南泥湾油田钻井岩芯古地磁学初步研究

PALEOMAGNETIC RESEARCH OF DRILLING CORES IN NANIWAN OIL FIELD

杨斌谊 吴汉宁 李学森 吕建军

Yang Binyi Wu Hanning Li Xuesen Lu Jianjun

热退磁处理可有效分离次生粘滞剩磁(低温分量)和原生剩磁(高温分量)。粘滞剩磁方向应与现今磁场方向一致;原生剩磁方向应与岩石沉积时的磁场方向一致。利用这一原理,通过矢量合成可确定钻井岩芯的原始方位。由于磁性矿物受当时磁场作用往往呈定向排列,导致岩石磁化率各向异性,反映了岩石的磁组构特征。磁组构主要表现了岩石沉积组构,因此,可通过磁组构研究岩石沉积的环境信息,确立古水流方向和砂体展布方向。南泥湾油田近期所钻探井中岩芯的古地磁定向和磁组构研究结果表明,该区储层砂体的展布方向即水流方向为近EW向。

Secondary viscous remanence(low-temperature component) and primary remanence(high-temperature component) can be effectively separated by thermal-demagnetizing process. The orientation of the viscous remanence should be correspondent with that of available magnetic field, and the primary remanence should be consistent with the magnetic field orientation of then deposition of rocks. The original direction of drilling cores can be determined by vector compounds in line with above principle. The anisotropy of rock magnetic susceptibility, caused by the oriented arrangement of magnetic minerals effected by then magnetic field,reflects the feature of the rock magnetic fabric. The magnetic fabric shows mainly as the rock depositional fabric, therefore, environmental information of rock deposition can be gained and pale-current orientation and extension direction of sand body can be defined by studying the magnetic fabric. A research on the paleomagnetic orientation and magnetic fabric from recent drilling cores in Nanniwan oil field indicates that the extension direction of reservoir sand body in the area(namely, water flow direction) is near EW.

10.11743/ogg20020420