This paper summarizes the application of high quality and high speed concentrated surface drilling technique for the first time in drilling and cementing surface interval of 14 wells in 56 hours with average time of 3.99 hr/well in phase II development of this field. The project was characterized by improvement mainly in 4 aspects: conductors were 15m shorter than normal; wellhead spacing reduced from 2m×2m to 1.5×1.8m; surface casing changed from seamless casing to erw casing; with additives; the strength of quick hardening cement reached 4.2MPa in 4 hours, 61% stronger, so the whole operation process was safe and smooth compared with that of Block J, which was the fastest then, the efficiency was improved by 55.7%, 3 hours saved each well. The success of this technique had 3 significant meanings: broke the wellhead spacing of 2m × 2m and realized the close wellhead spacing of 1.5m×1.8m successfully, so the wellhead platform dimension and project cost were; realized the quick hardening cementing of low temperature surface interval, resolved the leakage on concentrated drilling and cementing surface interval, explored the method of surface open-hole volume calculation, which laid basis for the concept of close wellheads and big platform and provided reference experience for the phase II overall development of SZ36–1 oil field. Key words: Bohai Liaodong bay, close cluster wells, concentrated drilling and cementing surface interval, high quality and high speed drilling, low temperature quick hardening cement.
SZ36–1 oil field is an oil field with oil in place of more than l00m tons in Liaodong Bay, up to now, COOBC has developed 4 platforms AI, B and J with 64 wells in development of its phase II, COOBC plans to drill 186 wells according to CNOOC's, requirements of "three news and three requirements", we put forward new offshore operation requirements and thinking in order to save offshore platform construction cost, as for drilling, we have three challenges and difficulties, short well spacing drilling, short surface conductor running, doubled wellhead platform in size facing these challenges and difficulties, COOBC has conducted a lot of technique study based on past experience and the characteristics and requirements of phase II development COOBC has also strengthen the research of drilling surface interval technology based on the innovation and probing of JZ9–3w platform.
Meaning of the challenge of phase II of SZ36–1 oil field we put forward 3 challenges for drilling operation in order to reduce engineering cost and increase efficiency in engineering design of SZ36–1 phase II.
Shorter wellhead spacing, from original 2m×2m to 1.5×1.8m, so, one well can be drilled in one row by the same rig the difficulties are evident.
Location accuracy is high with transverse error of less than 0.5m, otherwise, wellhead area can not be covered completely.
Short well spacing, easy to lose and blow in surface drilling which will bring severe influence to late phase engineering.
Short well spacing, severe requirement.
Offshore platform locating has changed from 16 wells for one time to 35 wells for two times with 6 wellhead reduced. so large platform can reduce engineering cost but cause difficulty to relative intense platform with the increase of drilling depth and deviation. The drilling difficulty is high.
Because of the concentrated well spacing, pile group effect resulting in block driving conductor piling depth reduced from 50m to 35m. According to JZ9–3 oil field's actual penetration analysis from engineering aspect, we can save 2800m conductor. But in loose surface interval, the shallower the conductor drilled, the easier the drilling fluid leaked because of the low formation strength at the conductor shoe, it is a difficult point and hard trial for drilling.
If the plan of concentrated well spacing and big platform can be realized, it is meaningful:
The number of offshore platforms can be reduced from 12 to 6 as well as engineering cost platform controlled area increased from 1.1km2 by 16 wells to 2.9 km2 by 35 wells.