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Research on Mud Flow Rate Measurement Method Based on Continuous Doppler Ultrasonic Wave 时间:2017-09-05 23:40 来源:未知作者:admin 点击: 次 Abstract:In deep-water drilling processes, the flow rate of drilling mud inside an annular pipe is significant judgment data for early kick detection. On the basis of the continuous-wave Doppler ultrasound, this paper proposes a new detection method of nonoriented continuous-wave Doppler ultrasound. The method solves the problem of the ultrasound having great attenuation in mud and not receiving effective signals by using a continuous ultrasound. Moreover, this method analyzes the nonoriented characteristics of ultrasound reflection on principle and proposes the detection of ultrasound Doppler frequency shift by detecting Lamb wave, which releases the detection of oil-based mud flow rate in a nonintrusive annular pipe. The feasibility of the method is verified through theoretical analysis and numerous experiments on a gas kick simulation platform. The measurement result has reached a flow accuracy approximating to the intrusive flow meter.
1. Overview
Early kick detection is an important method in preventing blowout accidents and plays a significant role in deep-water drilling processes. As an important judgment factor, emphasis is always placed on the flow detection of drilling mud in an annular pipe. However, the complicated nature of underwater environment and the detection of the mud flow that can only be conducted at the mud outlet cause serious hysteresis in gas kick detection results. The serious blowout accident that happened in the Gulf of Mexico, USA, in 2010 was greatly connected with the hysteresis in gas kick detection results. Knowing how to realize the detection of mud flow rate inside the annular pipe near the seabed and identifying the occurrence of the gas kick accident as early as possible are of great importance. However, two kinds of fluid flow detection methods exist: intrusive and nonintrusive. The intrusive flow meter will damage the original pipeline system and influence the drilling of the mud field, which makes the application of the intrusive method inevitably affect the original technological process. However, the deep-water drilling technology is complicated, and the requirement is high; thus, the change of the original technological process will bring about a cost increase. To have no influence on the original technological process, the best option is to have a nonintrusive flow detection method. Ultrasound flow detection is a typical nonintrusive flow detection method; however, mud drilling will cause ultrasound attenuation, and the common ultrasound detection method cannot detect effective echo signals. The continuous ultrasound will form a strong sound field in the mud and can spread further than the impulse ultrasound for the wave superposition factor. Nevertheless, few methods exist for detecting the flow rate of the continuous ultrasound. In addition, the measurement of the nonintrusive flow is difficult, because the flow mode of the annular pipe mud is complicated and the pressure at the seabed is remarkably high. On this basis, this study analyzes the nonoriented reflection of the continuous ultrasound in the drilling mud and establishes models. This work obtains the principle that part of the reflected ultrasonic waves transfer into Lamb waves when the reflection signal enters into a pipe wall from drilling muds. From these principles, the relationship between the reflection signal frequency spectrum and flow rate can be obtained. The related flow rate detection algorithm finally solves the problem of the difficulty of applying ultrasound in deep-drilling flow detection.