Study On Artificial Crack Propagation Of Tight Oil In Lucaogou Formation In Jimusar Depression And Evaluation Of Compressibility

Tight oil resources are widely distributed in China.The Jimsar lagagou formation,as a typical tight reservoir,has achieved important exploration results.Fracturing is a necessary technical means for the development of dense oil.It is very important to study whether a series of cracks with high efficiency of diversion are the symbol of the success of tight oil hydraulic fracturing,so it is very important to study the propagation of artificial fractures in tight oil reservoirs.In this paper,the detailed literature investigation of the dense oil reservoir of the reed trench formation in Jimsar sag is carried out.On this basis,the physical simulation experiments are carried out from the aspects of natural cracks,thin interbeds and construction displacement respectively.The experimental results show that,under a single homogeneous condition,when a hydraulic crack is encountered with natural cracks,two factors have a very obvious influence on the direction of the crack,which are the horizontal principal stress difference and the approach angle of the hydraulic crack and the natural crack,and the artificially in the case of high approaching angle or high horizontal principal stress.The crack will continue to extend through the natural crack,and the artificial crack can not penetrate the natural crack extension under the low approximation angle or the low horizontal principal stress.The ratio of the strength difference between the thin interlayer and the oil layer has a significant effect on the penetration of the fracture,and the greater the ratio between the interlayer and the reservoir,the more difficult it is for the artificial fracture to penetrate the interlayer.The larger the construction displacement,the more complex the final form of cracks.In order to further study the propagation law of artificial fractures,numerical simulation of artificial fractures of dense oil is carried out.The effects of fracturing fluid viscosity,fracture occurrence,stress magnitude and thin interbedding on fracture propagation are studied respectively.The numerical simulation results show that when the viscosity of the fracturing fluid increases,the width of the crack will increase and the crack length will decrease.The vertical expansion of fractures is very obvious by the difference of the main stress between the layers.When the principal stress is small,the cracks are more likely to expand in the vertical direction.In the last part of the paper,the main factors affecting the volume fracturing of tight oil are analyzed,which are the degree of development of natural fractures,the difference of in-situ stress and the brittleness of rocks.Combined with the characteristics of tight reservoirs in lagagou formation,a general plan for compressible evaluation of the area is given.