Study On Integral Fracturing Technology Of Heavy Oil Reservoir

The targeted block of this thesis is a newly discovered heavy oil reservoir of a certain oilfield in China, which is high in viscosity and great in depth. During the early stage of the hydraulic fracturing process, some problems such as the water appears too fast, the wells are inefficiency or the production capacity of the wells cannot meet the designed requirements may occur due to the lack of a unified understanding of the integral fracturing for heavy oil reservoir.This paper aims to improve the fracturing effect of this heavy oil reservoir, and the main works accomplished are as follows:①Comprehensively analyze the physical properties of the formation and the effect of the fracturing based on the early fracturing data and technology of the fractured wells in this block. Then combine the analysis of the parameters and the effect of fractures and using gray correlation method, to determine the main control factors of fracturing effect.②Starting from the geological characteristics of heavy oil reservoir with great depth and high temperature to establish a theoretical model of open hole completion or perforated completion aiming at different angles of inclination and azimuth, which can predict the sand production of wells by using various methods, such as the mathematical model of stress distribution around the wellbore, elastic-plastic mechanics, rock mechanics, and the Mohr-Coulomb’s strength criterion. Then compute the critical flowing pressure of bottom hole in the experimental well group and determine the critical flowing pressure of sand control in the heavy oil reservoir. After that, calculate the reasonable difference-in-pressure of the experimental well group according to the results of three-axis stress test.③Establish a three-dimensional and professional geological model of the target block through the analyze of the well logging data by using professional software, and make a fitting analysis of the pre-production data as well as the reserves in this block.④Considering the characteristics of the heavy oil reservoir which is based on the integral fracturing of the well group, and combined with the previous result of the reasonable difference in pressure, to make a optimized analysis of the fracture data such as the length and the diversion capacity of the fracture, the fracturing layer, the distance between wells and the production parameters in the targeted block by using a method which combines numerical simulation and hydraulic fracturing theory.⑤Based on the characteristic that there is a large difference in viscosity among the whole block, to optimize the combination of parameters in different layers and determine the relationship between the optimal combination of parameters and viscosity by using numerical simulation.⑥Use the method of orthogonal experiment to analyze the factors that may influence the effect of integral fracturing in heavy oil reservoir, select the optimal combination of parameters for the targeted heavy oil reservoir and solve the problem of determining the fracturing parameters that may influence the integral fracturing in it.⑦Make a optimization of the integral fracturing techniques that fit the heavy oil reservoir with great depth and high temperature according to the practical situation of the targeted block. Then analyze the secondary sand-adding fracturing and the conventional fracturing comparatively to optimize the parameters that are suitable for the secondary sand-adding fracturing in this block. According to it, some fracturing-design principles and conclusions can be obtained, which could provide a reliable, reasonable and scientific basis for a proper fracturing in the targeted block.