The Yurihara and Ayukawa oil & gas fields are located in a Yuri plateau 60 km away from Akita city. Japex has been operating in these fields for 25 years. In the future it will be considered to meet with a various problems in these fields such as following points. 1) Decrease of oil production caused by reservoir pressure depletion 2) Increase of water production. Therefore, technically and economically best methods of artificial lifts had been studied for Yurihara SK-16DH well. As a result, Japex had decided to give a field test of hydraulic jet pump (JP)+coiled tubing (CT) system for the first time. This system has advantage of easy operation and unnecessity of workover. And so Japex carried out some test of JP + CT system in 2006 and 2008. In consequence of the test, Japex has confirmed oil recovery enhancement and stability of oil/gas production.
Abu Dhabi Oil Co., Ltd. (ADOC) is currently operating three oil fields offshore Abu Dhabi; Mubarraz Field, Umm Al-Anbar (AR) Field and Neewat Al-Ghalan (GA) Field. In the Mubarraz Field, ESP's (electrical submersible pump) have been installed as an IOR method. The first ESP was installed in 1975 and over 320 ESP's have been installed and operated since then. At present, all 44 wells are ESP wells, and approximately 10 workovers are carried out annually. Numerous improvements have been applied to the ESP assembly to increase the lifetime of the ESP's. Currently, the average running lifetime is 3 to 4 years, and the maximum running lifetime is 4,077 days (11.2 years).
Super martensitic stainless steels (13Cr and 15Cr steels containing Ni and Mo) were developed for OCTG (Oil Country Tubular Goods) materials for high temperature sweet (slightly sour) environments. Corrosion performances of these CRAs (Corrosion Resistant Alloys) were evaluated and compared with those of 13%Cr and 22Cr duplex stainless steels for high temperature sweet gas environments, such as those in Minami-Nagaoka wells, based on application temperature limits claimed by steel makers and actual field results of 13%Cr tubing strings. The test results were compared with the evaluation results by J-Tube Mate (Corrosion performance evaluation software) and effects of acetic acid, formation water production (high Cl- concentration) at high temperatures were discussed. Effects of alloying elements such as Cr and Mo on pitting potential at ambient temperature were also discussed.
Water injection is one of the countermeasures against ground subsidence in the Southern Kanto Natural Gas Field. Generally, injection water contains suspended solids (SS) which could reduce the injectors' injectivity. The SS may pile up at the bottom of injectors. Furthermore they may plug pores of the formations for injection and the perforation holes of the casing. Accordingly injectors' injectivity declines due to such plugs. It is indispensable to increase the injectivity for the sustainable production operation with minimizing the ground subsidence in this field. In fact there was a conventional technique to recover the injectivity by use of jetted water. Though the flock of SS was removed from the inside of the casing by the jetted water, the effect was not remarkable if the plugging occurred in the formations. This study presents a new technique which can remove the plugs from the formation by use of compressed air. This method was improved to be more practical after trial execution at some fields. Finally this new technique was completed and the considerable results were yielded. As the permeability of the formation near the borehole was increased by the formation cleaning, the injectivity was enhanced substantially.
JHN Lufeng 13-1 Oil Field operated by JHN Oil Operating Company (JHN) is located in South China Sea. In the Oil Development Plan (ODP) phase, the maximum water production rate was estimated to be 42,000bpd through 12 production wells, and oil in water (OIW) value of discharging water to sea after treatment was requested to be less than 50 ppm according to Chinese government regulation. In the actual operation phase, the water production was beyond expectation since the reservoir type was strong bottom water drive. As of February 2009 which is the termination of petroleum rights for JHN, the water production rate was exceeding 200,000bpd through 27 production wells. Therefore, JHN had to modify the water treatment system and oil separation system step by step to maximize oil production and to meet required OIW value for discharging water to sea. JHN made every effort to ensure stable and efficient operation with respect to the environment system in line with Chinese environmental and safety regulations. In 2006, Chinese government has announced to all oil operating companies in South China Sea as to the reduction of oil volume in discharging water to sea. So, JHN had modification work for water treatment facilities, and applied acceleration chemical to separate oil and water in water treatment facilities to meet possible further strict control over discharging water.
Gas and condensate have been discovered in the offshore Joban fore-arc Basin. They derived from coal and coaly mudstone in the Upper Cretaceous to the Miocene sediments. Although thick Cretaceous marine argillaceous rocks deposited in the basin, especially in the east of the Abukuma Ridge, they have not been evaluated as an effective source rock. Therefore, organic geochemical characteristics and petroleum generation potential were studied for the Cretaceous argillaceous rocks in the basin. The argillaceous rock samples from the MITI Joban-oki, MITI Kesennuma-oki, and Kita-Ibaraki-oki TJ-1 wells and from outcrops of the Futaba and the Nakaminato Groups were submitted to total organic carbon, total nitrogen and total sulfur analyses, Rock-Eval pyrolysis, and bitumen extraction. Saturate hydrocarbons fractionated from the bitumens were further analyzed by GC-MS. Only a small number of samples from the Kita-Ibaraki-oki TJ-1 and the MITI Joban-oki wells show good petroleum generation potential (S2≥2.5 mgHC/gRock). These samples also have high Hydrogen Index (≥250 mgHC/gCo). Two biomarker ratios, (C27+C29+C31)/(C24∼C34) of n-alkanes and C27/(C27+C29) of steranes, indicate an evident negative correlation, suggesting source organic input. Two other ratios, pristane/phytane and C35/(C31∼C35) of homohopanes, also indicate a negative correlation, suggesting oxic/anoxic depositional environment. All these ratios correlate to petroleum generation potential, and good potential is accompanied by low ratios in (C27+C29+C31)/(C24∼C34) of (C-alkanes and pristane/phytane, and high ratios in C27/(C27+C29) of steranes and C35/(C31∼C35) of homohopanes. These results suggest that the Cretaceous argillaceous rocks in the offshore Joban Basin can have good petroleum generation potential in case of abundant marine organic matter deposited under anoxic environment. For petroleum exploration in the east of the Abukuma Ridge, it is important to predict the regional distribution of Cretaceous argillaceous source rocks that are rich in marine organic matter and deposited under anoxic environment.