Influence of formation water ion composition on cement lurry performance and countermeasures: Case study

Abstract

Logging data of Tazhong clastic rock formation shows that cementing quality of water layer is poor and the efficiency of cement displacement is low. Bohai Drilling Co., Ltd. has adopted a cement slurry system with excellent anti-channeling performance in Tazhong block and strictly controlled the cementing construction procedure, however, the cementing quality problem of water layer still exists. According to the cementing quality analysis, the influence of ions in formation water in Tazhong clastic strata on cement slurry performance was researched in this paper. The results show that ions in formation water has no negative impact on the loss of water and gas channeling resistance of the cement slurry system, however, has some adverse effects on the rheological property, thickening property and hardened strength. Furthermore, cement slurry consistency increasing caused by formation water is the key factor leading to poor cementing quality. Studies show that the carboxylic acid group and the magnesium ion chelate to form a network structure, which binds the free water in the cement slurry and causes the deterioration of the rheology. The magnesium resistance ability of the polymer becomes worse, when the proportion of the carboxylic acid group increases. Therefore, in order to improve rheology of cement slurry, a fluid loss agent with a small number of carboxylic acid group or no carboxylic acid group is required when the slurry or formation water containing a certain amount of magnesium ion. This investigation provides the theoretical guidance of the selection of cementing additives in the areas of which water containing high dosage of magnesium ion.

Keywords

• Tazhong clastic rock layer
• Formation water
• Cement slurry
• Countermeasure