A turbidite fan in the Eocene upper Wenchang Formation in the Enping Sag, Pearl River Mouth Basin (PRMB) has been studied using seismic, logging and borehole data. The fan is characterized by parallel progradation o...A turbidite fan in the Eocene upper Wenchang Formation in the Enping Sag, Pearl River Mouth Basin (PRMB) has been studied using seismic, logging and borehole data. The fan is characterized by parallel progradation on the dip seismic profile and is mound-shaped or lenticular-shaped on the strike seismic profile. The study of the core and logging data from well EP17-3-1, which is located in the front side of the turbidite fan, shows that this fan is a set of normal grading sand beds, interbedded within thick dark grey mudstones of semi-deep to deep lake deposits in the Wenchang Formation. The fan is interpreted as a sand/mud-rich turbidite fan that has an area of over 140 km2 and a maximum thickness of over 340 m. Combined with a study of the regional geological background and previous provenance analysis of the Eocene Wenchang Formation, the main potential provenances for the turbidite fan are considered to be the Panyu low-uplift and northern fault terrace zone. The Enping Sag is considered to be a half graben-like basin whose north side is faulted and whose south side is overlapped. Basement subsidence in the Eocene was mainly controlled by boundary faults which dip relatively steeply on the north side, causing the subsidence center of the Enping Sag in this stage to be close to the north boundary faults. Sustained faults developed in the Enping Sag during the Eocene caused an increase of the relative height difference between the north and the south uplift zone in the Enping Sag. Affected by the second episode of the Zhuqiong movement (39-36 Ma) in late Eocene, sediments which had accumulated on the Panyu low-uplift zone were triggered and moved toward the subsidence center of the Enping Sag and formed the turbidite fan. The second episode of the Zhuqiong movement is the most important triggering factor for the formation of the turbidite fan in the Wenchang Formation. Seismic attribute characterization shows that the low frequency energy is enhanced and high frequency energy is weakened when seismic waves propagate through the oil-bearing zone in this fan. Amplitude versus offset (AVO) anomalies are observed in the seismic data and abnormally high pressure is encountered. The turbidite fan in the Wenchang Formation has provided important information for sedimentary evolution in deep layers of the Enping Sag and pointed to a new direction for the hydrocarbon exploration in the study area.展开更多
珠江口盆地西江主洼地区文昌组沉积厚度大,断裂构造发育。基于精细地震解释成果,利用油区构造解析原理,分析西江主洼古近系断裂构造对油气成藏的控制作用。结果表明:西江主洼主要发育正断层和正走滑断层,可分为基底、盖层、晚期3套断裂...珠江口盆地西江主洼地区文昌组沉积厚度大,断裂构造发育。基于精细地震解释成果,利用油区构造解析原理,分析西江主洼古近系断裂构造对油气成藏的控制作用。结果表明:西江主洼主要发育正断层和正走滑断层,可分为基底、盖层、晚期3套断裂系统;古近纪断陷期分为3个阶段,即早始新世(E w 4 E w 3)NW—SE向伸展断陷期、中始新世(E w 2 E w 1)应力场顺时针旋转的转换断陷期、中晚始新世(E n 4 E n 1)SN向伸展断陷期;其中,文昌组二段沉积期的应力场旋转与惠州运动属于同一构造期。断陷期是烃源岩沉积和构造圈闭形成的主要时期,通过EW向切割基底断裂的盖层断裂将深部热源传递至古近系地层,有利于提高盆地古地温梯度,促进烃源岩热演化。南部缓坡带和断裂坡折带为研究区油藏的有利勘探区。展开更多
基金supported by the China National Science and Technology Project (2011ZX05025-006)
文摘A turbidite fan in the Eocene upper Wenchang Formation in the Enping Sag, Pearl River Mouth Basin (PRMB) has been studied using seismic, logging and borehole data. The fan is characterized by parallel progradation on the dip seismic profile and is mound-shaped or lenticular-shaped on the strike seismic profile. The study of the core and logging data from well EP17-3-1, which is located in the front side of the turbidite fan, shows that this fan is a set of normal grading sand beds, interbedded within thick dark grey mudstones of semi-deep to deep lake deposits in the Wenchang Formation. The fan is interpreted as a sand/mud-rich turbidite fan that has an area of over 140 km2 and a maximum thickness of over 340 m. Combined with a study of the regional geological background and previous provenance analysis of the Eocene Wenchang Formation, the main potential provenances for the turbidite fan are considered to be the Panyu low-uplift and northern fault terrace zone. The Enping Sag is considered to be a half graben-like basin whose north side is faulted and whose south side is overlapped. Basement subsidence in the Eocene was mainly controlled by boundary faults which dip relatively steeply on the north side, causing the subsidence center of the Enping Sag in this stage to be close to the north boundary faults. Sustained faults developed in the Enping Sag during the Eocene caused an increase of the relative height difference between the north and the south uplift zone in the Enping Sag. Affected by the second episode of the Zhuqiong movement (39-36 Ma) in late Eocene, sediments which had accumulated on the Panyu low-uplift zone were triggered and moved toward the subsidence center of the Enping Sag and formed the turbidite fan. The second episode of the Zhuqiong movement is the most important triggering factor for the formation of the turbidite fan in the Wenchang Formation. Seismic attribute characterization shows that the low frequency energy is enhanced and high frequency energy is weakened when seismic waves propagate through the oil-bearing zone in this fan. Amplitude versus offset (AVO) anomalies are observed in the seismic data and abnormally high pressure is encountered. The turbidite fan in the Wenchang Formation has provided important information for sedimentary evolution in deep layers of the Enping Sag and pointed to a new direction for the hydrocarbon exploration in the study area.
文摘珠江口盆地西江主洼地区文昌组沉积厚度大,断裂构造发育。基于精细地震解释成果,利用油区构造解析原理,分析西江主洼古近系断裂构造对油气成藏的控制作用。结果表明:西江主洼主要发育正断层和正走滑断层,可分为基底、盖层、晚期3套断裂系统;古近纪断陷期分为3个阶段,即早始新世(E w 4 E w 3)NW—SE向伸展断陷期、中始新世(E w 2 E w 1)应力场顺时针旋转的转换断陷期、中晚始新世(E n 4 E n 1)SN向伸展断陷期;其中,文昌组二段沉积期的应力场旋转与惠州运动属于同一构造期。断陷期是烃源岩沉积和构造圈闭形成的主要时期,通过EW向切割基底断裂的盖层断裂将深部热源传递至古近系地层,有利于提高盆地古地温梯度,促进烃源岩热演化。南部缓坡带和断裂坡折带为研究区油藏的有利勘探区。