COMPARISON OF MULTI-DETECTOR PULSED NEUTRON, NUCLEAR ATTRIBUTES OF MULTIPLE VENDORS IN PRUDHOE BAY ALASKA.

摘要

Various recovery mechanisms such as gravity drainage, water flooding and miscible injection have historically been implemented in the Prudhoe Bay Field, Alaska, which have changed the initial fluid distribution over most of the reservoir interval. In these areas of altered fluid saturations, the importance of accurately quantifying multicomponent fluid saturations is critical in planning well work activity and maximizing production and recovery. Early in field life, the quantitative approach to determining fluid saturations relied on vintage chemical neutron logging tools, which were later replaced by pulsed neutron technology. The increased complexity in fluids redistribution (more than three fluids) required a different approach for quantitative evaluations. The solution came through development of Multidetector Pulsed Neutron (MDPN) technologies, by broadening the range and sensitivity of nuclear attributes used to discriminate various fluids present in the reservoir. Recently, the MDPN technology diversified with more instruments being developed and field tested. While all share the same physics principle, the responses can vary due to instrumentation design, characterization and nuclear attributes extraction in the field. We field tested and evaluated the MDPN technologies of three developers. The selection of a fit for purpose MDPN technology is a multi- variable decision that takes into account the tool accuracy, repeatability, and sensitivity of various nuclear attributes for a specific recovery mechanism. In the current low oil price environment, it is very important to understand, discretize, and quantify each of these attributes in order to incorporate them in a value of information exercise, and then select the best value option that accurately characterizes the fluid saturation and distribution in the reservoir. This paper will describe in detail the results of field trials of three MDPN instruments in the Prudhoe Bay Field, on the North Slope of Alaska. A comprehensive comparison of raw data (including statistics and coherence analysis) and multi-vendor interpretations will be discussed along with inhouse results benchmarked to detail rock and fluid description, as well as production history and well work results.