Principle of Anti-Channeling Cementing Technology with MTA Method and Field Applications in Daqing/Shengli/Henan Oilfields

The MTA (mud cake to agglomerated cake) method is a new anti-channeling cementing technology in order to overcome the shortcomings of MTC (mud to cement) method and improve the cement quality of cement-formation 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 added into the drilling fluid before 50-200 meters above the cementing interval is drilled.(2) The pre-pad fluid (3-4 msup3/sup),which was prepared based on the agglomerated cake forming agent,was injected followed by cement 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 cement-formation interface and casing-cement interface was 100%,the high-quality 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.