Sunday, 16 June 2019

Unconventional resources

Oil and gas reserves are part of conventional resources. The extraction technology and worldwide price of oil and gas are the main criteria to define any oil and gas accumulation in terms of reserve and resource.

Any oil and gas resource which is economically and technically available to extract from underground is subject of Reserve term; while others would include in Resources. Future technology and hydrocarbon prices may bring Resources into account as reserves.

unconventional resources include Gas hydrates, Oil shale, Gas shale, Coalbed methane, and heavy oil resources. Such resources include the biggest part of carbon content in the world with a low concentration of oil and gas. Improvement in extraction technologies and increase in the price of oil and gas has made them a very good candidate for the world future oil and gas reserves.

The technology of oil and gas extraction from Unconventional resources are usually different from conventional. This technology should extract oil and gas from a lower concentration of hydrocarbons accumulated in unconventional resources. Such a technology is usually more expensive than conventional oil and gas reserves extraction methods.

Gas Hydrates

Largest gas resource of the world has accumulated as gas hydrates. Gas hydrates consist of ice crystals which its crystalline structure provides a cage for different small gas compositions (such as methane) captured between their inter-molecular free spaces.

Gas hydrates form in low temperature and high pressure condition available below deep seabeds and frozen lands. This is not the only criteria, the existence of hydrocarbon gas is necessary for gas hydrate accumulation. One liter of gas hydrate includes 16 liter of gas (methane) which evolves in ambient temperature and pressure conditions.

Seismic methods are of the most widely used methods for gas hydrate exploration. Seismic methods integrated with well data, provides information regard to gas hydrate containing sediments in terms of their elastic properties. It also provides information about reservoir parameters through the sediments far from well location on seismic lines.

Gas Hydrates in Oman Sea

Different initial seismic assessments carried out by NIOC Exploration Directorate revealed the presence of gas hydrate resources in Oman Sea deep waters. More qualitative and quantitative analysis was subject to research in RIPI. However there is no direct presentation of gas hydrate since not any wells have been drilled in Oman Sea, this issue would be addressed through thermo-dynamic modeling of gas hydrate-bearing sediments, in this research. Results of the research could provide sufficient information for NIOC-Exploration Directorate for any decision on first drilling in Iranian offshore Oman Sea with deep sea drilling technology to point to the direct proof of gas hydrates.

Based on initial data analysis carried out on 2D seismic lines in Oman Sea, vast distribution of gas hydrates have been observed and huge resources are expected to be found.

Gas Hydrate Seismic Quantification

After many technical discussions on the proposal provided by RIPI Gas Hydrate Exploration Team, between RIPI and NIOC-Exp experts in different geosciences disciplines, NIOC-Exploration Directorate Research and Technology Department signed a contract with RIPI on “Gas Hydrate Seismic Quantification: A pilot in Oman Sea”, which was valid for over 40 months.The research has started since May 2011 and results has been subjecting of designing a bigger project till now.

Expertise Involved in Oman Sea Pilot Research

Different disciplines from RIPI Geosciences

Department has been involved in this research program. NIOC-Exp. Geophysics team is also involved in the program as the main observer. The NIOC-Exp team ensured the quality of the activities carried out by RIPI through the research program.

As the first step in the research, a thermo-dynamic feasibility study of gas hydrate occurrence investigated the possibility of gas hydrate accumulation in Oman Sea sediments under Oman Sea pressure and temperature conditions.

Seismic methods are the main tools to achieve the goals of the research. Since no offshore well data in Oman Sea is available, seismic forward modeling of gas hydrate bearing sediments has been introduced as the best verification process through our research. Pre-stack and Post-stack analysis on real and forwarded seismic data and their comparison through different seismic inversion routines were also been investigated in order to study gas hydrate resources quantity.

However due to nature of the research, main activities involved would involve seismic methods; other expertise including Geology, Geochemistry, Petrophysics, rock physics and Drilling are cooperating in the research in different parts of this program.

Achievements

It has been designed to answer to two main questions through this research.

1. Is there any possibility of quantitatively appraise gas hydrate resources using seismic data while minimum geological and well data are available? Designing an optimized methodology of seismically investigate gas hydrate resources in Oman Sea is the main goal of this study.

2. Quantity of gas hydrate resources in a pilot scale in Oman Sea sediments would be investigated.

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