压裂“X”形裂缝提高单井措施效果的新方法
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摘要
为了提高特低渗透油藏新井的压裂效果,提出了采用定向射孔技术进行转向压裂从而形成"X"形水力裂缝的新方法。基于有限元三维应力分析,研究了定向射孔下水力裂缝的起裂机理。根据断裂力学理论,建立了基于复合应力强度因子的裂缝延伸和转向判据模型,推导确定了缝内压力分布、复合应力强度因子及裂缝扩展方向角的计算公式,编制了定向射孔转向压裂裂缝延伸形态的模拟软件,分析了射孔方位角、最大水平主应力和最小水平主应力差值对转向裂缝形态的影响程度,采用定向射孔和限流法压裂的施工方式,形成了在单个油层中压开"X"形裂缝的改造方法。现场试验了6口井,通过裂缝监测,证明该技术是可行的。
Low permeability reservoir is poor in physical properties and characterized by low permeability and low natural productivity. In response to these problems, experiments, theoretical discussion and the numerical stimulation method were utilized to study the reform manner in deflection fracturing of oriented perforation so as to generate the "X"-fracture in the single layer and enhance the individual well producing rate. This paper established the fracture extension model based on the strength divisor of the combined stress and the oriented judgmental criterion, derived the calculating formulas of the pressure distribution and the strength divisor of the combined stress and the direction angle of the fracture, compiled the simulation software of the fracture extension, and modality of the deflection fracturing of the oriented perforation, analyzed the influencing degree of the perforation angle, the max and the min horizontal stress to the fissure morphology, and provided the theory foundation for the detail designing of the "X"-fracture. Six wells have been tested in field and the technique has been proven feasible through fracture monitoring technique.
Low permeability reservoir is poor in physical properties and characterized by low permeability and low natural productivity. In response to these problems, experiments, theoretical discussion and the numerical stimulation method were utilized to study the reform manner in deflection fracturing of oriented perforation so as to generate the "X"-fracture in the single layer and enhance the individual well producing rate. This paper established the fracture extension model based on the strength divisor of the combined stress and the oriented judgmental criterion, derived the calculating formulas of the pressure distribution and the strength divisor of the combined stress and the direction angle of the fracture, compiled the simulation software of the fracture extension, and modality of the deflection fracturing of the oriented perforation, analyzed the influencing degree of the perforation angle, the max and the min horizontal stress to the fissure morphology, and provided the theory foundation for the detail designing of the "X"-fracture. Six wells have been tested in field and the technique has been proven feasible through fracture monitoring technique.
引文
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[2]张广清,陈勉.水平井水力裂缝非平面扩展研究[J].石油学报,2005,26(3):95-97,101.
[3]Romero J,Mack MG,Elbel J L.Theoretical model and numer-ical investigation of near-wellbore effects in hydraulic fractu-ring[R].SPE 30506,1995.
[4]刘继民,刘建中,刘志鹏,等.用微地震法监测压裂裂缝转向过程[J].石油勘探与开发,2005,32(2):75-77.
[5]王立军,张晓红,马宁,等.压裂水平井裂缝与井筒成任意角度时的产能预测模型[J].油气地质与采收率,2008,15(6):73-75.
[6]吴忠宝,胡文瑞,宋新民,等.整体水力压裂油藏裂缝—油藏耦合数值模拟研究[J].油气地质与采收率,2009,16(2):70-73.
[7]Yew C H,Mear M E,Chang C C,et al.On perforating andfracturing of deviated cased wellbores[R].SPE 26514,1993.
[8]中国航空研究院.应力强度因子手册[M].北京:科学出版社,1993:426-428.
[9]阳友奎,肖长富,邱贤德,等.水力压裂裂缝形态与缝内压力分布[J].重庆大学学报:自然科学版,1995,18(3):20-26.
[10]黄作宾.断裂力学基础[M].武汉:中国地质大学出版社,1991:177-180.
[11]Slepyan L I.Models and phenomena in fracture mechanics[M].New York:Springer,2002:30-35.
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