Petrophysical and geomechanical characterization of a marginal (Wabi) field reservoir in north-central Niger Delta.

Zorasi, Collins Baribor

Abstract

The aim of this study is to evaluate marginal field petrophysical and geomechanical parameters, and to develop a model for analysis of geomechanical problems, in order to mitigate stress-related issues in drilling, development and reservoir management for Wabi field, onshore Niger Delta. The increase in oil and gas demand globally has necessitated the re-evaluation of mature depleted and marginal fields for enhancement of hydrocarbon recovery and development in the Niger delta province. These oil and gas fields are situated in the young sedimentary rocks (known as shaly sand) of the formation basin called the Tertiary Niger Delta. Tertiary Niger Delta is an unconsolidated formation, the depositional environment of which had led to production and developmental difficulties, due to related geomechanical issues such as weak reservoir rocks, low pressure (depleted reservoir), and stack/multiple reservoirs with thick net pay and high porosity. The methodology leverages an integrated monitoring approach (i.e. seismic, core, wireline logs and DST in-situ stress measurements) along the borehole record, in order to facilitate continuous and static measuring of the mechanical properties of the penetrated rock, so as to develop a petrophysical and geomechanical characterization of the Wabi field. To understand the current condition of this field of study, identification of stress state and mechanical rock properties were investigated for reservoir development and management. This research focuses on geomechanical characterisation for the development of a geomechanical model to predict fault reactivation, fractures and sand production, which can lead to compaction and subsidence. The study concludes that the Wabi field has pockets of potential hydrocarbon reserves at different intervals with good reservoir qualities, which could enhance its development for production. Additionally, rock strength estimation in this field shows that the reservoir is stable; however, production of hydrocarbons from these zones may lead to subsidence. To account for this possibility, reservoir pressure maintenance should be planned in advance; if injection is anticipated, then the appropriate pressure should be used so as not to fracture or cause fault reactivation in the wells. The results of this study show the estimation of hydrocarbon reserves, while also helping to predict geomechanical problems and to suggest mitigation strategies for sand management. Finally, the results should be beneficial to the operators of marginal fields, who may start out with limited resources and the need to maximize profits.

Citation

ZORASI, C.B. 2019. Petrophysical and geomechanical characterization of a marginal (Wabi) field reservoir in north-central Niger Delta. Robert Gordon University [online], MRes thesis. Available from: https://openair.rgu.ac.uk

• Thesis Type: Thesis
• Deposit Date: Jul 21, 2020
• Publicly Available Date: Jul 21, 2020
• Keywords: Marginal oil fields; Wabi field; Geomechanical characterisation; Petrophyiscal characterisation; Shaly sands
• Public URL: https://rgu-repository.worktribe.com/output/950570
• Award Date: Sep 30, 2019