The South Furious Field is a complexly faulted, upthrust anticline with a prospective sequence consisting of a Middle Miocene, lower coastal plain prospective sequence consisting of a Middle Miocene, lower coastal plain clastic succession. The field is characterized by extremely incoherent seismic data from which only a late Middle Miocene unconformity can be mapped with confidence.

The dense faulting and the discontinuous nature of the reservoir sands have made attempts at log correlation virtually impossible. However, in the Eastern Area of the field an extensive set of RFT derived pressure data has revealed several correlatable pressure zones. The pressure zones have defined at least six major accumulations and several minor ones. Furthermore, at least two different aquifer regimes have been identified.

Early seismic interpretations, although unable to resolve the structural complexity of the prospective sequence, noted a correlation between hydrocarbon bearing intervals in wells and the occurrence of low frequent "wormy" shaped reflections on seismic sections. In area without well control such anomalies were used as hydrocarbon indicators. These together with the pressure zone correlations and a simplified faulting pattern derived from HDT interpretation were used to construct maps of the top seals of each of the major accumulations.

The maps derived from this approach have been used for development planning, well targeting and oil-in-place estimation. planning, well targeting and oil-in-place estimation

Introduction

The South Furious Field is located off the North Sabah coast in East Malaysia, in a marine concession held jointly by the Sabah Shell Petroleum Company and Pecten Malaysia (Fig. 1).

The field marks the culmination of an asymmetric, upthrust anticline in an area characterized by wrench fault tectonics and associated clay diapirism. Hydrocarbon reserves are confined to a Middle Miocene sequence of lower coastal plain sands and shales, variably encountered between 1000' and 8500 ss.

The field is characterized by extremely incoherent seismic data from which only a late Middle Miocene uncomformity can be mapped with some confidence. Much of the structural deformation predates this unconformity rendering it unsuitable as a model for the structural form of the underlying prospective sequence.

The dense network of faulting, the discontinuous nature of the reservoir sands and the geometric log distortions caused by the severe (and often rapidly changing) structural dips and high well deviation angles, have rendered attempts at log correlation virtually redundant. However, in the so-called Eastern Area of the field, isolated from the Central Area by an arcuate complex fault zone, an extensive set of RFT derived pressure data has revealed several correlatable pressure zones. The pressures zones have defined at least six major accumulations and several minor ones. Furthermore, at least two different aquifer regimes have been identified.

Early seismic interpretations, although unable to resolve the structural complexity of the prospective sequence, noted a correlation between hydrocarbon bearing intervals in wells and the occurrence of low frequent "wormy" shaped reflections on seismic sections. In areas without well control, such anomalies were used as hydrocarbon indicators. These together with a simplified faulting pattern derived from HDT* (dipmeter) interpretations, were used pattern derived from HDT* (dipmeter) interpretations, were used to construct maps of the top seals of each of the major accumulations.

The maps derived from this approach have been used for development planning, well targeting and oil-in-place estimations. Wells drilled since the establishment of this model have broadly confirmed its applicability and usefulness.

Historical Development

The South Furious Field was discovered in 1974 by well SF-2 (Fig. 2) drilled on the crest of the structure. Subsequently five exploratory appraisal wells were drilled between 1974 and 1976. The current structural model is based primarily on the interpretation of the 1977 Ultra High Resolution (UHR) seismic survey.

In the initial round of development drilling, carried out during 1979 and 1980, 16 wells were drilled including 4 in the Central Area, 11 in the Eastern Area and one isolated well to appraise the Southern Flank.

Structural and Tectonic

The South Furious Field marks the culmination of an elongated asymmetric, upthrust anticline. The structure is severely dissected by numerous E-W striking, high angle reverse faults (particularly on the Southern Flank) and by both N-S and E-W striking normal faults (Fig. 2). The field is divided into two equally complex areas, by an ill-defined arcuate fault zone. Particularly severe tectonism and associated diagenesis is indicated in the Central Area Southern Flank by core and production data.

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