二氧化碳注入对低渗透储层矿物及孔隙结构的影响*

Effect of Carbon Dioxide Injection on Mineral and Pore Structure of Low Permeability Reservoirs

赵 林 蒋尔梁 王树森 罗全民 李宾飞 朱 迪 柏 浩

ZHAO Lin JIANG Erliang WANG Shusen LUO Quanmin LI Binfei ZHU Di BAI Hao

注二氧化碳采油过程中，二氧化碳溶解于水形成碳酸，与储层矿物反应会改变岩心矿物组成和储层物性。 本文通过室内实验研究了二氧化碳驱、二氧化碳/水交替驱及二氧化碳吞吐3种不同注入方式下低渗透储层的矿 物、产出流体、储层微观结构以及渗透率的变化。研究结果表明：二氧化碳驱、二氧化碳水气交替驱、二氧化碳吞 吐3种注入方式均可使岩心渗透率增加，二氧化碳/水交替驱过程对岩心渗透率的影响最为明显；产出液中的钙 离子和钠离子浓度都明显上升，岩心矿物中方解石及长石含量下降，碳酸的溶蚀作用导致岩心中的斜长石和方 解石减少；在碳酸作用下岩心微观结构由致密、连通性差、粒间孔隙发育差状态变为疏松、连通性好、粒间孔隙发 育充分状态，溶蚀现象明显。

In the process of oil recovery with carbon dioxide injection，carbonic acid is formed when carbon dioxide dissolves in water，which reacts with reservoir minerals，and the mineral composition of rock and physical properties of reservoir are changed. In this paper，the changes of minerals，producing fluids，microstructure and permeability of low permeability reservoir under three different injection methods of CO2 flooding，alternate CO2/waterflooding and CO2 huff-and-puff were studied by laboratory experiments. The results showed that the core permeability could be increased by these three CO2 injection methods to some degree. Among them，alternate CO2/water flooding had the most obvious effect on the core permeability，the concentration of calcium and sodium ions of the producing fluids increased obviously and the dissolution of carbonic acid resulted in the reduction of plagioclase and calcite in the core so that the content of calcite and feldspar in the core mineral decreased. The original microstructure of rocks was dense，and the core possessed poor connectivity and poor development of intergranular pores. After the effect of carbonic acid， the microstructure of rocks was loose，and the core possessed good connectivity，well-developed intergranular pores and obvious dissolution.

10.19346/j.cnki.1000-4092.2021.04.015