PREDICTION OF HIGH QUALITY SOURCE ROCKS BASED ON SEQUENCE STRATIGRAPHIC FRAMEWORK OF WENCHANG FORMATION, PANYU 4 DEPRESSION, THE PEARL RIVER MOUTH BASIN
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摘要:
珠江口盆地番禺4洼“小而肥”,目前的探明石油地质储量已超出早期估算的地质资源量,早期对烃源岩的认识不足可能是其主要原因,尤其是对优质烃源岩的分布范围仍缺少精确刻画,在很大程度上限制了对该洼陷勘探潜力的认知。以该难点问题为切入点,利用最新钻井和地震资料,采取层序地层学开展了番禺4洼烃源岩的预测工作。通过地震资料上识别的各种反射特征,结合区内已有钻井资料识别的旋回特征,将番禺4洼文昌组划分5个三级层序,进而建立了等时地层格架。在此基础上,综合运用地震沉积学最新技术手段,精细揭示了番禺4洼文昌组文三段优质烃源岩的分布范围。研究结果表明,番禺4洼优质烃源岩分布面积较为广泛,尤其在北次洼和西次洼,优质源岩面积均超过了以往预期。这一研究成果对本区和珠江口盆地油气勘探具有一定指导意义。
Abstract:The Panyu 4 Depression in the Pearl River Mouth Basin is rather small but rich in hydrocarbon, and the current proved geological reserves have exceeded the early-estimated geological resources. Lacking of source rock knowledges, especially lacking of accurate description of high-quality source rocks, may be the main reason that greatly limited the recognition of the exploration potential of the depression. Taking this difficult problem as the standpoint to seek for breakthrough, this paper uses the latest drilling and seismic data and adopts the unique perspective of sequence stratigraphy to systematically make prediction of source rocks in the depression. According to the various reflection characteristics identified from seismic data and the cyclic characteristics from drilling data, the Wenchang Formation in Panyu 4 Depression is divided into five third-order sequences, and the isochronous stratigraphic framework is then established. On this basis, the distribution area of high-quality source rocks in the third sequence of Wenchang Formation in Panyu 4 Depression is revealed by using the latest seismic sedimentology techniques. The results show that the area of high-quality source rocks in the Panyu 4 Depression is relatively wide, especially in the North Sub-depression and the West Sub-depression, the area of high-quality source rocks exceeds previous expectations. The research results of this paper may provide clues for oil and gas exploration in this region and the Pearl River Mouth Basin.
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图 2 番禺4洼古近系层序地层格架[13]
Figure 2.
表 1 烃源岩地球化学特征统计表
Table 1. Statistics of geochemical characteristics of source rocks
样品深度/m 样品数 TOC/% S1+S2/(mg/g) HI/(mg/g) Tmax/℃ 氯仿沥青“A”/% 干酪根类型 Ro/% 3 273~3 639 15
1.6~10.5
2.31~76.08
136.3~696.2424~444
0.39~0.965Ⅱ1 0.63~0.66 -
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