稠油油藏自扩散降黏体系作用机理

Mechanism of the self-diffusion viscosity reducing system in heavy oil reservoir

针对稠油黏度大、常规降黏剂在多孔介质中与稠油作用不充分,导致稠油油藏采出程度低等问题,自主研发了高效复合自扩散降黏体系BXD,研究了该体系在不同温度、含水率等因素下对脱水稠油和W/O乳状液黏度的影响。通过沥青质红外光谱、相对分子质量、偶极矩测试以及微观形态观察等方法,研究降黏体系对稠油的主要作用机制。通过填砂管驱替实验,分析降黏体系的驱油效果及油藏适应性。研究表明,降黏体系BXD可以破坏W/O乳状液形态,含水率较低时阻止W/O乳状液的形成,随含水率增大形成O/W乳状液;BXD与油接触时可以迅速自发扩散,渗透进稠油中,削弱沥青质分子之间的氢键缔合,降低沥青质表观相对分子质量和偶极矩,部分拆散沥青质分子重叠堆砌的块状结构。BXD降黏冷采现场试验,油井增油效果明显,有望大幅度提高稠油油藏采收率。

Aiming at the lower recovery rate of the heavy oil reservoir resulted from the higher viscosity and incomplete interaction between conventional viscosity reducer and heavy oil in the porous media,an efficient and composite self-diffusion viscosity reducing system BXD was independently researched and developed,and the effect of the system on the viscosities of the dehydrated heavy oil and W/O emulsion were studied under different temperatures and watercut conditions.By means of asphaltene infrared spectrum,molecular weight,dipole moment test and microscopic morphology observation,the main mechanism of the viscosity reducing system on heavy oil was researched.Through the displacement experiment with sand-packing tube,the oil displaced effect and reservoir adaptability of the viscosity reducing system were analyzed.The results show that the viscosity reducing system BXD can destroy W/O emulsion shape,prevent the formation of the W/O emulsion when watercut is pretty lower,and form O/W emulsion with the rise of the watercut;when BXD is in contact with the oil,it can rapidly and instantaneously diffuse,seep into the heavy oil,weaken the hydrogen bond association between asphaltene molecules,reduce the apparent relative molecular mass and dipole moment of the asphaltene,and partially break up the block structure of overlapping asphaltene molecules.The field test of BXD viscosity reduction and cold production shows that the oil well has obvious oil incremental effect,which is expected to greatly improve the recovery of heavy oil reservoir.