砂岩储集层粒间孔隙保存机制

关于深埋藏、高温度条件下的砂岩储层孔隙保存研究在保存机理、适用条件、实验模拟等方面都存在着不少的争议。为了更好地剖析砂岩储层粒间孔隙保存的机理,在系统总结国内外学者近年来在砂岩粒间孔隙保存方面研究成果的基础上,阐述了颗粒包膜发育、孔隙流体超压、与外来盐体有关的热流扰动以及烃类充注等4种因素对储层质量的影响,并指出了孔隙保存机制未来的研究趋势与方向。研究结果表明:(1)颗粒包膜发育能够通过抑制石英增生而保存粒间孔隙,其中绿泥石膜主要集中发育在三角洲和河流相沉积环境中,砂岩粒度较粗且绿泥石膜粒表覆盖率较高的储集层易形成优质储层,其抑制石英胶结的效果优于伊利石膜,微晶石英膜则通过无定形硅与玉髓共生的纳米薄层以及微晶石英的集合来共同抑制石英增生;(2)孔隙流体超压主要通过抑制压实和压溶作用而成为浅层砂岩中一种主要的孔隙保存机制;(3)外来盐体的存在可以实现对地温的抑制,以减少砂岩储层的石英增生量,并且盐体较厚、侵位时间较早的砂岩更易保存较多的粒间孔隙;(4)油气充注对孔隙保存的影响程度尚难以定量评价。结论认为:目前对于影响深层砂岩粒间孔隙保存因素的分析预测仍停留在微观观测和实验模拟阶段,区域上的预测识别技术亟待进一步探索;基于孔隙保存机制认识下的砂岩储层孔隙度演化模拟是未来研究攻关的难点和重点。

Preservation mechanisms of intergranular pores in sandstone reservoirs

Studies on the preservation of pores in sandstone reservoirs under the conditions of great burial depth and high temperature are still in dispute in terms of preservation mechanisms, application conditions and experimental simulation. In order to better analyze the preservation mechanisms of intergranular pores in sandstone reservoirs, we reviewed domestic and foreign research achievements on the preservation of sandstone intergranular pores in recent years in this paper. Then, the effects on reservoir quality by grain coating development, pore fluid overpressure, heat flow disturbance related to foreign salt and hydrocarbon charging were described. Finally, the future research trend and direction on pore preservation mechanisms were pointed out. And the following research results were obtained. First, grain coating development can preserve intergranular pores by inhibiting quartz overgrowth. Chlorite coating is mainly developed in the sedimentary environments of delta and fluvial facies. Reservoirs with coarser sandstones and higher grain surface coverage ratio of chlorite coating tend to be high-quality reservoirs, and its inhibition on quartz cementation is superior to illite coating. Micritic quartz coating exerts an inhibition effect on quartz overgrowth by combining the nano-scale thin layer of syngenetic amorphous silicon and chalcedony with the aggregate of micritic quartz. Second, pore fluid overpressure is a kind of important pore preservation mechanism for shallow sandstones through inhibiting compaction and pressolution. Third, the existence of foreign salt can inhibit the geotemperature, so as to reduce the amount of quartz overgrowth in sandstone reservoirs. And in the sandstones with thicker salt and early emplacement, more intergranular pores can be preserved easily. Fourth, the influence degree of hydrocarbon charging on pore preservation can be hardly evaluated quantitatively. In conclusion, the analysis and prediction on the factors influencing the preservation of intergranular pores in deep sandstone reservoirs are still in the stage of microscopic observation and experimental simulation, and the regional prediction and identification technologies shall be explored further. What's more, the simulation on the evolution of sandstone reservoir porosity based on the cognitions of pore preservation mechanisms is the research difficulty and emphasis in the future.