珠江口盆地珠Ⅲ坳陷反转构造特征及有利反转构造区带评价

Inverted Tectonic Characters and Prediction of Potential Area in Zhu-3 Depression of Pearl River Mouth Basin

通过反转构造地震反射特征、分布特征及形成机理研究,分析了珠江口盆地珠Ⅲ坳陷反转构造形成期次,划分了该区反转构造样式,研究了反转构造对油气成藏条件的影响。研究认为该区发育古近纪末期断陷反转和新近纪晚期拗陷反转2期反转构造幕,早期反转构造发生在古近纪,是在断陷期—断拗转换期之上的叠加构造,晚期反转构造发生在新近纪,是盆地坳陷期之上的叠加构造。依据反转构造与先存断裂和构造的关系,珠Ⅲ坳陷反转构造样式可划分为断层限制型和褶皱挠曲型2个大类,细分为5类断层限制型和3类褶皱挠曲型反转构造样式。反转构造可以形成良好的油气聚集圈闭条件,但早期反转会使烃源岩埋藏变浅,难以达到生烃门限而导致生烃能力很小,晚期反转构造油气成藏条件良好,特别是坳陷西部较大反转构造是有利勘探区带。

This paper analyzes the formation period of the Zhu-3 Depression in Pearl River Mouth Basin, classifies the inversion tectonic styles and investigates their influence on hydrocarbon accumulation condi- tions based on the seismic reflection characteristics, distribution characteristics and formation mechanism of inversed tectonics. It is proposed that two inverted tectonic phases have developed in this area. One is the faulted-inversion which develops at the end of Paleogene,and it is the superimposed tectonic which devel- oped over faulted period to fault-depression transform period; the other is the depression-inversion which occurred during the late period of Neogene, and it is the superimposed tectonic which developed over de- pression period. According to the relationship between inversion tectonics and pre-existing faults and tec- tonics, the inversion tectonic styles of the Zhu-3 Depression of Pearl River Mouth Basin can be divided into two styles,identified as fault-limited which can also be subdivided into five fault-limited styles; and three fold-bending styles. Inversion tectonics could be served as excellent seals for oil and gas accumulation. However, since the hydrocarbon source rocks are shallowly buried during the early inversion stage,it is dif ficult to meet the threshold of hydrocarbon generation and adverse to the generation of oil.