ONGC Deepwater Drilling team has set one more record of drilling deepest ultra-deepwater well in India by successfully reaching the target depth of 7725m in well KG-DWN-2005/1-D-1 by Rig DDKG1.
ONGC sets record for drilling deepest well in India with Drillship DDKG1
Deepwater drillship DDKG1 was inducted in Deepwater exploration campaign of ONGC in July 2009 for a period of four years which ends soon after completion of current well in progress. During this period the Rig has drilled 25 wells including 20” casing sections of two deepwater wells against the plan of 24 wells. The well KG-DWN-2005/1-D-1 drilled by the rig DDKG1 has set two records – Firstly, the world record of oil well at deepest water depth of 3174m which was reported earlier and now drilling the deepest well in east coast of India for ONGC.
The achievement of drilling of world record water depth well by ONGC was published widely in world hydrocarbon industry media as well in global press reports as a demonstration of ONGC’s prowess in frontiers of offshore oil well drilling technology. This milestone stands as a symbol of ONGC’s technological capability in most challenging ultra-deep water oil field environment amongst the very few offshore operators of the world.
Well Design: There were two pressure ramps from 5500m and 7000m respectively. To design the well, both these pressure ramps were required to be addressed while maintaining adequate kick tolerance while drilling. This was successfully done with setting of 20” casing deeper (970m long at 4165m) and incorporation of 16” liner (4807m) in 17 ½” phase, thus deepening the setting depth of 13 3/8”casing at 6807m.
The inclusion of 16”liner required to under ream two hole sections, 17 ½” x 20” and 14 ¾” x 17 ½”. Smith Rhino under reaming service were utilized successfully to under ream both the sections. A close monitoring of well in terms of jetting conductor at record water depth in very unconsolidated formation due to long water column above it. Also, a long 20”casing string was run in a record water depth while working out correct mud weight and rheological properties of drilling fluid throughout in all the drilling phases, successful cementation of all casings for good well integrity and appropriate bit selections were the crucial features for such an ultra deepwater and deepest well to be completed successfully in record time.
Flat rheology SOBM was also a test case in this well. It was for the first time that flat rheology mud system was used to maintain ECD within limits of operability, effectively in this water depth. Maintenance of largest circulating volume of mud in an oil well ever and anywhere in the world was a challenge which was met to its fullest extent. Challenges related HSE and logistics issues in feeding the rig with supplies of well materials and chemicals etc. were also effectively met to achieve this feat in record time.
The well was drilled to target depth of 7725m in 67 days with maximum mud weight of 11.7ppg without any complication.