Daqing Oilfield is one of the earliest which develop displacement technology by polyacrylamide (PAM). 1 ton polymer can increase 100 to 120 tons of oil, the recovery from above 40% to nowadays 50%. In view of the geological and physicochemical characteristics, a series of technologies have been developed, such as polymer flooding mechanism, the productivity forecasting, proposal optimization, domestic excellent quality polymer production, surface injection, downhole separate layer injection, and separate layer testing during injection, etc.. The oilfield is characterized by heterogeneous multi- layer sandstone reservoir, during polymer flooding, separate layer injection technology is also needed to alleviate the interlayer differences, enhance oil recovery and improve the whole development effect. After polymer flooding in main oil layers, the object of polymer flooding in Daqing Oilfield turned to laminated layers with lower permeability and more interlayer differences, these layers were compatible to polymer solution with medium or low molecular weight, using polymer solution with the same molecular weight for displacement will cause difficult injection into these poor layers, and thus have an impact on polymer flooding effect. In order to solve this problem, a new technology is developed through injection of polymer solution with different pressure and different molecular weight in different layers, which can realize the adjustments of both separate layer polymer molecular weight and injection rate, and also field test was carried out in the polymer injection blocks, good results of well stimulation have been seen. This paper briefly introduces the development and practice of separate layer polymer injection technologies, presents its focus on the principle, string structure and parameters of eccentric different molecular weights polymer injection technology and its field applications in Daqing oilfield.

In this paper, we analyze the motivation of the cooperative R&D between private S&T enterprises and state military companies from the angle of informal innovation network. The military industry is a natural monopoly industry which regulated by government. As a result, the informal innovation is a valuable way for private S&T enterprises to entry into the industry by cooperating with state military firms. By investigation we find that there are special motivations for the partners. Through informal network, they can achieve the following motivation: Mastering the civil technology, gaining the official R&D fund, enhancing the social status of private enterprises, strengthening the contact with government officials. Finally, we analyze the rules of the cooperative R&D by mathematical method.

Summary Daqing oil field is one of the earliest to develop displacement technology by polyacrylamide (HPAM). One tonne of polymer can increase 100 to 120 tonnes of oil; the recovery increases from 40% (OOIP) to 50% (OOIP). In view of the geological and physicochemical characteristics, a series of technologies have been developed, such as polymer-flooding mechanism, productivity forecasting, proposal optimization, domestic excellent-quality polymer production, surface injection, downhole separate-layer injection, and separate-layer testing during injection. The oil field is characterized as a heterogeneous multilayer sandstone reservoir. During polymer flooding, separate-layer injection technology is also needed to mitigate the interlayer differences, enhance oil recovery, and improve the whole development effect. After polymer flooding in main oil layers, polymer flooding in Daqing oil field turned to lower-permeability layers. To obtain a better displacement effect, the injected-polymer molecular weight is usually determined according to the injectivity of high-permeability layers. However, if polymer solution with the same molecular weight is injected in each layer, it will cause blockage in low-permeability layers. In order to solve this problem, a new technology is developed that can control both separate-layer polymer molecular weight and injection rate; the injection profile was improved greatly in later field applications. This paper introduces the development and practice of separate-layer polymer-injection technologies, and presents the principle, string structure, and parameters of eccentric different-molecular-weight polymer-injection technology and its field applications in Daqing oil field.

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