四川盆地西部致密低渗砂岩气藏储层致密化进程及储层形成机理研究

In the worldwide, tight gas, shale gas and coal-bed methane are the three types of development valuable unconventional gas. In our country, the research of shale gas are at the beginning, progress has been made in tight gas and coal-bed methane, however, only tight sandstone gas has gained large development effectiveness under current economic and technological conditions. And now, problems still exist in the research of densification process, tight reasons and forming mechanism of tight low-permeability sandstone gas reservoir. In this research, Xujiahe tight gas sandstone reservoir in Sichuan basin is set as an example to make deep research about tight gas reservoir. Firstly,integrating the previous research about Paleoenvironment, ancient facies during deposition will be interpreted reasonablly, internal structure of the sandbodies will be deep anatomized by using the outcrop observation and core analysis. Secondly the data of rock thin sections, stained thin sections, scanning electron microscope, electron probe will be used to research reservoir pore characteristics , analysis the mineral micro-combination characteristics, Divide diagenesis into different stages, ascertain the forming order and the duration of main minerals. Finally, this research will find the generation and configuration relationship between primary pore and secondary pore, build a quantitative evaluation system to estimate the densification process of reservoir and describe the process of densification, clear the reservoir densification time and densification degree, and ultimately discuss the forming mechanism of tight low- permeability sandstone gas reservoir.

世界范围内非常规天然气藏中致密气藏、页岩气藏、煤层气藏具有开发价值。在我国，页岩气藏的研究方兴未艾，致密气藏及煤层气的研究已经取得了进展，而取得较大开发成效的仅有致密砂岩气藏，但这类气藏的储层致密进程、原因及储层形成机理仍有待深入研究。拟以四川盆地须家河组气藏为研究目标，结合前人古环境研究成果，从地面露头的详细刻画描述、岩心观察及描述入手，首先对须家河组储层形成的古岩相进行合理的解释，对储集砂岩的内部组构进行剖析研究，在此基础上，利用岩石薄片、铸体薄片、扫描电镜、电子探针等资料，对储层的孔隙特征及成岩矿物的微观组合特征进行分析，划分不同成岩阶段，研究各成岩阶段的特征矿物、特征矿物形成的先后次序及持续时间。研究原生孔隙与次生孔隙的生成及配置关系。建立储层致密化过程的定量评价体系，描述储层的形成过程，明确储层致密化阶段及致密化程度，最终探讨致密岩性气藏储层的形成机理。

致密砂岩气是我国目前已经投入经济开发的主要气藏类型之一，也是我国重要的能源来源之一，但这类气藏由于储层比较致密而难以开采。为寻找致密砂岩气藏，并有效开采这类气藏，对这类气藏储层的致密原因、形成机理、分布规律的研究显得分外重要。本次研究主要利用地震资料、野外露头资料、岩石薄片、扫描电镜、电子探针、流体包裹体等资料，对四川盆地西部地区的构造及其演化对储层的影响、砂体沉积特征及内部结构、成岩作用类型、各成岩阶段的形成的特征矿物、特征矿物形成的先后次序及持续时间,孔隙流体的变化规律等进行分析研究，首先定量统计不同胶结物的含量、胶结物的形成时期以及原生孔隙在压实作用下的定量变化、成岩作用过程中次生孔隙变化等，然后结合不同构造区带气藏埋深及温度变化，建立了储层孔隙演化过程的定量评价体系，描述了储层的形成过程，确定了储层的致密化阶段，从而明确了储层的形成机理。在研究过程中，在构造对储层的影响、成岩序列、绿泥石对优质储层的影响以及储层致密化进程这四个方面取得的成果对于寻找优质的致密砂岩储层，预测其影响因素方面具有比较好的针对性。