Weak Gel - Surfactant Complex Control And Flooding Technology Applied Basic Research

So far, the technology on weak gel for profile modification and oil displacement has become one of the main technologies to stabilize oil-output and control water-cut at the latter exploitation of oil field by water injection. For technical reasons and conflicts between short-term effects and long-term beneficial results, multi-cycle weak gel treatments with small scale are adopting in oilfields. However, generous practices show it exists that with the cycles of treatment increasing, the results of EOR gradually decrease. Therefore, for one thing, the mechanism of this phenomenon is being studied in order to improve the technology on multicycle weak gel. For another, it's time to take a fresh look at scale and cycles of treatment. Besides, it is urgent to search for new technologies in order to further enhance oil recovery. This article demonstrates a new technology combining weak gel and chemical flooding, namely weak-gel in-depth water-diverting and chemical flooding combination technology. That is adopting polymer flooding, surfactant flooding or combination flooding after weak gel treatment. It is a significant study on this technology to further enhance oil recovery for the oilfields by, weak gel treatment. It is also important to more efficiently enhance oil recovery for ones without gel treatment.In this article, physical models are employed to study multi-cycle weak gel treatments. The result shows that it really exists that with the cycles of treatment increasing, the results of EOR gradually decrease. The reasons are following. Firstly, the influence areas of every cycle are partly overlapping. Secondly, with the radial distance increasing, the result of profile modification by equal amount of gel injection becomes worse. Thirdly, the opportunity of injection is another important reason. Lastly, unfitting injection crafts cause worse effects. So, in. order to ease this problem, the following measures can be employed, namely adopting a series of agents, increasing the amounts of treatments with radial distance increasing, optimizing the opportunity and craft of injection.The research on the development of agents, the feasibility of this technology, the mechanism of EOR and the craft of weak-gel in-depth water-diverting and surfactant flooding combination technology is another main emphasis of this article.In this paper, a new kind of polymer, namely hydrophobic associating polymer, is adopted in the study on the development of agents. The formulation of weak gel used this polymer can suit the general need when the temperature of reservoirs is bellow 80 degree. It is well known that common weak gel can not endure high temperature (90-120â–¡) . So, two formulations are developed in this paper in order to satisfy the need of high temperature and salinity reservoirs.The weak-gel in-depth water-diverting and chemical flooding combination technology is not the one that simply puts the technique on weak gel and chemical flooding together. It involves the cooperation of the two techniques and the compatibleness of the two kinds of agents. And the two actions determine the feasibility of the technology and ways of injection. The result of our research shows that the application of polymer flooding, surfactant flooding or polymer-surfactant combination flooding after weak gel treatment can further enhance oil recovery. In addition to weak gel enhancing sweep efficiency and chemicals improving oil displacement efficiency, the two techniques have a good cooperation and thus the oil recovery is enhanced. In-depth water diverting by weak gel results in the following chemicals entering into low permeability layer in which remaining oils enrich.The research on the compatibleness of weak gel and surfactants shows that unformed weak gel and surfactants have a disagreeable interaction. However, pre-formed weak gel and surfactants have a good compatibleness. So, the direct contact of unformed weak gel and surfactants must be avoided.In this paper, take Huabei oilfield for instance, the adaptability of weak-gel in-depth water-diverting and surfactant flooding combination technology on this oilfield is estimated. To look on the physical property and fluid property of the reservoir, the gel can selectively enter into the stratums. With the formulations of weak gel with good temperature and salinity tolerance, the suitable craft and the proper opportunity of injection, weak-gel in-depth water-diverting and surfactant flooding combination technology has an excellent adaptability in Huabei oilfield.