Integrated Geophysical, Geological and Geotechnical Assessment of Surface and Subsurface Hazards for Drilling and Facilities Installation in the Swamp and Offshore Niger Delta

Abstract

Assessment of drilling hazards has traditionally been limited to pressure prediction and surface facility surveys. However, the current regulatory processes have imposed additional safeguards which mandate a detailed shallow subsurface drilling hazard assessment for all hydrocarbon wells and facilities installations in all environments. This work analyzed surface and shallow subsurface hazards for drilling and facilities installations in some Niger delta Fields and conducted a subsurface drilling hazard assessment (SSDHA) of new drill opportunities using available 3D seismic data, offset well data, and offset well drilling and production incident records. The work also included pore and fracture pressure predictions at the proposed wells using available pore and fracture pressure cubes, consistent with MDT/RFT hydrostatic pressure and LoT data from existing wells. Maps of the mudline, base of fresh water, base of regional shale, associated faults, and resulting isopach of the regional shale interval were generated to derisk the area of any potential hazards to rig approach, installations and establish controls to mitigate potential incidents. Then amplitude attributes within the shallow intervals were extracted to establish potential for accumulation of shallow hydrocarbon and incorporated to establish the SSDHA. Finally, existing offset well drilling reports in the vicinity of the planned wells and offset well production history data were reviewed to assess drilling and post production indicators of Loss of Containment (LoC). All analysis and interpretation were then integrated and rolled into a strategy for the assessment of subsurface drilling hazards in future wells to be drilled in the Niger Delta Swamp and shallow offshore fields consistent with new G&G Ops processes and standards.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015