Study On Damage Mechanism And Preventive Measures Of Water Injection In Low Permeability Sandstone Reservoir

With continuous increasing of the degree of oil and gas exploration and ever-growing demand for oil and gas resources, low permeable oil-gas resources have become the main target of exploration and development in China and around the world. Due to their advantages such as stable oil distribution, good oil quality, huge reserve scale and suitable for water-flooding, low permeability reservoirs are now standing as an important resource for the stable development of China’s petroleum industry. Meanwhile, the disadvantages such as poor res-ervoir properties, complex pore structure, low natural productivity and deep burial depth make low permeability reservoirs difficult and highly-costy for development. Thus, it has great significance to adopt targeted formation-protection measures in water injection process for field waterflooding and stable production.This paper analyzed and evaluated the potential formation damage of Ji Yuan oilfield through core porosity and permeability tests, mercury experiment, X-ray diffraction analysis, scanning electron microscopy analysis, ion composition analysis of injected water and for-mation water. Based on the results of formation damage experiment, Ji Yuan oilfield belongs to ultra-low permeability oil field, with small pore throat, nonuniform distribution of throat, poor pore connectivity. Speed sensitivity is medium weak, water sensitivity is from weak to intensively moderate and stress sensitivity is weak-to-moderate. Meanwhile, scaling and in-jected water can both cause some sort of damage to core permeability. According to formation damage evaluation results of Ji Yuan oilfield, this paper summa-rized classic models of formation damage at home and abroad, applied chip algebraic model to discuss the main damage mechanism of particle migration under different injection speed, core permeability, levels of suspended particles and size, and then compare the results to ex-perimental data for verification and analysis.Integrating optimization experimental results and a series of experimental data of clay anti-swelling agent, surfactant, scaling inhibitor, scale remover and combining them with wa-ter quality evaluation results, this paper drew up a specific measure plan that preventing the decline of water injectivity of Ji Yuan oilfield. It provided reliable theoretical evidence for Ji Yuan oilfield to ensure their normal production.