OIL-FIELD RESERVOIR CHARACTERIZATION WITH ORDER-OF-MAGNITUDE DYNAMIC RANGE IMPROVEMENT IN TRACER DETECTABILITY

THE USE OF TRACERS TO TAG WELL GAS WHICH IS REINJECTED INTO OIL RESERVOIRS HAS ACHIEVED CONSIDERABLE SUCCESS IN CHARACTERIZING THE STRUCTURE AND GEOMETRY OF THE RESERVOIRS. IDEALLY, THE TRACER SHOULD BE DETECTABLE OVER A WIDE DYNAMIC RANGE, PARTICULARLY IN FIELDS WHERE LARGE VOLUMES OF GAS ARE INJECTED. THE OBJECTIVE OF THE PROPOSED RESEARCH IS TO DEMONSTRATE ORDERS-OF-MAGNITUDE INCREASE IN DYNAMIC RANGE IN THE MEASUREMENT OF (85)KR, A MAN-MADE RADIOISOTOPE WHICH IS IDEALLY SUITED FOR TRACER APPLICATIONS. ATOM SCIENCES HAS DEVELOPED A DIRECT-COUNTING METHOD FOR (85)KR WHICH COMBINES ULTRASENSITIVE RESONANT IONIZATION DETECTION WITH MULTIPLE STAGES OF ISOTOPE ENRICHMENT TO ACHIEVE A DETECTIONDYNAMIC RANGE WHICH CAN EXCEED 10(12). THE SENSITIVITY AND DYNAMIC RANGE OF THE (85)KR TECHNIQUE WILL BE DEMONSTRATED ON UNTAGGED NATURAL GAS SAMPLES COLLECTED FROM A PRODUCING OIL FIELD. THE METHODOLOGY FOR EXTRACTING KRYPTON FROM THE SAMPLES - COMBUSTION OF HYDROCARBONS, GETTERING OF REACTIVE GASES, AND SEPARATION OF AR AND KR - WILL BE OPTIMIZED. THE CONCENTRATION OF KR IN THE WELL GAS WILL BE MEASURED IN ORDER TO DETERMINE THE AMOUNT OF ISOTOPE ENRICHMENT REQUIRED. PROCESSED SAMPLES WILL BE ANALYZED TO DETERMINE THE DYNAMIC RANGE AND DETECTION LIMITS FOR (85)KR MEASUREMENTS. FINALLY, WE WILL SPECIFY THE PERFORMANCE REQUIREMENTS FOR A (85)KR COUNTING FACILITY OPTIMIZED FROM OIL-FIELD CHARACTERIZATION.