The Influence Of Formation Water In Middle Tarim Basin On Cement

The well logging data shows that the cementing quality of oil and dry layer is well,but the cementing quality of water layer is poor.The Bohai drilling engineering company adopted the cement system with good anti channeling performance in the Tarim Basin block,and strictly controls the cementing procedure of cementing,but the quality problem of cementing still exists.In water layer,the cement at the wall interface invaded by formation water.According to the site investigation,it is found that the formation water salinity of the Tarim Basin is high and ion species is complex.Therefore,it is presumed that components of the formation water on the cement performance may be one of the reasons for the poor cementing quality of the water layer.The formation water of three water layers of the poor quality in the clastic rock strata are sampled at the site,then the ICP component analysis and titration test are carried out.Formation water and the cement compatibility experiments are in progress,including rheology,thickening time,anti channeling,sedimentation stability,and the performance of the slurry after hardening.A single factor experimental study on the types of formation water ions is carried out.,The microcosmic effect of formation water on cement slurry is analyzed by IR,XRD and SEM,and the reasons for reducing the cementing quality are found.In view of the effect of formation water on the performance of cement,the site cement system was investigated and optimized.The basic performance test of the optimized cement system was carried out.In order to meet the requirements of the site cementing,the optimized cement system was studied in the field.Formation water analysis results show that the Carboniferous Cl,CIII,and Silurian S have a salinity of about 10⁵ mg/L.The contents of Na⁺,K⁺,Ca²⁺,Mg²⁺,Sr²⁺,Cl^—are high,without acid gas.Compared with the cement with deionized water,the rheology of the cement with formation water changes significantly,which has a great influence on cementation displacement efficiency,resulting in poor cementing quality.Single-factor experiments shows that excessive magnesium ion content in formation water is the main cause of increasing viscosity.Because magnesium ions are not compatible with the loss additive BCG.IR analysis shows that the microscopic cause of this phenomenon is that BCG has a high content of carboxylic groups.The carboxylic goup and magnesium ions chelate to form a network structure,which binds the free water of the cement.Therefore,the loss additive BXF with lower content of carboxylic groups and the dispersant BCD-210L are selected to improve the rheology of cement.The basic performance of optimized cement system is good,and liquid compatibility is well.Optimized cement system meets the site cementing requirements.