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首页> 外文期刊>Marine and Petroleum Geology >Variation of system openness and geochemical features in overpressured sandstones of the Yinggehai Basin, offshore South China Sea
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Variation of system openness and geochemical features in overpressured sandstones of the Yinggehai Basin, offshore South China Sea

机译：沿海南海沿海南海盆地过度砂岩系统开放性和地球化学特征的变异

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摘要

Hydrocarbon discoveries in recent years in the Upper Miocene of the Yinggehai Basin show differences in overpressure magnitude, gas and mineral components. Overpressure close to or reaching the leakage threshold has induced high system openness for one field, but the overpressure of another field remains to be safely closed. A new vision to investigate the interplay between the system openness and the gas chemical and mineralogical features were conducted. The gas components in the high openness system are rich in high maturity hydrocarbons and inorganic CO2, which both have heavier carbon isotopes. Low maturity gases with lighter carbon isotopes are dominant in the low openness system. The abnormal carbon isotope ratio between iso-butane and n-butane in the high openness system confirms that early low maturity leakage has generated abnormal compositional and isotopic fractionation. Although the sedimentation process was uniform in the two systems, the high openness system has rare K-feldspar grains and chlorite, but it is rich in illite/smectite mixed layers (I/S). Precipitation is characterized by ankerite and kaolinite in the high openness system, whereas the low openness system primarily consists of calcite. The strong dissolution of K-feldspar grains and chlorite should have released abundant potassium and silicon. The high abundances of I/S and kaolinite, which are both sensitive to potassium and the rarity of quartz overgrowths in the high openness system, imply that the leakage of potassium/silicon from the sandstones has induced a mass imbalance between dissolution and precipitation. Even the sandstone porosity was slightly increased by the mass imbalance in the high openness system. The risk of hydrocarbon expulsion during brine leakage cannot be ignored.
机译：近年来迎宾盆地上部内海茂的碳氢化合物发现显示过压幅度，气体和矿物成分的差异。靠近或达到泄漏阈值的过压已经为一个领域引起了高系统开放性，但另一个领域的超压仍然安全关闭。进行了调查系统开放性与矿物学和矿物学特征之间的相互作用的新愿景。高开放式系统中的气体组分富含高固烃和无机二氧化碳，两者都具有较重的碳同位素。具有较轻碳同位素的低成熟度气体在低开放式系统中占主导地位。高开放式系统中异丁烷和正丁烷之间的异常碳同位素比证实，早期的低成熟度泄漏产生异常的成分和同位素分级。虽然沉降过程在两个系统中是均匀的，但高开放式系统具有罕见的K-Feldspar晶粒和亚氯酸盐，但它含有富含硫酸盐/蒙脱石混合层（I / S）。沉淀的特征在于高开放式系统中的Ankerite和高岭石，而低开阔系统主要由方解石组成。 K-Feldspar颗粒和氯酸盐的强烈溶解应释放丰富的钾和硅。 I / S和高岭石的高度丰富，它们对高开放系统中的石英过度生长的耐钾和石英过度生长的罕见性暗示意味着砂岩中钾/硅的渗漏诱导溶解和沉淀之间的质量不平衡。即使是高开放式系统中的质量不平衡均匀增加砂岩孔隙率。在盐水泄漏过程中碳氢化合物驱逐的风险不能忽视。

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