东营凹陷陡坡带深层砂砾岩体次生孔隙成因机制探讨

从岩心、薄片、扫描电镜以及FMI成像测井等资料分析发现,东营凹陷陡坡带深层砂砾岩体储层次生孔隙发育,在埋深大于3 500 m古近系砂砾岩储层中,普遍存在2～4个次生孔隙发育带,次生孔隙度主要分布在2%～10%,次生渗透率主要分布在0.1×10~(-3)～8×10~(-3)μm~2,为低孔低渗储层。研究认为长石、岩屑、碳酸盐和硫酸盐等酸溶组分的溶蚀以及构造运动是深层次生孔隙形成的主导因素。其主要形成机理有:1)有机质热演化过程中产生的酸性流体的溶解作用;2)去石膏化和去白云化以及硫酸盐热化学作用;3)异常高压环境中的幕式排烃、膏岩层导致的生油窗扩展作用以及盐度差导致的H~+浓度的升高;4)构造作用、脱水收缩作用等。

The mechanim of secondary pores in the deep-seated reservoir of glutenite body of steep slope belt in Dongying sag

From the analysis of the cores，thin section，SEM as well as FMI imaging logging data，there are 2～4 zones of secondary pores in the glutenite body which buried deeper than 3 500 m in the steep slope belt of Dongying sag. They are the reservoirs which have low porosity and low permeability and secondary porosity mainly distributed in the 2％ to 10％ as well as secondary permeability mainly distributed in the 01×10-3～8×10-3μm2. We think that the leading factors of the secondary porosity of deep reservoirs are tectonic movement and acidic components dissolution，such as feldspar，debris，carbonate and sulfate after our research. The main formation mechanism are： 1)The dissolution of acidic fluid which produced in the process of the thermal evolution of organic matter； 2)Degypsification，dedolomitization and thermochemical sulfate reduction； 3)Screen expulsion because of abnormally high pressure in the environment，gypsum rock bring about the expansion of oil generation window，as well as the H+ concentration increase caused by salinity difference； 4)Tectonism and synaresis etc.