Study On The Thief Zone Identification And Plugging Technology Of High Porosity And High Permeability Reservoir In Jidong Oilfield

The G104-5block of Jidong Oilfield is a typical unconsolidated sandstone reservoir. Thethief zones develop after long-term water flooding, which leads to the ineffectivenesscirculation of injected water, the low sweep efficiency. Thus, thief zone is the chief limitingfactor to further improve oil recovery in the middle-late stage of water flooding. This paperdescribes the thief zones of the pilot site in G104-5block with qualitative and quantitativeidentification. The qualitative identification is evaluated through the comprehensiveevaluation of reservoir static data and production performance data. Considering the situationof the target reservoir, the quantitative identification is evaluated by the dimensionlesspressure drop curve method and the approximate calculation method based on the pipe flowmodel. This paper studies the properties of clay-cement, inorganic chromium gel aspreliminary plugging slug or sealing slug, the properties of organic chromium gel,pre-cross-linking gelled swellable particle, grain filling gel and WT cross-linking system asmain slug. And, it studied the plugging properties of grain filling inorganic chromium gel, WTcross-linking system, grain filling organic chromium gel and organic chromium gel byphysical simulation with parallel double sandpacks.The research results show: the thief zones of G217-7, G217-6, G215-5, GJ514-5andG516-7are well-developed and their permeabilities are bigger than21.21μm2;0.3%HPAM+0.1%sodium dichromate+0.2%sodium sulfite is better as preliminary plugging slug;0.3%polymer+0.05%A+0.05%B+0.1%C+0.07%D(prefer) or0.3%HPAM+0.25%YG107+10%calcareous clay is better as main slug;0.5%HPAM+0.1%sodium dichromate+0.2%sodium sulfite or8%clay+8%cement is better as sealing slug.