Kangean Energy Indonesia (KEI) is operating several oil and gas fields in Indonesia. One of these fields was discovered in 1990's and in 2010-2011. KEI drilled 5 gas producers at one of offshore gas fields. In this drilling campaign, several operational challenges of drilling and completion were applied such as “Open-hole gravel pack in horizontal section”, “Installation of Subsea Xmas Tree (SSXT) from jack up rig” and so on.

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Recently, the number of HPHT (high pressure & high temperature) wells has been increasing due to development of deep oil & gas reservoir, and annular pressure build-up (APB) caused by heat transmission from wellbore to tubing or casing annulus and pressure increase during production is concerned to damage production casings. To manage APB especially in subsea well, four kinds of management were picked up and selected rupture disks expected to be most effective to prevent APB. This paper shows the process to select most effective management for APB, and well design to install rupture disks.

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A holistic approach has been developed to assist in determining the remaining gas in-place in a source rock reservoir (SRR) that can be produced by drilling horizontal wells and hydraulically fracturing. SRR analysis helps identify locations in a basin where source rocks have sufficient total organic carbon (TOC) and maturity to have production potential. The conditions under which the rock was deposited determines the TOC and the richness of a SRR. The maturity depends on the geologic burial and temperature history of the rock since deposition.
To identify the boundaries of a play area that meets these conditions, 1D modeling and mapping of analysis can be used. In addition to production potential, the SRR needs to have sufficient thickness and brittleness to be able to hold a hydraulic fracture and remain open after the fracturing job has been completed. Rocks in the subsurface cannot be too complexly folded and faulted. This complexity prevents the construction of a long horizontal well.

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The Castor Project is developing a underground gas storage facility in the east coast of Spain. It is able to contain 1.3 billion cubic meters of gas, 3 months consumption of Valencia region.
It takes the gas from the Spanish gas pipeline system for storage, and when the gas system requires it, these facilities will be able to return the gas to the Spanish gas pipeline system in the same conditions as it was received through a submarine gas pipeline.
Japan drilling company (JDC) had got involved in this project as a drilling contractor. This paper will explain about the Castor project outline, gas storage drilling outline and some troubles during drilling the wells for this project.

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The world's first gas production attempt from a marine methane hydrate deposit is planned in the early 2013 applying depressurization method to a deepwater shallow borehole. The well plan that includes drilling of one production well and multiple monitoring boreholes along with intensive data and sample acquisitions is established to realize scientific objectives and safe operation. The wells are constructed in unconsolidated sediments below 1000m deep water, so then special care is required to assure the zonal isolation during depressurization. The drilling of the holes started in February of 2012, one year advance of the flow test, at the test location in the north slope of Daini Atsumi Knoll in the Eastern Nankai Trough using drilling vessel Chikyu.
The wells were drilled, monitoring systems were installed, and valuable information from geophysical logging and core samples were obtained during the 2012 operation. Detailed plan for the production test will be finalized using data and operational experiences obtained.

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Bacterial sulfate reduction affects the sulfur isotopic composition of dissolved (sulfate ion) and solid species (sulfide and elemental sulfur) in the sediment core samples of MD179-3312, eastern margin of Japan Sea. Our dataset includes the sulfate concentration and δ³⁴S of interstitial water, the total sulfur contents and δ³⁴S, and the content of elemental sulfur in the squeezed cake and freeze dry sediment samples.
Sulfur isotopic composition of the freeze-dried samples including pore water is significantly different from the value of the seawater. Total sulfur content of approximately 10 times the amount of sulfate ions contained in seawater have been measured. This composition was formed by sulfate reduction of seawater sulfate ion supplied by in an open system. Sulfur isotopic composition of sediment decrease of up to 139 cm depth from the surface, and then become almost constant.
After an initial fractionation by sulfate reduction, through a repeated cycle of sulfide oxidation to elemental sulfur and subsequent disproportionation, sulfate reducing bacteria can deplete sedimentary sulfides in ³⁴S. The extremely light isotopic composition of sulfur in the sediment indicates an open system bacterial sulfate reduction.
This study is supported by MH21, Research Consortium for Methane Hydrate Resources in Japan.

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Methane hydrate dissolves sea water with pressure and/or water temperature changing in the sea floor because of unstable solid. Therefore, it is important to measure volume of methane gas for recognition of methane hydrate in the seafloor. However, the studies of measuring volume of gas in the seafloor are hardly found. Gas volume can calculate from volume of water and sediments. Therefore, we investigate possibility of using TDR method as measuring water content in seafloor sediments at first in this study. We recognize TDR method is useful of measuring water content in seafloor sediments. Moreover, we found two levels' calibrations, one is by Kanto loam by TDR probe for seafloor and small TDR probe and another is by seafloor sediment by small TDR probe, are useful when the sediments are not enough.

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Methane is one of the major end products from photosynthetic organic matter. Based on stable carbon and hydrogen isotopic compositions of methane, biological pathways mainly consisting of carbon dioxide reduction coupled to molecular hydrogen oxidation and acetate fermentation and abiological pathways such as thermal degradation of organic matter have been systematically classified. However, recent advances in subseafloor biosphere research have unveiled the complexity of processes involved in the transformation, migration and fate of methane. Particularly, it has been recognized that marine sediments with high flux of methane harbor novel lineages of microorganisms, the physiological traits of which are largely unknown due to their resistance to cultivation. In this review article, microbiological investigations that shed light on DNA-based microbial community structures and metabolic diversity and activity related to methane production and consumption in organic-rich marine sediments are briefly summarized.

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