Manufacturing And Properties Evaluating Of Toughness Reinforced Agent For Oilwell Cement

Cement sheath are the main composites for cementing well and isolating the pay zone together with casing pipes. Perforating operations with shaped-charge is the main threaten for cement sheath inner broken and boundary cementation failure and zone channeling even borehole isolation invalid. The fiber in cement can improve the strength, toughness, anti-cracking and anti-contraction of hardened cement. The compositing of fiber and cement is aimed at the improvement of the cement annuli's toughness and the zone isolation quality. A novel flexbilizing agent is designed by mixing farraginous short fibers that can greatly improve the performance of cement annulus.The optimal content of thirteen kind of fiber is confirmed by testing the flexure strength. Two kinds of high elastic modulus fiber (named KB and KH) and a kind of low elastic modulus fiber (named D) are selected which can enhance the toughness obviously. The optimized formulation is obtained by compositing those three fibers. The flexibilizer FR is composted with KB and D fiber and the optimum content is 1.6 percent by the weight of cement according to the experimental results of flexure strength, impact resistant potential and bullet shooting experiments.In order to characterize the properties of flexibilizer of oil well (named FR), the cement's mechanical performance and cement slurry's engineering performance are tested and compared with a plasticizer for oil well cement (named S). The mechanical tests approve those results: the flexibilizer FR can increase cement's toughness remarkably. This flexibilizer FR is better than S and it can improve the cement slurry's engineering performance. When flexibilizer FR is mixed with cement, it can improve the cement's flexural strength by 10.26%~24.74%, enhance the impact resistant potential by 7.39%~34.14% and decrease the compressive modulus of elasticity by 10.95%~21.62%. This fiber-reinforced cement don't produce visible crack when shooting with shaped charge. The flexibilizer FR does not have bad effect on the slurry density and flowing property of oil cement. The filter loss and bleedingrate are reduced, the rheological character is excellent, and the consistency curve appears right angle shape. The flexibilizer FR also have excellent after expansion and will compensate the cement's shrinkage. This flexibilizer FR has good compatibility with other additives for oil well cement. Especially when FR is cooperated with fluid loss agent (named J), their performance is preferable to used FR only.The microscopic appearance of flexibilizer FR in cement is observed by SEM and also the distribution and bounding of the fiber in cement. The experiment show that the fiber is well cohered with cement, the fiber reinforced cement's structure becomes compact and the fibers bridge the crack.The oil field applications of this fiber-reinforced cement are done in Jiangsu oilfield and Dagang oilfield. The cement slurry's property is checked in oil field scale. These tests show that the cement slurry with flexibilizer FR meets the technical requirement of cementing operation and these results are accord with the indoor testing. The flexibilizer FR is used simply and successfully as do not need especial technology in the course of oil field mixing and cementing operation.