摘要：The accurate prediction of fracturing pressure for pay zone is the very important guidance to hydraulic fracturing design and operation. The pore pressure around the wellbore happens to change variously as the fracturing fluid entering the pay zone. The change of pore pressure affects the stress-state and the fracturing pressure around the wellbore. In this paper, a new concept of the effective membrane pressure coefficient is presented according to the wall building capacity of the fracturing fluid, then the change of pore pressure around the wellbore is studied, and it is proven that the prediction model for fracturing pressure is improved.

摘要：Hydraulic fracturing treatments of oil wells are greatly affected by the perforation parameters selected. The three-dimensional finite element model together with the tensile criterion of rock materials is employed to systematically investigate the influence of perforation parameters, such as perforation density, perforation orientation, perforation diameter, and perforation length as well as wellbore ellipticity, in vertical wells on the formation fracturing pressure. Based on a six-month simulation research in the University of Petroleum, China, several conclusions are drawn for the first time. Perforation density and perforation orientation angle are the most important parameters controlling the formation fracturing pressure. As the perforation density increases, the fracturing pressure decreases, not linearly but progressively. The fracturing pressure increases with the perforation orientation angle only when the angle is less than 45 degrees, and the relationship becomes very flat when the angle is 45 degrees. However, with regards to the perforation diameter and perforation length, their influences are much slighter. The wellbore ellipticity has a significant effect on the formation fracturing pressure. It is obvious that fracturing pressure increases linearly with the ellipticity of the wellbore.