Mechanism of permeability damage caused by CO2 flooding development for old oil fields
TIAN Wei1,2
1. Research Institute of Petroleum Exploration & Development, SINOPEC Zhongyuan Oilfield Company, Puyang 457001, China; 2. Postdoctoral Research Station of Mechanics, University of Science and Technology Beijing, Beijing 100083, China
Abstract: In order to systematically study reservoir damage caused by CO2 transfer in old oil fields, the effects of CO2 on physical properties and fluids of the reservoir are studied by using natural cores and formation fluids of target reservoirs in laboratory experiments.The results show that main minerals in the target reservoir include iron dolomite, plagioclase and calcite, and clays in the target reservoir mainly include illite, chlorite and ironite/smectite.The dissolution of calcite is mainly characterized by the formation, fracture, fragmentation and disappearance of the dissolution cone, and there is no new substance formed except the reverse reaction.The dissolution reaction of feldspar mainly results in the formation of two types of secondary minerals on its surface, but the amount of dissolution is greater than that of new secondary minerals.In the early stage of interaction between CO2 and rocks, NaCl crystals and secondary minerals form on the surface;In the later stage, NaCl crystals disappear and a large amount of secondary minerals form.Compositional differentiation of crude oil occurs after contacting with CO2, which reduces the fluid flow capacity in deep reservoir.CO2 injection has eventually increased the permeability of the reservoir by more than 60% and increased the reservoir space by 9.24%.The research results explain reasonably the difference mechanism of CO2 gas injection capacity between oil and water wells, clarify the main controlling factors for CO2 gas injection capacity in old oil fields, and provide important technical support for CO2-EOR in old oil fields, as well as an important reference for the implementation of China's carbon emission reduction projects.
田巍. 老油田CO2驱开发渗透性伤害机理研究[J]. 现代化工, 2021, 41(S1): 194-198.
TIAN Wei. Mechanism of permeability damage caused by CO2 flooding development for old oil fields. Modern Chemical Industry, 2021, 41(S1): 194-198.