| Water coning in the exploitation process of bottom water reservoir hinders the increase of oil recovery, even it could trigger the vocalically water flooding, shortening the production duration. At present, nitrogen foam has been used in the anti-water coning in plenty of oil fields, which were condition reservoir. In order to broaden its applied range, under the high temperature and high salinity reservoir condition of Tahe oil field which reservoir temperature is106～117℃and the formation water salinity is21.2×104mg/L, the thesis investigated the foaming ability, the mobility control ability, stability in the porous media and the anti-water cone effect of nitrogen foam.By utilizing the Waring-Blender-way, under the condition of100℃and formation water, through compounding nonionic foaming agents with zwitterionic foaming agents, temperature and salt tolerance foam systems-NL was screened, then enhanced foam system-NLW was determined by adding stabilizer agents. Under the110℃and injection water, the foaming volume of NL and NLW was520mL and350mL, the foam drainage time was271s and2464s, respectively, the aging temperature of the two systems was110℃and100℃, after120d’s aging, their foaming volume was350mL and410mL, their drainage time was both232s, proving that NL was more stable.According to the systematic investigation of NL characteristic, some results were found:(1) by increasing the concentration of foaming system (0.1%-0.6%), both of foaming volume and drainage time were promoted;(2) salt could enhance foam stability sharply;(3) with the rise of temperature, the foaming volume augmented exponentially, both of drainage time and the foam complex index decreased;(4) the foaming volume and drainage time increased with the increase of pressure as logarithmic and polynomial, respectively;(5) although the oil would affect the foaming ability of low concentration foaming system, by increasing the concentration, the oil tolerance of system could be strengthened;(6) the screened system could lower the oil-water interfacial tension to some limited extent.Under the condition of120℃, injection water and the20MPa back pressure, the mobility control ability of nitrogen foam was studied in detail, when the gas liquid ratio was2:1, and injection rate was3.5m/d, the ability was highest, furthermore, the higher the core permeability was, the greater the mobility control ability of nitrogen foam was. By checking the effect of aging duration on the stability of nitrogen foam, found that the longer the aging duration was, the weaker the nitrogen foam stability was. Through calculating the residual resistance factor after5d’s contacting with oil, the stability of nitrogen foam was influenced dramatically, which decreased by56.93%. After comparing the stability of common and enhanced foam, the NL performed more significantly, which was62.03%less than NLW.A nitrogen foam anti-water coning model for bottom water reservoir was set up, through which the applying condition of nitrogen foam was determined and optimized. The experimental suggested that the earlier the injection time was, the higher the height of water avoidance of horizontal well was, the more impressive the effect of anti-water coning was; when0.5PV pure nitrogen foam was injected from production well bottom with3d’s soaking, the nitrogen foam would receive the most significant oil recovery; simultaneously, the nitrogen foam could perform effectively on anti-water cone when the advance rate of the bottom water ranged from2.5to7.5m/d as well.The investigation of this thesis could not only deepen the theoretical cognition of nitrogen foam, but also build a stable foundation for the anti-water coning pilot of Tahe oil field meanwhile. |
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