Source rock characteristics and hydrocarbon expulsion potential of the Middle Eocene Wenchang formation in the Huizhou depression, Pearl River Mouth basin, south China sea
Source rock characteristics and hydrocarbon expulsion potential of the Middle Eocene Wenchang formation in the Huizhou depression, Pearl River Mouth basin, south China sea
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DOI：
10.1016/j.marpetgeo.2015.06.010
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发表时间：
2015-11
影响因子：
4.2
通讯作者：
Hang Jiang;X. Pang;Hesheng Shi;Qiuhua Yu;Z. Cao;R. Yu;Di Chen;Z. Long;F. Jiang
中科院分区：
文献类型：
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作者：
Hang Jiang;X. Pang;Hesheng Shi;Qiuhua Yu;Z. Cao;R. Yu;Di Chen;Z. Long;F. Jiang
珠江口盆地惠州凹陷中始新世文昌组是南中国海油气勘探的重要地质单元。研究了WC源岩的地质和地球化学特征，包括分布、沉积环境、有机质类型、生烃潜力和热成熟度。通过一维盆地模拟和改进的生烃潜力方法，评价了生烃历史、排烃强度和排烃数量。WC源岩分布广泛，厚度较高(多大于200微米，最大厚度大于1000微米)，沉积环境为湖相弱氧化-弱还原沉积环境，盐度较低。烃源岩有机质丰度低至高(有机碳丰度主要在0.27~3.59%之间，平均1.39%~1.39%)，以II1型和II2型干酪根为主，具有较大的中高热演化生烃潜力(凹陷边缘有机质丰度一般在0.65%~1.2%，凹陷中心有机质丰度一般在1.2%以上)。烃源岩在中新世早期成熟(Ro=0.50%)，开始生烃。在Ro为0.8%时达到排烃门限，在Ro为1.1%时排烃速率最大。H26凹陷、H21凹陷、X24凹陷和X23凹陷的排烃强度较大，最大排烃强度分别为104×106、71×106、62×106和53×106 t/km2。综合排烃效率约为75%。惠州凹陷WC烃源岩排烃总量约690.1×108t。
The Middle Eocene Wenchang (WC) formation in the Huizhou depression of the Pearl River Mouth basin is an important geological element for petroleum exploration in the South China Sea. In this study, the geological and geochemical characteristics of the WC source rocks, including the distribution, sedimentary environment, organic matter type, hydrocarbon generation potential and thermal maturity were investigated. Hydrocarbon generation history and hydrocarbon expulsion intensity and quantities were evaluated through one dimensional basin modelling and an improved hydrocarbon generation potential methodology. The WC source rocks are widely distributed and have an elevated thickness (mostly thicker than 200 m, with a maximum thickness greater than 1000 m); they were deposited in a lacustrine weak oxidation–weak reduction sedimentary environment with low salinity. The source rocks have low to high organic matter abundance (TOC mainly ranges from 0.27 to 3.59 wt% with an average of 1.39 wt%) dominated by II1–type and II2–type kerogen, resulting in significant hydrocarbon generating potential under moderate–high thermal evolution (Romainly ranges from 0.65% to 1.2% on the margins of sags and greater than 1.2% in the centre of sags). The source rocks became mature (Ro= 0.5%) in the early Miocene and began to generate hydrocarbons. They reached the hydrocarbon expulsion threshold at 0.8% Roand the hydrocarbon expulsion rate became greatest at 1.1% Ro. The expulsion intensities in the H26 sag, H21 sag, X24 sag and X23 sag are relatively large, with their greatest expulsion intensities being 104 × 106, 71 × 106, 62 × 106and 53 × 106t/km2, respectively. The comprehensive hydrocarbon expulsion efficiency was approximately 75%. About 690.1 × 108t of hydrocarbons were expulsed from the WC source rocks in the Huizhou depression.