Feasibility Analysis of Acid Fracturing in Offshore Low Permeability Sandstone Reservoirs and Study on Acid Fluid System
Conventional matrix acidification operations cannot achieve overall transformation of low permeability offshore sandstone reservoirs,and due to the low permeability of some reservoirs,acid cannot enter the formation smoothly.Therefore,taking the Weizhou X low-permeability sandstone reservoir as the research object,a feasibility analysis study on acid fracturing suitable for offshore low-permeability sandstone reservoirs was carried out,and the corresponding acid system was selected to evaluate the comprehensive performance of the acid system.The results indicate that the target oilfield reservoir contains a certain amount of carbonate minerals,and the reservoir has good brittleness.The horizontal principal stress difference coefficient of the reservoir section is between 0.114 and 0.130,which provides the material basis for acid fracturing construction.Fracturing construction can cause the formation of complex fracture networks in the reservoir.A set of acid system suitable for acid fracturing construction of low permeability offshore sandstone reservoirs was constructed using organic acid HCW-1,organic acid salt HCF,and high-temperature corrosion inhibitor HSJL-3 as the main treatment agents.The acid system has low surface tension and corrosion rate,as well as strong iron ion stability and anti-expansion ability.In addition,the natural core of the reservoir section has significantly improved the fracture conductivity after being corroded by acid fracturing working fluid,and the surface of the core is intact without any phenomenon of particle detachment.The research results suggest that the target offshore low-permeability sandstone reservoir has the conditions for acid fracturing construction,and acid fracturing construction can be adopted to increase production and transform it.
Offshore oil fieldsLow permeability sandstone reservoirAcid pressureFeasibility analysisAcid solution system
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