PTRL5006 Take-home Assignment #2

PTRL5006 Take-home Assignment #2 S2 2018
This assignment should be submitted to Turnitin as a single word document, with references
included. In your own words, answer each of the following questions. Use references but avoid just
quoting or paraphrasing a single source, but rather use several sources to explain your response. Do
not rely on a single source or paraphrase a single source but study the questions from several
General Information
For referencing, I advise the use of Zotero (available free from which has both web
browser plugins and Microsoft word plugins so that you can, with a click, save a reference from for example to your Zotero database and then from work simply add citation
from the new Zotero tab in work and (after choosing a journal style format) type the title or author
and add the citation. At the end, use create bibliography to add all the references to the end of your
answers. There is plenty of help about Zotero available from the web. However, any referencing
program will work.
• Use your own or referenced and relevant figures to explain concepts.
• Check your references follow a consistent style (author-date or numeric)
• Link between paragraphs of the text
• Structure your text for ease of reading
Question 1 – Mixed Carbonate-Siliclastic Systems (30 marks) – 500 words
Find a recent paper dealing with a “mixed carbonate-siliclastic system”. Choose 1 of the facies within
that paper (e.g. carbonate intertidal flats or intertidal restricted lagoons).
1. Describe the facies in terms of its composition of grains and structures from the paper and
explain all geological terms with references. For example, if your facies is described as
“bioturbated dolomicrobialite fining-upwards mudstone with wavy cross-laminated
sandstone”. You would need to explain the terms bioturbated, dolomicrobialite, finingupwards,
mudstone, wavy cross-lamination and sandstone”.
2. Include a picture of the facies from the paper.
3. Using figures from the paper (or draw your own), show on a cross-section or 3D perspective
view whereabouts this facies was deposited in the sedimentary system.
4. Is this facies deposited in a highstand, lowstand or transgressive systems tract? Explain why
this is important for the development of the system.
Question 2 – Low Permeability Reservoirs (30 marks) – 500 words
First choose either a) sandstone or b) carbonate low-permeability reservoirs for this question and
then answer the following three questions:
a. Find three examples of this low-permeability reservoir rock from different papers and
explain why these reservoirs have low permeability and what are the factors controlling
permeability (e.g. diagenesis, burial/compaction, sorting) in each case?
b. Choose one of these factors and explain, with reference to other papers, what this process is
and how it occurs.
c. Describe the mechanisms of migration in low permeability reservoirs.
Question 3 – Risk Management (40 marks) – 800 words
Choose one of Option A, B or C
Option A
With reference to at least three papers, explain under what conditions salt diapirs make good
hydrocarbon traps. What risks are there in estimating reserves around salt diapirs?
Option B
With reference to at least three papers, explain how seal capacity and what mechanisms can lead to
seal failure. How can risk of seal failure be assessed for reservoir potential?
Option C
With reference to at least three papers, explain how the depositional environment of the source
rock affects the quality of the source rock (HI etc.). How can understanding the source rock quality
be used to reduce risk on estimating the reservoir value?