Simulation Study On Multi-crack Extension Of Thin Lamination Crack In Vertical Well In Q Area

For the development of thin and poor reservoir, hydraulic fracture is an extremely effective measure to enhance production, but it is the key problem to study multiple fracture propagation law when stimulating these types of pay zones. A three-dimensional crack propagation mode is conducted by the FEM software ABAQUS, and the influences of parameters on fracture initiation and propagation such as mechanical properties, geologic parameters, construction parameters et al are studied. Besides, qualitative and quantitative analysis of these factors are conducted to study the strength of the various factors. A three-dimensional multiple fracture propagation model based on the geology of the Q well is established to study the effects of artificial interlayer, viscosity of the fracturing fluid, pumping rate on the geometrical shape and growth of multiple fracture, the results is successfully applied on oil field.Through the simulation of crack propagation, the following conclusions are as follows:(1) The following conclusions are drawn from the study of single factor on fracture propagation law:fracture length is proportional to the magnitude of elastic module and minimal horizontal stress difference, reversely proportional to the magnitude of the viscosity of the fracturing fluid and tensile strengths in oil layer; fracture height is proportional to the magnitude of pumping rate and the viscosity of the fracturing fluid, reversely proportional to the magnitude of elastic module and minimal horizontal stress difference; maximal fracturing width is proportional to the magnitude of pumping rate and the viscosity of the fracturing fluid, reversely proportional to the magnitude of elastic module and minimal horizontal stress difference.(2) The following conclusions are drawn from the orthogonal study of factors on fracture propagation law:The difference of elastic modulus has the greatest influence on the fracture length, followed by pumping rate, minimal horizontal stress difference and viscosity of the fracturing fluid have the minimal influence on the fracture length; the viscosity of the fracturing fluid and minimal horizontal stress difference have the greatest influence on the fracture height, pumping rate and the difference of elastic modulus have the minimal influence on the fracture length; the viscosity of the fracturing fluid has the greatest influence on the maximal fracturing width, followed by pumping rate, minimal horizontal stress difference and the difference of elastic modulus have the minimal influence on the fracture length.(3) Breakdown pressure is very sensitive to pumping rate, elastic modulus, rock strength, followed by viscosity of the fracturing fluid, and not sensitive to minimal horizontal stress difference(4) Because of the low pumping rate, the fluid pressure in the fracture is not high enough to break through the stress difference between oil and interlayer, multiple fractures propagate independently in oil layers, the fracture propagation behavior are similar, but the rock between injection points are more likely to break.(5) Fracturing thin interbedded with variable pump rate will make sure multi-fracture communicate with each other, but also prevent excessive growth of fracture height, communicate edge and bottom water, cause the failure of the fracturing program. With the low viscosity can control the excessive growth of fracture height.In this paper, the system study of the key factors influencing multi fracture height is conducted, the proposed model can exactly characterize the process and mechanism of multi hydraulic fracturing, The obtained results are valuable for design and engineering practice of multi hydraulic fracturing.