| Horizontal well technology is a technological revolution in oil industry, and it is one of the most important methods of thick layer sustainable production and marginal low permeable formation exploitation in Daqing Oilfield. But horizontal well will get much more damage than vertical wells during the course of drilling, completion and production due to longer drilling period and larger contact area in formation. Additionally, low permeable reservoir has less natural oil productivity, so acidizing stimulation method is needed for seriously damaged horizontal wells that can't adopt fracturing to remove near well bore zone pollution and improve oil production.So we started the research on horizontal well acidizing.This technology is researched to remove the pollution for horizontal wells based on the developing situation and particularity of horizontal wells in Daqing oilfield. Based on the investigation of reservoir geological properties, formation fluid and mud pollution situation in No.5 and No.8 Oil Production Plant, new composite acid fluids that rely mainly on hydrochloric acid and organic acid are developed through orthogonal experimental design, which has feature of long corrosion inhibition effect. Due to the heterogeneity in one section, low density temporary plugging agent is researched to provide uniform treatment.Sectional acidizing technique with small diameter packer is also researched to solve the problem of long interval acid placement. This technique can communicate the wellbore and formation through sliding sleeve and realize sectional acidizing by dividing the whole horizontal perforation interval into multi-sections. Acid placement theoretical simulator for horizontal interval is also established. Four wells have been treated by this method with 100% success ratio and 100% effectiveness; fiuld production is increased by 3.5t per day. This technology provides technical support for horizontal wells exploitation, and has good economic and social benefits.
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