桂中坳陷泥盆系生物礁分布预测

Prediction of Devonian Reef Distribution in Guizhong Depression

桂中坳陷泥盆系盆地经历了五大演化阶段,包括早泥盆世的初始裂陷和初始扩展,中泥盆世的抬升和裂解,以及晚泥盆世的扩展—萎缩。从早泥盆世埃姆斯期至晚泥盆世早期均有生物礁发育,但以中泥盆世的裂解阶段最为繁盛。泥盆系剩余重力异常总体特征表现为两高两低特点,其中心分别位于宜州、合山和马山、柳江附近。由重力资料划分出研究区的台地、台沟分布,再由地震异常圈定了中泥盆统分层系生物礁分布。在泥盆系应堂组—东岗岭组四个层段共圈出异常体17个,位于忻城县和大塘镇之间的异常体规模最大,面积达307km2。该带距离古断裂较远,油气保存的可能性较大,是未来桂中油气勘探的首选区带之一。

Over than 5000-m thickness of marine Devonian carbonate system deposited in Guizhong Depression is a marine residual basin. The basin experienced for five main evolution stages during Devonian period. It is considered to be hydrocarbon potential in southern China. Organic reefs that developed from Early Devonian Emsian to early Late Devonian are distributed between mudstones and carbonate rocks, which plays an important role in hydrocarbon accumulation. Based on geological and geophysical data, the distribution rule of Devonian reefs is discussed. By seismic and gravity anomaly, the authors constructed the lithological stratification of the Devonian reefs, predicted the locations of paleo-platforms in the depression, and predicated zones where reef mounds are probably concentrated. 17 potential reef reservoir bodies of seismic anomaly are sited from Devonian Yintang Fm to Donggangling Fm, of which the largest one with an area of 307km^2 is located between Yicheng and Datang. It is suggest that it will be the first selective one for drilling target because it is far from ancient faults and so probably has a good preservation condition of hydrocarbon.