The Champion field offshore Brunei (Borneo) produces oil from very unconsolidated sand formations. Laboratory measurements on cores indicated that copmaction and the subsequent subsidence could be some 2 meters, which is substantial in view of the very shallow water depth of some 10 meters. A refined prediction of compaction is required to quantify: the safety margin for offshore structures the magnitude of compaction drive vs. planned water injection projects
Radioactive bullets were shot in a production well around an isolated reservoir sand. This reservoir will be depleted in a few years time.
A logging tool containing two gamma-ray detectors was developed to measure changes in the inter-bullet distances. These changes should be indicative for compaction. Modification of Schlumberger CSU software was necessary to record gamma-ray peaks on LIS tape sampled at one-inch intervals. A special log manipulation program that integrated the gamma-ray logs was employed to determine the bullet positions with high precision.
The first two half yearly logging runs have been carried out. Preliminary results indicate that a compaction of 5 millimeters in a 7.5 meter subsurface interval at a depth of 600 meters can be measured.