The Horizental Stress Field Distribution Of Offset Wells And Horizental Stress Analysis With Well-logging Technologies

Oil& gas ,as the liquid inside the pores of the crust of the earth, the procedures of its generation, immigration and accumulation was the process of the hydraulic and accumulation in the pores driven by the terrestrial stress. The research on terrestrial stress is one of the important aspects of oil& gas industry, which is also one of the main paths of research of the oil &gas bearing basins evolvement and oil& gas immigration drives ,also the research and development base for the oil& gas reservoir fracturing technologies. The well-logging technique has been showing its advantages because of being continue ,reliable, economic and high resolution.The paper introduces the model (eformingporous& elastic horizontal stress changing model) , which is being used in Schlumberger and has taken the Young's modulus and Poisson's ratio into account.The forth order 2D partial differential equation in terms of stress function has established by researching the offset wells stress fields and boundary of the drilling affected areas, together with the stress calculation beyond the areas affected. The analysis calculating formulas for plane stress have been come up with finally. The stress model has been turned from the stress changing of the plane stress to the one based on the research of stress of the offset wells.The mathematics model for the stress analysis is established via the stress model and the boundary conditions mentioned above, which can be applied for the stress calculating (Polar Coordinates,right angle)of any spot inside the stress field of the researching area , and the calculating formulas for the maximum and minimum main stress and their direction of any spot of the stress field have been concluded eventually. the calculation and ploting of stress field is obtained by computer programming.Furthermore, with the developing of the oil& gas reservoir fracturing technologies, the research of the offset wells horizontal stress changing is vital for the reconstruction of the oil &gas reservoirs , which are meaningful for the development of the operation of petroleum engineering in the Oilfields.