Quantitative evaluation of perforation damage in large-sized sandstone targets
The high-speed metal jet of perforation penetrates the oil and gas layer while forming a compaction zone near the perforation hole,which causes damage to the porosity and permeability of the oil and gas layer and seriously affects the production capacity of oil and gas wells.Currently,the testing of perforation effect mainly involves experiments on cement targets,steel targets,or small sandstone targets under ground conditions,which is insufficient to evaluate the perforation effect and flow efficiency under in-situ formation conditions.This leads to a lack of understanding of the mechanism and quantitative evaluation methods for the compaction damage in perforation channels.Therefore,a large physical simulation device and experimental technology for simulating the in-situ formation conditions were developed.Based on the steady-state airflow injection technology,an automatic scanning system of cores was used to measure the permeability at arbitrary points and the longitudinal and transverse wave velocities of sandstone targets.Furthermore,by combining micro-CT and scanning electron microscopy techniques,a quantitative evaluation of the damage degree of perforated sandstone was realized.The results shows that there was no obvious crack in sandstone targets.Compared with the perforation data on concrete target,the penetration depth of sandstone target is smaller,with a range of 17％to 40％for different bullet types.Temperature has no significant effect on perforation depth.The radial direction of the perforation channel could be characterized by four regions:broken zone,transition zone,compaction zone and original zone.The average thickness of the compaction zone is 17.10 mm to 79.95 mm,and the compaction damage rate is 12％to 63％.The inner wall of the hole is subject to shear expansion,resulting in increase of porosity and permeability.The compaction zone is subject to plastic extrusion,which reduces the throat diameter significantly.The research results of this paper have reference significance for clarifying the damage mechanism of perforation channel and guiding the design and optimization of perforation parameters.
万方数据
维普
