| Cementing is an important stage in the oil and gas well's building, In order to reliably isolate the reservoir formation and other parts of the same section separated, it is necessary to carry out cementing. Achieve this phase of operation related to the subsequent production of oil and gas wells, and ultimately related to the mining cost.In addition, the exploitation of oil wells, the casing and cementing the status of technology to monitor the quality of mine is also one of the most important geophysical task. Cementing operations from the current situation, can not guarantee the quality of the entire Well Cementing all qualified and reliable, so cementing quality testing and evaluation is a long-term study. The traditional method of using sound waves Cementing Evaluation Logging can only be the quality of cement and casing to determine the I interface and the wall of cement and cement II interface quality, and not to judge the quality of cement within the mixed cement.In this article, the author designed a new type of cementing quality logging tool- scanning gamma-gamma casing thickness and cement density logging tool. The logging tool is used to test the casing thickness and the density of cement outside the casing in the evaluation of the quality of cementing. In the monitoring of casing technology and the oil, gas well cementing quality, the logging tool used to determine the casing thickness; divided Coupling Coupling and evaluation of the situation; to determine the relative well casing eccentricity axis; determine the centralizer and the pipe casing shoes depth distribution; found deficiencies casing; perforating eye to determine the location and volume of distribution; governing outer space to determine the height of cement; found flaws in the cement, as well as to determine the type of defects; to determine the density of cement; evaluation of tube outer space the degree of sealing and fluid tube channeling the possibility of slot.In this paper, the scanning gamma - gamma string cement thickness and density of the working principle of logging tool, in this based on the structure of the downhole tools and hardware circuit design, software design. According to design, modular hardware design ideas, from the gamma detector design, step-by-step, step by step to complete the design of high voltage power supply, transformer design, low-voltage power supply design, circuit design pulse shaping, angle, temperature measurementunit design, cable pressure , angle, temperature signal processing circuit design, telemetry unit design, design transfer agreement. In those based on the design is completed, the next bit to the design of software, namely the completion of the cable Subroutine pressure measurement, temperature, angle measurement subroutine, serial send, receive subroutine, gamma probe data acquisition subroutine, Manchester coding and send subroutine. Finally, a scanning gamma - gamma string cement thickness and density logging tool system debugging and logging test results surface scan gamma - gamma string cement thickness and density of stable logging tool, the probe count rate is accurate, the logging data can be accurate, it generally applicable to the use of cement density (1.8-1.9g/cm~3) and increase the density of cement (2.0-2.3g/cm~3), also apply to the use of lightweight concrete density ( 1.4-1.6g/cm~3) Detection of cementing quality.The measurement results of the instrument with the acoustic variable density logging tool measurements together, can more accurately determine the quality of cement cemented cementing, to achieve a comprehensive assessment of oil and gas wells cementing quality.
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