Publications

Massive lost returns combined with formation over pressuring create a significant and dangerous drilling problem. Conventional means of controlling the well by maintaining a hydrostatic pressure greater than the formation pressure through circulation down the drill pipe and returning up the annulus becomes impossible. Alternate means of controlling the well and safely drilling ahead must be used. In an offshore exploration well where limited pre-planning for such an occurence can be done, the logical way of approaching the problem is drilling with a floating mud cap.Utilising a floating mud cap in itself is both a large operational and logistical problem, especially in a remote location. Solving these problems requires good planning, close supervision, and co-operation and co-ordination with the various service companies.Hartogen Energy Philippines Limited and its group of partners while drilling Sentry Bank Reef No. 1 and 1A wells encountered a highly over pressured mid-miocene pinnacle reef at 4078 ft with an overall thickness of 1450 ft. Full penetration and evaluation of this reef requires the use of a floating mud cap.This paper discusses the logistical, operational, and technical problems encountered including well control, optimising mud composition and usage, and formation evaluation. Logistically, the location of the well was remote from all accessible supplies of mud materials. large reserve stocks and continued supply of barite was essential, with up to 2000 barrels of 13.2 ppg mud being used every day during the drilling and well evaluation.