The Acidification And Modification Of The Low Permeability Oilfield And Its Application In The Oil Field Of Moliqing

The types of Moliqing reservoir stratum belong to hyposmotic sandstone. The contents of feldspar and debris and other unstable components in the reservoir are relative high. The components mentioned above easily occurred various kinds of physical and chemical reactions under the external fluid actions. The contents of cuttings and feldspar are up to 20 – 30%. Clay minerals and carbonates are the main factors damaging the reservoir area. The main types of clay minerals include the chlorite, kaolinite, illite and eamonn layer. Calcite is a main component of carbonate. The reservoir has potential alkali sensitivity, velocity sensitivity, acid sensitivity, water sensitivity and so on.In this work, hydrochloric acid, mud acid and fluoroborate systems were respectively used to acidify the different core from five well in oil field of Moliqing. The removing blockage effects of the different acidification system were evaluated by detecting the permeability to water. It suggested that the optimum fluorine acidification and normal mud acidification system possess the better removing blockage effect to the core in oil field of Moliqing. Hydrochloric acid and hydrofluoric acid had almost no effect. Even if the authigenic hydrofluoric acid had certain effect, but it produced secondary pollution, and caused the secondary blockage to the core.Besides, the optimum acidification system obtained was applied in practical production of oil field of Moliqing. On the premise of using foam acidizing steering technology, mud acid process did not increase oil production of the test well. However, when fluoroboric acid was used to remove blockage along with the produced foam acidizing steering technology for temporary plugging to high permeable reservoirs, the desired increase yield effect was obtained. Everyday increased oil of a well was 8.38 tons, and everyday decreased moisture content of a well was average 44.62%.In conclusion, the results of the research indicated that the fluoroboric acid acidizing system had good corrosion ability to rock and clay minerals, and had good performance of retardance, which could enable fluoroboric acid further break down into hydrofluoric acid to acidify the deep reservoirs when fluoroboric acid reach deep reservoirs.