大庆深层致密气水平井大规模压裂条件下套管变形分析

Casing deformation analysis of deep tight gas horizontal wells in Daqing under conditions of large-scale fracturing

为了进一步明确大庆深层气致密储层在大规模压裂过程中套管变形影响因素,开展了大庆深层致密气水平井大规模压裂条件下套管变形分析。运用有限元方法,通过建立套管—地层—水泥环耦合力学模型,对压裂过程中地应力差、固井质量、地层杨氏模量、温度变化等4个因素引起的套管受力变化影响规律进行分析。研究表明,套管所受应力随地应力差增加而升高,随地层杨氏模量、温度的降低而升高,但变化趋势较缓,导致套管变形风险相对较小;固井水泥环缺失会导致套管受到应力急剧升高,当地应力差达到50MPa时,套管存在变形风险。研究成果可为大庆深层致密气大规模压裂套管变形防治提供理论依据。

In order to further understand the influencing factors of casing deformation during large-scale fracturing in deep tight gas reservoirs in Daqing Oilfield,an analysis on casing deformation under the conditions of large-scale fracturing has been carried out.Through the establishment of coupling mechanical model about casing-formationcement sheath,the influence law in casing stress changes caused by the four factors including in-situ stress difference,cementing quality,formation Young′s modulus,and temperature changes during the fracturing operation was analyzed with the finite element method.Studies show that the stress on the casing rises with the increase of in-situ stress difference,and with the decrease of the Young′s modulus and temperature of the formation,but the change trend is rather slow,which result in a relatively small risk of casing deformation.The lack of cement sheath could cause the stress rise sharply on the casing.When the in-situ stress difference reaches 5MPa,there is a risk of casing deformation.The research results can provide a theoretical basis for the prevention and treatment of casing deformation of deep tight gas reservoir in Daqing Oilfield under conditions of large-scale fracturing.