Petrography and Diagenesis of the Tertiary Surma Group Reservoir Sandstones, Bengal Basin, Bangladesh

M Farhaduzzaman,W H Abdullah,M A Islam,Md Shofiqul Islam

doi:10.13189/ujg.2015.030304

M Farhaduzzaman, W H Abdullah + Show 2 more

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https://doi.org/10.13189/ujg.2015.030304

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Abstract

The aim of this research was to evaluate petrographic characteristics of the Tertiary Surma Group sandstone reservoirs. The diagenetic constituents, processes and their impacts on reservoir quality were evaluated. A total of 33 core samples collected from 8 different wells located in 7 different gas fields of Bangladesh were used for the current study. The standard petrographic microscope, scanning electron microscope (SEM/FESEM) and XRD were used in the current study. The framework grains, mineralogy, matrix, pore properties and cements were identified and counted properly. The framework grains were in accordance to dominance quartz (76-91%), rock fragments (5-16%) and feldspar (3-14%). The identified important diagenetic components were quartz cements, authigenic clays, carbonate cements and dissolution. The early to intermediate stage of the diagnostic realm was estimated in the studied samples, e.g., mechanical compaction, chloritization, carbonate precipitation, dissolution, quartz overgrowth and authigenesis of clays. The reservoir quality was not much affected by the effects of diagenesis. However, it seems to be controlled mostly by the mechanical compaction including its grain size, sorting and fabric. In addition the authigenic cements slightly modified its porosity and permeability status during diagenesis. The measured average thin section porosity and its permeability suggested good to excellent reservoir quality for hydrocarbons.

Highlights

The detail description of the rock was carried out using the standard petrographic microscope and scanning electron microscope (SEM and FESEM) along with the XRD analysis
The Eastern Foldbelt Petroleum System is a northeastern Oligocene-Miocene system which is characterized by anticlinal traps with channel cuts created within Middle- to Late Miocene reservoir sandstones capped by the upper marine shale, the top part of Surma Group[25]
It is already stated that the development of silica cement while diagenesis is dealing with the silica source, timing and mechanisms

Summary

Introduction

The sandstones are deposited at the continental margin under the quartzose sedimentary provenance to [12,13] These sandstones are good quality reservoir rock with ~20% porosity [14, 15, 16] and permeability of 200400 milli darcy [18]. The detail description of the rock was carried out using the standard petrographic microscope and scanning electron microscope (SEM and FESEM) along with the XRD analysis It provides valuable information on the texture, composition, microstructure and classification focusing on the diagenetic properties of the Surma Group sandstone reservoir of Bengal Basin, Bangladesh. The Eastern Foldbelt Petroleum System is a northeastern Oligocene-Miocene system which is characterized by anticlinal traps with channel cuts created within Middle- to Late Miocene reservoir sandstones capped by the upper marine shale, the top part of Surma Group[25]. The estimated gas reserve Gas Initial In Place (GIIP) at 2P (proved+probable) is 26.84 Trillion Cubic

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