Acid Fracturing Technology String Optimization Design

Along with the implementation of improved oil recovery measures in oil field,the acid fracturing technology is increasingly mature,more and more oil companies aplay the technology in oil and gas production operations. The acid fracturing technology can effectively improve the reservoir permeability,reservoir transformation,increase the production of oil and gas wells. In the construction process of acid fracturing, acidizing fracturing string is the only load-bearing member and an important component of the power transmission system. Therefore, analysis of force and deformation and strength check of the column is directly related to the success of acid fracturing construction, is of vital importance to the construction of acid fracturing. The string combination optimization design, to ensure the safety of construction and maximize the economic benefit of oil field.In the paper,I first investigated the acid fracturing string and supporting tools,such as packer, sandblasting, hydraulic anchor and tubing. Fully understand the structure principle,work mode, and the using condition of all parts of the string combination, well prepared for tube optimize design.Through analysing of the reasons of string combination itself influencing the acid fracturing process failure,Some countermeasures are put forward,such as improve the technical performance of the downhole tool,optimize string design, improve the acidizing and fracturing string safety reliability. And awareness of the importance of analysing the stress of acid fracturing string and determining the reasonable setting pressure of the packer. In-depth study of five basic effects of acidizing and fracturing pipe string including the piston effect、expansion effect、temperature effect spiral bending effect and viscous flow effect,and the buoyant weight,internal and external pressure of the string.Make analysis on the factors of influencing stress and deformation of the string combination,and draw the diagram of the detailed stress, strain, and deformation of pipe string,show the intuitive results of the force and deformation of the pipe string, put forward proposals for the selection of the pipe string.Editing acid fracturing string optimization software with VB program,introduce the system software installation requirements, operating environment,installation procedures,and software functions and using methods.Through a variety of input parameters, we can get the string axial force distribution curve、the axial stress distribution curve、the equivalent stress distribution curve、the safety coefficient of distribution curve, tubing elongation curve,then get the string optimization results. Application of the finite element analysis software ANSYS, establish a model diagram of packer and divid mesh of the packer. Calculate the deformation of packer rubber cylinder with different setting pressure and the contact stress between rubber and casing. Through the calculation, finally determine the reasonable setting pressure of the packer. Through theoretical analysis and example calculation,provide theoretical and technical support for the design and optimization of the acid fracturing pipe string.