| The exploitation and depletion of oil and gas energy has led to the exploration and development of petroleum expand to complex and deep reservoirs.For the low pressure and leakage formations,long cementing section encountered in complex cementing,low density cement slurry is the most effective method.However,common low density cement slurry has many disadvantages,such as unstable system density,poor compatibility with drilling fluid,complex composition and large amount of additives,which leads to poor cementing quality and high cost.To solve these problems,this paper develops a low density cementing fluid which based on the slag MTC technology,drilling fluid technology and multifunctional curable liquid separation technology.The problem of slag solidified body cracked in high temperature was studied,and investigated the influence of fiber on the mechanical properties of solidified body.In this paper,experiments have been carried out to optimize the material formulas which determined the SS95 slag with high potential activity and unique hydration characteristics as cementitious material,CMC as suspending agent,alkali metal hydroxides as activator and HX-31L as retarder.The engineering properties of the system were evaluated,which shows that the system is stable and its density is controllable in the range of 1.3g/cm3～1.6g/cm3,as well has the characteristics of good compatibility with drilling fluid,comprehensive curing performance and high strength.It can not only achieve the purpose of sealing and filling well,but also improve the displacement efficiency and the quality of the interface cementation,and finally improve the cementing quality.The mechanical properties of the solidified body were evaluated by compressive strength,tensile strength.The hydration products of the slag at high and low temperature were analyzed by modern test and analysis method.The analysis shows that,with high temperature,the hydration speed is fast and the hydration product is rich.When temperature is higher than 90℃,the main hydration products are honeycomb and spherical C-S-H gel as well zeolite minerals.The contact area between the products is little,which led the cementation is poor,and the structural is easily destroyed.The spherical C-S-H gel with high ratio of C/S is unstable,and it is easy to change the shape of the crystal and produce internal stress in the interior,leading to the initiation or propagation of microcracks.The hydration products of slag contain less crystal content which make it prone to drying,shrinkage and cracking.The influence of fiber on the mechanical properties of the solidified body was investigated.The results show that the addition of SiC whisker and brucite fiber can improve the strength of the slag solidified body.Combined with XRD,SEM,TG,IR analysis,it can be seen that the addition of the fibers has little effect on the hydration of slag,which is only as a physical admixture to enhance the toughening effect of the solidified body.In the force stage,the fiber can control the formation and development of micro cracks through bridging,pulling out,filling and so on,so as to maintain the mechanical integrity. |
