南薇西盆地重磁场特征及油气资源远景

结合南薇西盆地及邻区的重、磁力异常特征分析与综合反演，文章对该区油气有利远景区进行了预测。南薇西盆地北部坳陷和北部隆起以高重高磁特征为主，火山活动强烈。中部坳陷、南部隆起及南部坳陷的北部表现为整体低重、低磁背景上的局部团块状高重、高磁异常，为火山岩与碳酸盐台地的综合反映。南薇西盆地新生界厚度呈北东向条带状薄厚相间的特征，南部坳陷新生界厚度最大，中部坳陷次之。盆地北部处于莫霍面隆起区，而南部莫霍面相对较深，为减薄型陆壳的特征。北部坳陷和北部隆起居里面整体较浅，可能与南海扩张引起岩石圈的强烈伸展减薄、地幔物质上侵有关。中部坳陷和南部隆起的居里面明显浅于南部坳陷，表明中部坳陷和南部隆起的热活动强于南部坳陷。重磁场特征及其反演结果与石油地质特征表明，南薇西盆地的中部坳陷、南部隆起及其西南盆地外围的区域应为盆地最好的油气远景区，其次为南部坳陷，北部坳陷和北部隆起油气潜力不大。在油气远景区内，局部团块状、等轴状的重力高异常区部分可能为碳酸盐台地，生物礁较为发育，应为未来的勘探目标。 

GRAVITY AND MAGNETIC FIELD CHARACTERISTICS AND HYDROCARBON PROSPECTS OF THE NANWEIXI BASIN

Characteristics of gravity and magnetic anomalies and their geological significance are analyzed in order to identify prospective zones for hydrocarbon exploration in the Nanweixi Basin. The northern depression and northern uplift of the Nanweixi Basin are characterized by high gravity and high magnetism, indicating strong volcanic activities in this region. The central depression, southern uplift, and the northern part of the southern depression are characterized by local high gravity and magnetic anomalies with clumpy and isoaxial shape on the overall low gravity and magnetic amomaly background, which is a comprehensive reflection of volcanic rocks and carbonate platforms. The thickness of the Cenozoic in the Nanweixi Basin is characterized by NE trending thin-thick bands, and the thickness in the southern depression is the largest, followed by the central depression. The northern part of the basin is located in the upheaval of the Moho surface, while the Moho surface is relatively deep in the southern part of the basin, which manifests as the feature of thinned continental crust. Curie surface of the northern depression and northern uplift are relatively shallow, which may be related to the strong extension and thinning of lithosphere and the mantle material invasion caused by the expansion of the South China Sea. Curie surface in the central depression and the southern uplift is shallower than which is in the south depression, indicating that the central depression and the southern uplift have much stronger underlying thermal activities than those of the southern depression. The Nanweixi Basin has relatively favourable hydrocarbon prospects from the gravity and magnetic field characteristics and their inversion results and the petroleum geological features. The central depression, southern uplift and the southwestern peripheral regions of the basin are the best potential hydrocarbon prospect zones, followed by the southern depression. In the favourable hydrocarbon zones, some high gravity anomaly area with local clumpy and isoaxial shape may indicate carbonate platform and organic reef, which should be the future exploration target.