Geo Trivia

15/08/2019

8. Thermal Evolution of source rocks in Khorat, Thailand.
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We will not have the oil/gas fields unless the source rocks have been subsided to a great depth at high temperature environment for a certain time.

09/07/2019

7. Reservoir Rocks and Source Rocks of Permian limestones
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The gas fields in NE Thailand have been producing gas from the Permian limestone. From the geological map of Thailand, the Permian limestone, shown as orange color, is widely exposed in the western part of the mono-cline Khorat Plateau and continued dipping down Under the Khorat Plateau. This Permian limestone is the sources and reservoirs for hydrocabons. The Permian limestone in NE Thailand was studied in detailed by several geologists. The results of the study showed that during Permian, thick successions of coastal to open marine siliciclastic and carbonate sediments were deposited across NE Thailand. Most people thought that the Upper Permian time was the continuation of the Middle Permian and must be eroded away after the big uplifted tectonic event.
***************************************************************** After the petroleum exploration and development has been started in NE Thailand, more and more sub-surface data were collected. Abundant anhydrites were noticed in several wells drilled. These anhydrites indicate a shelfal environment in which oolitic and subkha deposits occurred. These formations could have been deposited during Lopingian (Upper Permian) and conformably overlain the Middle Permian. The Lopingian (Upper Permian) was not be preserved and was eroded away during the later tectonic events, but they could have been survived and preserved underneath the great Khorat Plateau.
*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*. Please be noted that the end of Permian is a big event of mass extinction. However, it is noticed that the end of Permian event is not a single event but a double-phased events, first at the Guadalupian-Lopingian boundary (G-LB) and second at the Lopingian-Induan (Permo-Triassic) boundary (Isozaki, et al., 2008). The globally G-LB was started when a sudden transgression in Guadalupian accompanied by a cooling system and an oceanic anoxia condition that led to an extinction of reef ecosystems and a mass extinction as a whole. Approaching the end of Guadalupian, volcanic and basalts eruption dominated followed by rapidly regression. Lopingian (Upper Permian) was the time for shore appearance and hot climate.

05/07/2019

I would like to summarize the 6 sections posted last year before i stop posting. It is about the gas fields in NE Thailand.
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Gas in NE Thailand was found at the depth of 3 km in the carbonate rocks (limestone of Permian age) and is dry gas with minor condensate in limited areas. The H2S gas and water are found at a variable amount from field to field. Chloride and Carbon Dioxide are also found in the gas too.
H2S is extremely poisoning gas.
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I propose “Thermochemical sulfate reduction (TSR)” is the major mechanism for generating H2S because it can explain the presence of CO2 and water in the reservoirs.
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I want to emphasize that to ignite the “TSR”, (1) sulfates, (2) hydrocarbons and (3) high temperature are vitally needed.

04/07/2019

It has been a year that I stop updating this page to help my daughter raising her two daughters. Now I am back and will continue the story of the gas discovered in Khorat, NE Thailand. By studying the origin and its alteration, I wonder that a big geologic event had been missing from the geologic history of Thailand.

03/07/2019

24/03/2019

I visited a mine in the jungle on the top of a high mountain in Laos. That reminded me of thousand years ago ....

24/07/2018

Thank you for visiting my page. The information I share below is my interpretation from the sub-surface data, meaning, I gather the facts that we have seen and explain how they come using geochemistry. The next thing to do is to find my interpretation fit to the geological knowledge especially the geological map. There is a problem, it is not fit.
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PROBLEM !!!!! my interpretation can not fit the geological map. So the problem must be solve!!! I will explain later.

13/03/2018

The Geo Trivia records more than 200 viewers. Thank you to all viewers. Please visit my page regularly although I may not write very often. The story here may not be a standard scientific article, I gather a lot of references. I hope the stories and my views will create positive discussion and promote geological education in a time when geological education is inactive and lack of enthusiastic.

To express my thinking on various geological subjects from my working experiences.

13/12/2017

(6) What happen to the gas reservoirs in Khorat Plateau during “TSR” ?
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"TSR" is the process of selective consuming hydrocarbon (Zhu Guang You et al., 2007). During "TSR" process, the chemical activity of methane (C1) is weaker than that of C2 and C3 … etc… Meaning the heaviest hydrocarbons must be altered first and C1 is the last. This process decreases the amount of heavy hydrocarbons. In addition, the high temperature condition also increases the thermal maturation and increases the thermal cracking of heavy hydrocarbons. Hence,at the end, the gas pool will become very dry.
By the fact that one field here is producing methane and condensate. It can simply be explained that the “TSR” had stopped before the gas was completely turned to methane (C1) either by the use up of sulfates or the thermal maturation was disrupted.
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This article is a series of “Gas Fields onshore Thailand”. It is my personal interpretation. The onshore gas fields mentioned here are located in the NE of Thailand where known as Khorat Plateau.
(1) Gas Fields onshore Thailand
(2) Gas Characteristics in NE Thailand
(3) Origin of H2S
(4) Why I believe “TSR” is the major mechanism to generate the H2S
(5) How “TSR” works?
(6) What happen during “TSR”?

16/11/2017

5. How “TSR” works ? …. .. “TSR” ทำงานอย่างไร?
Three factors are vitally and inevitably needed to ignite “TSR” to begin. They are: (1) sulfates, (2) hydrocarbons and (3) high temperature. The gas traps must be subsided to a great depth where the temperature is more than 100 degC. The gas traps in NE Thailand are at depth 3 km at the 120 degC. This is perfect for the “TSR”. However, at high temperature, the thermal cracking also begins. Therefore, while H2S is forming by TSR process, the thermal cracking is also working and crack down the hydrocarbon molecules from wet gas to dry gas.

16/11/2017

Gas fields in Khorat, NE Thailand
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5. How “TSR” works ? …. .. “TSR” ทำงานอย่างไร?
***********************************************************************
Three factors are vitally and inevitably needed to ignite “TSR” to begin. They are: (1) sulfates, (2) hydrocarbons and (3) high temperature. The gas traps must be subsided to a great depth where the temperature is more than 100 degC. The gas traps in NE Thailand are at depth 3 km at the 120 degC. This is perfect for the “TSR”. However, at high temperature, the thermal cracking also begins. Therefore, while H2S is forming by TSR process, the thermal cracking is also working and cracking down the hydrocarbon molecules from wet gas to dry gas.