X-RAY INSTRUMENT FOR FORMATION BULK DENSITY DETERMINATIONS IN MEASUREMENT-WHILE-DRILLING APPLICATIONS

THE MEASUREMENT OF BULK DENSITY AS A FUNCTION OF POSITION IN BOREHOLES IS OF MAJOR IMPORTANCE FOR DETERMINING THE CHARACTERISTICS OF GEOLOGICAL FORMATIONS. THE BEST APPROACH FOR MEASURING BULK DENSITY INVOLVES THE SCATTERING OF HIGH ENERGY PHOTONS IN THE FORMATION BY COMPTON PROCESSES. HOWEVER, ONLY RADIOACTIVE GAMMA-RAY SOURCES ARE CURRENTLY AVAILABLE FOR USE IN BOTH MEASUREMENT-WHILE-DRILLING (MWD) AND WIRELINE DENSITY INSTRUMENTS. THESE INVOLVE SUBSTANTIAL CONCERNS WITH SAFETY AND ENVIRONMENTAL CONTAMINATION. RESEARCHERS ARE DEVELOPING AN X-RAY SOURCE, TERMED THE DOUBLE-ENDED X-RAY TUBE (DXT), FOR MWD APPLICATIONS. THIS NOVEL, COMPACT SOURCE IS EXPECTED TO OFFER ABSOLUTE SAFETY AND IMPROVED MEASUREMENT ACCURACY IN THE HIGHLY STRESSING MWD ENVIRONMENT. THE OVERALL OBJECTIVE IS TO DEMONSTRATE THE TECHNICAL FEASIBILITY OF THE DXT CONCEPT. THIS WILL BE ACCOMPLISHED BY PERFORMING THREE TASKS: (1) DESIGN AND ASSEMBLE A DXT EXPERIMENT FOR OPERATION AT HIGH VOLTAGE; (2) PERFORM TESTS TO EVALUATE AND DEMONSTRATE THE DXT OPERATING CHARACTERISTICS WITH THE GOAL OF ACHIEVING AN X-RAY OUTPUT OF >40 MRADS/MIN. AT A DISTANCE OF 1 METER; AND (3) DEVELOP THE CONCEPTUAL DESIGN FOR A LOW-COST DXT SYSTEM FOR MWD APPLICATIONS.