西江主洼相对低地温条件下油气成藏特征和勘探潜力分析

An analysis of hydrocarbon accumulation and exploration potential under a lower geothermal condition in Xijiang sag

相对于周边地区,珠江口盆地西江主洼古今地温和地温梯度相对较低。与邻近勘探程度较高的惠州凹陷相比较,从地热在沉积物成岩、成烃演化过程中的作用特点以及构造活动等方面,对西江主洼相对低地温条件下的油气成藏特征和勘探潜力进行了分析。相对低的地温条件导致西江主洼油气成藏相对较晚(现今成藏),油气主要集中于深层古近系文昌组和恩平组。与惠州凹陷多期成藏、上下成藏、新近系上组合段是重要勘探目的层相比较,西江主洼的勘探重点和优势在深层。

In Pearl River Mouth basin, Xijiang sag is relatively lower in palaeo-geotherms and geothermal gradients than adjacent areas. By comparison with Huizhou sag with higher exploration maturity, hydrocarbon accumulation and exploration potential in Xijiang sag are analyzed from geother- mal roles in sediment diagenesis and hydrocarbon generation and tectonic movements. The relatively lower geothermal condition has resulted in relatively later hydrocarbon accumulation, and most hydrocarbon is concentrated in Paleogene Wenchang and Enping Formations in Xijiang sag. In contrast with Huizhou sag that has multi-phase accumulations, upper and lower accumulations and most important targets in upper Neogene, the exploration focus and advantage in Xijiang sag is in deeper intervals.