泥饼仿地成凝饼(MTA)法防窜固井,是针对MTC固井技术的不足、为更好地提高固井二界面胶结质量而提出的新技术。该方法是钻开封固段前50~200m,在钻井液中加入0.5%~3.0%的泥饼改性剂并维持该比例至完井,固井时以凝饼形成剂为基础配置3~4m3前置液,注入该前置液后随之注入水泥浆,不改变油井水泥浆体系,但对钻井液泥饼进行了处理。其整体固化胶结机理是,用凝饼形成剂对泥饼界面进行修饰、处理并使其与泥饼改性剂初步反应生成凝饼胶结物,再逐渐形成致密凝饼。为了验证MTA方法的实际固井效果,在大庆油田、胜利油田和河南油田的23口老区调整井(常规油井16口,稠油井7口)中进行了现场应用。应用结果表明,固井一、二界面质量合格率100%,其中大庆油田应用井固井质量优质率和合格率分别提高13.01百分点和1.15百分点,胜利油田应用井固井二界面质量合格率提高约30百分点,河南油田应用井平均总井段优质率达到90.48%。
The MTA (mud cake to agglomerated cake) method is a new antichanneling cementing technology in order to overcome the shortcomings of MTC (mud to cement) method and improve the ce ment quality of cementformation interface. The procedure of MTA method can be divided into two steps: (1) The mud cake modifier ranging from 0. 5% to 3% (which shall be kept until well completion) was add ed into the drilling fluid before 50-200 meters above the cementing interval is drilled. (2) The prepad fluid (3-4 m3) ,which was prepared based on the agglomerated cake forming agent,was injected followed by ce ment slurry injection. The cement slurry system is not changed in this new technology. Its principle is that, the agglomerated cake forming agent is used to modify and dispose the mud cake interface and make it react with mud cake modifier initially to form agglomerated cake cement and finally to form tight agglomerated cake. In order to verify the actual effect of MTA method, the field application was done in 23 adjustment wells (including 16 conventional oil wells and 7 heavy oil wells) in the old area of Daqing Oilfield,Shengli Oilfield and Henan Oilfield. The application results showed that the qualification rate of cementformation interface and casingcement interface was 100%, the highquality rate and qualification rate of cementing quality in Daqing Oilfield increased by 13.01 and 1.15 percentage points, respectively. The qualification rate of cement-formation interface increased by 30 percentage points in Shengli Oilfield, the average high-quality rate of all intervals reached 90.48 % in Henan Oilfield.