Modeling of porosity and permeability for hydrocarbon Exploration: A case study of Gongola arm of the Upper Benue Trough. (February 2020)

• Record Type: Journal Article
• Authors: Epuh, E.E.; Joshua, E.O.
• Is Part Of: Journal of African earth sciences. Volume 162(2020)
• Publication Date: 2020-02
• Subjects: Porosity -- Permeability -- Irreducible water saturation -- Bound water saturation -- Shaly sand reservoir; Earth sciences -- Africa -- Periodicals; Earth sciences -- Middle East -- Periodicals; Geology -- Africa -- Periodicals; Geology -- Middle East -- Periodicals; Sciences de la terre -- Afrique -- Périodiques; Sciences de la terre -- Moyen-Orient -- Périodiques; Géologie -- Afrique -- Périodiques; Géologie -- Moyen-Orient -- Périodiques; Earth sciences; Geology; Africa; Middle East; Periodicals; Electronic journals; 556.05
• DOI: 10.1016/j.jafrearsci.2019.103646
• Languages: English
• ISSNs: 1464-343X

Abstract

Abstract: Irreducible water saturation is one of the fundamental parameters in characterizing hydrocarbon formations, playing key role in volumetric and recovery calculations and permeability definition within a reservoir. The determination of the reservoir permeability using the irreducible water saturation in a shaly sand transition zone has been problematic due to the presence of the bound water saturation. In this research, a model was developed based on the Coates and Dagan permeability model formulation using the dual water model parameters. In this model formulation using the three models, a sensitivity coefficient for conditioning the permeability field at the transition zone was introduced. The sensitivity factor is a quotient function of bound water saturation and the total water saturation. The localized nature of the well data in the determination of the depositional architecture (porosity and permeability) were extrapolated away from or interpolated between acquisition locations using the areal coverage provided by seismic data. The analysis of the well information from the Kolmani River showed that the hydrocarbon lies at depth between 2071m and 2194m (Cenomenian-Turonian Yolde formation). The acoustic map within the reservoir shows the occurrence of dense uniform marine shales and sandstones. It also shows the depositional process has been uniform and sequential. High density clastic materials were also discovered within the reservoir. The permeability results obtained by equating the bound water and total water saturations to the irreducible water saturation gave the 26mD and 16mD as the upper (clean sand) and lower (pure shale) limits of the effective permeability values for the reservoir. The result obtained using the new model showed that the effective permeability is 21mD within the transition zone. Other petrophysical results showed that the reservoir has an effective porosity of 20% and effective water saturation of 12%. Based on these reservoir results, it is understood that the well is highly compact and will not flow during production. Highlights: This paper presents a new model for shaly sand formation permeability evaluation within the transition based on the application of the Dual water model formation parameters such as: water saturation and porosity to the geometric model of Dagan (1979) based on the utilization of the Coates permeability model (1974). The resulting model for the shaly sand formation represents a significant improvement in the determination of the various boundary values permeability within the shaly sand reservoir formation. The research is a work on Gongola arm of the upper Benue Trough within the Nigerian Frontier Inland Sedimentary Basin (NFISB). The model has helped to delineate the contribution of authigenic clay minerals whose open structure is able to trap water and generally affect permeability. The boundary value problems of determining permeability within the transition zone has been formulated. The 21mD value obtained is called the transition zone permeability at the prospect horizon and it falls within the range observed by previous resersers.