ABSTRACT: Locating Remaining Reserves using Inside Tubing PNS Logging

Chima, Njoku , Brunei Shell Petroleum, Seria, Brunei

Most BSP reservoirs are structurally complex with a history of commingled production. Thus prediction of present fluid contacts from simulation models is difficult. In other to reduce/eliminate the cost of dry in-fill wells or re-completion activities, it is important to use cost-effective methods to locate by-passed or remaining reserves prior to such activities. One of such methods successfully employed in BSP is Inside Tubing Pulsed Neutron Spectrometry (IT-PNS) logging.

IT-PNS service is a technique of logging a PNS tool from inside the tubing string with the well closed in to production. Data from over 20 BSP wells, covering single and dual string completions, show that this technique can be used to distinguish the present formation fluid type, even in low permeability, fresh water reservoirs. It was also observed that there is no constraint in terms of the (casing-tubing) annular fluid type.

The technique is being used to reduce uncertainty in the present fluid distribution, thereby reducing our workover cost and optimising our recovery factor. New activities have been identified in short notice while uneconomic activities have been dropped off the rig sequence, resulting in enormous cost savings.

This technique shows that:

(i) Qualitative interpretation of formation fluid type can be done using IT-PNS.

(ii) There is no need to use a rig for fluid type logging.

(iii) The annular fluid type will not affect the final interpretation.

(iv) Three to four inelastic passes are adequate for interpretation of liquid phase.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia