Depositional environment and structural interpretation of Samba Field offshore of the lower Congo basin using seismic data, well log and core data

Abstract

The study development field is located in block 0 in the Lower Congo basin, West Africa. The main objective of this thesis is to study geological structure and depositional environment of Samba field using 3-D seismic data, well log and core data. For this purpose, software of Epos application by Paradigm has been used.

The samba field has two reservoirs Vemelha and Mesa with approximately 375 and 123 ft thickness respectively.

For structural interpretation an area of 123, 6 km2 was interpreted using section by paradigm software. The interpretation was conducted using 900 traces and 1000 lines, resulting in a grid which was used to generate structural maps. Structurally, the Samba field is a domo structure bounded SW by major big fault.

The core description was used to identify the lithologies present in the field. In this context, 434 ft of core were described both from Vermelha and Mesa reservoirs. Three main facies were recognized from Vermelha formation named by A, B, and C and also three main facies were recognized in Mesa formation taking the designation D, E and F.

Six wells were used for well log interpretation. The well logs selected to the present study were: gamma ray, resistivity and neutron-density combination.

The key approach of this study was to develop facies models by integrating data from the core description and well logs interpretation. In fact, as it is well known, the interpretation between well logs and core description data is helpful to determine the depositional environments. As a result three depositional facies, based on various lithic contents, were recognized in the present case study: facies A: characterized by dolomitized sandstone deposited in shallow lagoon settings, facies B: composed by very fine to coarse sandstones which can be deposited in tidal channel and facies C: characterized by very fine sandstones to siltstones which was interpreted as a foreshore complex.

The facies interpretation was a fundamental tool used to confirm that Vermelha formation was deposited in a quiet and the same time agited energy environment, and Mesa formation was deposited in a shelf margin settings.