Productivity Increase Estimation for Multi Stage Fracturing in Horizontal Wells for Tight Oil Reservoirs

Abstract

Abstract Hydraulic fracturing is widely used to exploit the tight and low permeability oil and gas reservoirs. With recent technological advances, horizontal wells, along with Multi Stage Fracturing (MSF) have come up with a great effective combined solution for tight reservoirs. The combined technologies overcome formation damage, increase reservoir contact, enhances productivity from fractures; hence make tight reservoirs development economical. On the other hand, drilling a horizontal well with placing multi stage fractures along its lateral is an expensive job. The feasibility of this job should be done to analyze the productivity enhancement provided by the Multi Stage Fracturing before commencing drilling operation. This work developed a simple, easy to use empirical correlation to calculate oil productivity enhancement in terms of fold of increase (FOI) for Pre-Frac analysis. In this paper, an approach has been put forward to evaluate the FOI in Multi Stage Fractured system for horizontal wells in the form of a correlation. The approach used is based on two 3-D simulation modelling scenarios; one with hydraulic fractures and the other without. The fracture case has been run for a wide range of parameters like number of fracture stages, formation permeability, fracture spacing, fracture conductivity and fracture half length, while the other case was run with changing formation permeability only, which served as the base case. The productivity index for both cases corresponding to same formation permeability was used to compute FOI for all different scenarios. A general empirical correlation for estimation of increase in oil productivity due to multi-stage fracturing in horizontal wells is derived through the use of multivariate regression. Correlation is obtained by 70% data points with the accuracy results of 5.20%, 0.54% and 7.79 Mean absolute percentage error, Mean percentage error and standard deviation respectively. The obtained correlation is tested against 30% of unused data points and found to generate acceptable results with 5.20%, 0.50% and 7.40 Mean absolute percentage error, Mean percentage error and standard deviation respectively. The developed correlation is accurate enough to capture even the minor changes in flow inside wellbore as well as interference between adjacent fracture stages. It will serve as a handy tool for pre analysis of fracture performance as compared to the costly and time consuming analytical or simulation models.