Lithological Characteristics of XY Field, Shallow Offshore Niger Delta Basin, Nigeria

Abstract

Aims: The purpose of this study is to delineate litho-stratigraphic sequences penetrated by well 01, 02 and 03 within the XY field and also to describe the litho-stratigraphic characteristics of the sequences delineated using ditch cuttings, textural/lithological attributes and the distribution of the index minerals (ferruginous material, glauconites, carbonaceous detritals and shell fragments. Study Design:  The result of the lithostratigraphic analysis carried out on three wells from the XY field are presented and discussed. Place and Duration of Study: The study was carried out in the shallow offshore Western Niger Delta, Nigeria from wells 01, 02 and 03 of XY field from July 2018 to September 2018. Methodology: The ditch cutting samples for the three wells were lithologically analysed under a stereo-binocular microscope Olympus model SZ 2 ILST. The dominant and secondary rock types, colour, average grain size, roundness, sorting and accessory minerals, sand-shale percentage, fossil and nature of cement and stage of diagenesis were the parameters used for the assessment of the samples. The lithologic descriptions were complemented using logs analyses. Results: Lithological investigation of the three wells reveals that the lithofacies are generally made up of grey to dark grey shale and mudstone/siltstones interbedded with fine-medium and coarse-grained sandstones. Two units of lower paralic sequence and upper paralic sequence were assigned to the studied section of the three wells, based on their lithologic characteristics. The lower unit is composed mainly of shale and mudstone/siltstone interbedded with sands, while the upper unit is dominantly sanded alternating with shales/mudstones. On the basis of the foregoing, only one of the three formational units of Niger Delta was encountered.