Fracture network swept volume (FSV) is an effective means to directly evaluate the fracturing effect of multi-fractured horizontal wells (MFHWs). In the paper, first, the multi-level evaluation system was established by using the analytic hierarchy process (AHP) to describe the nonlinear relationship of various factors. Then, grey relation analysis (GRA) was used to calculate the weight factor and determine the main factors that influence the effect of volume fracturing. Finally, coupling GRA with FL to calculate the Euclidean distance, which is used to predict FSV. The hybrid model reported here has been successfully applied to the tight oil field in Western China. Practical application results demonstrated a good agreement between the measured initial production and the output of the model. The appraisal factors were ranked in order of their weight factor, the results shown that fracturing fluid volume, fracture density, brittleness index, displacement, proppant amount, horizontal stress difference, breakdown pressure and muddy content as primary parameters. The research results provide a new idea for predicting the FSV of horizontal wells in tight oil reservoirs.

1. Introduction

The commercial development of unconventional oil and gas has accelerated the energy independence of the United States and pushed the wave of energy revolution to the world [1-3]. China is also rich in tight oil resources, which are mainly distributed in large basins such as Ordos Basin [4], Junggar Basin [5-6], Songliao Basin [7-8], and Sichuan Basin [9-10]. It has been proved by a large number of field practices that horizontal well combing volume fracturing technology has become the key technology for efficient development of tight oil reservoirs [12-14]. New fracturing tools and materials have further promoted the development of volume fracturing technology, and the development effect has been greatly improved [15-17]. However, due to technical and economic limitations, the problem of how to effectively evaluate the effect of volume fracturing has not been effectively solved, in which the FSV is the key index to evaluate the effect of volume fracturing. As the geological and engineering parameters of different fracturing sections of horizontal wells are quite different and different parameters affect the FSV in different degrees [18-21], the evaluation and prediction of the FSV are faced with great challenges. Therefore, how to efficiently and economically predict the FSV of each fracturing section of a horizontal well is one of the important tasks faced by field engineers.

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