Research Of Deepwater Drilling Gas Cut Detection Algorithm And Software Design

Petroleum is closely related to people's basic necessities.In recent years,there are more than 60% of the large oil and gas fields found in sea bed.It shows that marine oil and gas will be an important source which is needed for people to live and produce in the future.However,how to ensure the safe production of deep sea oil drilling has become a crucial issue.So if gas cut is detected timely in the deep water drilling process,the occurrence of blowout accident will be greatly reduced.At present,the commonly used methods of gas cut detection at home and abroad contain mud pit level detection,differential flow-in and out detection,while drilling gas cut detection,multi-parameter integrated detection,etc.A new method of gas cut detection based on non-directional continuous ultrasonic Doppler principle is proposed in this paper after analyzing the advantages and disadvantages of the commonly used method and the application situation.The ultrasonic waves propagate in the drilling fluid will be reflected back while encountering gas bubbles,and the Doppler shift occurs between the transmitted signal and the received signal due to the reflection of the bubble flowing with the drilling fluid.The flow rate information and the bubble content information of the drilling fluid are obtained by analyzing the received signal.In this topic,the processing of the acquisition signal is the key point,and the analysis of the signal from the time domain and the frequency domain is put forward.The peak-related information of the signal is extracted in the time domain,and estimating the power spectrum to get the average frequency and power in the frequency domain,as the reaction of flow rate and the gas content of the fluid in the echo signal,and based on this to obtain the relationship between the characteristics of these signals and the flow rate and gas content.Due to the randomness of the size and distribution of the bubbles in the pipeline,and taking into account the attenuation characteristics of the acoustic wave when propagating in the drilling fluid,weighting is applied to the analysis of the signal.The software implementation of signal analysis includes signal acquisition,real-time data analysis,storage and display of results,and historical data processing.At last,the simulation experiment is carried out on the gas cut simulation experiment device,including the water experiment with different flow rate and gas content and the mud experiment with different density,flow rate and gas content.Experiments were carried out repeatedly for each experimental condition,and a great number of experimental data is collected.The flow rate and gas content of the fluid are detected by the collected data.The results of these experimental data show that the time domain analysis method and frequency domain analysis method proposed in this paper can detect the gas cut in drilling fluid.