The gel microsphere developed by China University of Petroleum is a kind of new profile control agent. Since the end of 2004, it was begun to use in oilfields and almost 100 wells of over 40 domestic oil fields have done on-site experiments successively, which has made good effect in the low-permeability oil reservoirs. In recent years, Professor Zhao Fulin, who is seriously ill, pays much attention to the development of the technology. Under the instruction of Professor Zhao, the research group led by Ye Weibao has tackled the key problems and developed a series of microspheres attained by co-polymerization process which are used for deep profile control in those middle-high permeability fractured oil reservoirs with water flooding development. By way of different polymerization methods (emulsion method, diversion method, suspension method), we can prepare viscoelastic gel microspheres whose initial grain size is 100～1000μm、1～10μm or ＜1μm. Meanwhile, by adjusting the co-polymerization materials and the formula, the microsphere with different expansion ratio and strength is attainable. Relying on the adjustment of the four “degree”, namely different granularity, expansion degree, strength and concentration, meets the requirements of different oil fields.

Co-polymerized microsphere has been applicable to many oil fields, including the high-middle permeability reservoirs such as Yong8 fault block of Xinlicun Oil Field of Donnxin oil production plant in Shengli Oil Field, which is a normal temperature normal pressure average viscous oil reservoir that is characterized with high pore, high permeability and relax cementation. The porosity of its reserve is between 27.7% and 33.1%, and the average porosity is 31.7%; the average permeability is 1.039mm2. The permeability contrast is 5.0, and the dart-coefficient is 1.56. Affected by long-term washing of the injected water, logging twi-interpretation shows strong heterogeneity and serious water channeling completely (comprehensive water content 88.5%), such as the injection layer Shaer 51-52 layer of Yong8-7 well group. Seen from the data of intake profile, Shaer51 of the well is injection layer of high water absorption layer, and the relative water absorption capacity is 83.6%. From August 13, 2011 to September 15, 2011, co-polymerized microsphere was adopted to control the profile. After the operation, the water injection oil pressure increased from 3.0MPa to 4.7MPa, and the FD value increased by 0.49. After the profile control, the main flowing line of the well Yong8-7 has changed, and 4 oil wells had the effect of oil enhancement and water content decline, for example, the water content of Yong8 Ping14 decreased from 71.5% to 55.2%, the oil production per day increased from 4.2t to 7.5t. As for the middle-permeability oil reservoirs, there is also an example. Two wells of Block8-3 in Bingnan Pingfangwang Oil Field were operated with microsphere deep profile technology. The well PF4-2-73, which corresponded to the well PF4-2-7, shown good effect. Its water content dropped from 89% to 76% (declined by 13%), and the oil production per day increased from 3.2t to 6t.. Another well, PF3XN8, corresponded to the well PF3-83. In the process of operation, the water content of the well PF3-83 dropped from 71% to 58% (dropped by 13%), and the oil production per day increased from 2.6t to 3.8t. The effect of profile control started to show.

Concerning the low-permeability fractured oil reservoirs, co-polymerization with different size was adopted to control the profile. At first, the oil field experiment was done in Block Tang169 of Yangchang Oil Field in Jilin Xinmu Oil Field and Mabei Oil Field of Qinghai Oil Field. After the injection of microspheres, the oil pressure increased, and the rising momentum of the corresponding oil well’s content was effectively controlled. For example, the outline of the well Mabei103 in Mabei Oil Field was as follows: depth of injection 895m, average permeability 32×10-3mm2, porosity 22%, water flooding speed measured by the tracer agent 1.65m per day. From July 14, 2011 to November 3, 2011, the injection lasted 100 days, the accumulative injected profile control liquid was 1256m3, and the injected microsphere was 12.7t. In the process of operation, the oil pressure stably increased from 10.4MPa to 11.6MPa. In the process of profile control, two wells of the corresponding 3 wells came into effect obviously. The water content of the well Mabei 1 dropped from 88% to 73% (dropped by 15%); the water content of the well Mabei H4-1 dropped from 78% to 70% (dropped by 8%).

Besides, under the instruction of Professor Zhao Fulin, the research group has tackled the description of the underground fluid pathways and quantitative plugging technology. On the base of chemical tracer agent, a explanation model was developed to describe the underground fluid pathways. According to the reaching time of the tracer agent which can be calculated through the wave crests of the tracer agent’s producing curve, the number of the pathways between two oil wells, the diameter of the pore-throats, and other parameters are attainable. The ultimate function is to choose the pathways needed to plug, calculate the amount of plugging agent and decide the grain size of the granular plugging agent. This technology was firstly applicable to Yong8-61 well on January 23, 2010. 27 pathways of the corresponding 8 wells were detected, including 22 permeable pathways and 5 channeling pathways (2 big channeling pathways and the rest were small ones). The maximum permeability reached 8.61μm2，and the diameter of the pore-throats is 26.24μm. Based on the description of channeling pathways with tracer agent, quantitative plugging was taken according to the channeling volume. After the measurement, the injection water pressure increased from 3.0MPa to 6.4MPa, the PI value increased from 0.46MPa to 3.49MPa and the FD value increased from 0.13 to 0.87. By analyzing the explanatory achievements of the absorption profile before and after the profile control, the relative water-intake capacity of the main water-intake layers before the plugging dropped from 83.2% to 48.1%, and the heterogeneity between two layers was greatly improved. As for the corresponding 8 oil wells, the comprehensive water content dropped by 2.3%, the oil increased 18.6t per day and the dynamic liquid level ascended 72m again. By November 10, 2011, the oil increased by 7176t accumulatively, and the period of validity was 410 and was still valid. For example, the water content of Yong8-Cexie6 dropped from 94% to 76%, and the produced oil per day increased from 1.0t to 4.6t; the water content of Yong8 Ping10 dropped from 64.2% to 60.4%, and the produced oil per day increased from 13.5t to 17.9t.