Experimental And Applied Study On Air Foam Flooding Of Low Permeability Reservoir

In this article the practical problems which appeared during the development of Xifeng Oilfield, such as serious oil formation plugging, water injection pressure increased fast, no injection, low oil well production, the effect of acidified-decreased pressure-increasing injected and fractured stimulation unconspicuous, the short effective period. Testing methods of casting thin sections, SEM, high pressure Hg injection, contant-speed mercury injection and nuclear magnetic resonance and so on were used to make a detailed research about reservior characteristics of Xifeng oilfield. The external factors which plugged the reservior were studyed deeply. Deep causes were detailed analyzed of the effect of acidified-decreased pressure-increasing injected and fractured stimulation were not obvious of Xifeng oilfield. On this basis, put forward some simullation and flooding measures, such as the organic sour dissolve blocking technology, lead acid fracturing technology and air foam flooding technoloy and so on. The experiments were evaluated and studyed detailed, obtained good effect. At last, provide a strong theoretical basis and technical support for the field implementation.(1) Inluenced by the sediment environment and later diagenesis, micro fissure was well developed in Xifeng Oilfield. The rock of reservior was mainly feldspar lithic sandstone, the content of acid sensitivity clay was high; the micro-pore structure was complicated, the throat radiu was small, connection was poor, sensitived about the foreign solid and liquid material. Oil reservoir was strong heterogeneity. The affected efficiency of injection water was low, moving fluid saturation was not high.(2) The Compatibility of the formation water and the injection water was poor in Xifeng oilfield. When the ratio of the formation water and the injection water was9:1, the scaling was the most serious. The ingredients were mainly calcium carbonate and the content accounted for more than85%.(3) In the current injection, the water injection development will not make the reservoir temperature down to below wax chromatography for10years, and the strata won’t form a wax blocked. Wellbore temperature field simulation results show that position of the post-mortem wax of the well bore was in commonly about900m.(4) The reasons of the micro-pore structure was complicated, the throat was narrow, the content of acid sensitived clay was high were the internal causes that why the stimulation measures of soil sour dissovle blocking and hydraulic fracturing were not obvious, and the effective period was short in Xifeng oilfield. Application of organic acid reservoir acidification can not only remove reservoir jams so as to step-down pressure and increase injection, and also can effectively prevent the damage occurred; Lead acid fracturing technology combined the advantages of the acidification and fracturing. The combination of the two techniques could effectively reduce the filtrate on reservoir of injury, in the same time, extended the valid period of the well stimulation.(5) The application of air foam flooding of the low-permeability reservoir in Xifeng oilfield, could not only realize crude oil in a low temperature oxidation, rise to fall stick, the role of black flooding, but also could to effectively prevent steaming breakthrough, improving the affected efficiency of injection water, controlling the water cone to enhance oil capacity. More beneficial to to save the water resources, and protected the ecological environment of the oil-producing areas.