A new productivity prediction model for horizontal wells in tight oil reservoirs after volume fracturing

Abstract

It is very difficult to predict the productivity of a horizontal well in a tight oil reservoir after volume fracturing as many factors affect its productivity and these factors are interconnected with each other intricately. Therefore, a new productivity prediction model considering the impacts of multiple geologic and engineering factors has been proposed in this work. In this study, firstly, three-dimensional geological parameters of the study area were obtained by establishing its three-dimensional geological model. Secondly, a sweet spot evaluation model by coupling key geological parameters was established, and productivity impact factors and reservoir sweet spot factors were calculated to pick out the main factors affecting productivity and reservoir geological quality; moreover, the fracture development factor was calculated based on the rock mineral composition to assess the reservoir engineering quality. Finally, a prediction model of ultimate recoverable reserves (EUR) of horizontal wells was established based on the reservoir comprehensive quality index, to predict the productivity dynamically. The new model was adopted to predict productivities of some horizontal wells in a typical tight oil reservoir in western China. The results show that the geological factors affecting productivity in descending order are horizontal section length, reservoir thickness, oil saturation, permeability and porosity. The field application has confirmed that the reservoir comprehensive quality index has a good correlation with EUR. The productivities of 45 horizontal wells predicted by the model had an average relative error of 6.3%, proving that the model has good practicability. The research results can guide the evaluation of volume fracturing effects and schemes for horizontal wells in tight reservoirs.