Water hammer diagnostics is an important fracturing diagnosis technique to evaluate fracture locations and other downhole events in fracturing.The evaluation results are obtained by analyzing shut-in water hammer pres...Water hammer diagnostics is an important fracturing diagnosis technique to evaluate fracture locations and other downhole events in fracturing.The evaluation results are obtained by analyzing shut-in water hammer pressure signal.The field-sampled water hammer signal is often disturbed by noise interfer-ence.Noise interference exists in various pumping stages during water hammer diagnostics,with significantly different frequency range and energy distribution.Clarifying the differences in frequency range and energy distribution between effective water hammer signals and noise is the basis of setting specific filtering parameters,including filtering frequency range and energy thresholds.Filtering spe-cifically could separate the effective signal and noise,which is the key to ensuring the accuracy of water hammer diagnosis.As an emerging technique,there is a lack of research on the frequency range and energy distribution of effective signals in water hammer diagnostics.In this paper,the frequency range and energy distribution characteristics of field-sampled water hammer signals were clarified quantita-tively and qualitatively for the first time by a newly proposed comprehensive water hammer segmentation-energy analysis method.The water hammer signals were preprocessed and divided into three segments,including pre-shut-in,water hammer oscillation,and leak-off segment.Then,the three segments were analyzed by energy analysis and correlation analysis.The results indicated that,one aspect,the frequency range of water hammer oscillation spans from 0 to 0.65 Hz,considered as effective water hammer signal.The pre-shut-in and leak-off segment ranges from 0 to 0.35 Hz and 0e0.2 Hz respectively.Meanwhile,odd harmonics were manifested in water hammer oscillation segment,with the harmonic frequencies ranging approximately from 0.07 to 0.75 Hz.Whereas integer harmonics were observed in pre-shut-in segment,ranging from 6 to 40 Hz.The other aspect,the energy distribution of water hammer signals was analyzed in different frequency ranges.In 0e1 Hz,an exponential decay was observed in all three segments.In 1-100 Hz,a periodical energy distribution was observed in pre-shut-in segment,an exponential decay was observed in water hammer oscillation,and an even energy distri-bution was observed in leak-off segment.In 100-500 Hz,an even energy distribution was observed in those three segments,yet the highest magnitude was noted in leak-off segment.In this study,the effective frequency range and energy distribution characteristics of the field-sampled water hammer signals in different segments were sufficiently elucidated quantitatively and qualitatively for the first time,laying the groundwork for optimizing the filtering parameters of the field filtering models and advancing the accuracy of identifying downhole event locations.展开更多
基金support from the National Natural Science Foundation of China(No.52374019).
文摘Water hammer diagnostics is an important fracturing diagnosis technique to evaluate fracture locations and other downhole events in fracturing.The evaluation results are obtained by analyzing shut-in water hammer pressure signal.The field-sampled water hammer signal is often disturbed by noise interfer-ence.Noise interference exists in various pumping stages during water hammer diagnostics,with significantly different frequency range and energy distribution.Clarifying the differences in frequency range and energy distribution between effective water hammer signals and noise is the basis of setting specific filtering parameters,including filtering frequency range and energy thresholds.Filtering spe-cifically could separate the effective signal and noise,which is the key to ensuring the accuracy of water hammer diagnosis.As an emerging technique,there is a lack of research on the frequency range and energy distribution of effective signals in water hammer diagnostics.In this paper,the frequency range and energy distribution characteristics of field-sampled water hammer signals were clarified quantita-tively and qualitatively for the first time by a newly proposed comprehensive water hammer segmentation-energy analysis method.The water hammer signals were preprocessed and divided into three segments,including pre-shut-in,water hammer oscillation,and leak-off segment.Then,the three segments were analyzed by energy analysis and correlation analysis.The results indicated that,one aspect,the frequency range of water hammer oscillation spans from 0 to 0.65 Hz,considered as effective water hammer signal.The pre-shut-in and leak-off segment ranges from 0 to 0.35 Hz and 0e0.2 Hz respectively.Meanwhile,odd harmonics were manifested in water hammer oscillation segment,with the harmonic frequencies ranging approximately from 0.07 to 0.75 Hz.Whereas integer harmonics were observed in pre-shut-in segment,ranging from 6 to 40 Hz.The other aspect,the energy distribution of water hammer signals was analyzed in different frequency ranges.In 0e1 Hz,an exponential decay was observed in all three segments.In 1-100 Hz,a periodical energy distribution was observed in pre-shut-in segment,an exponential decay was observed in water hammer oscillation,and an even energy distri-bution was observed in leak-off segment.In 100-500 Hz,an even energy distribution was observed in those three segments,yet the highest magnitude was noted in leak-off segment.In this study,the effective frequency range and energy distribution characteristics of the field-sampled water hammer signals in different segments were sufficiently elucidated quantitatively and qualitatively for the first time,laying the groundwork for optimizing the filtering parameters of the field filtering models and advancing the accuracy of identifying downhole event locations.
