异常高压与页岩气保存

页岩气的高产层往往都具有较高的压力系数。为探讨页岩异常高压与页岩气保存的关系，通过研究常规与非常规储层异常高压的形成机制与破坏机制，并以四川盆地 JY-1井五峰－龙马溪组为例，从沉积、成岩、埋深、抬升不同阶段解析异常高压的形成与破坏；并与美国Barnett 页岩及中国相关井对比分析其 TOC 质量分数＞2％的有效厚度、成熟度、脆性矿物等，结果表明：（1）沉积大量有机质是页岩气形成异常高压的前提，这些有机质随埋深增加生烃排气体积增大，而页岩又具有自封闭性，这使得页岩异常高压的形成具有必然性；（2）页岩气的自封闭性使得常规破坏异常高压的机制并不会对其形成致命影响，但也有一些宏观因素会导致其逐渐破坏，如强烈隆升、断层过度发育、顶底板差等；（3）埋藏与抬升过程中，流体压力变化导致的沿应力面的破裂会使流体逸散并加大宏观破坏因素的影响。高产页岩气层是由大构造背景与沉积环境共同控制，而相控起到决定性的作用。

Abnormal overpressure and shale gas preservation

High production shale gas reservoir is characterized by overpressure coefficient.The abnormal high pressure formation mechanism and failure mechanism of conventional and unconventional reservoirs are studied so as to explore the relationship between shale overpressure and shale gas preservation.Focus is put on the research of different phases of sediment,buried depth and uplift,as well as on the analysis of formation and destruction of abnormal overpressure in the Wufeng-Longmaxi Formation of Well JY-1 in Sichuan Basin.Comparison is also made with the Barnett shale and domestic related drilling wells in order to analyze its fraction of TOC>2% of effective thickness, maturity,brittle minerals,etc.It is recognized that large number of deposition of organism is the premise of formation of abnormal overpressure. These organism materials exhaust volume of hydrocarbon as the buried depth increases and the self-sealing behavior of shale help bring about the formation of abnormal overpressure.Normal destructive mechanisms have little influence on the overpressure of shale because of the self-sealing behavior of shale,but some macroscopic destructive mechanisms,such as strong uplift,overgrown faults,bad bottom and top beds can influence it inch by inch.Micro-fractures along stressed surface caused by change of fluid pressure make the fluid diffusion and improve the influence of macroscopic destructive mechanisms.Tectonic setting and sedimentary environment control the capacity of shale gas and sedimentary facies play a more decisive role.