AN ATTEMPT TO OPTIMIZE CASING PROGRAM DURING THE LATER DEVELOPMENT PERIOD IN BURIED HILL RESERVOIR OF RENQIU

The thorough changes took place in buried hill reservoir of Renqiu during the later development period. This paper discussed the assumption to change the previous bit program of ?444. 5× 241. 3mm and casing program of ?339. 7×177. 8mm into the bit pro gram of ?444. 5× 216mm and the casing program of ?339. 7×139. 7mm. It was performed in 6 wells in 1997. Compared to previous project in vertical sections of 3 wells, the average penetration rate increased 3. 18m/h, the average drilling cycle reduced 10d, the average wellconstruction period reduced 12. 5d. In the buried hill well section with bad drillability, small diameter three roller bit made by Hudges and Reed co. of America was used, compared to abrasive bits, 4. 6 pieces bit were saved in each well, the drilling cycle reduced 12. 07d, the penetration rate increased 6m/h(6. 1 times), the bit cost reduced 2816yuan/m and the periodic cost reduced 12950yuan/m. In 6 executive wells, 252. 1t casing were saved with a value of 2092- 4 thousand yuan. Economic and social benefits were also obtained in terms of drilling fluid and environmental protection.