Research And Performance Evaluation Of Low Water Loss And Low Density Cement Slurry System

Due to the continuous development and improvement of low-density cement slurry technology,it is more and more widely used in the cementing construction of complex oil and gas reservoirs such as low pressure,low permeability,easy to leak and long sealing section.However,the existing low-density cement slurry system still has many shortcomings.The performance of lightening materials and additives is still insufficient and it can not meet its application in many projects.In recent years,with the in-depth study of polymer materials,polymer materials with different properties emerge in an endless stream.Thermosetting resin composites with light weight,high hardness,corrosion resistance and wide sources of materials have become the research hotspot of lightening materials.Nanomaterials have unique physical and chemical properties.In recent years,nanomaterials have been widely used in cementing.In this paper,the bisphenol A epoxy resin was used as matrix to prepare epoxy resin hollow microspheres by W/O/W double emulsion method,and nano-Si O₂ was connected with silane coupling agent to prepare epoxy hollow/nano-Si O₂ composite mitigation materials.It has a good hollow structure.The particle size distribution is concentrated in 14.8?40.7?m.It has good thermal stability,low crushing rate,and good shear resistance.The basic performance of cement slurry prepared with it as lightening material is good,water loss is about 50m L,and the compressive strength is high,up to 10.5MPa.In order to further reduce the water loss of low-density cement slurry and significantly improve the compressive strength of cement stone,polymer/nano-Si O₂ fluid loss reducer was prepared by surface modification and grafting of nano-Si O₂ modified by vinyltriethoxysilane,sodium styrene sulfonate,N,N-dimethyl-2-acrylamide,itaconic acid and octadecyl dimethyl allyl ammonium chloride.The structure characterization results show that the synthesized polymer/nano-Si O₂ fluid loss additive is the expected target product.The polymer/nano-Si O₂fluid loss additive has good filtration control effect,and can control the water loss below50m L,high temperature resistance at 250?and compressive strength up to 16.2MPa.The mechanism of polymer/nano-Si O₂ fluid loss additive is mainly through plugging,bridging,adsorption and other functions to fill the pores of cement filter cake,making the filter cake structure more compact,so as to achieve the purpose of water loss reduction.The nano-Si O₂has a certain pozzolanic effect,which can plug the pores of the cement filter cake,promote the hydration of the cement,react with CH twice,and accelerate the development of the mechanical properties of the cement stone.The low-density cement slurry was prepared with epoxy hollow/nano-Si O₂ lightening material and polymer/Nano-Si O₂ fluid loss reducer.The cement slurry system with density of1.30?1.50g/cm³ was designed by adjusting the proportion of admixture.Through the evaluation of water loss,compressive strength and initial and final setting of cement slurry system and the microstructure analysis of cement stone,it shows that the designed low density cement slurry has good basic properties,the water loss is less than 50m L,and high compressive strength,which is 13.3?16.9MPa for 48h.