Study On The Polyacrylamide Inverse Emulsion Drive-adjusting Reagent

The disadvantages of produced water from oil well during the water injection exploitation in oilfield include consuming the displacement energy, reducing the final percent recovery of oil-bearing sand, the corrosion and fouling of pipes and equipments and increasing the load of dehydration station, etc. The oil well may be changed into worthless abandoned well, which may produce enormous resources waste. Therefore, it is important to reduce the specific yield of produced liquid. It has been widely noticed worldwide about the related research of water block and drive-adjusting reagent. Seventy years have passed since the related technology about various drive-adjusting reagents was investigated. Series of water treatment technologies have been formed through research experiments and development for a long time during the water injection exploitation in oilfield. There are many kinds of chemical water block and drive-adjusting reagents used worldwide, the water base gel polyacrylamide of anion type was developed fast.However, the drive-adjusting technology with gel polyacrylamide present used has many disadvantages, which districted the application scale. Firstly, the polyacrylamide is pulvis. It is difficult to solve it, which make it is inconvenient to field use. Secondly, it is difficult to control the gel form time and gel intensity. Therefore, it is difficult to take effect into the deep stratum. Finally, the crosslinking system tends to separate because of the different sorption performance of stratum to polymer and crosslinking agent, which leads to the decreasing availability of plugging agent. With regard to the above problems, this paper has conducted the research on polyacrylamide inverse emulsion deep drive-adjusting reagent with the aim to develop a new kind of drive-adjusting reagent and satisfy the need of water treatment during the exploitation in oilfield.In this paper, the polyacrylamide emulsion deep drive-adjusting reagent, which has the advantages of easy dissolution and high effective concentration, was investigated. By the system research on the plugging mechanism, emulsion polymerization mechanism, crosslinking mechanism and structure design of plugging agent, the polyacrylamide emulsion and phenolics drive-adjusting reagent was prepared successfully. This paper took use of the inverse emulsion polymerization technology into the water injection exploitation in oilfield firstly and solved the difficult problem of uneasy control of gel form time and gel intensity as well as inconvenient formulation in field. The drive-adjusting reagent and inversion reagent are dispersed into water on ground, and then they are injected to drive-adjusting block by water well. After some time, the inversion phase deemulsification of polyacrylamide inverse emulsion will occur at the circumstances of temperature and existed water in stratum. Gel will be formed during the crosslinking reaction between polyacrylamide and crosslinking agent. The inversion phase deemulsification does not occur until the drive-adjusting reagent, which viscosity is low at this time, reaches the required stratum. To assure the application effect of plugging agent, this paper established the predictive model for application effect of polyacrylamide emulsion drive-adjusting reagent. The optimization of injection scheme in field also guided the field application.The investigation content includes the following three parts. First, the preparation process of polyacrylamide inverse emulsion was developed. The polyacrylamide inverse emulsion was synthesized by the investigation of polymerization system and polymerization conditions. The polyacrylamide inverse emulsion with the molecular weight of 6400-10500 thousand has the following advantages: high effective content, excellent stability. The experiment results showed that the optimum content of emulsifying agent was 8wt%. The system was unstable when the content of emulsifying agent was low. The molecular weight of product was low when the content of emulsifying agent was high. The molecular weight of product increased with the increasing monomer concentration. However, the temperature of emulsion polymerization increased and the stability of emulsion weakened with the increasing monomer concentration. Therefore, the optimum monomer concentration was 45wt%, the oil-water ratio was 1:1 and the optimum beginning temperature of polymerization was 10~25℃. Second, the synthesis process and crosslinking mechanism of crosslinker were developed. The homogeneous inverse emulsion drive-adjusting reagent was synthesized by polyacrylamide and crosslinker. And the physical chemical property evaluation and plugging performance evaluation were conducted. The results showed that the crosslinking was in deference to two-step crosslinking mechanism. The crosslinking intensity increased with the increasing polymer concentration and content of crosslinker. When the temperature was lower than 50℃, the crosslinking degree was at low level. The simulation experiments for well core showed that the drive-adjusting reagent can be controlled easily and has excellent plugging performance. Finally, the test scheme in field was optimized by the mathematical simulation investigation. The water plugging and drive-adjusting test was conducted in the water wells in Gugao Oilfield. The water decrease and oil increase effect was obvious. The field application results showed that the drive-adjusting reagent can be resolved easily. And the drive-adjusting reagent has low cost. The gel form time and gel intensity can be controlled easily. The product can reach the deep plugging stratum, change the flow direction, control the water and increase oil. The economic effect was obvious and the input output ratio can reach 1:3. The application prospect of the drive-adjusting reagent was excellent.