Papers by Hidehiro Ishikawa
Journal of Applied Geophysics, 2003
In Mexico, an experimental study with a Long-Offset Time-Domain Electromagnetic Method (LOTDEM) w... more In Mexico, an experimental study with a Long-Offset Time-Domain Electromagnetic Method (LOTDEM) was carried out in the Tampico -Misantla basin of northeastern Mexico. The main objective was to evaluate this method for hydrocarbon exploration. The selected area is suitable for LOTDEM experiments because high quality seismic data, geological information and well logging data are available. The results obtained are excellent, and allow us to determine the types of fluids present in the rock pores and fractures of the studied geological structures. Resistivity anomalies correlate in position and depth with the geological structures observed in the seismic sections where the LOTDEM survey was carried out, and with well logging data from the nearby Franco Española oil field. In the studied area, these structures are 800 -1200 m deep, in carbonate rocks with high clay content and are invaded by salt water. Consequently, the resistivity and primary porosities are very low. The main reservoirs of oil and gas in this region are a naturally fractured basinal facies, consisting of fine-grained limestones and shaly limestones, that corresponds to the Cretaceous units San Felipe, Agua Nueva, Tamaulipas Superior and Tamaulipas Inferior. The fractured rocks reservoirs are very difficult to detect, even with well logs. However, the results of this survey show the higher resolution, the greater depth of investigation, and the advantages that the LOTDEM method present compared to the traditional frequency domain electric and electromagnetic (FEM) methods. D
The three components and total intensity of the geomagnetic field were measured using STCM and a ... more The three components and total intensity of the geomagnetic field were measured using STCM and a proton precession magnetometer during the DELP 1987 Ogasawara cruises. The total intensity anomalies are generally negative and small in amplitude in the trough, their lineation pattern can hardly be defined. However, the anomaly patterns of the three vector components of the geomagnetic field show widely distributed lineation features trending north-south over the trough. Two total intensity negative peaks in the northern and southern ends of the trough are located at around the same positions as the free air gravity negative anomaly peaks. 1987年秋のDELP航海により小笠原トラフ周辺海域において地磁気連続測定を行った.測定に於いては船舶用フラックスゲート地磁気三成分測定系ならびに曳航型プロトン磁力計により観測を行ったが,後者については航海中船上測定系に異常が出たことなどもあって完全な三成分対全磁力比較検討の材料とは成らなかったものの,全磁力についてはこの海域に於て地質調査所などから多ぐのデータが提供されているので,解析に支障は無いと思われる.船舶上での三成分磁力測定はかねてから神戸大学理学部により信頼度の高いデータが得られる様に成ってきたが,本観測地域の例にもみられるように低緯度でかつ海底の基盤もまた低緯度で発生したと予測される地域の地磁気観測には三成分磁力計は必要不可欠なものである.この報告にも,従来より明瞭な地磁気縞模様の...
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Papers by Hidehiro Ishikawa