Combining Technique Of Scale Inhibition And Corrosion Control Of Oil Wells In Jiangsu Oilfield

In the process of oil field development, particularly with increasing of water production, scale and corrosion have become serious problems, which greatly affected oil production and transportation, resulting in high production cost and economic lose. This research aims at developing combined techniques to handle the scale and corrosion in oil producers.The squeezing life of scale inhibitor is important to the squeeze treatment, which can be affected by the inhibitor and reservoir conditions. The adsorption of scale inhibitor in porous media influences the squeezing life greatly, as well as the squeezing operation parameters, and formation properties. In this study, different models for predicting the scale inhibitor squeezing life have been analyzed, and an improved squeeze empirical model based on laboratory data has been derived, and computer software has been developed. The reliability of the software is verified through comparision of the field data and the predicted data.The reasons and affecting factors of scale and corrosion were analyzed, and the trends of scale and corrosion were predicted using the softwares OFISTP3.0 and SDcorr₁.1 separately. The results showed that the calcium carbonate scale is serious without the calcium sulphate scale under the formation condition of JiangSu Oilfield, and the corrosion rate is high(0.177 mm/a) due to the high content of SRB.In order to facilitate the application of inhibitor squeeze technique in JiangSu Oilfield, scale inhibitors have been selected based on laboratory experiments, including compatible tests, scale inhibition efficiency and MIC (minimum inhibitor concentration) experiments and dynamic adsorption experiments. Corrosion inhibitors were also selected based on the important corrosion factors in the field, especially the CO2 corrosion. Convenient coupon weight and advanced electrochemical methods were used in the evaluation of corrosion inhibitors. The effects of combined scale and corrosion inhibitors on scale and corrosion control were also studied. The results demonstrated that the SA1320C is best for scale control, 956 and BUCT are both preferable for corrosion inhibition, and the combination of SA1320C and BUCT is satisfactory for both scale and corrosion control.Finally, field operation procedures and combined (scale and corrosion) inhibitor dosing techniques have been developed for oilfield application. Dosing of corrosion inhibitors in the annulus between casing and oil tube was also investigated. Up to now, scale-inhibitor squeezing technique has been applied in two oil wells, dosing corrosion inhibitors in the annulus technique has been applied in two oil wells, and good scale and corrosion inhibition results have been obtained. Combined scale inhibitor squeeze and solid corrosion inhibitor technique is being applied in one well. The efficiency of the scale and corrosion inhibition techniques can be monitored by measuring the flow-back concentration of scale inhibitor and corrosion inhibitor in produced water, and through the inspection of oil tubes during workover operations.