Research On Design And Application Of Cement Slurries In Jilin Deep Natural Gas Field With High Carbon Dioxide Content

In recent years, the exploration and development for Jilin Oilfield mainly focus on thedeep oil and gas resources, and good oil and gas resources were found in the oil and gas wellshaving been drilled. However, downhole conditions become more and more complex with theincrease of well depth, especially part of deep natural gas fields with high carbon dioxide,which brings new challenges to cementing. Carbon dioxide severely corrodes productionstring and cemented rock, which reduces the service life of gas wells. In order to solve theabove problems and improve the cementing quality of Jilin deep gas fields with high carbondioxide, it is imperative that developing a cement slurry system can be applied for Jilin deepgas fields to prevent the carbon dioxide corrosion.Given the existing prominent problems of cement jobs in Jilin deep gas fields with highcarbon dioxide, based on the findings of carbon-dioxide corrosion resistance cement slurriesat home and abroad, this paper determined the evaluation methods of carbon-dioxidecorrosion cement sheath and design principles of carbon-dioxide corrosion resistance cementslurries by studying the carbon-dioxide corrosion mechanism to cement slurry, and completedthe design of Portland and phosphate cement slurries. Also, the results showed the goodability to resist the carbon-dioxide corrosion after Portland carbon-dioxide corrosionresistance cement slurries were applied for the cement jobs of two test wells.(1) Design of Portland corrosion resistance cement slurriesBy observing the corrosion resistance of conventional anti-channeling cement slurriesand different materials within360days at a temperature of95℃and a carbon-dioxide partialpressure of2MPa, this study determined the basic materials used to develop the carbon-dioxide corrosion resistance cement slurries for Jilin deep gas fields with high carbon dioxide,and screened the anti-corrosion admixture F11F to meet the high-temperature and deep-wellcementing demands of Changling gas field with high carbon dioxide. Investigating thecorrosion resistance performance and cemented rock microstructure of F11F within28days ata temperature of150℃and a carbon-dioxide partial pressure of2MPa was to determine otherhigh-temperature oil well cement additives with matching the F11F, and form the Portlandcarbon-dioxide corrosion resistance cement slurries which take F11F admixture as the core.(2) Design of phosphate corrosion resistance cement slurriesThis paper developed the phosphate cement by analyzing the preparation, hydration mechanism, carbon-dioxide corrosion resistance, etc of magnesium phosphate cement andcalcium phosphate cement. Through the analysis of the cemented rock microstructure andphosphate cement hydration products, combined with phosphate hydration characteristics andsurface properties, the matching retarder and fluid loss agent were developed. Testingphosphate cement rheological properties, anti-channeling performance, overall performanceand the compatibility with phosphate cement indicated a good corrosion resistance ability tocarbon dioxide.Portland cement slurries which take F11F admixture as the core have applied forcementing tests on two wells of Jilin deep gas fields-Changling fault central Herjin upliftstructure with high carbon dioxide in2009, and completed the cementing task successfully. Sofar, these test wells have worked more than3years, and there are no abnormal conditions ofcarbon-dioxide corrosion. These indicate that the new cement slurries which take F11Fadmixture as the core can effectively restrain the carbon dioxide corrosion and meet thedesign requirements.