Research On Low Density Cementing Slurry System In Longdong Block Of Changqing Oilfield

Longdong Block of Changqing Oilfield is located in the Loess Plateau and the Ordos Basin.It belongs to the Yishan slope structure,with an average elevation of 1140m?1400m and a relative elevation difference of about 260m.The formation in this block is undercompacted,with low bearing capacity,large porosity and high permeability in the upper strata,and differential pressure leakage is easy to occur during well cementing.In view of the formation characteristics,reservoir characteristics,cementing difficulties and requirements of Longdong block in Changqing oilfield,this paper analyzes the formation characteristics,pressure prediction and other factors,and carries out the research on the low density cementing slurry system suitable for Longdong area in Changqing oilfield through the comprehensive study on the well loss and other difficulties.Through the research and application of the cement slurry system,the pressure of annular fluid column can be effectively reduced to prevent the loss of cement slurry,reduce reservoir pollution and effectively reduce the cost.After a lot of investigation and research,combined with literature and cementing construction data,this paper introduces the development of low density cement slurry system at home and abroad,and analyzes the characteristics of leaky formation in Longdong block.Glass beads Y6000,strengthening material GQ-A,early strength agent GJ-A,supporting admixture GJ-S and disdistant USZ were selected to form A low density cement slurry system with A density of 1.15?1.20 g/cm^3,and A low density cement slurry system with good mobility and high strength.And carried on the field practical application.Through construction application,it is found that the cement slurry system studied can effectively improve the phenomenon of cementing loss in Longdong block.The application of the research results is of great significance for improving the bearing capacity of the formation,ensuring the quality of cementing and protecting the development of oil and gas reservoirs in Longdong area.