| How to improve oil production has become the focus of the research field, which horizontal well technology is a kind of important means,the horizontal well can increase sweep efficiency and improve the production efficiency,reduce the comprehensive cost.Horizontal well development has also brought about the upgrading of related technologies, such as the development of horizontal wells in the process of water channeling, water flooding and other issues, how to carry out the horizontal well water plugging is an urgent problem to be solved.At present, the method of blocking water in vertical wells is very mature, but because of the special structure of horizontal well, the effect of the method s very poor.It is badly needed to carry out technical research on the actual situation of horizontal wells.The progress of water plugging technology in horizontal wells can improve the productivity of horizontal wells, reduce the comprehensive cost of oilfield development, improve the efficiency of oil field, and provide a good technical means for the design, development and management of horizontal wells in the future.There are three main method in horizontal well completion:open hole completion, screen completion and perforation completion.In the development process of horizontal wells, the water type is divided into two types:water coning and crack advance.According to the different methods of horizontal well completion and water type, the current main methods of oilfield horizontal well water plugging are:mechanical pipe column method and chemical agent general injection water and horizontal well annular chemical packer(ACP) method.Mechanical pipe column method for blocking has limitations, for the use of screen pipe completion of horizontal wells, the water shutoff method is not good,and layer water variable transverse flow along the slotted into the wellbore.Chemical agent general injection technology also has a certain degree of limitations in chemical agent for the general injection method for water plugging in the process, because there is no separation, blocking agent once in production layer, then it is likely that will cause great harm on the production layer.If the water level is found, the horizontal well annular space chemical packer (ACP) method can be used. The technique can well plugging level layer of water, and can overcome the chemical agent injection method limitations and risks of general, not only effectively blocked the water layer,but also protect the reservoir, greatly improve the underground water operation effect of blocking, is the domestic and foreign research and application of the main water shutoff technology, domestic for ring air chemical packer technology research and development is currently in the initial stage.At the end of the last century Dowell, Schlumberger successfully used ACP method in Nigeria,Saudi Arabia and so on.It verify the the technology and obtains the certain effect, which opened a new chapter in water shutoff in horizontal well. The technology in China is still in the research stage.The polymer gel strength, and thixotropic performance is not good, vulnerable to the effect of gravity caused sealing is poor.Thixotropic cement is not good in terms of safety,at the same time it is easy to pollute reservoirs. A variety of common horizontal well plugging agent is difficult to meet the performance requirements of ACP technology.To synthesis the ACP material is urgent affairs.In this paper, the synthesis and performance evaluation of the water shutoff agent for the horizontal well annular are studied.Firstly, the synthesis of the agent required skeleton material, monomer, thixotropic agent, cross-linking agent, triggered agent were screened, it is concluded that the starch as skeleton, acrylic acid as monomer, titanium triethanolamine as thixotropic agent, N, N-methylene bis acrylamide as cross-linking agent, hydrogen peroxide or ammonium persulfate or ammonium persulfate and sodium bisulfite for initiator by graft copolymerization reaction to synthesis the water shutoff agent for the horizontal well annular. The reaction mechanism was discussed. The reaction can be divided into free radicals, chain initiation, chain growth, chain termination process. In addition to containing the graft copolymer of starch and acrylic acid in the product,there is acrylic acid homopolymers.Secondly, the conditions of the reaction were studied systematically. Effects of reaction time, reaction temperature, initiating agent concentration, acrylic acid/starch quality ratio, reactant concentration, thixotropic agent concentration, concentration of cross-linking agent and acrylic neutralization degree on the properties of the product influence. Such a condition was optimized,as the reaction time for 12h, reaction temperature is 70℃, initiator concentration is 0.05%, the concentration of the reactants is 40%, the thixotropic agent concentration is 0.1%, the concentration of cross-linking agent is 0.1%, acrylic acid/starch quality ratio is 1,acrylic neutralization degree is 70%. Through orthogonal experiment,selecting the starch/acrylic acid mass ratio,reactant concentration,cross-linking agent concentration and neutralization degree of acrylic acid to optimize.Finally, the shear dilution,thixotropic,temperature and shear of thixotropic effect were studied by the DV-Ⅲ viscometer and MR301 rheometer. The results showed that ACP material has good shear thinning properties.The higher the temperature,the structure of the material recovery rate is shorter,the thixotropic performance is strong;the shear rate increases,the structure of the material recovery rate is shorter,the thixotropic performance is strong.The grafting efficiency of the product was 33.49%.The grafting rate of the product was 25.61%.The surface structure was analyzed by IR. The result showed that Grafting of acrylic acid onto starch.It is proved that the ACP material has strong water absorption performance through the water absorption experiment.The degradation experiments showed that the ACP material can be effectively degraded under the action of the gel breaking agent or biological enzyme.At present, only the study of the ACP synthesis of the factors, as well as the formula under the low temperature (<90 degrees C), the high temperature formula has yet to be further studied. |
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