Ye Weibao, a senior engineer of China University of Petroleum, led a research group of profile control with microsphere and several domestic research institutions and some corporations in oil fields to tackle key points jointly since 1999, experiencing three phases: study on the mechanism of profile control, laboratory assessment and application to the field. After ten years’exploration and experiment, especially in recent years under the guidance of Professor Zhao Fulin and professor-level senior engineer Xiao Jianhong who have tackled the difficulty of the preparation of profile control material in such severe conditions as low permeability, high temperature and high salinity successively, the successfully developed belongs to the high-end products among the same kind of plugging agents in oil fields at home and abroad at present. By far the researchers have developed three generations of eight series of gel microsphere products used for profile control, which can meet different kinds of oil fields.By way of controlling the polymerization process and the component content, adopting materials of different conductivity and co-polymerizing with a few hydrophobic monomer, the expanding rate and the maxim expanding volume of the microsphere in the waste water are controllable and the electrical transformation of the microsphere surface in the process of the hydration can be realized, in order to adapt the requirements of adjusting waterflooding profile in different permeability formations; the co-polymerized microsphere still has good elasticity after its hydration and proper pressure difference can breakthrough the plugging of the pore-throats, then the microsphere “migrates” to the next pore-throat and re-transforms re-forming plugging, and changes the direction of the water flow gradually and realizes in-depth profile control step by step; the core of the microsphere is a bond gel, even soaked in the water or cut it is not easy to be spoilt, bearing considerable mechanical strength and good temperature-resist and salinity-resist performance; the microsphere product of any concentration can disperse in the injected water homogeneously, and it can be injected on line.

The in-depth profile control technology of gel microsphere is applied in 21 oil fields such as Gudao, Xianhe, Haiyang, Bingnan and Dongxin of Shengli Oil Field, the oil recovery 1 and 3 of Qinghai Oil Field, the oil recovery 1 of Zhongyuan Oil Field, the oil recovery 4 of Huabei Oil Field, the Huaidong Oil Field in Xinjiang province, Duha Oil Field. The total amount of the operated well groups is 110. By July,2009, the cumulative amount of injected microspheres in all the oil fields is 2300t, and the cumulative increased oil is 124200t, that is to say, each ton microsphere promotes 54t increased oil. The most effective one is the Yong8 fault block of Dongxin oil recovery in Shengli Oil Field. Yong8 fault block is a high temperature high salinity and seriously heterogeneous middle-high oil-permeable reservoir. When there is no effective method to control the profile, profile control with microspheres will be developed. Since 2006, the oil field experiment of profile control with gel microspheres had been done in 6 well groups of Yong8 fault block, and the total amount of the injected microspheres is 481.24t. After the profile control, the annual reduction rate of the daily oil recovery capacity of the well groups dropped from 16.8% to 10.8%; by the end of December, 2008, the amount of the affirmed accumulative increased oil of the profile controlled well groups is 1.58*104 t, producing economic benefit ￥30.97million, and the input-output ratio is 1:3.5. The typical example of the well group is Yong8-7 whose productivity before profile control is 64.4*23.3*63.8％, while the productivity after the profile control is 168.6*58.8*65.1％. Through continuous measurements of the intake profile, it is found that the microspheres can change the intake profile of the injection water wells periodically. This periodical adjustment is beneficial for the oil recovery enhancement to the largest degree. The offshore oil fields, restricted by the environment, have strict requirements of the profile control plugging agents and the manners. There is no way of profile control except for waterflooding, but the gel microsphere on-line profile control technology can meet the high standard of the offshore environment and the requirement of the seawater injection allocation.

From March, 2005 to March, 2006, the three water wells of B25A platform of Shendao offshore oil field had been injected microspheres 226t, and the water content of the nine out of the corresponding eleven oil wells dropped to different degree, and the average water content dropped by 3.6%. By December, 2007, the accumulative increased oil is 15275t, and the input-output ratio is 1:7.2. After two years when waterflooding followed profile control, the water content of the central well CB25A-4 stably decreased, and the period of validity lasted 1079 days.

The normal tertiary oil recovery with polymer is only applicable to the first and second reservoirs, whereas the gel microsphere in the process of polymerization is added into hydrophobic monomers and cationic materials, which improves the plugging performance and applicable scope of the microspheres. At present, the microsphere series can satisfy those oil reservoirs whose temperature is from 20 to 130℃ and mineralization is below 300,000, especially applicable to V reservoirs to which polymer flooding can not apply. For example, the geological outline of Bing5 block of Bingnan Oil Field is as follows: the depth of oil layer 2380～2900m, permeability 28*10-5μm 2, the temperature 108℃, the mineralization of the formation water 109593mg/l. Taking the water well B5-12 as experimental well group, the injection time is from October 12th, 2007 to November 19th, 2007, and total amount of injected microspheres is 5t. After the profile control, the oil pressure of the water injection wells increased by 6～7MPa, and the intake profile improved obviously. Before the profile control, the oil productivity of the corresponding oil well B5－26 was 30.8*5.2*83％, while the present productivity is 29*9.2*68％, that is to say, the productivity per day increases by 4.0t and the water content drops by 15％. The amount of increased oil of the well groups in a period is over 500t, which has obvious effect.

The gel microsphere on-line deep profile control technology has tackled the difficult deep profile control technology of low permeability, high temperature and high salinity in the oil field development with injected water, which is meaningful for the two themes “Oil recovery enhancement and reserves-production ratio” in all the large domestic oil fields.