Abstract: In recent years, due to the exploration and development of oil and gas continue to develop in deep formation, the number of the cementing for long sealing section and large temperature difference also increases rapidly. It was pointed out that the shortage of cementing slurry for long sealing section and large temperature difference mainly lie in:(1) The use of retarder in different temperature range leading to ultra-retarding of cement slurry and the present research do not solve the problem in essence, the amount of retarder is large and has the poor salt resistance; ( 2 ) The sharp drop in viscosity of polymer additives at high temperature causing the stability deteriorates of cement slurry; ( 3 ) The difficulties in sealing annular space using low density cement; ( 4 ) The stability of cement slurry with high density is poor under the condition of high temperature and high pressure, based on summarizing the domestic and foreign research statuses. Considering these difficulties, the technical countermeasures of cementing slurry for long sealing section and large temperature difference were proposed, including: ( 1 ) The molecular structure of retarder is designed reasonable and the low temperature sensitive retarder researched has the advantage of strong salt-resistant and add a little;(2) Explore the essence of"bulge"phenomenon caused by AMPS copolymer; ( 3 ) Select and modify the closely packed model combined with the characteristics of well cementing engineering, to improve the application performance of high density and low density cement slurry; ( 4 ) Carry out the synthesis and production of high temperature suspension stabilizer.

Key words: large temperature difference;cementing slurry challenges;key technology;technical countermeasure