The Calibration System Of Depth Wheel Based On Virtual Instrument

Depth measurement is the fundament of cable logging. Its accuracy defines the evaluation of logging result and ensures the carry-out of follow-up work and acquiring of accurate information of oil and gas reservoir. The calibration of depth measuring system is inevitable during well logging. Thus the acquiring of precise error rectification coefficients of its depth wheels is of great significance.On account of the abrasion of depth wheel and the stretch of logging cable, the paper presents a corresponding error rectification theory and put forward a fast and effective method. A reliable depth wheel calibration system is designed as well. The main research contents of this paper are as follows:(1) A error rectification method is put forward based on characteristics of the abrasion of depth wheel. An overall calibration system design is carried out, with advantages like low cost, high speed and high accuracy.(2) Stepper motor and servo motor, along with PCI controller, are used to build a motion control sub-system. Precise motion control of the depth system is carried out by the module based on stepper motor, while tension control of the logging cable is carried out by the module based on servo motor.(3) Linear encoder is used to measure length. PCI counter is used as the core of data acquisition sub-system to collect data from depth wheel rotary encoder and linear encoder. Depth wheel calibration is realized by comparing test data with standard data.(4) Software design is carried out on base of the hardware above. After software requirement is analyzed and overall structure is built, virtual instrument program is written based on LabVIEW to conduct full-automatic error rectification, manual motor control and encoder calibration. The program is user-friendly and have multiple functions like stable data storage, accurate result generating, parameter configuration, and report printing.(5) A test system model is made to conduct an experiment of the calibration of a type 2530 martin-decker depth measuring system. The system error is analyzed in brief. The calibration result is essentially consistent with that got by casing collar logging(CCL), with a limit error of 63?m, indicating that the accuracy of the system meets the requirement.