A Research Of Earth Stress And Rock Strength Parameter In Hydraulic Fracture

The technology of waterfrac treatment is a new emerging one which is used in many fields after several years’development and it will have a bright future.It is widely used when the later stage of oil field development comes and especially to the reservoir who has low permeability will make it a good method to attain we pepole’s goal of increasing production of oil. People pay great attention to it since the improvement of oil field development technology become obviously known to us.When the waterfrac treatment is applied to layers,the hight of the formed fissures will not be a fixed value but varys with different time and space. The essence of technology of waterfrac treatment is to inject fluids to layers to make them collapse and make fissures come into being so the goal of project will be attained.The earth stress is a stress which lies in earth crust interior, groud stress field has closed relations with oil and gas that is proved by research results which are related to exploration activity and oil filed development. Research on structure stress applying to exploration activity have being rapidly carrying out not only in china but also in abroad. The main research content is the evolutionary of earth stress, the layout of earth stress, the direction of earth stress and the size of earth stress.Recently, methods as mathematical simulation,physical experiment simulation and some other method like fluid potential calculation to ascertain the groud stress field are feasible.In oil field development, the main research about earth stress is aroud the layout of earth stress and the layer rocks’character and so on. Another important parameter is rock strength. Rock’s mechanics character is related to its longitudinal wave slowness time and transverse wave slowness time in area which is short of rock core information especially in area where logs are not sufficiently drived.The way to use logging material to calculate rock parameters of mechanic and research rock strength is bascally on mechanic,meanwhile,the condition of the experience formulas can be discussed by prossing five logs to get a reasonable conclusion about the use of the experience formulas to provide a practical data so as to save the cost. From the two parameters called earth stress and rock strength,collapse pressure together with the stability of wellbore and the height of fissures are predicted and finally be calculated.