During large-scale hydraulic fracturing in shale gas horizontal wells,a cement sheath easily loses its integrity due to thefluctuation and continuous change of wellbore temperature and pressure and the cyclic loading ...During large-scale hydraulic fracturing in shale gas horizontal wells,a cement sheath easily loses its integrity due to thefluctuation and continuous change of wellbore temperature and pressure and the cyclic loading and unloading,which will threaten wellbore integrity.In order tofigure out the failure mechanism of cement sheath integrity under strong alternating thermal loads and prevent the failure of cement sheath barriers during large-scale hydraulic fracturing in shale gas horizontal wells,this paper adopted the independently developed experimental device to test and evaluate the sealing integrity and mechanical integrity of the full-scale combination of production casing,cement sheath and intermediate casing under strong alternating thermal loads.And the integrity experimental results of two kinds of full-scale cement sheaths(conventional and high-strength cement sheaths)under three kinds of strong alternating thermal loads(cycle number for the occurrence of discontinuous CO_(2) bubble:4 and 14;cycle number for the occurrence of continuous CO_(2) bubble:5 and 15;alternating thermal load:30-120℃ and 30-150℃)were obtained.And the following research results were obtained.First,alternating thermal load has a significant negative impact on the integrity of cement sheath,and with the increase of alternating temperature and temperature difference,the thermal cycle number characterizing the sealing integrity of cement sheath reduces sharply.Second,the interfacial mechanical property indicators that characterize the shearing force between cement sheath and casing and the axial and radial bonding strength decrease with the increase of the alternating temperature.Third,the micro annulus in cement sheath is mainly caused by discordant deformation between the casing and the cement sheath materials,and the mechanical degradation and deterioration of the set cement induced by the alternating thermal load aggravate the failure of the sealing integrity of cement sheath to a certain degree.In conclusion,the research results can provide a reference for the design of large-scale fracturing in deep shale gas horizontal wells.展开更多
The representation and acquisition of a product gene is a crucial problem in product evolutionary design. A new methodology of product gene representation and acquisition from a population of product cases is proposed...The representation and acquisition of a product gene is a crucial problem in product evolutionary design. A new methodology of product gene representation and acquisition from a population of product cases is proposed, and the methodology for product evolutionary design based on a population of product cases is realized. By properly classifying product cases according to its product species, the populations of product cases are divided and a model is established. Knowledge of the scheme design is extracted and formulated as the function base, principle base, and structure base, which are then combined to form a product gene. Subsequently, the product gene tree is created and represented by object-oriented method. Then combining this method with the evolutionary reasoning technology, an intelligent and automatic evolutionary scheme design of product based on the population of product cases is realized. This design method will be helpful in the processing of knowledge formulation, accumulation, and reuse, and in addressing the difficulty of acquiring design knowledge in traditional design. In addition, the disadvantages of manual case adaptation and update in case-based reasoning can be eliminated. Moreover, by optimizing the design scheme in multiple levels and aspects of product function, principle, and structure etc., the level of creativity in the scheme design can be improved.展开更多
基金Project supported by the National Natural Science Foundation of China“Study on Casing-Cement Sheath-Formation Integrity under Alternating Temperature,Pressure and Their Coupling Effects”(No.:51904261)China Postdoctoral Science Foundation(No.:2019M653478)。
文摘During large-scale hydraulic fracturing in shale gas horizontal wells,a cement sheath easily loses its integrity due to thefluctuation and continuous change of wellbore temperature and pressure and the cyclic loading and unloading,which will threaten wellbore integrity.In order tofigure out the failure mechanism of cement sheath integrity under strong alternating thermal loads and prevent the failure of cement sheath barriers during large-scale hydraulic fracturing in shale gas horizontal wells,this paper adopted the independently developed experimental device to test and evaluate the sealing integrity and mechanical integrity of the full-scale combination of production casing,cement sheath and intermediate casing under strong alternating thermal loads.And the integrity experimental results of two kinds of full-scale cement sheaths(conventional and high-strength cement sheaths)under three kinds of strong alternating thermal loads(cycle number for the occurrence of discontinuous CO_(2) bubble:4 and 14;cycle number for the occurrence of continuous CO_(2) bubble:5 and 15;alternating thermal load:30-120℃ and 30-150℃)were obtained.And the following research results were obtained.First,alternating thermal load has a significant negative impact on the integrity of cement sheath,and with the increase of alternating temperature and temperature difference,the thermal cycle number characterizing the sealing integrity of cement sheath reduces sharply.Second,the interfacial mechanical property indicators that characterize the shearing force between cement sheath and casing and the axial and radial bonding strength decrease with the increase of the alternating temperature.Third,the micro annulus in cement sheath is mainly caused by discordant deformation between the casing and the cement sheath materials,and the mechanical degradation and deterioration of the set cement induced by the alternating thermal load aggravate the failure of the sealing integrity of cement sheath to a certain degree.In conclusion,the research results can provide a reference for the design of large-scale fracturing in deep shale gas horizontal wells.
文摘The representation and acquisition of a product gene is a crucial problem in product evolutionary design. A new methodology of product gene representation and acquisition from a population of product cases is proposed, and the methodology for product evolutionary design based on a population of product cases is realized. By properly classifying product cases according to its product species, the populations of product cases are divided and a model is established. Knowledge of the scheme design is extracted and formulated as the function base, principle base, and structure base, which are then combined to form a product gene. Subsequently, the product gene tree is created and represented by object-oriented method. Then combining this method with the evolutionary reasoning technology, an intelligent and automatic evolutionary scheme design of product based on the population of product cases is realized. This design method will be helpful in the processing of knowledge formulation, accumulation, and reuse, and in addressing the difficulty of acquiring design knowledge in traditional design. In addition, the disadvantages of manual case adaptation and update in case-based reasoning can be eliminated. Moreover, by optimizing the design scheme in multiple levels and aspects of product function, principle, and structure etc., the level of creativity in the scheme design can be improved.
