Research On Physical Properties Of Oil Well Cement Stone Reinforced By Inorganic Mineral Fibres

The cement-based materials were used in deep and complex condition well that the self-performance development had been constrainted severely and could not fit the oil and gas well cementing engeering development as a representative brittleness material and numerous flaws.The inorganic mineral fibres had become an leading edge and hotspot in the matrial reaserch for their natural compatibility,excellent mechanical property,lower cost and environmental personalities as new kinds of fiber materials,.Using these new type of fibres in thoughing the cement paste for developing the cement sheath integrity and sealing that was important to impulse the cementing material development and guarantee the oil and gas well long-term security.The mechanical performance and strengthening mechanism of inorganic mineral fibres using in oil cement paste had been reaserched and explored in this paper,the main work and results showed as:1.Calcium carbonate whiskers,brucite fibers and basalt fibres could improve the compress strength,flexure strength,split tensile strength and the tension-compression ratio of the oil well cement pastes significantly.Howerer the improvement was extraordinary different with the fibre dosage and sprcies in the cement pastes.The compress strength and split tensile strength of hybrid fibers reinforced cement pastes could be increased remarkably whereas the flexure strength of the cement pastes were different way.Based on the experimental data,the ternary hybrid fibres reinforcement of the cement pastes was not as well as the binary hybrid and with single fibre that could be the negative hybrid effect.To evaluate and analyse the cement sheath,the elastic and plastic deformability,preventing the fracture development stress-strain relationship and etc were more siglificant than the mechanical strength and the traditional mechanics theory could not fit the problem to explain the increasing performance of the fibre reinforced cement paste.2.The uniaxial compression process of the inorganic mineral fibre reinforced cement pastes could be well descrbed by the stress-strain curves.In this paper the constitutive relation of cement pastes with different fibres were proposed in different mathematical expression as below:As the stress-strain constitutive equations of the fibre reinforced cement pastes,the inflexibility of the cement pastes were severely influenced by the fibres' inflexibility and the inorganic mineral fibre with higher inflexibility could impove the inflexibility of the cement pastes significantly.The descending stage of the cuve of the cement pastes with the brucite fibre was influenced most remarkable as the certain range of b1 parameter of the stress-strain curve were maximum.Meanwhile the descending stage of the cement pastes with different fibres was controlled by the species of the reinforced fibres.The constitutive relation of cement pastes could fit the hybrid fibres reinforced cement pastes mechanical analysis as well and could be the reference frame for the engineering project.3.The dosage of the the inorganic mineral fibres could fit the mathematical fitting relationships with the peak stress and elasticity modulus of the fibre reinforced cement pastes,meanwhile could not fit the peak strain well.Both inorganic mineral fibres' characteristics and hybrid effect could be exhibited in the stress-strain curve of binary hybrid reinforced cement pastes.The stress-strain curve of the ternary hybrid fibres reinforcement of the cement pastes were complex and exhibited negative hybrid effect.The different stage of toughing improvement of inorganic mineral fibres reinforced cement pastes could be analysed by compressive toughness index and coefficient of bearing caoacity and that also certified the toughing performace of cement pastes were improved by inorganic mineral fibres.4.The result of fracture toughness property experiment showed that the double-K parameter model,G-function and J-function could analyze and evaluate the toughing of the inorganic mineral fibres reinforced cement pastes well.In a certain range,the brucite fibers and basalt fibres could improve the unstable fracture toughness and initial fracture toughness of the cement pastes well.The KIC and fracture energy of the cement pastes could be further promoted by the binary hybrid fibres howerver theternary hybrid fibres had happened to negative hybrid effect.In conclusion,that was suggested to be cautious to use the ternary hybrid inorganic mineral fibres in this paper.The relationship between KIC and splitting tensile strength of the inorganic mineral fibres reinforced cement pastes could fit the binary equation as Klc s = ? + ?ftenc + ?ftenc 2,it would means that the splitting tensile strength of the inorganic mineral fibres reinforced cement pastes could be a reference data to judge the the anti-cracking ability under certain conditions.5.The interface layer physical model of the calcium carbonate whisker reinforcement of the cement pastes were established and calculated in this paper.That explained the calcium carbonate whisker could form a water film when it was mixed with the cement slurry and developed an interface layer between the calcium carbonate whisker and the cement matrix.That could condence the weaken zone of the interface layer,increase the tensile strength of the cement pastes and stimulate the hydration reaction.The brucite fibers could be dispersed as filamentous with homogeneous distribution in the cement pastes and develop the compactness and anti-cracking ability of the cement pastes.At a high dosage,the brucite fibers could not disperse well and aggregate together as filling effect.With a high L/D ratio and size the basalt fibers could reinforce the cementing action with matix as ribs distributing in the cement pastes that could decrease the quantity and scale of the cracks and improve the strength of the cement pastes and consume the fracture energy.The hybrid fiber could reinforce the cement pastes in different destruction stage with different characteristics,fiber size and L/D ratio.6.The KIC and peak of uniaxial compression strength of hybrid fiber reinforced cement pastes could be quantitative analyzied by the strengthening coefficient and hybrid effect coefficient.The hybrid fiber reinforced cement pastes showed the hybrid effect remarkable with positive hybrid effect and negative hybrid effect.The peak of uniaxial compression strength of hybrid fiber reinforced cement pastes exited the positive hybrid effect and the KIC of hybrid fiber reinforced cement pastes exited the negative hybrid effect and the hybrid effect of the ternary hybrid fibres reinfocement were decreased comparing with the binary hybrid fibres reinforcement that illustrated the binary hybrid fibres could be mutual interfered each other.The fracture energy,peak strength and peak strength could be the judge basis of the cement paste toughing by synthesis analysis and optimal proportion of hybrid fibers were SM5%+XW0.3%.