Abstract

Hundreds of horizontal and deviated cluster wells will be drilled in Halfaya oil field. Placing a nearly 3900 meter long and slim column of cement slurry along 7" production casing/liner in 8 1/2" hole proves to be a great challenge operation done on these wells. The long cement isolation interval translates into large temperature differences between the bottom hole and the top of cement with high circulating pressure during cementing job. In this case, the temperature difference can reach to 60∼70°C and Max. Inclination range is nearly 90 degree. On the other hand, the complicated geological conditions such as: abnormally high pressure (Max. PFP: 2.15g/cm3) with gypsum/salt zones, potential fractured losses and the presence of H2S, CO2 and high salinity aquifer etc. have also brought great difficulties for cementing. So, all these factors results in poor cementing quality in existing wells. This paper focuses on how we developed a new and high performance cement formulation and supporting technologies to effectively solve the cementing difficulties in this oilfield. The new developed cement slurry with density range from 1.30g/cm3 to 1.90g/cm3 has gotten high performance like leak resistance, good rheology ability and especially has good early strength development at the top of cement column. This technology can ensure the cement sets uniformly along the long column and ensure proper zonal isolation. Up to now, 12 wells cementing job have been conducted successfully, 95% of the CBL/VDL well logs show excellent cementing bonding quality. This paper discuss the details of a properly designed cement system and cementing operation and show field implementation result as kind of reference to the future similar cementing cases.

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