisms. This resulted in the ability to better model field performance and to forecast tertiary oil production more accurately. Introduction The Handil field, discovered in 1974, is a giant mature oilfield located in the Mahakam Delta of East Kalimantan, Indonesia. The field comprises over 500 hydrocarbon accumulations in structurally stacked and compartmentalized deltaic sands. Hydrocarbon accumulations are found at depths as shallow as 300 mSS and continue down to 3000 mSS. The structure of the field is a simple anticline, 10 km long and 4 km wide and is divided in a northern and southern compartment by an east-west fault (Fig. 1).

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper is presenting a workflow applied successfully during the summer 2003 on the Tambora Field in East Kalimantan, Indonesia. The combination of a modeler (PETREL) together with a geosteering application (INFORM) in real time was a new approach to generate scenarios of tool response to formation changes in a horizontal drain. The aim of this paper is to share our experience and describe the workflow, which came as a real help to geosteering as events can be anticipated with a certain reaction time.

This paper is presenting a workflow applied successfully during the summer 2003 on the Tambora Field in East Kalimantan, Indonesia. The combination of a modeler (PETREL) together with a geosteering application (INFORM) in real time was a new approach to generate scenarios of tool response to formation changes in a horizontal drain. The aim of this paper is to share our experience and describe the workflow, which came as a real help to geosteering as events can be anticipated with a certain reaction time. The first steps of the project consisted in preparing the 3D model, incorporating all geophysical and geological information to get a complete overview of the distribution of the petrophysical properties through the field. Once the drilling started and before entering the reservoir, the model was updated with the new picks and eventually new horizon interpretation. The GR and Resistivities were modelled and a set of synthetic logs along the well trajectory was exported from the 3D modeler into a geosteering application. Then a series of simulations of expected logs were run giving the asset team a set of possible scenarios to foresee possible situations during drilling and prepare contingency plans beforehand thereby enabling efficient geosteering. The geomodeler enabled to build a 3D Earth model, which can be easily updated with real time data: it was also seen as a good communication tool. Geological Settings The Tambora field lies in the swamp environment of the upper Mahakam delta, 10 km south of Badak/Nilam. Tambora is primarily a gas field, although there are small oil rims to the north (Fig.1). The field produces from a series of interbedded deltaic sandstones (mainly distributary channel deposits), shales coals and locally limestones between 2,500 and 4,300 meters. These formations are classified into four main zones: D, E, F and G (Fig.2). The distributary channel reservoirs (lateral bars) in Tambora G zone can only be developed with horizontal wells (see reference 1) due to their low permeability. As there is no 3D seismic for the field, the 3D understanding of the sand bodies distribution is driven by the well data and the geological concept. In this context, the preparation of a geosteering job with alternative scenarios is very important.