Characterization of a fractured basement reservoir using high-resolution 3D seismic and logging datasets: A case study of the Sab'atayn Basin, Yemen.

Waleed Bawazer,Mostafa M Kinawy,Aref Lashin,Emmanuelle Puceat

doi:10.1371/journal.pone.0206079

Waleed Bawazer, Mostafa M Kinawy + Show 2 more

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https://doi.org/10.1371/journal.pone.0206079

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Journal: PloS one	Publication Date: Oct 25, 2018
Citations: 13	License type: CC BY 4.0

Affiliation: Al Azhar University, King Saud University, Benha University

Abstract

The Sab’atayn Basin is one of the most prolific Mesozoic hydrocarbon basins located in central Yemen. It has many oil producing fields including the Habban Field with oil occurrences in fractured basement rocks. A comprehensive seismic analysis of fractured basement reservoirs was performed to identify the structural pattern and mechanism of hydrocarbon entrapment and reservoir characteristics. A 3D post-stack time migration seismic cube and logging data of 20 wells were used and several 2D seismic sections were constructed and interpreted. Depth structure maps were generated for the basement reservoir and overlying formations. The top of the basement reservoir is dissected by a set of NW-SE step-like normal faults (Najd Fault System) and to a lesser extent, by secondary NNE-SSW oriented faults (Hadramauwt System). The Najd Fault System is dominant and dissects the reservoir in the middle of the field into two prospective uplifts. The northern and northeastern areas constitute the deep-seated downthrown side of the reservoir. Hydrocarbon emplacement is through the fault juxtaposition of the fractured basement against the organic shale source rock of the overlying Madbi Formation. Hydrocarbons are hosted in basement horsts formed by fault-controlled blocks and overlain by the regional seal of the Sab’atayn Formation. The basement reservoir rock is mainly composed of granite, quartz-feldspar, weathered silica, and mica minerals. Fractures were identified from the outcrops, cores, image logs, and the petrophysical analysis. Hydrocarbon saturation was observed in the upper and middle parts of the reservoir, more specifically in front of the highly fractured sections. The fracture porosity was less than 5% and the dead oil had an API gravity of 40° with no H2S or CO2. In conclusion, the structural highs of the Habban Field are of interest because most oil producing wells are drilled into them. We recommend extending the drilling and development activities in these uplifts.

Highlights

Basement reservoirs are a subset of naturally fractured reservoirs and the term “basement” refers to crystalline formations ranging from intrusive and extrusive magmatic bodies to the family of low- to medium-grade metamorphic rocks [1,2,3,4,5,6,7,8,9]
The aim of this work is to perform comprehensive seismic and petrophysical analyses of a naturally fractured basement reservoir located in Block S2 of the Habban Field in the Sab’atayn Basin to detect reservoir characteristics and identify the structural/stratigraphic elements that control the hydrocarbon entrapment using the three-dimensional (3D) seismic data and well logs [20,21,22,23,24,25]
The Sab’atayn Basin is one of the two prolific Mesozoic basins located in central Yemen

Summary

Introduction

Basement reservoirs are a subset of naturally fractured reservoirs and the term “basement” refers to crystalline formations ranging from intrusive and extrusive magmatic bodies (especially granites) to the family of low- to medium-grade metamorphic rocks [1,2,3,4,5,6,7,8,9]. The term basement is used for a range of intrusive or extrusive igneous and metamorphic rocks beneath an unconformity at the base of a sedimentary sequence. It is not common that hydrocarbons are retrieved from crystalline basement rocks, naturally fractured basement reservoirs have been known and exploited by the hydrocarbon industry since 1948 [14]

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