Gas Hydrates, As Future Energy And Safety In Its Operation

1. Gas Hydrates, As Future Energy And Safety In Its Operation Amir Badakhshan

6. Gas Hydrates • What are they? • Why are they important? • Where are they found? • Hydrates as energy resource • Hydrate as a problem • Controls on the Occurrence of Gas Hydrate • Exploitation schemes • The Future of Methane Hydrates

7. Hydrates - What are they? • Gas Hydrates are solids formed from hydrocarbon gas and liquid water • They resemble wet snow and can exist at temperatures above the freezing point of water • They belong to a form of complexes known as clathrates

8. Clathrates - What are they? • Clathrates are substances having a lattice-like structure or appearance in which molecules of one substance are completely enclosed within the crystal structure of another • Hydrates consist of host molecules (water) forming a lattice structure acting like a cage, to entrap guest molecules (gas) LATIN: “clathratus” means to encage Source: U.S. Geological Survey

9. Types of Hydrates The following gases when combined with water under the right conditions are known to produce hydrates: • Natural gas molecules ranging from methane to isobutane • Hydrogen sulfide • Carbon dioxide

10. Hydrates - Why are they important? • A very large potential source of natural gas • A hindrance to the natural gas industry • Often cause plugging of lines and equipment (like an “ice” plug) • In drilling, under well control situations, hydrates may plug lines and chokes

12. Where are Hydrates found? • Hydrates are found in situ in the deep oceans of the world, on the ocean floor or in the sediments below the seafloor • Hydrates are found in situ in permafrost regions • Hydrates are also found in extraterrestrial environments

13. A Natural Gas Resource? • Conditions for hydrate formation are satisfied in more than 90% of the ocean floors, but hydrates will only be present if there is a source of natural gas and a structure suitable for gas accumulation • It has been estimated that total worldwide hydrate resources are as much as 1016 m3, or twice as large the combined fossil fuel resource.

14. Comparison between Arctic and Marine Resource

15. A Natural Gas Resource? • Possibly as much as 98% of the hydrate resource is below the world’s oceans • The remaining 2% that is found on land, below permafrost, is estimated to be twice the size of the conventional natural gas resourse • Natural gas has been produced from hydrates for decades in Russia

16. A Natural Gas Resource? • It is estimated that gas contained in naturally occurring gas hydrates may exceed 16 trillion tons of oil equivalent • One cubic foot of hydrate can hold 170 standard cubic feet of gas

17. Hydrates as a suitable fuel source • Denser source of hydrocarbons than conventional sources • Amount of conventional fossil fuels will decline in next century • Redirect/dispose of greenhouse methane away from the atmosphere • Cleaner fuel source than oil, coal, and oil shale • Abundant supplies in deep sea and permafrost

18. Challenges of Hydrate Utilization as a Fuel Source • Hydrates decompose releasing hydrocarbons as a gas when removed from low temp/high pressure environment • High costs of long pipelines across unstable continental slopes • Pipelines in deep cold water become plugged with hydrates during transport

19. A Problem in the Natural Gas Industry? • In the 1930’s it was discovered that natural gas hydrates were blocking gas transmission lines, frequently at temperatures well above the freezing point of water • This discovery led to the regulation of the water content in natural gas pipelines

20. A Problem in the Natural Gas Industry? • It has since been determined that gas hydrates may exist at temperatures as high as 20-30 oC. • As the pressure increases, hydrates can exist at higher temperatures

21. CO2 emissions [includes Construction/Operation/Fuel Preparation]

22. Projected world energy supply

23. Controls on the Occurrence of Gas Hydrate • Formation temperature • Formation pressure • water salinity • Gas chemistry • Availability of gas and water • Gas and water migration • Presence of reservoir rocks and seals

26. Effect of water composition on the hydrate curve

27. Hydrate-forming conditions for natural gases

28. Exploitation schemes DEPRESSURISATION: At fixed temperature, operating at pressures below hydrate formation pressure. INHIBITION: Inhibition of the hydrate formation conditions by using chemicals such as methanol and salts. HEAT SUPPLY: At fixed pressure, operating at temperatures above the hydrate formation temperature. This can be achieved by insulation or heating of the equipment.

29. capital cost with transport distance

30. The Future of Methane Hydrates • Worldwide gas production in the next 30-50 years • Areas with unique economic and/or political motivations could see substantial production within 5-10 years • We need to better understand the mechanisms of hydrate disassociation and its role in global warming, either as an accelerator or and inhibitor

31. References • Clathrate Hydrates of Natural Gases, by E. Dendy Sloan, Jr., Marcel Dekker, Inc., New York,1998. • Goho, Alexandra. “Energy on Ice.” Science News. 6/25/2005, Vol. 167, Issue 26 • “Controlling, Remediation of fluid hydrates in deepwater drilling operations,” by B.Edmonds, R.A.S. Moorwood and R. Szczepanski, Ultradeep Engineering, March 2001. • IADC Deepwater Well Control Guidelines. International Association of Drilling Contractors. Houston, Texas, 1998. • “Lab work clarifies gas hydrate formation, dissociation,” by Yuri F. Makogon and Stephen A. Holditch. Oil & Gas Journal, Feb.5, 2001. • “Experiments illustrate hydrate morphology, kinetics,” by Yuri F. Makogon and Stephen A. Holditch. Oil & Gas Journal, Feb.12, 2001. • SPE, OTC...

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33. نتیجه گیری: نتایج اصلی زیر بر اساس مطالعات صورت گرفته در این پایان نامه در رابطه با اثر عوامل موثر بر ضخامت محدوده پایداری هیدرات گازی، منشا و حجم گاز در رسوبات هیدراتی دریای عمان و همچنین تولید گاز و بررسی عملکرد مخزن در طول دوره برداشت حاصل گردید(نتایج هر بخش از مطالعه به صورت جداگانه در هر کدام از فصل های این پایان نامه آورده شده است). این نتایج می تواند به منظور برنامه ریزی بلند مدت و سرمایه گذاری کلان صنعتی به منظور استحصال گاز از این مخزن مورد استفاده قرار گرفته و منجر به ترغیب جهت مطالعات بیشتر در این خصوص گردد.

34. آنالیز حساسیت انجام شده بر روی مدل ترمودینامیکی، به وضوح نشان می دهد که گرادیان گرمایی زمین،موثرترین عامل در تعیین ضخامت محدوده پایداری هیدرات در مخزن هیدرات گازی دریای عمان است. • رسوبات هیدرات گازی دریای عمان قطعا حاوی ترکیبات ترموژنتیکی هستند که از مخزن هیدروکربوری واقع در بخش های عمیق تر دریای عمان نشات می گیرند و می توان رسوبات هیدراتی دریای عمان را کلاهک هیدراتی این مخزن دانست.

35. مقدار گار به دام افتاده در رسوبات حاوی هیدرات در دریای عمان، 11 تا 21 تریلیون مترمکعب پیش بینی می شود. این مقدار گاز به دام افتاده در رسوبات هیدراتی دریای عمان و گاز آزادی که در زیر لایه هیدراتی قرار گرفته است را می توان به عنوان منبع انرژی آینده در نظر گرفت. • در طول دوره تولید گرمای محسوس لایه هیدراتی، فرایند حاکم بر تجزیه هیدرات و تولید گاز می باشد.

36. در پایان دوره تولید، مقدار گاز تولید شده در نتیجه تجزیه هیدرات بیشتر از 42% کل گاز تولیدی(بیشتر از 1/6 میلیارد متر مکعب گاز) را تشکیل می دهد. این نشان می دهد که هیدرات سهم قابل توجهی در تولید گاز از مخزن هیدراتی دریای عمان دارد. • نتایج شبیه سازی مونت کارلو نشان می دهند که با احتمال 90% ، بازیابی هیدرات و فشار جربانی چاه در بخش مورد نظر از مخزن هیدرات گازی دریای عمان در پایان دوره تولید، 15% و 7300 کیلوپاسکال است. • با توجه به فشار متوسط بالای مخزن، دمای بالای زون هیدراتی و افت فشار کم فشار جریانی چاه در پایان دوره تولید، می توان تولید گاز را بدون به کارگیری روش دیگری از روش های برداشت و بدون تشکیل یخ، با روش کاهش فشار ادامه داد.