New Zealand Gas Development Sets New Performance and Environmental Milestones Onshore and Offshore - The Role of Drilling Fluid Selection and Performance in the Pohokura Development

摘要

The Pohokura Gas Field lies off the West Coast of New Zealand in the Taranaki Basin. To develop this field, a total of nine wells were drilled, from both onshore and offshore locations. The extended-reach wells drilled from land set new records for New Zealand, drilling to a measured depth of 7,409 m (24,309 ft) on POW 03, the longest well. The five wells drilled from the offshore drilling unit featured tortuous well paths through the reactive and dispersive shales of the Taranaki Basin. The Pohokura reservoir sands are low-porosity "tight" sandstones, notoriously susceptible to fluid-related production impairment. In addition to these challenges, the onshore and offshore environmental regulations applied both by the local regulator and self-imposed by the operator are among the most strict in Asia. The fluids-specific challenges associated with this project included the design of a synthetic-based fluid and cuttings handling system that could maintain the fluid-on- cuttings discharge at the lowest practicable level, design of a highly inhibitive and lubricious water-based drilling fluid for the offshore drilling campaign, plus the development and testing of non-damaging drilling fluids for the reservoir sections of all wells. To achieve these goals, extensive laboratory testing and comprehensive reviews of field experience from other operations were undertaken. Key Performance Indicators were agreed between the operator and fluids provider. These benchmarks were reviewed on a well-by-well basis and used to facilitate ongoing continuous performance improvement.