Casing Program Optimization and Application in Complex Formation of the YD Oilfield

In the YD Oilfield, the complex geologic environment, coexistence of multiple pressure systems and high pressure asphalt formation that easy overflow or lost circulation have been the challenge to drilling and optimization of casing program. By analyzing drilling data, determing the setting depth of casing, reviewing pore pressure of Gachsaran Formation, together with the bottom-up designing method, three exclusive casing programs for drilling complex formations in the YD Oilfield were determined.Due to abnormal high pressure existed in parts of Gachsaran salt water formation, a special casing program was developed for dealing with it. But for the normal-pressure Gachsaran Formation, a simplified and efficient casing program was also developed to improve ROP and lower the drilling cost.As for the high-pressure Kazhdumi asphalt formation, two casing programs were developed with prolonged 244.5 mm intermediate casing for special drilling and isolating Kazhdumi Formation. The optimized casing programs were satisfactorily applied in more than 20 development wells in the YD Oilfield. The casing program for high-pressure salt water formation achieved safe drilling in some Gachsaran Formation. The conventional casing program highly enhanced the ROP and shortened the drilling cycle. The casing programs for the asphalt formation fully ensured the drilling safety in high-pressure asphalt formation. These optimized casing programs have laid a good foundation for Phase Ⅱ development of the YD Oilfield, and will provide the reference for similar carbonate reservoir development at home and abroad.