Development Of A New Full-spectrum Litho-density Logging Tool

Litho-density logging tool is one of the most important components for the nuclear welllogging technology instrument, and many international and domestic logging companies fo-cus on developing this type of instrument. The level of instrument performance is directly re-lated to logging results, thereby affecting the value of the logging data. The development ofhigh-performance litho-density logging tool has far-reaching significance for oil productionlogging. This article mainly introduces the full spectrum litho-density logging method, whichis based on in-depth study of current litho-density logging tool and new requirements of mod-ern logging. By inheriting traditional logging technology, the full spectrum lithology densitytool is designed by the author, and related spectra processing software has been studied. Thisarticle has significant impact in the following areas:First, compared to traditional logging instruments, the full spectrum lithology densitytool uses full spectrum acquisition. Therefore, it has high data acquisition speed, various datacollection, and high vertical resolution. Moreover, the full spectrum lithology density tool cancomplete spectrum and provide more accurate stratigraphic information under the well with175°C high-temperature.Second, a new pulse conditioning circuit is designed to meet the acquisition require-ments, which aims at the characteristics of quick and narrow for nuclear pulse. The pulseconditioning circuit includes the amplification of forming circuit, baseline restoration circuit,the peak detection circuit and so on, which all contribute to a good testability for the pulse.Third, data acquisition and data processing is based on FPGA design, which has all ofthe digital integrated circuit in it. At the same time, high-speed AD helps complete the digitalquantization, and dual-port RAM technology ensures real-time system. In this way, the effi-ciency of data acquisition and upload is greatly enhanced.Forth, by using the reference source to stabilize high pressure, spectrum stabilizationcircuit with high-pressure dynamic stability of the PC software ensures the stability of thephotomultiplier tube high voltage value, and makes the instrument working normal.Last, by designing the full spectrum data processing software, the spectrum can be dis-played visually and instructions can be issued directly. The software also can do pretreatmentto spectra. Recording debugging data and testing instrument can be finished at the same time.Through natural background experiments and high-temperature environmental testing,137Cs spectrum, which is got from litho-density logging tool, is coincident with the standarddrawing. And errors are in the standard error range. The instrument works effectively andperforms stably under high temperature environment that meet the design requirements.