DESIGN AND INITIAL FIELD-TEST RESULTS OF A NEW PULSEDNEUTRON LOGGING SYSTEM FOR CASED RESERVOIR CHARACTERIZATION

摘要

The state-of-the-art in pulsed-neutron surveillance is constantly challenged by the many and varied wellbores and formations encountered. Pulsed neutron systems are routinely applied to determine Sigma and Carbon/Oxygen saturations, reservoir porosity, though-casing density, lithology, gas-detection, and water flow. To optimize the system design given these many parameters a new pulsed-neutron system has been developed that utilizes an array of four Lanthanum Bromide (LaBr_3) detectors built into a 1.6875-inch O.D. array. Beyond exceptional peak resolution, high speed and high temperature performance, these higher density halide detectors are shown to provide incremental improvement to C/O response. Given a high-performance detector array and neutron generator, the next concern was design of high-throughput pulse processors. The pulse processors utilize a proprietary digital-filtering and pulse-height algorithm and the operational performance is demonstrated both in terms of throughput and peak resolution. Tool specific calibrations and operating parameters are stored in non-volatile memory in the tool; in this manner the system can be automatically configured. Demonstrations of measurement precision, calibration, and data quality control are shown via laboratory and fieldtests. The field-test data also demonstrates how the system operation is configured for a specific analysis mode.