Hydrocarbon Accumulation Models in the Shallow Formations of ZhuI Depression, Pearl River Mouth Basin
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    Abstract:

    The ZhuI depression is an important region in the Pearl River Mouth Basin whose exploration prospect is good. Recently, the important areas for oil—gas exploration in the ZhuI depression focus on the Neogene Hanjiang Formation and Yuehai Formation while the shallow formations are in a weak zone, which severely limits the exploration progress in shallow formations. Based on researches of formers, this paper integrates the seismic, well logging and oilfield production data to study the factors and models of hydrocarbon accumulation in the shallow formations of ZhuI depression which can provide guide and suggestion on oil and gas prospecting of similar reservoirs. The result shows that, firstly, shallow reservoirs in the ZhuI depression mainly circle around the hydrocarbon generation center while favorable area of hydrocarbon accumulation is less than 15~20 km. At the same time, fullness is higher when reservoir is closer to hydrocarbon generation center especially in PY4 subsag and Huizhou sag. Secondly, matching relationship between fault occurrence and oil migration orientation controls oil and gas migrating to the shallow formations which can be regarded as an index to divide oil source faults into three types. “Forwardsource” fault is characterized by facing oil source, “forwardsource” fault is backing it, while “forwardsource” fault is distinguished from them by that the trend of fault is parallel or intersected with direction of hydrocarbon expulsion at small angles. Thirdly, structure ridges control fardistance lateral migration so the traps far from hydrocarbon generation center can accumulate hydrocarbons too. Taking internal structure of fault zone and “source—transportation” configuration into consideration, the hydrocarbon accumulation models of the ZhuI depression can be divided into four types including “forwardsource” type, “backsource” type, “followsource” type and “farsource” type. And the distinctions between different positions are clear. Oil and gas transports along hanging wall in “forwardsource” type, which mainly exists in the Huizhou sag and the anticline reservoir or fault reservoir can be found in hanging wall. The induced fracture zone in the footwall of fault is main migration pathway in “backsource” type. This type mainly exists in the Enping sag and then divide into anticline reservoir and fault reservoir, too. “Followsource” type exists in the PY4 subsag, Enping sag and the Huizhou sag. The induced fracture zone both in hanging wall and footwall of fault is effective migration pathway. However, the transporting ability of hanging wall is better than footwall. At the same time, the distance between reservoir and hydrocarbon generation center is relatively far at “farsource type” in which structure ridges play a key role in lateral migration of oil and gas. The differences between sags and between regions in the same sag are apparent. “Followsource” type is the uppermost model in the study area.

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HAO Xin, WU Zhiping, YAN Shiyong, XIE Fei, HU Yang, Liu Lihua, HE Min.2017. Hydrocarbon Accumulation Models in the Shallow Formations of ZhuI Depression, Pearl River Mouth Basin[J]. Geological Review,63(1):113-121.

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History
  • Received:June 01,2016
  • Revised:August 11,2016
  • Adopted:
  • Online: January 20,2017
  • Published: