In the enhanced geothermal systems wells, casing temperature variation produces casing thermal stresses, resulting in casing uplift or bucking. When the induced thermal stresses exceed casing material's yield stre...In the enhanced geothermal systems wells, casing temperature variation produces casing thermal stresses, resulting in casing uplift or bucking. When the induced thermal stresses exceed casing material's yield strength, the casing deforms and collapses. The traditional casing design standard only considers the influence of temperature variation on casing material's yield strength. Actually, for commonly used grades of steel pipe, casing's material properties-such as yield strength, coefficient of thermal expansion, and modulus of elasticity change with temperature variation. In this paper, the modified thermal stress equation is given. Examples show that the allowable temperature of the material grade N80's casing is only 164 ℃, which is much lower than that of the traditional design standard. The effective method to improve the casing pipe's allowable temperature is pre-stressed cementing technology. Pre-stressed cementing includes pre-tension stress cementing and pre-pressure stress cementing. This paper focuses on the design method of full casing pre-tension stress cementing and the ground anchor full casing string pre-tension cementing construction process.展开更多
Rolling contact fatigue（RCF）properties of SAE 8620 steel after case carburizing have been investigated under two contact stresses of 4.0and 5.5GPa.Results show that the RCF life ranges from 2.5×10^6 to 3×1...Rolling contact fatigue（RCF）properties of SAE 8620 steel after case carburizing have been investigated under two contact stresses of 4.0and 5.5GPa.Results show that the RCF life ranges from 2.5×10^6 to 3×10^7 cycles under the contact stress of 5.5GPa,while it can be more than 1×10^8 cycles under the contact stress of 4.0GPa.The rated fatigue life L_（10）（lives with the 10%failure）is also drastically shortened from 9.8×10^6 to 5.4×10^5 cycles when the contact stress is increased from 4.0to 5.5GPa.Theoretical calculations and fractographs show that the maximum shear stress and the contact area increase with increasing the contact stress,making RCF tend to occur earlier.展开更多
基金supported by the Hydrogeology Survey And Comprehensive Evaluation of Large Basin and Deep Typical Southeast Coastal Region(No.12120114025101)
文摘In the enhanced geothermal systems wells, casing temperature variation produces casing thermal stresses, resulting in casing uplift or bucking. When the induced thermal stresses exceed casing material's yield strength, the casing deforms and collapses. The traditional casing design standard only considers the influence of temperature variation on casing material's yield strength. Actually, for commonly used grades of steel pipe, casing's material properties-such as yield strength, coefficient of thermal expansion, and modulus of elasticity change with temperature variation. In this paper, the modified thermal stress equation is given. Examples show that the allowable temperature of the material grade N80's casing is only 164 ℃, which is much lower than that of the traditional design standard. The effective method to improve the casing pipe's allowable temperature is pre-stressed cementing technology. Pre-stressed cementing includes pre-tension stress cementing and pre-pressure stress cementing. This paper focuses on the design method of full casing pre-tension stress cementing and the ground anchor full casing string pre-tension cementing construction process.
基金Item Sponsored by National Natural Science Foundation for Youth of China(51301042)
文摘Rolling contact fatigue（RCF）properties of SAE 8620 steel after case carburizing have been investigated under two contact stresses of 4.0and 5.5GPa.Results show that the RCF life ranges from 2.5×10^6 to 3×10^7 cycles under the contact stress of 5.5GPa,while it can be more than 1×10^8 cycles under the contact stress of 4.0GPa.The rated fatigue life L_（10）（lives with the 10%failure）is also drastically shortened from 9.8×10^6 to 5.4×10^5 cycles when the contact stress is increased from 4.0to 5.5GPa.Theoretical calculations and fractographs show that the maximum shear stress and the contact area increase with increasing the contact stress,making RCF tend to occur earlier.
