THE ROLE OF FORMATION PRESSURE MEASUREMENTS AND SAMPLES IN UNDERSTANDING THE POTENTIAL OF DEEP WATER DISCOVERIES IN OFFSHORE ANGOLA

摘要

Exploration wells in the deep water, turbiditic sands in offshore Angola have discovered a number of significant reservoirs. The data acquisition strategy makes extensive use of formation pressure measurements and samples which are critical to the understanding of a reservoir's economic potential. The high permeability sands provide data of the highest quality and confidence. To date, over nine hundred pressure measurements and over two hundred samples have been acquired. The confidence in the measured pressure gradients and the quality of the samples is very high. The observed subtle changes in pressure gradient demonstrate variations in fluid properties which are confirmed by subsequent PVT analysis of the recovered samples. The paper discusses the application of recent technical advances in formation test methods and instrumentation. A number of operational procedures, developed specifically for the acquisition of high quality data in high permeability environments are also presented. The paper concludes that, in these well defined turbiditic sands, the information obtained from formation testing is sufficient in some cases to preclude well testing and, furthermore, provides information that cannot be obtained by other means. The case is made that the use of the instruments has achieved results which cannot be obtained from other means such as well testing. The ability to take both pressures and samples at multiple depths throughout the reservoirs has produced a detailed understanding of critical economic factors.