Measurement While Drilling Signal Detection And Process Of Directional Well In Oilfield

The hole direction parameters of drilling tool must be measured promptly and accurately during the process of directional drilling in oilfield, and the hole trajectory while completion is also needed, so that Measurement While Drilling signal detection and process become an important factor of weighing directional drilling level.Centrifugal weight and magnetic compass are adopted in the traditional inclinometers, while accelerometer with high sensibility and precision, and the fluxgate sensor with high anti-vibration are used in modern times. Single/multiple point and continuous inclinometers are developed by combining new type sensors with computer technology. MWD(Measurement While Drilling) system, combining downhole logging with real-time transmission, which can make sure real-time detection and high quality measurement material, mainly in Wireless measurement while drilling technology will become the development direction of directional well in the future.With the development of petroleum exploration and production, the geology status has become more complicated, the number of deep well, ultra-deep well, high-temperature well, high-pressure well and so on, will become more and more. The main parameters of MWD of directional well in oilfield are accelerometer and fluxgate sensor signals, in order to improve the detection precision of measurement will drilling signal, the mathematic models of fluxgate and accelerometer are established, and the measurement while drilling error is analyzed.The sensors of measurement while drilling are affected by the environmental factors, such as temperature, humidity, power supply fluctuation, which enormously induce the measurement veracity, so that the measurement precision is not high and the stability is not good, must be compensated. Hardware compensation, linear compensation and nonlinear compensation for fluxgate and accelerometer signals are formed to a synthesized compensation scheme.Hardware compensation and linear compensation for sensor signals of measurement while drilling have some effect, but most of sensors are nonlinear, which are affected by the environmental factors in the process of measurement. Range sensor is compensated nonlinearly by wavelet neural network, nonlinear compensation algorithm for sensor signals is established, BP algorithm training wavelet, which has a better effect than linear compensation. Then, based on the idea of dynamic, the neural Elman neural network is constructed for measurement of drilling signal compensation, which further improves the precision and has a highly operation speed. And the compensation scheme based on genetic Elman neural network is also presented, after using GA-Elman neural network, the inclination and azimuth have improved a lot compared to the actual values, approaching theoretical values approximately. At last, based on ant colony algorithm, adaptive idea, and Elman neural network, a compensation scheme is presented of adaptive ant colony Elman neural network for measurement while drilling signals, which induced the compensation error to a greater extent.Based on the cooperative design idea, Measurement While Drilling system of directional well in oilfield is designed, in which embedded design is applied to improve the real-time performance, the In System Programming technology is applied to shorten system developing time and declines the development cost, model design is applied to expand and communicate conveniently. This measurement while drilling system has a higher precision then the system in the oilfield at present, which improves the drilling level of directional well, and the stability, real-time performance, accuracy and security are also improved to some extent.At present, the mud pulse signal transmission method was applied to the most of wireless measurement while drilling system, so the key factor of wireless MWD system is the transmission speed. The drilling fluids is mainly composed by clay, rock debris, barite powder, and bubble produced by air existing in free state. Therefore signal transmission speed become even more complex. The computing model of mud pluse signal transmission speed considers the relation with drilling fluid density and gas content. It also considers the influence of density and contraction difference between the solid and liquid, and the transmission speed variation of positive pulse or positive pulse.