The Arab Formation distributed in the West Mubarras Concession, offshore Abu Dhabi, U.A.E., consists of limestone, dolomite and anhydrite. The way of lithological succession in the Arab Formation is well explained by shallowing upward sabkha deposional model. Reservoir rocks can be classified into five types as a result of complex combination of sedimentary facies originated from different environments and diagenesis at various timing of burial history. They are “Limegrainstone”, RD1-1, RD1-2, HD1-1 and HD1-2 respectively.
“Limegrainstone” has intergranular porosity which causes high permeability. Bloky calcite cement reduced porosity at downflank of the structure.
RD1-1 and RD1-2 are dolomites originated from grainstone or packstone. RD1-1 preserves original intergranular porosity which causes highest permeability among all dolomite reservoir rocks. Porosity in RD1-2 is mainly moldic which was derived from leaching of grains. Because of poor continuity between molds, permeability of RD1-2 is considerably lower than that of RD1-1.
HD1-1 is a coarse grained “sucrosic dolomite” with intercrystalline pores. Large pores sometimes causes high permeability. Porosity decreases toward downflank of the structures because of crystal interlocking enhanced by reaction with formation water.
HD1-2 is a very fine crystalline dolomite originated from limemudstone or wackestone. Due to very small size intercrystalline pores, even in fairly porous rocks permeability is very low.

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To clarify the timing of primary migration of petroleum hydrocarbons in the Japanese Tertiary Niigata Sedimentary Basin, maturation levels of some crude oils and condensates were evalutaed based upon biomarker compositions (steranes and hopanes). Consequently, it was revealed that most oils were at the similar organic maturation levels. This maturation level can be represented by 0.45 to 0.50 of the degree of sterane epimerization (20S/(20S+20R) ratio of C₂₉-sterane) and about 0.3 of the degree of sterane cracking(L/(L+H)ratio=(C₂₁+C₂₂)/(C₂₁+C₂₂+C₂₇+C₂₈+C₂₉) ratio of five 5α-steranes). This can be also correlated to the 0.6 to 0.7 of Ro% (vitrinite reflectance) in the Niigata Sedimentary Basin. This indicates that the primary migration of petroleum hydrocarbons from mudstone source rocks started prior to this maturation stage. Considering that the generation of petroleum hydrocarbons starts at about Ro%=0.5 in the Niigata Sedimentary Basin, primary migration most probably occurs at Ro%=0.5 to 0.7.
There is a marked difference among L/(L+H) ratios of condensates in which the sterane epimerization is nearly at the end point. The different L/(L+H) ratio of each condensate oil (0.48 to 1.00) shows a difference in maturation level. The L/(L+H) ratio of steranes can be applied to evaluate the organic maturation at a relatively higher stage. The L/(L+H) ratio is also useful as a parameter for the evaluation of thermal cracking of C-C bond in source rock.

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Accurate analysis of kerogen type is important in source rock evaluation, because its chemical structure is closely related to composition of hydrocarbons generated. In this work, whole rock and isolated kerogen samples from Noshiro GS-1 well were investigated by flash pyrolysis techniques, and the products were examined by gas chromatography and gas chromatograph-mass spectrometry.
Phenolic compounds were dominant in pyrolysis products of terrestrial kerogen (woody-coaly type), whereas aliphatic hydrocarbons were major products in marine kerogen (amorphous type). The ratio of phenolics/aliphatics was well correlated to the results of visual kerogen and Rock-Eval analyses.
Pyrolysis products of whole rock samples were less amount than those of kerogen. However, the phenol/C₁₂ ratio has been suggested to be effective for kerogen typing. The results show that phenol/C₁₂ ratio of gas-prone kerogen is above 2.0 and that of oil prone kerogen is below 0.5 for both kerogen and whole rock samples.

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Natural gas produced in the Minaminagaoka and Higashikashiwazaki gas fields of TEI-KOKU OIL COMPANY (TOC) is transported to the market in Niigata, Nagano, Gunma, and Saitama Prefectures through TOC's pipelines. The total length of the pipelines is about 520km. As the main use of such natural gas is town gas, the quantity of transported gas has increased year by year in response to the growth of towns. The demand for town gas depends on weather. Therefore the demand for natural gas changes greatly not only seasonally but also hourly. It is very important to adjust the production rate in order to match such demand. Natural gas used for town gas must be supplied continuously without any interruption, and the securing of the safety in the pipeline operations is becoming increasingly important. Considering the above situation, tele-metering and tele-controlling system was introduced to supervise and control the pipeline operations.
The supervisory control system for gas pipelines was initiated in December, 1981, and the control center was established in the TOC's building at Kashiwazaki city, Niigata. This paper describes the outline of the system and its operational aspects.

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Regarding recent development for new concepts and technology concerning offshore oil field development (especially in marginal offshore oil field), possible offshore development systems become more various, which require many experts for various subjects such as hydrodynamics, structural engineering, marine engineering, system engineering and meteorology in addition to drilling engineering and petroleum engineering when applied systems are selected among many possible ones.
The purpose of this project is to develop the assistance tool program named “EPODS” (Evaluation Program for Offshore Development System) for the decision maker of oil field developments. The program is expected to be used at various stages of the decision making such as preliminary stage before bidding for a concession, conceptual study stage after aquisition of the concession and final study stage before start of actual development design.

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