Log & Image Viewer: Background Info.

Designed by PGA Ltd

CONFIDENTIALITY & GENERAL DISCAIMER

The Log and Image Viewer Report and Dataset is the property of Petroleum Geological Analysis Limited and its partners. It is made available for use under the terms of the accompanying report licence agreement.

 

Every reasonable effort has been made by the authors to verify the technical data presented in the Report and Dataset. However, Petroleum Geological Analysis Limited, Quantock Geological Services, Saker Geological Services and the University of Reading accept no responsibility for any actions taken by any party as a consequence of statements, conclusions and recommendations made in the Report and Datatset.

DATA FORMATS

Web-Browser Format

The web-page presentation format enables the photomicrographs to be displayed beside the petrographic log using a web-browser such as Internet Explorer. This new display format makes it much easier to view and use the photomicrographs in context with the petrographic log. This format was developed by Grenville Lunn of Petroleum Geological Analysis Ltd.

 

The storage directories underlying the web pages contain all the photographic images as high resolution jpeg files named by well and depth interval. All the images have also been saved as relatively small/low resolution "thumbnail" images in order to rapidly display all the files relating to a well on a single web page.

 

IMPORTANT NOTE: In order for the web pages to function properly, the files names, directory names, and directory structure should not be modified.

 

PDF and Excel Formats

The log images used for the web-browser are relatively low resolution GIF images. Higher resolution versions of the petrographic logs are provided in PDF format in the associated PDF Report Library, together with PDF versions of the photomicrographs and descriptions. An Excel spreadsheet listing of the photomicrograph samples and descriptions is also provided.

SAMPLE BASE

The petrographic logs are based upon thin sections of conventional core, cuttings and outcrop sample material from the Iraq Petroleum Company wells and measured outcrop sections stored in the University of Reading Middle East Archive. Most of the thin sections in this collection were prepared at the time the wells were drilled and samples were collected, between the 1930’s to 1961. At the time, the IPC routinely made thin sections from every cuttings sample interval and from representative core samples throughout the penetrated section in their exploration wells, and from every bed sampled at outcrop. Cuttings sample intervals are generally every 5 or 10ft (1.5 or 3m) and short cores were cut at regular intervals. The primary use of the thin sections was for micropaleontological identifications. Cores were cut for both reservoir appraisal, and in non-reservoir section, for micropaleontological analysis. Some of the older wells, such as Adaiyah-1, were extensively cored.

 

The thin sections are generally slightly thicker than the standard for modern petrographic work. Also, they are not stained and they have glass cover slips cemented into place, which prevents any retrospective staining. As a consequence of the thickness and lack of staining, identification of dolomite versus calcite and some other minerals is problematic. However new thin sections, stained where appropriate, were also prepared as part of our studies over a number of key intervals in selected wells.

 

Sample depths are drillers depths, measured along hole from the drilling datum. No data are available on the well trajectory in these old wells. Generally the IPC labelled cuttings thin sections with both top and bottom depths (i.e. 1745-50), but there are some instances where only one depth is recorded. Samples from cored intervals are almost always labelled as such (i.e. 1745-50 CORE). Some core samples are labelled with the top and base of the cored interval (i.e. 1745-50 CORE), whilst others give specific depths within the core (e.g. 1747 CORE). Some thin sections were prepared from "core chips", which can easily be mistaken for cuttings and vice versa. The core chips are representative lithologies from cored intervals that have been crushed up by the IPC for storage in small glass test-tubes. (Note that the IPC's conventional boxed cores were retained in Iraq. The UK archive contains "core chips" and "core chunks".) Where core chips have been thin sectioned, it is not always clear whether the slides are of cuttings or core, unless they are specifically labelled as "CORE". The larger "core chunks" are hand-size sub-samples taken for a specific reason, usually because they contained macrofossils, sent to the UK for identification. A small number of whole core photographs of such macrofossils are included in the image data set.

 

On the well logs, the photomicrograph sample points are displayed at the top of the relevant sample interval (i.e. the photomicrograph sample dot for cuttings sample 1350-1360ft is plotted at 1350ft).

 

Sample types have also been cross-checked against known core depths. This has enabled most of the cuttings thin sections to be correctly assigned, leaving a small number of unassigned samples from cored intervals. These will mostly be core thin sections but in some instances could represent cuttings returns from within the cored intervals.

 

The outcrop sampling frequency is generally of the order of 4 metres. Some intervals are sampled at a lesser or higher frequency as dictated by the geological detail and accessibility, with for example, sampling on steep cliff faces being less frequent.

 

The precise position of the outcrop sample within each bed is not recorded by IPC. The photomicrograph sample points are displayed at the middle of the relevant sample interval (i.e. the photomicrograph sample dot for Bed 2510-2520m is plotted in the middle of the bed at 2515m).

 

ORIGINAL REPORTS

The petrographic logs presented in this study, with a couple of exceptions noted below, were originally presented in the following reports:

Sedimentary Geology and Diagenetic History of the Jurassic to Permian Rocks of Northern Iraq (1988)

Sedimentary Geology and Diagenetic History of the Cretaceous Rocks of Northern Iraq (1989)

Sedimentary Geology and Diagenetic History of the Cretaceous Rocks of Southern Iraq (1994)

Sedimentary Geology of the Mesozoic Outcrops of Iraq (2003)

 

Full details of the original reports are provided on our website www.pgal.co.uk.

 

The exceptions are:

1) For Khleisia-1, the Cenozoic to Mesozoic log is from the report "Sedimentary Geology and Diagenetic History of the Ordovician to Tertiary Rocks of Syria (1991) and the Paleozoic section from the report "Paleozoic of Iraq and Adjacent Areas (1998)".

 

2) The Cenozoic petrographic logs for the Kirkuk 85, 109 and 115 have not been included in any of our previous reports.

 

PETROGRAPHIC LOGS AND PHOTOMICROGRAPHS FROM OUR PREVIOUS REPORTS

PETROGRAPHIC LOGS

The original petrographic logging for the North Iraq wells was undertaken between 1987 and 1991 by Dr. Augustus Wilson of Saker Geological Services, and the late Prof. Bruce Sellwood of the University of Reading. At this time we had no access to the IPC wireline logs or to any other well records beyond what was available in the public domain. In 1992, subsequent to completing the North Iraq and Syria projects, a set of composite logs was provided by one of the IPC partners to use in the reports.

 

These IPC composite logs provide resistivity and SP logs, casing points, and show and test data. This information was digitised and is presented in our Iraq Overview Report "Petroleum Geology and Exploration Potential of Iraq: An Overview and Extensive Data Base (2006)". The logs were also incorporated into the petrographic logs for the South Iraq Cretaceous Report at the time the logs were made in 1994.

 

For this study the wireline logs have been added to the left margin of the petrographic logs for the North Iraq wells. The formation tops have been reviewed and adjusted in the light of the wireline log data and the stratigraphic terminology has been updated to agree with that of the Iraq Overview Report. However no significant adjustments have been made to the petrographic data and interpretations. In general the sample control in these wells is very good, with few problems with cavings. There are some instances where shaly lithologies may be under-represented in the thin sections, either due to drilling techniques or to a bias to sampling of carbonate lithologies for micropaleontological purposes. The original thin section coverage is also limited in some more friable sandstone intervals where the cuttings consist of disaggregated sand grains (e.g. some of the Cretaceous sandstones of South Iraq). Where samples were available, we made new epoxy-impregnated thin sections over these important intervals.

 

PHOTOMICROGRAPH IMAGES

Most of the photomicrographs images presented in this study (together with the smaller number of SEM images and whole core photos) were originally captured on 35mm film in 1987-1991. At the time, only around 40% of the images were included in the reports due to the need to constrain the size and production costs in the original hard copy format. For this study all the original negatives have been scanned and all images of reasonable quality have been included.

 

The descriptive captions for the images have been written and reviewed by Dr. Wilson, based on the images themselves, their context within the logs, and the available notes written at the time the photos were taken by himself and Professor Sellwood. However, it has not been possible to review or re-photograph any of the thin sections as we no longer have access to the sample material. The University of Reading sold the entire collection to a major oil company in 2003.

 

The photomicrographs and descriptions illustrate and emphasise the depositional and diagenetic features, reservoir factors, hydrocarbon shows and organic richness. A few tentative foram and other micropaleontological identifications are included in the descriptions, but the micropaleontology of the samples has not been fully evaluated. However, the photomicrographs contain a large number of images of microfossils which can be utilised by micropaleontologists.

 

KIRKUK CENOZOIC PETROGRAPHIC LOGS AND PHOTOMICROGRAPHS

The petrographic logs and associated photomicrographs for the Oligocene section of wells Kirkuk 85, 109 and 115 were prepared in a pilot study on the Cenozoic section that was not completed due to the sale by the University of Reading of the entire archive in 2002. The draft logs were revised and photomicrographs described in 2009 by Dr. Cathy Hollis (Senior Lecturer in Petroleum Geoscience and Petrophysics, at the School of Earth, Atmospheric and Environmental Sciences, The University of Manchester) in association with Grenville Lunn, PGA Ltd. This work was completed without access to the original thin sections.

 

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