Abstract
Donghe block of Tarim Oilfield is a long horizontal sandstone reservoir with many small layers and serious heterogeneity. After conventional acidification, there were some problems such as small production increased and water content increased. Through the analysis, the main reason was that in the acidizing engineering, the acid fluid entered the high permeability zone preferentially, while the low permeability layer which needed to be reformed most cannot be improved, and the interlayer heterogeneity was intensified. In view of the problems such as the difficulty of uniform distribution acid and the unsatisfactory effect during the acidizing transformation of Donghe block, the acidizing of diverting-steering technology was proposed. The mechanism of viscous diverting was analyzed and optimized the viscoelastic surfactant DCA-1, which is suitable for the steering of sandstone reservoir acid, and evaluated its diversion performance indoors. Production tests were conducted on the well DH20-4H before and after the acidizing process. The production tests show that the daily oil production rate is 18 t, the daily water production rate is 1.71 t, and the water content of the reservoir is 51% before the acidizing process. After performing acidizing to the sandstone formations, the production tests show that the daily oil production was improved to 1.71 t, no water was produced, and the water content of the reservoir is 0%. The effect of acidizing is obvious. This paper suggests that viscoelastic diversion acid system could be used for acidizing in other horizontal wells with large heterogeneity. Field experiment and application showed that acidizing of diverting-steering technology has achieved good stimulation effect in Donghe block, so it has important reference significance for the transformation of sandstone reservoir acidizing uniformity in long well section.
