Study On Scaling Mechanism And Scale Inhibition Performance Of ASP Flooding Gathering Pipeline

Alkaline/Surfactant/Polymer（ASP）flooding has become an important technology in oilfield production.However,the scaling problem of gathering and transportation pipelines in the process of ASP flooding seriously affects the efficiency of crude-oil gathering as well as the transportation and the improvement of oilfield economic benefits.Breaking through the bottleneck problem that restricts the ASP flooding technology is of great significance for improving oil recovery.Therefore,the focus of the later development of ASP technology applications refers to studying the fouling mechanism of ASP gathering pipelines and the scale inhibition method for gathering pipelines.At present,the fouling mechanism of ASP flooding gathering pipelines is not clear,and the research and development of the optimal scale inhibition method and new scale inhibitor still cannot meet the actual production needs.Combined with the composition and characteristics of the ASP flooding,the work studied the effects of the components of the ASP flooding on the scaling of common calcium carbonate scale,barium sulfate scale,and silicon scale in the oilfield from the macro and micro perspectives.Besides,the scaling mechanism in the ASP flooding gathering pipelines was revealed.The scale inhibition performance of scale inhibitors was systematically studied by taking the main scale calcium carbonate scale of ASP flooding gathering pipelines as the research object to discuss the differences in the scale inhibition effects of different scale inhibitors under ASP flooding and conventional conditions.A new type of high-efficiency scale inhibitor was developed for calcium carbonate scale in ASP flooding gathering pipelines under laboratory conditions by considering the structure-activity performance of scale inhibitors.Besides,the effect of the physical scale inhibitor and the effect of physical and chemical synergistic scale inhibition were evaluated to study the optimal scale inhibition method for ASP flooding gathering pipelines.The main research contents and results are as follows.（1）The work studied the experimental data of each component and the microscopic characterization results of calcium carbonate crystals under ASP flooding.The scaling mechanism of calcium carbonate scale in ASP flooding gathering pipelines was because the chain molecular structure of HPAM increased steric hindrance and hindered aggregations between vaterite clusters.The sulfonic acid group in SDBS molecules and Ca²⁺in the solution formed chelates through coordination bonds and adsorbed on the surface of calcium carbonates at the solid-liquid interface.It changed the formation process of the calcium carbonate nucleus.Sodium ions were introduced by Na OH,and Na Cl was formed with chloride ions.The higher the salinity of Na Cl,the greater ionic strength.The crystal could fully grow and precipitate in a long induction period.（2）The analysis showed that HPAM inhibited barium ions under ASP flooding to form barium sulfate scale to a certain extent.The inhibition effect gradually increased with increased HPAM concentration;however,the increase was small.Moreover,the addition of the Na OH component promoted the formation of barium sulfate scale.The promotion effect increased with increased Na OH concentration and decreased with increased temperatures.SDBS promoted barium in ionic form,but the promotion effect gradually weakened with increased SDBS concentration.（3）The macro and micro effects of each component of ASP flooding on silica scale were explored.The theoretical analysis,the data analysis results obtained in the work,and the characterization results of XRD,FT-IR,and SEM showed that ASP flooding promoted the formation of amorphous silica and silicate micelles.The amount of silica scale was mainly affected by the composition of the alkali solution.The surfactant had little effect on the process of silica scale.Although the polymer component promoted silicon in the ionic state to a certain extent,the promotion effect disappears under the alkali solution.The interaction between the components in the process of silica scale formation in the ASP flooding system was revealed from the mechanism:The interaction between Na OH and HPAM changed the hydrolysis degree of HPAM and released the silicon captured by HPAM.The silicon generated silicate scale crystallization,silicate gel,and amorphous silica under HPAM and SDBS,and silica scale gradually grew and precipitated.（4）The structure-activity relationship between the scale inhibitor structure and its scale inhibition performance on calcium carbonate scale was studied based on the evaluation and comparison of the scale inhibition performance of scale inhibitors in the ASP flooding system and the conventional system.The amino group and the carboxyl group were the reasons for the outstanding scale inhibition performance of the scale inhibitor.L-lysine with both amino and carboxyl groups in the molecule was selected to modify citric acid,and a new carbon quantum dot scale inhibitor Ly-CCQDs was developed by one-pot hot melt polycondensation.The scale inhibition performance of the product on Ca CO₃ in the ASP flooding system was studied under various factors by optimizing the reaction conditions.The optimum synthesis conditions are as follows:The molar mass ratio of anhydrous citric acid to L-lysine was 3:1,with a synthesis temperature of 200°C,and the synthesis time of 2 h.The optimization of scale inhibition performance showed that when the reaction temperature was 50°C,the calcium ion concentration was 200 mg/L,with a dosage of Ly-CCQDs of 20mg/L and the reaction time of 8 h.The scale inhibition rate of Ly-CCQDs on calcium carbonate could reach98.64%.（5）The scale inhibition effects of two physical scale inhibitors under different reaction conditions were dynamically evaluated using the indoor dynamic cycle evaluation device designed in the laboratory,and the effective scale inhibition distance was measured.The changes in calcium carbonate crystal forms before and after the action of physical scale inhibitors were characterized by XRD and SEM.The dynamic experimental method was used to simulate the ASP flooding system.The synergistic effects of two physical scale inhibitors,three-component scale inhibitors,and newly developed Ly-CCQDs were explored under the calcium ion concentration of 200 mg/L,a reaction temperature of 50°C,and a flow rate of0.08 m/s.The three scale inhibitors under physical scale inhibitors improved the scale inhibition effect and reduced scale inhibitors.The synergistic effect of Ly-CCQDs and electronic anti-scaling instruments had the optimal scale inhibition performance for ASP flooding gathering pipelines,and the highest scale inhibition rate reached 99.45%.