The Research On Micro-fracture Characteristics Based On Digital Analysis Method

With the improvement of oil exploration and oil development technology, the proportion of fractured oil and gas reservoirs in oil and gas reserves increased year by year, most of effective oil fields being fractured reservoirs (natural, artificial).Therefore, it is of important significance to understand and evaluate formation fracture for drilling and development in oil and gas fields. In the previous analysis of fracture micro morphology,owning to the absence of quantitative methods, researchers could only use such qualitative means as the surface roughness or test methods to indirectly research fracture conductivity and the rule of crack closure. Therefore, the results were not of high accuracy and reliability.The paper starts with the fracture micro morphology, building model to quantitatively reflect the mechanical characteristics of fracture and flow characteristics of fracture through frature surface morphology and physical parameters of rock. So, the result can make a more accurate prediction to the exploitation of fractured reservoirs. The paper is based on the previous studies, summarizing the main content of rock fractures study on micro characteristics, the measurement methods and description methods of rock fracture surface morphology. On this basis, a digital analysis method for describing rock fracture surface morphology is put forwad, which is realized by laser scanning system. In this way, the concept of the degree of coincidence is forwarded to make a quantitative description to two surfaces characteristics of fracture based on the previous studies of our team.Then the specific realization and application of the methond is introduced. By comparing and analyzing the conventional method of fracture microscopic surface morphology and the digital analysis method, the relative merits of two methods and the limitations of the conventional have been summarized. Based on four core samples scanning data and digital graphic (the spacing distribution histogram of fracture, the spacing contour maps of fracture surfaces) got by the digital analysis method, the paper build a fracture closure model and a fluid flow model of rock fracture combining mechanical properties of rock. Then a series of4rock plate compression test and four core samples displacement experiment had been made to verify prediction accuracy of the model, Afer the experimental results are analyzed and summarized, it is clear that the model predicted error is low, less than15%. Analyzing the causes of error, taking the effect of experimental conditions into account, the fracture microscopic characteristic model based on the digital analysis method makes a good predict effect. Comparing evaluation effects of other fracture microscopic characteristic methods, the fracture microscopic characteristic model based on the digital analysis method can make a better analysis and quantitative predict to the microscopic characteristics of fracture, which can provide a new way of thinking and quantitative evaluation methods to the evaluation of fractured core and development evaluation of fractured reservoirs.