长庆某气田完井液缓蚀剂的研究和应用

长庆某气田平均井深为3400m，储层上部有多个厚水层，通过定量测定各层的犄蚀速率，从上层到下层的纵向腐蚀分布是腐蚀速率逐渐增大。按照NACERP0775—91规定，腐蚀速率高，数值区间处于中度腐蚀和严重腐蚀之间，而且固井工艺采用局部固井降低成本的措施。提出了使用完井液复合缓蚀荆来延缓外部水对套管的腐蚀。通过对多种缓蚀剂的成分、配伍性和成膜、缓蚀性能的对比评价，优选出了适应该气田完井液体系的缓蚀剂MIG，经室内电化学和高温高压等试验，其缓蚀率达到86％以上，与钻井液配伍性能稳定且价格适中。现场2口井的应用表明，加入MIG缓蚀剂对钻井完井液的性能基本无影响，用前置液对固井段井筒环空钻井液和套管外壁清洗后，MIG复合缓蚀剂不影响固井第一、第二胶结面的质量，并且现场施工方便、简单、安全。

Study and application of the corrosion inhibitor for completion fluid in a gas field of Changqing oilfield

Several thick water bearing formations are overlying on the reservoirs of a gas filed with average depth of 3400m in Changqing oilfield. The general tendency of vertical corrosion distribution seen from quantitative data of corrosion rate is incremental from the top down. According to the standard of NACE RP0775-91, the corrosion rate is high and is some magnitude between moderate corrosion and severe corrosion. It is proposed that the compound corrosion inhibitor for completion fluid can be used to retard the corrosion of external water to casing. A few inhibitors were selected and their properties sucn as composition, compatibility, film forming ability and corrosion control were determined, and MIG was the optimum product. It can be seen from the laboratory electrochemical and HTHP tests that it had a corrosion control ratio of more than 86%, a stable compatibility with drilling fluid and a moderate cost. The in-situ application in two wells showed that MIG hardly had influence on the physical and chemical properties of the drilling and completion fluids, the quality of cementing and was preferable and qualified which indicated MIG had no effect on the qualities of first and second cementing interfaces and also the field operation is conven ient, simple and safe.