致密砂岩束缚水饱和度和微观孔喉结构关系实验研究

Experimental study on the relationship between irreducible water saturation and micro pore throat in tight sandtone

致密砂岩气藏在开发过程中普遍存在产水现象,容易造成井筒积液、产量快速递减甚至停产等问题,认识致密砂岩地层水赋存规律,从而评价产水规律及其对产能的影响,是致密气规模化开发必须解决的关键问题。以中国海油鄂尔多斯盆地矿区盒八段致密储层为研究对象,选取典型岩心8块,每一块岩心均依次开展了孔渗分析、核磁共振实验、高压驱替实验和恒速压汞实验,从而揭示致密砂岩束缚水饱和度及与之一一对应的微观孔喉量化关系。实验结果表明,临兴矿区盒八段致密储层束缚水饱和度整体在40%~70%,且赋存在小于0.1μm的孔隙内以及较大孔隙的亲水表面上;束缚水饱和度随着喉道半径平均值、渗透率的增加而降低,具有较好的线性关系。本文所提出的方法为定量评价致密砂岩气藏的产水能力提供了基础依据和指导。

Water production is common during the development of tight sand gas reservoir,which will cause liquid loading in wellbore and quick production decline,even leading to shut down of gas well production.How to reveal the occurrence regularity of formation water in tight sandstone and to evaluate its producing regularity and effect on gas well productivity is a key problem that has to be solved for large scale development of tight sand gas.In this paper,taking He8 Member tight sandstone in CNOOC gas filed in the Ordos Basin as research objects,8 typical sandstone samples are selected for carrying out the experiments of porosity and permeability measurement,unclear magnetic resonance,high pressure displacement and constant-rate mercury injection individually,with which the quantitative relationship between tight sandstone irreducible water saturation and its micro pore throat is established.Experiment results show that the irreducible water of He8 Member in Linxing gas filed distributes in the pores with the radius less than 0.1μm and on the surface of large pores.The irreducible water saturation is 40%-70%and it decreases with the increase of average throat radius and permeability,showing a good linear relationship.The proposed method in this paper can provide fundament and guidance to quantitatively evaluate water production in tight sand gas reservoir.