Assessment of updated low frequency model in delineating bypassed hydrocarbon reservoir: A 4D seismic study of ’X’ - field, offshore, Niger Delta, Nigeria

Aniefiok Sylvester Akpan

doi:10.17485/ijst/v13i36.770

Abstract

Aim/objectives: The aim of this research is, to use Time lapse (4D) seismic and investigate the influence of low frequency update in deterministic model-based seismic inversion employed in delineating a prospect saturated with bypassed hydrocarbon accumulation. Method: The dataset employed in this study incorporates 4D seismic volumes with fifteen (15) years production, interval between 2001 baseline and 2016 monitor seismic vintages. The inversion was carried out using full bandwidth of the updated low frequency and bandpass filtered low frequency approaches. The seismic vintages (baseline and monitor) were simultaneously inverted into acoustic impedance volumes for the two approaches. The formation fluid and lithology were discriminated through fluid replacement modelling (FRM) based on the colour separation between brine and gas saturation scenarios. Findings: The two inversion methods employed reveal six (6) zones suspected to be saturated with bypassed hydrocarbons. The delineated bypassed zones are masked in the full bandwidth approach,depicting the effect of the updated low frequency model. Meanwhile, the bandpass filtered approach result presents a better delineated bypassed reservoir as the zones are more pronounced when compared with the full bandwidth approach. Porosity estimate reveals that the bandpass filtered approach is characterized with excellent porosity in the suspected bypassed zones. The results equally gave more reliable and full delineated bypassed zones. Originality and novelty: The dataset employed in this study were obtained from a producing hydrocarbon field which, interest is to maximize the production of oil/gas. The study will bridge the inherent gab observed in using model-based seismic inversion approach to analyse and interpret seismic data in order to delineate hydrocarbon prospects. The research reveals that,the model-based seismic inversion method is still very effective in delineating hydrocarbon prospect when the updated low frequency is bandpass filtered to remove the model effect which influences the inverted acoustic impedance results. Keywords: Porosity; frequency; bypassed; reservoir and impedance

Highlights

The global demand for energy increases yearly with increase in population mostly in the emerging developed nations
This paper demonstrates the effect of updated low frequency in delineating bypassed hydrocarbon reservoir in X-field
Bypassed reservoirs saturated with pockets of hydrocarbon accumulation were mapped using full bandwidth and bandpass filtered model-based inversion method

Summary

Introduction

The global demand for energy increases yearly with increase in population mostly in the emerging developed nations. Oil exploration and production companies are faced with the task of increasing this source of energy to meet up with its rate of huge demand, which becomes difficult in recent times. This increasing demand for oil and natural gas has prompted oil/gas exploration and production companies into exploring various measures to enhance the production of oil and natural gas. One of such measures is time-lapse (4D seismic), which involves repeating seismic acquisition over a producing or abandoned oil/gas field in order to monitor production related changes, inefficiencies in the production process and delineates bypassed hydrocarbon accumulation [2,3,4]

Objectives

Methods

Results

Conclusion