Abstract

In the Semangkok field the hydrocarbon-bearing formations are two sandstones which contain rim type oil accumulations. The paper discusses the seismic and exploration drilling carried out for field delineation and other studies conducted to determine an optimum reservoir development strategy. The discussion includes the geology, preliminary development assumptions, and use of symmetrical element numerical models to determine the number of wells, well locations and initial completions, and the recommended reservoir depletion plan. Selection of the optimum development plan included geologic uncertainty, facilities options and interrelations plan included geologic uncertainty, facilities options and interrelations of the two oil sandstones.

Introduction

The Semangkok field is located in the South China Sea, 35 kilometers off the east coast of Peninsular Malaysia in a water depth of 64 meters (Figure 1). Esso Production Malaysia Inc. (EPMI) has explored the field and is developing it as a contractor to Petroleum Nasional Berhad (PETRONAS), the Malaysian national oil company. The field is scheduled to go on production in 1984.

The structure that contains the field is an east-west trending anticline that is cut by faults at both ends. The field is located in the downthrown western fault block of the Semangkok anticline. The hydrocarbon-bearing reservoirs are Late Miocene group E sandstones that contain rim-type oil accumulations with associated gas caps. Commercial quantities of oil are found in two of the sandstone units in this field. These two primary reservoirs, E-6/16 and E-34/36 sandstones, are interpreted to be delta plain bar and channel deposits. Group E strata consist of sandstone, plain bar and channel deposits. Group E strata consist of sandstone, siltstone, shale, and coal sequences of marginal marine environments.

Two detailed reservoir simulation studies using symmetrical element models have been carried out to optimize the proposed field development plan. These major modelling efforts have enabled selection of optimum well location and spacing, initial completion, and reservoir drive mechanism. The reservoir models were also used to quantify the effects of reservoir heterogeneity, aquifer strength and benefits of gas injection and recovery efficiency for the field.

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