济阳坳陷古近系页岩文石含量与烃源岩热演化的对应关系

发布时间：2018-06-29 11:15

本文选题：济阳坳陷 + 古近系　；参考：《石油学报》2017年08期

【摘要】：文石在济阳坳陷古近系湖相页岩中较为常见,多发育于富碳酸盐矿物的页岩中,属于化学成因。统计发现,济阳坳陷古近系湖相页岩文石含量的变化包络线与埋藏深度具有明显对应关系。在埋深2 300 m以上的地层中,文石含量变化不大;当埋深超过2 300 m时,文石含量包络线随埋藏深度的加大而快速降低;埋深达到约3 000 m,文石含量包络线降低的速率达到最大;当埋深超过约3 500 m时,页岩中的文石大部分消失。文石含量包络线的这种变化趋势与烃源岩热演化阶段基本一致,表明页岩地层中文石的含量变化明显受有机质热演化的控制。为进一步验证该解释,将研究区富文石和富方解石的页岩样品分别与有机酸(乙酸)和油层水在高温高压下进行多组溶解实验,测试实验前后碳酸盐矿物的溶解程度,结合不同埋藏深度烃源岩热演化的流体特征分析文石含量的变化趋势。分析认为:文石含量与有机质成熟演化过程中排出的有机酸浓度成反相关,有机酸生成的越多,文石的溶解越严重。当埋深大于3 500 m时,烃源岩进入高成熟—过成熟阶段,有机酸的生成逐渐停止,文石含量的减少也趋于停滞,并在页岩孔隙水中开始重新结晶出较稳定的方解石。
[Abstract]:Wenshi is common in Paleogene lacustrine shale in Jiyang depression, and is mainly developed in carbonate rich shale, belonging to chemical origin. It is found that the variation envelope of Paleogene lacustrine shale dolomite content in Jiyang depression has obvious correlation with burial depth. In the strata with buried depth above 2 300 m, the content of aragonite changes little, and when the depth of burial is more than 2 300 m, the envelope of the content of aragonite decreases rapidly with the increase of burial depth. When the buried depth is about 3 000 m, the rate of decrease of the envelope of the content of aragonite reaches the maximum, and when the buried depth is more than 3 500 m, most of the aragonite in the shale disappears. The variation trend of the content envelope of aragonite is basically consistent with the thermal evolution stage of source rock, which indicates that the variation of Chinese stone content in shale strata is obviously controlled by the thermal evolution of organic matter. To further verify the interpretation, the dissolution experiments of the shale samples of Fuwenite and calcite were carried out at high temperature and high pressure with organic acid (acetic acid) and reservoir water, respectively. The dissolution degree of carbonate minerals was measured before and after the experiment. Combined with the fluid characteristics of thermal evolution of source rocks with different burial depths, the variation trend of aragonite content is analyzed. It is concluded that the content of aragonite is inversely related to the concentration of organic acid excreted during the process of organic matter maturation and evolution. The more organic acids are formed, the more serious the dissolution of aragonite is. When the buried depth is more than 3 500 m, the source rock enters into the high maturation-over mature stage, the formation of organic acid gradually stops, the decrease of the content of aragonite tends to stagnate, and the stable calcite begins to recrystallize in the shale pore water.
【作者单位】：中国石油大学地球科学与技术学院;
【基金】：国家自然科学基金项目(No.41572123) 山东省自然科学基金项目(ZR2014DM013)资助
【分类号】：P578.6;P618.13

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