The Effect Of The Addition Of Metakaolin On The Cementation Performance Of Cementing Interface And The Mechanism Study

Failure of cement sheath which caused by weakness of the second interface in cementing process is seriously impact life cycle of oil or natural gas well production, at the same time improve the security risks and cost of well repair and abandon in later period. Therefore, people put forward UF (Universal Drilling Fluid) technology and MTC (Mud to Cement) technology to improve the performance of the second interface. However, UF technology seriously hurt performance of drilling fluid in engineering which cause high cost and waste. Process of MTC technology is very complex, its waste that difficult to deal with is also damage to environment. Focusing on the problem, the article explored rheology behavior, filter cake thickness, filtration property, sedimentary stability of drilling fluid which add man-made geological polymer, metkaolin, through experiment. Researched and discussed influence and mechanism of the performance of the second interface effected by drilling fluid which contain metkaolin through SEM?EDS?XRD and FT-IR.Test of drilling fluid engineering performance show that, under a low adding amount (5-25%), metkaolin has a more obvious influence on performance of drilling fluid than barite in same adding amount, however, in allowable range. Metkaolin added into drilling fluid is helpful to reduce fluid loss, form a thinner filter cake and improve sedimentary stability of drilling fluid. The rule of influence is clear, as partical size and adding amount changed, each key performance parameters changed in the rule.Test of the second interface strength show, the strength improved obviously after metkaolin added into drilling fluid as barite's succedaneum. Specification, amount, curing temperature and washing time are influence factors. When curing temperature and washing time under same condition, amount of MK-800 more than 20%, strength of the second interface improved more than 500%. As curing temperature rise, the strength improved, the same rule also showed in washing time test.Results of mechanism analysis show that 1) Metkaolin take part in deposition on the second interface in contact process between drilling fluid and the interface, and being one of the most important composition of filter cake.2) Reciprocal action happen between slurry and filter which contain metkaolin, silica-alumina mixed oxide in metkaolin can react with calcium hydroxide created by hydration of cement and then form non-crystal gel product.3) Due to the hydration and activating reaction, filter connected with cement by the gel product is the main reason of the second interface strength improving.In the research, influence of adding metkaolin into drilling fluid satisfied requirement of engineering, at the same time can improve strength of the second interface obviously. It's hopeful to overcome disadvantages of UF technology and MTC technology and MTC, and being a new technology to improve strength of the second interface. In addition, the technology has a lower cost, high reliability and is more friendly to environment, the research value is considerable.