Study On The Reservoirs Scaling Mechanism And Inhibiting Technology Of Chunhua Oil Region

Chunhua oil region is a typical low permeability reservoir. With the extensive develop- ment of water-flooding oilfield, injection pressure was increasing, daily fluid production was declining, and severe scaling problems were encountered in the oil wells and the reservoirs, which have great influence on the production of oilfields. In this paper, the main types of scaling is inorganic scale including magnesian calcite with XRD analysis. The forming mechanism of carbonate scale was studied in Chunhua low permeability oil region with static simulation tests and dynamic displacement tests, and the main factors of scaling process such as temperature, pressure and water compatibility etc were confirmed. The results of static simulation tests showed that the temperature increasing of the reservoirs and sudden pressure dropping from the reservoirs to well bores were the main causes of scaling in reservoirs and well bores. It was aslo observed in the F41 swelling and displacement experiments that the salinity of injected water was not main reason which caused the reservoirs plugging and pressure increasing, and the quality of injection water was very important to the control of scaling in oil field. The evident growth of scale crystal was observed in the tests with SEM analysis, and the scale crystal formed in the core of rocks was the main cause of pressure increasing and core permeability dropping.A squeezing adsorptive scale inhibitor(LY-1) and a relevant stratum(well) scale inhibiting technology was developed. The evaluation tests of the scale inhibiting showed that the scale inhibiting effect of LY-1 was prior to the inhibitor which was used in Chunhua oil region, and the scale inhibition rate was over 85% when the concentration of LY-1 was 5 mg·L-1 at 90℃conditions, the effective concentration of LY-1 scale inhibitor was 5 mg·L-1 in well bore cond- itions (6MPa,60℃), and could be 15 mg·L-1 in the reservoirs condition of stratum (10MPa,120℃). The service life of LY-1 inhibitor could be prolonged by increasing the contents of the squeezing inhibitors. Meanwhile, study on the effect of pH on the scale inhibition ratio, the results showed that pH have little effect on scale inhibition ratio. In this paper, the adsorption– desorption performance of LY-1 inhibitor with core displacement test was also studied, it was deduced that LY-1 could be easily adsorbed on the stratum and difficult to be desorbed from the rocks, and could be applied in permeability oilfield by squeezing technology successfully.LY-1 using squeeze technology has been applied in 6 wells of Chunhua oil region, the validity period of pickling and daily fluid production was increased ever since application of LY-1 in the oilfield. Among them, the concentration of LY-1 maintained 50 mg·L-1 after implementing squeeze technology 113 days in F41X1 well. The cumulative oil increment of 6 wells was up to 5294 t, and obvious economic benefits.