3-d Stress Field And Full-length Integral Fracturing Technology Research Based On The Prestack Elastic Parameter Inversion

In Daqing Oilfield, several million tons of reserves in low permeability reservoirs is difficult to develop effectively without fracturing, and the essential problem is to find out the spatial distribution of artificial fractures and the match with sand and well pattern after fracturing, in order to establish effective drive system and develop low permeability reservoir effectively.In fracturing design, fracture simulation is limited to half-length fractures based on well data in and abroad, and there are few report on quantitative overall full-length fracture simulation in 3D stress field at present.The key problem is to establish 3D rock mechanical field and stress field thousands of meters underground of porous heterogeneous reservoir with high temperature, high pressure and multiphase fluids and identify the magnitude and direction, in order to obtain full-length 3D simulation of the fractures in the whole field and quantitative description of the fractures.Inter-discipline collaboration of geology and engineering in building 3D stress model is the key point.According to the current problems in developing low permeability fields, this thesis focus on petrophysical and geostress problems, guided by relevant subjects such as petroleum geology, geological mechanics, geophysics, reservoir geology, petrophysics, data processing and numerical simulation, reservoir transformation and petroleum engineering, the technology of 3D stress field and fracture simulation with prestack elastic parameter inversion is formed. According to the formula of different classic stress, the new calculating method is established which is the 3D stress field model, the model is made through establishing the principle of superimposed stresses coupling in three-dimensional network. The direction of the maximum principal stress is determined in three-dimensional space by using ray tracing scheme to locate the maximum stress node outside wellbore and link them in sequence. And the intial stress field model is obtained to determined the stress magnitude and orientation of a random particle in the 3D space in the anisotropic reservoir.According to the mechanism of rock failure, the rock failure model considering the 3D inhomogeneous deformation of rock mechanics and stress field is established. Combining the reservoir geological model with the 3D rock mechanics parametric model together with stress field model, the 3D full-length numerical simulation on artificial fracture is studied, and the actual attitude of fracture beyond the well point is quantitatively determined and simulated, making it come true that the artificial full-length fracture is simulated with numerical method and described quantitatively in 3D space.By overlying geological modeling, ground stress field and the whole spread sewing length of artificial fracture, process the Non-Darcy irregular well pattern ensemble fracture optimize modeling. Including:1)ensure the well-drain direction by the maximum horizontal principle stress;2) ensure the well-drain pattern by fracture anisotropy degree;3) ensure well spacing size by fracture extending scale. achieve the best matching of horizontal well, vertical well and three-dimension-spread fracture by developing rational matching research of three-dimension-spread fracture with well pattern and sand body;4) present the new developing model of hyposmosis nonhomogeneity reservoir vectorization space formula well pattern, extend the valid swept volume. Achieve the valid developing of the hyposmosis nonhomogeneity Non-Darcy reservoir by implementing ensemble fracture,individually designing, establishing water injection developing valid driving system.