Research On High Temperature And High Pressure Cementing Slurry System For Preventing Gas Channeling

With the rapid development of deep and ultra-deep natural gas exploration and exploitation,a new challenge is posed to the anti-gas-channeling ability of high temperature and high pressure cementing slurry while enjoying the industrial oil flow.Therefore,from the perspective of the cement slurry system,effective technical measures to improve the active anti-gas channeling ability of cement slurry should be proposed according to the high temperature and high pressure cementing conditions at the current stage.Through a lot of theoretical analysis and experimental research,on the basis of the existing evaluation method of the anti-high temperature and anti-gas-channeling ability of the oil well cement slurry,this paper innovatively proposes the evaluation method of high-temperature ability of molecular weight viscosity resistance of liquid polymer admixture and the key performance index of anti-gas-channeling ability of two cement grouts before initial setting and during static gelation strength transition time which are suitable for high temperature and harsh cementing conditions and used to evaluate the effects of different admixtures on the high temperature resistance and anti-gas-channeling ability of the cement slurry system.The composition and proportion of the cement slurry system are optimized to significantly improve the high temperature resistance and anti-gas-channeling ability of the cement slurry.A high temperature and high pressure cementing anti-gas-channeling cement slurry system is developed and successfully applied on site.The valuable reference and reference are provided for the design,formulation optimization and key performance control of deep-well and ultra-deep well cementing anti-gas-channeling cement slurry system at home and abroad.The main understandings and conclusions formed in the study are as follows:(1)The molecular weight viscosity measurement method can effectively evaluate the temperature resistance of the organic polymer liquid phase admixture and improve its screening efficiency.The selected high temperature fluid loss agent J1 and high temperature retarder H3 have good resistance to high temperature of 150?180?,and also make cement slurry featured by small water loss,right angle thickening and linear adjustment of thickening time.(2)Based on the displacement and free sedimentation process of cement slurry under the well,the established high temperature and high pressure settlement stability test method is efficient and reliable.Through experiments,it is found that:High temperature fluid loss agent J1,micro silicon,liquid silicon and nano SiO2 can significantly improve the high temperature settlement instability of 1.90?2.30g/cm3 cement slurry,and improve the ability of cement slurry to withstand high temperature of 150?180?.(3)Fine silica sand makes the early strength of cement stone better,and coarse silica sand makes the long-term strength of cement stone increase more;combined with the rheological properties of cement slurry,the minimum addition amount of silica sand and the optimal experimental collocation ratio of coarse and fine sand are obtained under the temperature of 150?180?.On this basis,the expansion agent B1,latex,micro-silicon,liquid silicon,nano-SiO2 and their complex formulation can further improve the high-temperature compressive strength of the cement stone.(4)Before initial setting of the cement slurry,the internal pore permeability characteristics are good with mostly free water,which is a dangerous time for cement slurry gas.The transportation mechanism in cement slurry of underground natural gas in the"supercritical fluid" state mainly includes:The seepage mode of the displacement transport and the migration mode that destroys the internal structure of the cement slurry.The permeability before initial setting should be reduced and the static gelling strength transition time should be shortened by cementing cement slurry to improve the ability of cement slurry to prevent migration of high temperature and high pressure fluids.Through experiments,it is found that:the high temperature drop loss agent J1 can effectively reduce the permeability of the cement slurry before initial setting,but also prolong the static gelling strength transition time;different anti-caries agents have different ability and the action period to improve the anti-gas-channeling of the cement slurry,so the complex formulation has better effect.For example,the compounding formulation of silicone anti-caries agent and expansion agent B1 or the compounding formulation of silicone anti-caries agent,expansion agent B1 and latex can significantly improve the ability of cement slurry to prevent migration of high temperature and high pressure fluids.(5)The high temperature and high pressure cementing anti-gas-channeling slurry system is designed and formed with good field application according to the effective technical measures for high temperature resistance and anti-gas-channeling of cement slurry in the research.