Air channeling in the annulus between the casing and the cement sheath and/or between the cement sheath and formation is the main factor affecting the safe operation of natural gas wells at high temperatures and press...Air channeling in the annulus between the casing and the cement sheath and/or between the cement sheath and formation is the main factor affecting the safe operation of natural gas wells at high temperatures and pressures.Prevention of this problem requires,in general,excellent anti-channeling performances of the cement sheath.Three methods to predict such anti-channeling performances are proposed here,which use the weightless pressure of cement slurry,the permeability of cement stone and the volume expansion rate of cement sheath as input parameters.Guided by this approach,the anti-channeling performances of the cement slurry are evaluated by means of indoor experiments,and the cement slurry is optimized accordingly.The results show that the dangerous transition time of the cement slurry with optimized dosage of admixture is only 76 min,the permeability of cement stone is 0.005 md,the volume shrinkage at final setting is only 0.72%,and the anti-channeling performances are therefore maximized.The effective utilization of the optimized cement slurry in some representative wells(LD10–1-A1 and LD10–1-A2 in LD10–1 gas field)is also discussed.展开更多
Cementing carbonate reservoirs is generally a difficult task.The so-called thixotropic cement slurry has gained considerable attention in this regard as it can help tofix some notable problems.More precisely,it can ea...Cementing carbonate reservoirs is generally a difficult task.The so-called thixotropic cement slurry has gained considerable attention in this regard as it can help tofix some notable problems.More precisely,it can easilyfill the leakage layer;moreover,its gelling strength can grow rapidly when pumping stops,thereby increasing the resistance to gas channeling,effectively preventing this undesired phenomenon in many cases.High-temperature thixotropic cement slurry systems,however,are still in an early stage of development and additional research is needed to make them a viable option.In the present study,using a self-developed composite high-temperature thixotropic additive as a basis,it is shown that the compressive strength can be adjusted by tuning the proportion of silica sand,the high-temperature retarder,fluid loss additive and dispersant(compatible with the thixotropic additive).According to the tests,the developed high-temperature thixotropic cement slurry system has a 14 d compressive strength of 29.73 MPa at 150°C,and a thickening time of 330 min when the dosage of retarder is 2%.At the same time,the rheological property,water loss,permeability,water separation rate,and settlement stability of the cement slurry system meet the requirements of cementing construction.展开更多
The effect of high density pulse electric current (HDPEC) on the solidification structure of the low temperature melt(LTM) of commercial A356 alloy was investigated. In the experiments, the HDPEC was discharged in the...The effect of high density pulse electric current (HDPEC) on the solidification structure of the low temperature melt(LTM) of commercial A356 alloy was investigated. In the experiments, the HDPEC was discharged in the LTM (953?K, 903?K and 873?K). By the control experiments, the results showed that the solidification structure of the LTM of A356 alloy is refined apparently when the HDPEC is discharged in low temperature melt. However, the holding time of melt treated has an adverse effect on the solidification structure. The longer the holding time of the melt treated with HDPEC, the coarser the microstructure. With the same discharge voltage, the lower the temperature of LTM, the more obscure the refinement of solidification structure. Finally, the mechanism of microstructure refining by HDPEC was analyzed.展开更多
基金funded by the CNOOC Scientific Research Project“Study of cementing key properties and its matching technology of LD-10 gas field”(Grant No.CCL2019ZJFN1227).
文摘Air channeling in the annulus between the casing and the cement sheath and/or between the cement sheath and formation is the main factor affecting the safe operation of natural gas wells at high temperatures and pressures.Prevention of this problem requires,in general,excellent anti-channeling performances of the cement sheath.Three methods to predict such anti-channeling performances are proposed here,which use the weightless pressure of cement slurry,the permeability of cement stone and the volume expansion rate of cement sheath as input parameters.Guided by this approach,the anti-channeling performances of the cement slurry are evaluated by means of indoor experiments,and the cement slurry is optimized accordingly.The results show that the dangerous transition time of the cement slurry with optimized dosage of admixture is only 76 min,the permeability of cement stone is 0.005 md,the volume shrinkage at final setting is only 0.72%,and the anti-channeling performances are therefore maximized.The effective utilization of the optimized cement slurry in some representative wells(LD10–1-A1 and LD10–1-A2 in LD10–1 gas field)is also discussed.
基金funded by the National Natural Science Foundation of China(51974355).
文摘Cementing carbonate reservoirs is generally a difficult task.The so-called thixotropic cement slurry has gained considerable attention in this regard as it can help tofix some notable problems.More precisely,it can easilyfill the leakage layer;moreover,its gelling strength can grow rapidly when pumping stops,thereby increasing the resistance to gas channeling,effectively preventing this undesired phenomenon in many cases.High-temperature thixotropic cement slurry systems,however,are still in an early stage of development and additional research is needed to make them a viable option.In the present study,using a self-developed composite high-temperature thixotropic additive as a basis,it is shown that the compressive strength can be adjusted by tuning the proportion of silica sand,the high-temperature retarder,fluid loss additive and dispersant(compatible with the thixotropic additive).According to the tests,the developed high-temperature thixotropic cement slurry system has a 14 d compressive strength of 29.73 MPa at 150°C,and a thickening time of 330 min when the dosage of retarder is 2%.At the same time,the rheological property,water loss,permeability,water separation rate,and settlement stability of the cement slurry system meet the requirements of cementing construction.
文摘The effect of high density pulse electric current (HDPEC) on the solidification structure of the low temperature melt(LTM) of commercial A356 alloy was investigated. In the experiments, the HDPEC was discharged in the LTM (953?K, 903?K and 873?K). By the control experiments, the results showed that the solidification structure of the LTM of A356 alloy is refined apparently when the HDPEC is discharged in low temperature melt. However, the holding time of melt treated has an adverse effect on the solidification structure. The longer the holding time of the melt treated with HDPEC, the coarser the microstructure. With the same discharge voltage, the lower the temperature of LTM, the more obscure the refinement of solidification structure. Finally, the mechanism of microstructure refining by HDPEC was analyzed.
