Detecting and predicting the distribution of unproducible reservoir in Bongkot field, Gulf of Thailand

Abstract

Bongkot field is located in the Malay basin, Gulf of Thailand under a concession of PTT Exploration and Production Public Company Limited. The main purposes of this project are to characterize unproducible reservoir sandstones and map horizontal and vertical distribution areas of these unproducible reservoir sandstones in the Bongkot field by using the RFT (pressure, mobility and porosity), mud log and well log data from 35 wells. Unproducible reservoir sandstones are those with the worst reservoir characteristic (porosity and permeability-as reflected by mobility) are reported to be present in the Bongkot field. From this study, the unproducible reservoir sandstones can be classified into three classes; good, moderate and poor reservoirs owing to their mobilities and porosities. The result of horizontal distribution of reservoir sandstones shows that the greater Bongkot North is a transitional zone from producible of North Bongkot to unproducible reservoir sandstones of the South Bongkot. Vertical distribution of reservoir sandstones reveals that unit 2C contains producible and a good class of unproducible reservoir sandstones. Formation 1 composes of only unproducible reservoir sandstones (of moderate and poor classes). The difference in reservoir quality horizontally is thought to be due to facies and/or structural controls while vertically it is thought to be due to a difference in diagenesis (formation of authigenic minerals, compaction and cementation) effects.