Gas Field In Japan Research Articles

The Use of Formic Acid and Organic Mud Acid for Stimulation of Volcanic Rocks in Minami-Nagaoka Gas Field, Japan

Summary Unlike acid stimulation in sandstone and carbonate formations, acid stimulation of volcanic formations is not well documented in the literature, and its effectiveness and applicability are not well understood. This study aims to evaluate acidizing of volcanic rocks (especially rhyolite) as a well stimulation technique through a comprehensive experimental and modeling investigation using formation samples from a volcanic reservoir, the Minami-Nagaoka gas field in Japan. The experimental study consists of rock characterization, solubility tests, coreflooding tests, and batch reactor tests. The rock samples are investigated with computed tomography (CT) for textural characteristics and with X-ray diffraction (XRD) analysis for lithological characteristics. With these results, candidate acid systems are selected, and their effectiveness in terms of the capability of dissolving volcanic rocks is evaluated through acid solubility tests. Acid coreflooding tests are performed using undamaged plug cores to evaluate permeability responses caused by acid/rock reactions under high-temperature and high-pressure conditions (300°F and 3,000 psi, respectively). Batch reactor tests are conducted to quantify damage due to secondary/tertiary reactions. The mineralogical and textural characteristics of the rock samples let us select formic acid as the preflush acid and a mixture of formic acid and hydrofluoric acid (HF) called organic mud acid (OMA) as the main treatment acid. The composition of OMA was a mixture of 9% formic acid and 1% HF or 10% formic acid and 0.5% HF in this work. Results of the coreflooding tests with the preflush acid indicated permeability enhancement in all the samples and, especially in cores with cemented fractures filled by carbonate minerals, substantial permeability enhancement was observed. On the other hand, cores treated with OMA after the preflush indicated further permeability enhancement in some cases without cemented fractures, whereas other cases showed permeability impairment after the OMA injection. Furthermore, results of the batch reactor tests with formic acid indicated low precipitation risks, whereas those with OMA suggested higher precipitation risks. Detailed analysis on the thin sections and residuals of the batch reactor tests with OMA highlighted the precipitation of unique fluorides, and the precipitation risk was modeled and quantitatively evaluated with geochemical simulations. Although there is more room to investigate the risks of the usage of OMA for the volcanic rocks, the results in this work suggest the use of formic acid as a main treatment acid, as in carbonate acidizing, for wells with abundant cemented fractures in near-wellbore regions. This paper provides insights on acid stimulation in volcanic rocks (especially rhyolite). The results provide a fundamental understanding on the acid/rock reactions and the potential benefits/risks for productivity enhancement of wells in the subject volcanic reservoir.

Boron in formation waters from oil and gas fields in Japan

Boron in formation waters from oil and gas fields in Japan

Pilot test of study on brine injection into shallow formation for mitigating land subsidence in the Southern Kanto Gas Field in Japan

Abstract. In the Southern Kanto Gas Field, natural gas dissolved in water has been produced for over 80 years. In order to produce the natural gas dissolved in water, formation water must be pumped from a reservoir in the gas field. The production of formation water is considered to be one of the causes of land subsidence. Because brine injection into shallow formations is expected to be effective to mitigate land subsidence, our association is planning to conduct the pilot test study. In this test, the production and injection of brine are going to be performed, and we will observe a deformation of the shallow formation and a change of ground level and the bottom hole pressure. As a result of these tests, if the land subsidence mitigation effect by injection into shallow formation is confirmed, it is expected that it will be connected to increased production and to reservoir management in consideration of land subsidence mitigation in the future.

Methanothermobacter tenebrarum sp. nov., a hydrogenotrophic, thermophilic methanogen isolated from gas-associated formation water of a natural gas field

A thermophilic and hydrogenotrophic methanogen, strain RMAS(T), was isolated from gas-associated formation water of a gas-producing well in a natural gas field in Japan. Strain RMAS(T) grew solely on H(2)/CO(2) but required Casamino acids, tryptone, yeast extract or vitamins for growth. Growth of strain RMAS(T) was stimulated by acetate. Cells were non-motile, straight rods (0.5×3.5-10.5 µm) and occurred singly or in pairs. Bundles of fimbriae occurred at both poles of cells and the cell wall was thick (approximately 21 nm, as revealed by ultrathin section electron microscopy). Strain RMAS(T) grew at 45-80 °C (optimum, 70 °C), at pH 5.8-8.7 (optimum, pH 6.9-7.7) and with 0.001-20 g NaCl l(-1) (optimum, 2.5 g NaCl l(-1)). Phylogenetic analysis revealed that Methanothermobacter thermautotrophicus ΔH(T) was most closely related to the isolate (95.7 % 16S rRNA gene sequence similarity). On the basis of morphological, phenotypic and phylogenetic characteristics, it is clear that strain RMAS(T) represents a novel species of the genus Methanothermobacter, for which we propose the name Methanothermobacter tenebrarum sp. nov. The type strain is RMAS(T) ( = DSM 23052(T) = JCM 16532(T) = NBRC 106236(T)).

Ability of anaerobic microorganisms to associate with iodine: 125I tracer experiments using laboratory strains and enriched microbial communities from subsurface formation water

Iodine-129 ( 129I) is a fission product with a half-life of 15.7 million years. Because of its long half-life, high mobility, and high affinity to the human body, 129I is considered as one of the most problematic radionuclides in nuclear waste disposals in deep geological formation. In this study, 16 strains of anaerobic microorganisms, including nitrate-reducing bacteria, iron-reducing bacteria, sulfate-reducing bacteria, and methanogens, were cultured anaerobically with a radioiodine tracer ( 125I) to determine whether they possess the ability to associate with iodine. We evaluated it by association efficiency, that was determined by measuring the decrease in 125I activity in the culture supernatant. It was found that the efficiency of about half of the strains was below detection limit (1.0%), and that of the remaining strains varied from 1.0% to 6.3%, although it was not statistically significant. Similar experiments were conducted by using anaerobic microbial communities inhabiting the iodine-rich subsurface formation water collected from the Minami-kanto gas field in Japan. The specific uptake of iodine by the microbial communities was estimated to be 0.71–2.0 μg g −1 dry weight of biomass, indicating that the association ability was, if present, very limited. These results suggest that anaerobic microorganisms, in contrast with aerobic microorganisms, neither enhance nor repress the mobility of 129I, in the case of discharge of this radionuclide from disposal facilities into the surrounding environment.

Radium geochemistry in Na–Cl type groundwater in Niigata Prefecture, Japan

Radium isotopes in 23 Na–Cl type groundwater sampled mainly from deep wells in Niigata Prefecture, which is the site of the largest oil- and gas-fields in Japan, were measured along with U isotopes, chemical components and hydrogen and oxygen isotope ratios to elucidate the distribution and behavior of Ra in a brackish environment underground. Also analyzed were U and Th isotopes in 38 rock samples collected from outcrops at 17 locations. Ra-226 concentrations (8.86–1637 mBq kg −1) of groundwater samples roughly correlated with total dissolved solid (TDS) concentrations and other alkaline earth contents. Their 228Ra/ 226Ra activity ratios (0.32–5.2) were similar to or higher than the 232Th/ 238U activity ratios (0.6–1.7) in the rocks. The most likely transport mechanism of Ra isotopes into groundwater was due to their α-recoil from the solid phase, probably from the water–rock interface where Th isotopes had accumulated, and adsorption/desorption reaction based on the increase in 226Ra contents with TDS.

Methanolobus profundi sp. nov., a methylotrophic methanogen isolated from deep subsurface sediments in a natural gas field

A mesophilic, methylotrophic methanogen, strain MobM(T), was isolated from a natural gas field in Japan. Strain MobM(T) grew on methanol and methylamines, but not on H(2)/CO(2), formate, acetate or dimethyl sulfide. The cells were motile, irregular cocci (diameter, 0.9-1.2 microm) and occurred singly, in pairs, as tetracocci or (occasionally) as aggregates. Strain MobM(T) grew at 9-37 degrees C (optimally at 30 degrees C) and at pH 6.1-7.8 (optimally at pH 6.5). Sodium and magnesium were required for growth, at 0.1-1.0 M Na(+) (optimally at 0.35 M) and 10-400 mM Mg(2+) (optimally at 15-25 mM). The G+C content of the genomic DNA was 42.4 mol%. 16S rRNA gene sequencing revealed that the isolate is a member of the genus Methanolobus, but distinct from its closest neighbours, Methanolobus tindarius DSM 2278(T) (sequence similarity, 98.0 %) and Methanolobus vulcani DSM 3029(T) (98.1 %). On the basis of phenotypic and phylogenetic features of MobM(T), it is clear that this strain represents a novel species of the genus Methanolobus, for which the name Methanolobus profundi sp. nov. is proposed. The type strain is MobM(T) (=DSM 21213(T)=NBRC 104158(T)).

Diversity of Indigenous Anaerobes and Methane Conversion System from Reservoir Oil by Indigenous Anaerobes in Depleted Oil Fields

We developed methods and technology to identify oil and gas fields that are likely to support the restoration of methane deposits, and identified the main characteristics of microbes inhabiting depleted oil and gas fields. To evaluate the potential for microorganisms to inhabit oil and gas fields in Japan, we investigated the existence of methane-producing archaea (MPA) and hydrogen-producing bacteria (HPB) using PCR-DGGE (Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis) analysis. Reservoir brine from Yabase oil field (Akita Pref., Japan), which was incubated under strictly anaerobic conditions at 50°C, actively produced methane, indicating that Yabase oil field is a suitable site for methane generation. Moreover, analysis of the enrichment culture revealed that it is possible for indigenous anaerobes inhabiting an oil field to generate methane from oil components. Additionally, findings established a methanogenic pathway composed of MPA such as Methanoculleus sp., Methanothermobacter thermoautotrophicus, and Methanosaeta sp. and hydrocarbon-degrading hydrogen-producing bacteria (HD-HPB) related to Thermotoga sp., Petrotoga sp. and Clostridiaceae str. These results strongly suggest that Yabase oil field has the technological potential for the microbial restoration of methane.

Microbial diversity and methanogenic potential in a high temperature natural gas field in Japan

Microbial diversity and methanogenic potential in a high temperature natural gas field in Japan

Methanogen Diversity in Deep Subsurface Gas-Associated Water at the Minami-Kanto Gas Field in Japan

Methanogen diversity and methanogenic potential in formation water obtained from the Minami-kanto gas field in Japan were investigated by using 16S rRNA gene libraries and culture-based enrichment methods, respectively. This region is the largest gas field that produces natural gases of dissolved-in-water type in Japan. Although the microbial population density was below statistical quantification limits (1 × 104 cells ml−1), autofluorescent coccoid and rod-shaped cells indicative of methanogens were observed. The represented genera in the archaeal 16S rRNA genes libraries were comprised of Methanobacterium, Methanospirillum, Methanocalculus, Methanococcus, Methanolobus and Methanosaeta. The dominant archaeal sequences were related to the hydrogenotrophic methanogens in the genus Methanobacterium. Of the methanogenic substrates tested using the formation water-based medium,H2-CO2 yielded the highest methane production. These results strongly suggest that the formation water of the Pleistocene strata in the gas fields harbor viable hydrogenotrophic methanogens and have possibly been making a contribution to ongoing methanogenesis.

Microbial diversity and methanogenic potential in a high temperature natural gas field in Japan

Microbial diversity and methanogenic potential in formation water samples from a dissolved-in-water type gas field were investigated by using 16S rRNA gene libraries and culture-based methods. Two formation water samples (of 46 and 53 degrees C in temperature) were obtained from a depth of 700 to 800 m. Coenzyme F(420)-autofluorescence indicated that 10(3)-10(4) cells per ml of active methanogens were present, accounting for at least 10% of the total cell count. The 16S rRNA gene sequence analysis indicated that the diversity of Archaea and Bacteria of the two samples was quite limited; i.e., the archaeal libraries were dominated by the sequences related to Methanobacterium formicicum and Methanothermobacter thermautotrophicus, and the bacterial libraries were dominated by the sequences related to Hydrogenophilus and Deferribacter. Of the methanogenic substrates tested using the formation water-based medium, only H(2)-CO(2) gave rise to methane formation. Those dominant archaeal and bacterial genera have the potential to use hydrogen for growth at the in situ temperatures, suggesting that the formation water of the Pliocene strata in the gas field has been provided with hydrogen, probably from underneath the strata, and thus on-going active methanogenesis has been occurring to date.

Effects of thermal cracking of hydrocarbons on the homogenization temperature of fluid inclusions from the Niigata oil and gas fields, Japan

The changes of the homogenization temperature (Th), when hydrocarbons in inclusions were cracked thermally, were experimentally evaluated. In the experiments, the hydrocarbon-inclusions in quartz were heated in an autoclave, and the Th between before and after heating were compared. In the experiments, the Th decreased after heating. The amount of decrease became greater as the heating temperature or the duration time or both increased. The experiments also revealed that the samples with higher Th showed a greater decrease after heating. Because the experiments have been performed in a closed system, mass transfer between inclusions and the enclosing medium was impossible. No volumetric changes in the hydrocarbon inclusions were observed after heating. Therefore, the temperature depression after heating should be caused by the pyrolysis of the hydrocarbons in the inclusions. In the Shin-Kumoide SK-1D well of the Niigata oil and gas field in Japan, the Th of hydrocarbon inclusions decreases from 73 to 30 °C between 4040 and 4810 m in depth successively. This temperature range is lower than the present formation temperature by from 60 to 140 °C, and shows a trend opposite to the normal geothermal gradient. Therefore, it should reflect the degree of the thermal cracking after trapping rather than the trapping temperature.

南長岡における天然ガス生産，輸送のライフサイクルインベントリ（ＬＣＩ）調査

The authors investigated life cycle carbon dioxide and methane inventories for the exploration, exploitation and transportation (incl. their capital) of natural gas produced in Minami Nagaoka Natural Gas Field in Japan. Around 22% of total domestic natural gas production was exploited from the field in 2001.According to the results obtained through the investigation, 5.18g-CO2-eq. of carbon dioxide and methane is released by the exploration, exploitation and transportation of 1 MJ of the natural gas. The amount is almost 10% of the carbon dioxide emission by the combustion of the natural gas. Hence, the emission data by its production should be counted for precise implementation of LCA.The largest carbon dioxide emission source is the release of carbon dioxide which is extracted from underground with natural gas and separated from the target gas (CH4). The next largest emission is released natural gas during its transportation by pipe lines. Because of re-construction of roads or development of the route area, the pipe lines are required to detour. For the diversion process, certain amount of natural gas inside the pipes is released to the environment. These releases are more than 70% of the total GHG emission obtained by this investigation.

枯渇油・ガス田の有効利用

Teikoku Oil Co., Ltd. operates Minami-Nagaoka gas field, one of the biggest natural gas fields in Japan. Increasing demand of natural gas requires that Teikoku Oil should reinforce its production capability, including number of production wells, in Minami-Nagaoka. From a viewpoint of stable supply of gas resources, importance of natural gas underground storage has been widely recognized. Teikoku Oil established, for the first time in Japan in 1969, the underground storage system in Sekihara gas field, which was a depleted gas reservoir located a few kilometers north to Minami-Nagaoka. Since then, it has played a great role for peak shaving and/or emergency stockpile in Minami-Nagaoka gas production operation. At present, approximately 140 MMNm3 of natural gas is stored with the maximum deliverability of 1.6 MMNm3/day. Some technical issues encountered and solved during the storage operation for these 30 years are discussed in this lecture. In addition, Teikoku Oil notices that its experiences gained through the underground storage of natural gas in Sekihara could be directly applied to underground storage of carbon dioxide. Namely, injecting and storing man-made emissions of carbon dioxide, a greenhouse gas, in underground is considered as one of the possible measures against a global warming problem. Teikoku Oil is a member of a national research project on the underground storage of carbon dioxide led by RITE (Research Institute of Innovated Technology of Earth) and SEC (Safety and Environment Center for Petroleum Development). A pilot test to inject and store 15, 000 tons of carbon dioxide into a water zone is scheduled in and after 2003, for which one injection and two observation wells have already been drilled in Minami-Nagaoka. This noteworthy project is also introduced in this lecture. A key concept common to the both topics above is “utilization of depleted gas/oil reservoirs.”

日本の主要なガス田より産する天然ガスの有機地球化学的研究

日本の主要なガス田より産する天然ガスの有機地球化学的研究

Helium flux from a sedimentary basin

The tritium– 3He ages of groundwaters collected from the Saijo Basin in Japan were measured. The ages vary between 11.7 and 16.3 years. The 4He flux of >3×10 4 atoms/cm 2 s is calculated by the 4He concentrations and ages. In addition the helium flux of 8.3×10 5 atoms/cm 2 s is calculated at the Higashi-Niigata gas field in Japan. The above two estimates are consistent with the continental helium flux reported in the literature, suggesting that helium flux on the Earth's crust is uniform.

Neogene diatoms as the important source of petroleum in Japan

Major oil and gas fields in Japan are located in the area extending from central Hokkaido through northeast Honshu. Most productive horizons are generally found in the late Middle Miocene (approximately 12-10 Ma) Onnagawa Formation of the Akita basin and equivalent formations of other basins. These formations are composed mainly of chert, siliceous shale, diatomite, mudstone, marlite, and acidic pyroclastic rocks. Source rock potentials by Rock Eval analyses in the Miocene Ohdoji and Wadagawa Formations from the Aomori basin, equivalent to the Onnagawa Formation, show the highest values as compared with other formations in the basin. Average contents of TOC, S 1, and S 2 generally increase from argillaceous rocks→diatomites→siliceous shales→cherts. Organic matter in siliceous shales belongs to type I, in argillaceous rocks to type III, and in diatomites and cherts to intermediate types between II and III. Maturation of organic matter in these rocks in generally lower than that in average source rocks. Besides n-alkanes and aromatics, many unknown components were found in the hydrocarbons produced from kerogen by pyrolysis gas chromatography. They are probably related to naphthenes and alkylbenzenes. Based on the relative amounts of aromatics (toluene + p-xylene), light n-alkanes (C 8–C 10), and heavy n-alkanes (C 11–C 20), these rocks are classified into three groups. They are light n-alkanes and aromatics-common (mainly cherts), heavy n-alkanes-rich and aromatics-poor (chiefly siliceous shales), and light n-alkanes-poor and aromatics-rich (mainly diatomites) groups. Compositional ratios among stigmastane, ergostane, and cholestane of steranes determined by gas chromatography/mass spectrometry on bitumen may indicate that the type of organic matter is of open marine origin. Chemical indicators of maturity, e.g., the composition of saturated hydrocarbons such as CPI and isomerization of steranes and triterpanes, may support the poorly biogeochemical transformation of organic matter into petroleum. Diatoms, which appeared in the Late Cretaceous and became increasingly important in the Miocene, are the principal primary producers of organic matter in the marine environment during the Cenozoic. Excellent organic components and higher biological productivity show that diatoms might be the most important sources of petroleum during the Neogene in Japan.

Relation between hydrocarbon composition and carbon isotopic composition of natural gases from oil and gas fields in Japan

Relation between hydrocarbon composition and carbon isotopic composition of natural gases from oil and gas fields in Japan

Origin of natural gas of dissolved-in-water type in Japan inferred from chemical and isotopic compositions: Occurrence of dissolved gas of thermogenic origin.

Carbon isotopic ratios of methane (δ13C(C1)) and chemical compositions were measured for natural gases of dissolved-in-water type (dissolved gases) from several gas fields in Japan. Most of the samples have low δ13C(C1) values (-69.1∼-66.4‰) and contain small amounts of C2+(CnH2n+2, n≥2) hydrocarbons. These two features indicate that they are of biogenic origin as has been suggested by previous researchers. However, several samples from the Yaizu gas field have high δ13C(C1) values (-34.3∼-33.8‰) which cannot be of biogenic origin, but thermogenic origin. This is the first report to confirm the occurrence of dissolved gas of thermogenic origin in Japan.

Importance of Neogene Siliceous Rocks as the Source of Petroleum in Japan

Abstract Major oil and gas fields in Japan are located in the area from the central Hokkaido through northeast Honshu. Most productive horizons are generally found in formations of the late Middle Miocene (approximately 12-10 Ma) Onnagawa provincial stage of Japan. These formations are composed mainly of hard mudstone, siliceous shale, diatomaceous mudstone, marlite, and acidic pyroclastic rocks. Source rock potentials in argillaceous rocks of the Miocene Ohdoji Formation in Aomori, the Onnagawa Formation in Akita, and the Lower Teradomari Formation in Niigata show the highest values as compared with other formations in these areas. Average contents of organic carbon and hydrocarbons of siliceous sediments such as diato-mite, siliceous shale, and chert in the Aomori basin indicate the higher values as compared with other argillaceous sediments. Diatoms, which appeared in the late Cretaceous, are the principal primary producers of organic matter in the marine environment during the Cenozoic. Organic components and biological productivity show that diatoms have been the most important source of petroleum during the Neogene in Japan.