| The horizontal well has many advantages: the big drainage area, the high production rate, the high penetrating capacity, the high recovery ratio, and the ability to avoid the obstacle and terrible environment etc. In recent years, with person's continuous practice and the development of the process technique about well drilling and well completion etc, the technique for the horizontal well is developed into the focus in the research and practice of the petroleum industry. For the low permeability reservoir, the permeability is low, the filtrational resistance is strong, and the interwell communication is poor. Sometimes, the production rate for the horizontal well also can't arrive at the standard of the economic production. Hydraulic fracturing stimulation technique for the horizontal well has been applied to increase the production rate and the final recovery efficiency. As to enlarge drainage area of oil and gas and to improve the production rate for the horizontal well, more fractures need to be fractured usually. However, there are some difficulties in the fracturing: the temperature field distribution, the proppant transport, the fracture propagation and the production prediction for the post-fracturing.At present, the study about the basic theory of the hydraulic fracturing horizontal well is not perfect, study in some fields are done just now, while others still can't be researched at home and abroad. There is no flawless theoretical model to direct the optimization design and site operation of hydraulic fracturing horizontal well, this makes the success ratio of hydraulic fracturing horizontal well low and risk high. In order to solve some difficulties in the hydraulic fracturing for horizontal well, improve the theory of hydraulic fracturing, direct the fracture design for the horizontal well accurately, improve the success ratio and effect of the hydraulic fractured horizontal well, so the basic theory of hydraulic fractured horizontal well is studied in this paper. The study of this paper has important significance and value; it promotes the development of the basic theory of hydraulic fractured horizontal well and directs site operation.On the basis of others, following aspects are studied in this paper:(1) According to the principle of conservation of energy, established the mathematical model for the temperature field of horizontal wellbore. In this model the effect of heat proceeded by friction and fluid diverting of multiple fractures on fracturing fluid's temperature is considered. The model is resolved with "shooting method" in this paper. Fracturing fluid's temperature considering the frictional heat is higher than no frictional heat, and that, the longer the wellbore is and the bigger the viscosity is, the larger the temperature difference is between considering frictional heat and no considering it. This study plays asignificant role in determining the fracture fluid's gelout time and directing the optimum design of the fracture fluid.(2) According to the theory of elastic mechanics and fracture mechanics, established the mathematical model for the stress field distribution around the horizontal well bore and the model of fracturing pressure and fracturing angle. The minimum horizontal principle stress is key in the process of fracturing; with the decrease of the rock temperature around the horizontal wellbore, the fracturing pressure decreases accordingly. It can calculate the fracture pressure accurately and provides the reliable theoretical evidence for fracturing treatment of horizontal well.(3) On the basis of rock mechanics and fluid mechanics, using the continuity equation, mass conservation equation and energy conservation equation are used, and what is more, the relational expression between far terrestrial stress and the inlet pressure of fracture when single fracture propagating offered by Geertsma and Deklerk and the model of calculating the fracture geometry is applied. Established the two-dimensional model of multiple fractures propagating simultaneously. Mixed Discrete Value Combi... |
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