At present,evaluation on reservoir damage induced by fracturing fluid mainly refers to The Evaluation Measurement for Properties of Water-based Fracturing Fluid:SY/T5107-2016(referred to as the industry standard below...At present,evaluation on reservoir damage induced by fracturing fluid mainly refers to The Evaluation Measurement for Properties of Water-based Fracturing Fluid:SY/T5107-2016(referred to as the industry standard below).However,the fracturing fluid displacing core process stipulated in the industry standard is not consistent with the fast invading process of fracturing fluid into the reservoir under high pressure during the actual fracturing construction.Besides,the influences of fracturing fluid residues,gel breaking mode,original water saturation and other factors are not taken into consideration in the experiments to evaluate the damage of fracturing fluids.Thus,the accuracy of evaluation results is influenced.In this paper,tight sandstone cores of the Lower Jurassic Ahe Formation(J1a)in Dibei area of Kuqa Depression of the Tarim Basin were selected as samples.The invading process of fracturing fluid into a tight sandstone reservoir was simulated by modifying experimental process and method.Then,the damage degree of fracturing fluid to gas reservoir was evaluated and the damage mechanisms of fracturing fluid were analyzed systematically.And the following research results were obtained.First,themodified evaluationmethod takes into account the influences of several factors,such as the originalwater saturation of gas reservoir,the instantaneous“breakdown”effect of high-pressure during fracturing and the fracturing fluid residues,so it can evaluate the damage degree of fracturing fluid to tight sandstone gas reservoirsmore objectively.Second,the evaluation results based on the industry standard showthat the damage degree of fracturing fluid to the permeability of tight sandstone gas reservoirs ismedium to strong,whereas the damage degree evaluated by themodifiedmethod is medium to weak.Third,the retention of fracturing fluid residues in fractures is the main cause of permeability damage.The residues can easily block fractures and fracture surface pores.Most of them retain in the pores in the surface layer of matrix cores(invasion depth less than 3 cm),so residues are filtered by matrix pores.Fourth,when fracturing fluid migrates inwards from the core surface,high molecular polymers retain in the form of thin-film lamellar,local flaky nodular and crystal inclusion in turn in the reservoir pores.Fifth,under the experimental conditions,salting-out crystals appear and are unevenly distributed in the cores.In fractures,salting-out crystals and high molecules are polymerized to form composite inclusions.In matrix pores,salting-out crystals and a small number of fragments(e.g.illite)are enclosed to form a complex.Sixth,migratory particles caused by speed sensitivity are usually combined with residues and high molecular polymers to form composite inclusions,thus blocking pores and fractures.展开更多
A kind of signal acquisition circuit and the related signal processing method of the capacitanceelectromagnetic flowmeter (EMF) were introduced. The circuit can eliminate the influence of distributed capacitanceon the...A kind of signal acquisition circuit and the related signal processing method of the capacitanceelectromagnetic flowmeter (EMF) were introduced. The circuit can eliminate the influence of distributed capacitanceon the input impedance of the operational amplifier, and greatly improve the input impedance of the detection circuitto overcome the disadvantage of high signal source impedance. The rotating capacitor filter is a signal processingmethod based on the phase-sensitive detection technology. It can extract the weak signal from the strong and widebandbackground noise, so it is very suitable for the processing of capacitive electromagnetic flow signals. Throughthe comparison of the signal amplitude obtained at different flow rates and the comparison of signal spectrumcomponents before and after the filter, the effectiveness of the bootstrap signal acquisition circuit and rotatingcapacitor filtering method is verified.展开更多
The combination of magnetotelluric survey and laboratory measurements of electrical conductivity is a powerful approach for exploring the conditions of Earth's deep interior. Electrical conductivity of hydrous sil...The combination of magnetotelluric survey and laboratory measurements of electrical conductivity is a powerful approach for exploring the conditions of Earth's deep interior. Electrical conductivity of hydrous silicate melts and aqueous fluids is sensitive to composition, temperature, and pressure, making it useful for understanding partial melting and fluid activity at great depths. This study presents a review on the experimental studies of electrical conductivity of silicate melts and aqueous fluids, and introduces some important applications of experimental results. For silicate melts, electrical conductivity increases with increasing temperature but decreases with pressure. With a similar Na^+ concentration, along the calc-alkaline series electrical conductivity generally increases from basaltic to rhyolitic melt, accompanied by a decreasing activation enthalpy. Electrical conductivity of silicate melts is strongly enhanced with the incorporation of water due to promoted cation mobility. For aqueous fluids, research is focused on dilute electrolyte solutions. Electrical conductivity typically first increases and then decreases with increasing temperature, and increases with pressure before approaching a plateau value. The dissociation constant of electrolyte can be derived from conductivity data. To develop generally applicable quantitative models of electrical conductivity of melt/fluid addressing the dependences on temperature, pressure, and composition, it requires more electrical conductivity measurements of representative systems to be implemented in an extensive P-T range using up-to-date methods.展开更多
Selected milestones in the development and use of electrical tomography in powder conveying, slurry processing and multi-phase flow are highlighted. The ability to map concentration in opaque mixtures under process-re...Selected milestones in the development and use of electrical tomography in powder conveying, slurry processing and multi-phase flow are highlighted. The ability to map concentration in opaque mixtures under process-realistic conditions was a major innovation for the method and has had far reaching implications. Subsequent developments have enabled velocity information to be abstracted resulting in the ability to measure component flux and motion.展开更多
基金Project supported by National Natural Science Foundation of China“Basic study on drying of tight gas reservoir and enhancing gas seepage capacity”(No.51534006).
文摘At present,evaluation on reservoir damage induced by fracturing fluid mainly refers to The Evaluation Measurement for Properties of Water-based Fracturing Fluid:SY/T5107-2016(referred to as the industry standard below).However,the fracturing fluid displacing core process stipulated in the industry standard is not consistent with the fast invading process of fracturing fluid into the reservoir under high pressure during the actual fracturing construction.Besides,the influences of fracturing fluid residues,gel breaking mode,original water saturation and other factors are not taken into consideration in the experiments to evaluate the damage of fracturing fluids.Thus,the accuracy of evaluation results is influenced.In this paper,tight sandstone cores of the Lower Jurassic Ahe Formation(J1a)in Dibei area of Kuqa Depression of the Tarim Basin were selected as samples.The invading process of fracturing fluid into a tight sandstone reservoir was simulated by modifying experimental process and method.Then,the damage degree of fracturing fluid to gas reservoir was evaluated and the damage mechanisms of fracturing fluid were analyzed systematically.And the following research results were obtained.First,themodified evaluationmethod takes into account the influences of several factors,such as the originalwater saturation of gas reservoir,the instantaneous“breakdown”effect of high-pressure during fracturing and the fracturing fluid residues,so it can evaluate the damage degree of fracturing fluid to tight sandstone gas reservoirsmore objectively.Second,the evaluation results based on the industry standard showthat the damage degree of fracturing fluid to the permeability of tight sandstone gas reservoirs ismedium to strong,whereas the damage degree evaluated by themodifiedmethod is medium to weak.Third,the retention of fracturing fluid residues in fractures is the main cause of permeability damage.The residues can easily block fractures and fracture surface pores.Most of them retain in the pores in the surface layer of matrix cores(invasion depth less than 3 cm),so residues are filtered by matrix pores.Fourth,when fracturing fluid migrates inwards from the core surface,high molecular polymers retain in the form of thin-film lamellar,local flaky nodular and crystal inclusion in turn in the reservoir pores.Fifth,under the experimental conditions,salting-out crystals appear and are unevenly distributed in the cores.In fractures,salting-out crystals and high molecules are polymerized to form composite inclusions.In matrix pores,salting-out crystals and a small number of fragments(e.g.illite)are enclosed to form a complex.Sixth,migratory particles caused by speed sensitivity are usually combined with residues and high molecular polymers to form composite inclusions,thus blocking pores and fractures.
文摘A kind of signal acquisition circuit and the related signal processing method of the capacitanceelectromagnetic flowmeter (EMF) were introduced. The circuit can eliminate the influence of distributed capacitanceon the input impedance of the operational amplifier, and greatly improve the input impedance of the detection circuitto overcome the disadvantage of high signal source impedance. The rotating capacitor filter is a signal processingmethod based on the phase-sensitive detection technology. It can extract the weak signal from the strong and widebandbackground noise, so it is very suitable for the processing of capacitive electromagnetic flow signals. Throughthe comparison of the signal amplitude obtained at different flow rates and the comparison of signal spectrumcomponents before and after the filter, the effectiveness of the bootstrap signal acquisition circuit and rotatingcapacitor filtering method is verified.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41402041 & 41322015)the Fundamental Research Funds for the Central Universities of China
文摘The combination of magnetotelluric survey and laboratory measurements of electrical conductivity is a powerful approach for exploring the conditions of Earth's deep interior. Electrical conductivity of hydrous silicate melts and aqueous fluids is sensitive to composition, temperature, and pressure, making it useful for understanding partial melting and fluid activity at great depths. This study presents a review on the experimental studies of electrical conductivity of silicate melts and aqueous fluids, and introduces some important applications of experimental results. For silicate melts, electrical conductivity increases with increasing temperature but decreases with pressure. With a similar Na^+ concentration, along the calc-alkaline series electrical conductivity generally increases from basaltic to rhyolitic melt, accompanied by a decreasing activation enthalpy. Electrical conductivity of silicate melts is strongly enhanced with the incorporation of water due to promoted cation mobility. For aqueous fluids, research is focused on dilute electrolyte solutions. Electrical conductivity typically first increases and then decreases with increasing temperature, and increases with pressure before approaching a plateau value. The dissociation constant of electrolyte can be derived from conductivity data. To develop generally applicable quantitative models of electrical conductivity of melt/fluid addressing the dependences on temperature, pressure, and composition, it requires more electrical conductivity measurements of representative systems to be implemented in an extensive P-T range using up-to-date methods.
基金support of co-workers in the tomography groups at University of Leeds and the University of Manchester with funding to enable us to develop the frontiers of tomography provided by EPSRC (EP/D031257/1)
文摘Selected milestones in the development and use of electrical tomography in powder conveying, slurry processing and multi-phase flow are highlighted. The ability to map concentration in opaque mixtures under process-realistic conditions was a major innovation for the method and has had far reaching implications. Subsequent developments have enabled velocity information to be abstracted resulting in the ability to measure component flux and motion.
