Experimental Study On Influence Of Scale On Jiyuan Oilfield And Damage Prevention

By core measurement and mercury intrusion porosimetry of samples in Jiyuan field, it was concluded that the formation had a small porosity and low permeability with small pores and micro throats as the major type and thus the field was a typical low-permeability reservoir. The injection water of Jiyuan field had a high concentration of SO42-and formation water had a high concentration of Ba2+and Sr2+, which would easily produce barium/strontium sulfate scale during waterflooding. The barium and strontium scale would highly reduce formation permeability during injection. Therefore, study on scale dissolving mechanism and evaluation of the effect of scale solvent had a critical meaning for oilfield stimulation and stable production.Based on water analysis data of Chang8block Jiyuan field, this paper analyzed the type and amount of scale in formation and its variation tendency under different mixing ratios, by theoretical scale prediction study and experimental research. Through X-ray diffraction analysis and soluble acid experiments, the major type of scale in this block was barium sulfate.Analysis of scale dissolving mechanism of solvent YHJD-1through infrared spectra and NMR showed that chelation between amino carboxylic groups and metal ion resulting chelate would accelerate scale dissolving and thus attain the goal. This paper studied the impacts of scale solvent concentration, reaction time, temperature, and pH value on barium scale dissolving effect by employing a new method to evaluate efficiency of chelating scale dissolving agent. The analysis results showed that9%YHJD-1concentration would achieve82.41%dissolving ratio; the ratio increased as reaction time, temperature and pH value increased, and this method provided a more accurate dissolving ratio.This paper studied the impacts of different mixing ratios, solvent types, concentrations and amounts on core plugging removal effect by core flow tests. Through the analysis, all factors had some influence on scale removal effect, and the permeability recovered to different levels afterwards which provided robust theoretical foundation for scale removal plan of Jiyuan field.