Application of model-based inversion technique in a field in the coastal swamp depobelt, Niger delta

Okoli Austin,Zaidoon Taha Abdulrazzaq,Okechukwu Agbasi,Onyekuru Samuel I

doi:10.14419/ijag.v6i1.10124

Okoli Austin, Zaidoon Taha Abdulrazzaq + Show 2 more

Open Access

https://doi.org/10.14419/ijag.v6i1.10124

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Abstract

Considering the heterogeneity of the reservoir sands in the Niger Delta basin which are primary causes of low hydrocarbon recovery efficiency, poor sweep, early breakthrough and pockets of bypassed oil there arises a need for in-depth quantitative interpretation and more analysis to be done on seismic data to achieve a reliable reservoir characterization to improve recovery, plan future development wells within field and achieve deeper prospecting for depths not penetrated by the wells and areas far away from well locations. An effective tool towards de-risking prospects is seismic inversion which transforms a seismic reflection data to a quantitative rock-property description of a reservoir. The choice of model-based inversion in this study was due to well control, again considering the heterogeneity of the sands in the field. X-26, X-30, and X-32 were used to generate an initial impedance log which is used to update the estimated reflectivity from which we would obtain our inverted volumes. Acoustic impedance volumes were generated and observations made were consistent with depth trends established for the Niger Delta basin, inverted slices of Poisson impedances validated the expected responses considering the effect of compaction. This justifies the use of inversion method in further characterizing the plays identified in the region.

Highlights

Seismic is sensitive to impedance which is a function of velocity and bulk density
Considering the heterogeneity of the reservoir sands in the Niger Delta basin which are primary causes of low hydrocarbon recovery efficiency, poor sweep, early breakthrough and pockets of bypassed oil there arises a need for in-depth quantitative interpretation and more analysis to be done on seismic data to achieve a reliable reservoir characterization to improve recovery, plan future development wells within field and achieve deeper prospecting for depths not penetrated by the wells and areas far away from well locations
Acoustic impedance volumes were generated and observations made were consistent with depth trends established for the Niger Delta basin, inverted slices of Poisson impedances validated the expected responses considering the effect of compaction

Summary

Introduction

Seismic is sensitive to impedance which is a function of velocity and bulk density. Seismic reflection occurs at a boundary between layers of different impedances. Seismic inversion tends to reverse the process going back from the convolution model to the reflectivity and to the impedances. Sheriff, (2002), define inversion as deriving from field data a model to describe the subsurface that is consistent with the data It could be explained as determining the cause from observation of effects, it means solving for a special distribution of parameters, which could have produced an observed set of measurements. Deterministic Inversion is good for getting a regional understanding of reservoir properties and for simplifying the stratigraphic interpretation by wavelet removal. It models the earth as a sparse blocky layered model replacing the assumption of modelling the earth as having continuous reflectivity. We attempt to show the application of model-based inversion in characterizing two reservoirs of interest in the field

Geology of the study location

Data and methodology

Result and discussion

Conclusion