| 四川盆地志留系页岩成岩特征及其对孔隙发育与保存的控制 |
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| 引用本文： | 卢龙飞,刘伟新,魏志红,潘安阳,张庆珍,腾格尔.四川盆地志留系页岩成岩特征及其对孔隙发育与保存的控制[J].沉积学报,2022,40(1):73-87. |
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| 作者姓名： | 卢龙飞 刘伟新 魏志红 潘安阳 张庆珍 腾格尔 |
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| 作者单位： | 1.页岩油气富集机理与有效开发国家重点实验室, 江苏 无锡 214126 |
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| 基金项目： | 国家自然科学基金（U19B6003-02,41972164）~~； |
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| 摘 要： | 四川盆地五峰组—龙马溪组富有机质页岩成岩过程较为复杂，成岩作用类型多样，对页岩孔隙尤其是有机孔隙的发育和保存具有重要控制作用。在早—中成岩期，泥质页岩主要遭受机械压实、黄铁矿与碳酸盐胶结、蒙脱石伊利石化等作用的破坏改造，导致大量原生无机孔隙丧失，而硅质页岩主要经历机械压实和生物蛋白石重结晶作用，由于生物蛋白石重结晶作用使机械压实作用受到有效抑制，相当一部分孔隙得以保存。进入生烃门限后，有机质热成熟作用成为成岩主导因素，干酪根成熟开始生成液态烃，并滞留于保存下来的无机孔隙中，继而在高—过演化阶段裂解生气，有机孔隙大量生成。龙一段一亚段硅质页岩因在进入生烃门限后仍保存有较多无机孔隙，原位滞留的烃量多，它们热裂解生成的沥青和在沥青内形成的有机孔隙的量也较多；而二、三亚段泥质页岩则相反，原位滞留的液态烃及其裂解生成的有机孔隙较少。盆内五峰组—龙马溪组页岩热成熟度Ro值大部分在2.0%~3.0%范围，处于“有机孔隙生成窗”内，表明在达到最大埋深时有机孔隙仍处于大量生成阶段。构造抬升阶段由于泄压及压力平衡再调整，深埋藏压实作用和构造应力压实作用对有机孔隙产生一定程度的改造和破坏，而调整过程流体超压条件的保持则对有机孔隙起着非常重要的保护作用。五峰组—龙马溪组页岩经历了早成岩期无机孔隙损失、中成岩期液态烃大量生成与滞留、晚成岩期滞留烃裂解生气有机孔隙大量生成和构造抬升期有机孔隙调整改造的多阶段演化过程，实现了有机孔隙与无机孔隙的继承与转换。从液态烃逐渐裂解至裂解高峰期因所形成热解固体沥青充填作用和生成有机孔隙数量较少尚不足以弥补热解沥青的填充量而导致总孔隙度持续降低，随着热裂解作用的不断进行，有机孔隙开始大量生成从而实现了热解沥青内部规模性扩容，总孔隙度逐渐增大，在Ro为2.0%~3.0%范围有机孔隙进入发育高峰期，但至Ro>3.0%后开始出现降低趋势，特别是至Ro>3.5%后明显大幅降低，构造抬升期流体超压保持较好条件下孔隙结构有所变化但总孔隙度仍较为稳定。
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| 关 键 词： | 成岩作用 有机孔隙 孔隙保存 页岩 四川盆地 |
| 收稿时间： | 2020-07-20 |
Diagenesis of the Silurian Shale,Sichuan Basin: Focus on pore development and preservation |
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| LU LongFei,LIU WeiXin,WEI ZhiHong,PAN AnYang,ZHANG QingZhen,Tenger.Diagenesis of the Silurian Shale,Sichuan Basin: Focus on pore development and preservation[J].Acta Sedimentologica Sinica,2022,40(1):73-87. |
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| Authors: | LU LongFei LIU WeiXin WEI ZhiHong PAN AnYang ZHANG QingZhen Tenger |
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| Institution: | 1.State Key Laboratory of Shale Oil and Gas Accumulation Mechanism and Effective Development, Wuxi, Jiangsu 214126, China2.Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China3.SINOPEC Exploration Company, Chengdu 610041, China4.Oil & Gas Resources Survey, China Geological Survey, Beijing 100083, China |
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| Abstract: | The effect of diagenesis on organic matter enriched shale characteristics of the Wufeng Formation-Longmachi Formation in Sichuan Basin is very complicated and plays an important role in the development and preservation of inorganic and organic matter. In the early and middle diagenesis stage， argillaceous shales were subjected mainly to intense mechanical compaction， pyrite and carbonate cementation， and illitization， which resulted in the loss of many primary inorganic pores. While siliceous shales mainly experienced mechanical compaction and the recrystallization of biological opal， some primary inorganic pores were preserved due to the inhibition of compaction. After entering the hydrocarbon generation window， the thermal evolution of organic matter became the governing factor of diagenesis， in which liquid hydrocarbon was generated and thermally cracked in the high-over mature stage， accompanied by the formation of organic pores. There was much residual porosity in siliceous shale， leading to much stranded hydrocarbon and organic pores， while less stranded hydrocarbon and organic pores are found in argillaceous shale. Thermal maturity in most areas of Sichuan Basin is in the range of 2.0%-3.0%， within the scope of the “organic pore generation window”. As decompression and pressure balance readjustment occurred in the tectonic uplift stage， the organic pores are transformed and destroyed by deep burial compaction and tectonic compaction， and fluid overpressure is favored for the preservation of organic pores. Shales of the Wufeng Formation-Longmachi Formation experienced four important diagenesis stages， i.e.， inorganic pores lost in the early diagenesis stage， hydrocarbon generation and expulsion in the middle diagenesis stage， organic pore generation in the late diagenesis stage， and pore transformation in the tectonic uplift stage. The total porosity was reduced to its minimum value in the early period of liquid hydrocarbon cracking and increased gradually in a major period of thermal cracking， maximizing at a Ro that was about 2.0%-3.0% and reducing after 3.0%. With good fluid overpressure in the tectonic uplift stage， total porosity remained stable as pore structure changed slightly. |
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| Keywords: | diagenesis organic pores preservation of pores shale Sichuan Basin |
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