OPTIMIZATION AND APPLICATION OF ACID FLUID FOR REACIDIZING ZHUANGXI ARENACEOUS CARBONATE

The main pay zone of both Zhuang-120 and Zhuang-121 blocks in Shengli Oilfield is ES2. It is a special formation of 50% or so of carbonate and more than 40% of arenaceous composition, which formed as special geologic sedimentation. Therefore, the treatment of acidizing and inJection increase to this formation should be different from that to conventional sandstone or carbonate formations. Based on this, determined optlmlzing rules of acid fluid system for reacidizing, conducted simulation study in lab, chose optimally organic chemical retarded acid fluid system. By means of the mechanlsms such as retarded agent adsorption on the surface of rock, reaction balance of organic acid and carbonate, etc., this system can protect formation framework, decrease second damage, and realize deep acidizing. Considering that reinjection of produced water bearing emulsified crude would result in formation damage, the formation was preflushed with organic solvent at first, and then acidized. Pilot tests of acidizing two wells in these two blocks were conducted in September and october respectively, and obvious effects had been observed.