Abstract
Using downhole annular electromagnetic flow measurement to obtain annular flow in real-time is a foundation of microflow control drilling technology. The existing annular flow electromagnetic measurement method based on low-frequency rectangular excitation is affected by slurry interference and formation fluid invasion, which results in large noise generated on the electrode output signal. These noise causes the instability of the flow measurement system output and lower accuracy. Double-frequency rectangular wave excitation has the advantages of excellent zero-point stability attributed to low-frequency rectangular wave excitation and fast response speed with great ability to suppress slurry interference. First, the double-frequency rectangular wave excitation for annular flow electromagnetic measurement is researched, and its corresponding electromagnetic induction signal process is investigated. In order to verify the feasibility of downhole annular electromagnetic flow measurement, a flow verification platform for comparison of standard and detected parameters is established for simulation experiment, and the ability to suppress slurry interference and response speed of the technology in downhole slurry flow measurement are analyzed. The test results show that the downhole annular electromagnetic flow measurement based on double-frequency rectangular wave excitation can not only satisfy the requirements of regular electromagnetic flow measurement but also suppress the annular slurry interference effectively.
Highlights
With the expansion of oil and gas exploration field, the drilling security problems of deep-sea environment, complex strata, shallow gas layer, and matured oil fields caused by strata high pressure due to water injection are becoming severe
Downhole microflow control drilling technology can deal with overflow and blowout effectively in narrow secure density window drilling, and using downhole annular flow measurement to obtain the annular flow information in real-time is the core of realizing downhole microflow control drilling [1]
We proposed an annular electromagnetic flow measurement technology for drilling engineering by electromagnetic flowmeter based on doublefrequency excitation
Summary
With the expansion of oil and gas exploration field, the drilling security problems of deep-sea environment, complex strata, shallow gas layer, and matured oil fields caused by strata high pressure due to water injection are becoming severe. The existing electromagnetic flowmeter mostly measures the flow of ordinary conductive fluids based on low-frequency rectangular wave excitation. In this model, two coil excitation structures M and N are designed to generate the magnetic field in certain directions. The downhole annular flow electromagnetic measurement with lowfrequency rectangular wave excitation has great zeropoint stability but unstable electromagnetic flow sensor output affected by slurry interference. Awi is the amplitude demodulation result of the electrode output flow signal under double-frequency rectangular excitation. 18 data are taken as the result of amplitude demodulation while averaging, and this demodulation result is served as the accordance of the annular flow calculation
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