ONGC has become the first E&P company in India to execute Under Balance Drilling. Drilling Services, Mumbai region has implemented Under-Balanced Drilling (UBD) pilot project in the Heera and Mumbai High fields. The objectives are:
Zero damage to formation and thereby enhancing oil production from the wells.
Reduction of NPT due to mud losses
Reservoir assessment while drilling.
Improve well placement in the reservoir section by real time analysis
In line with above objectives, drilling was initiated using base oil which was replaced by produced fluid as the drilling proceeded. Average ECD of 4.1 MWE was achieved during drilling of first well and which was further reduced to 3.9 MWE in second well. Lower completion was run and packer was set in flowing conditions in both wells.
Project Planning: Designing under balanced drilling process in which produced fluid was to be stored and circulated for drilling that also on an offshore rig was a colossal task. Each project activity was planned and executed with exhaustive deliberations. With full support from each of the many stake holders, project was designed and built to the execution stage.
A Hazard Identification (HAZID) analysis for identification of Hazards was carried out through independent facilitator and all the observations of the HAZID were closed. Subsequently during Hazard Operability (HAZOP) analysis, Process Flow Diagrams (PFD), Process & Instrumentation Diagrams (P&ID), Valve Numbering Diagrams (VND) and detailed procedures has been discussed and finalized. Further, OISD has given its consent for the UBD project. Detailed Drilling Well On Paper (DWOP) has been deliberated and drafted for the execution of UB drilling phase.
Drilling up to landing point in three wells of HK has been completed by 17th March 2016. UBD equipment rig up was started on 6th March 2016 while rig was preparing the wells for UBD. After initial teething during commissioning, Under Balance Drilling phase in first well HK#2H was started on 6thApril 2016. Drilling was initiated with 100 psi of under balance by injecting Nitrogen in concentric annulus of 9-5/8” x 7” tie back casing while pumping base oil as drilling fluid.