New Mechanical and Damage Skin Factor Correlations for Hydraulically Fractured Wells

摘要

Hydraulic fracturing is one of the most common well stimulation techniques. Hence, considerable amount of efforts has been devoted to study their performance under different prevailing conditions. Description of hydraulically fractured wells using the existing commercial reservoir simulators requires the use of very fine grids, which is very cumbersome, costly and impractical. In this work a two dimensional single-well mathematical simulator has been developed, which is based on finite-difference methods, and simulates linear Darcy flow in a hydraulic fractured well. Based on the results of our in-house simulator different correlations have been developed for calculation of fracture (Sf), face damage (SfD), and chocked damage (Sck) skin factors. These formulations benefit from relevant dimensionless numbers expressing the effect of geometry and those used to quantify the extent of damages occurred during fracturing operation. The results indicate that in-house Sf values are more accurate than those available in the literature. SfD, reflecting the reduction of the permeability of the rock close to the fracture, is more realistically captured here when damaged thickness is assumed to decrease linearly towards the tip of the fracture. This is more superior to the uniform thickness assumption made in the literature, which overestimates SfD. It is also shown the available analytical expression for calculation of Sck, which is a reflection of reduction of fracture permeability, overestimate Sck hence, a more realistic correlation has been developed for this purpose. The skin correlations developed here enables the engineers to study the productivity of a fractured well using simple open-hole system. They can also be used for the optimum design of a hydraulic fracture system by minimizing flow resistance for a given fracture volume and fracture permeability. This can be achieved readily by conducting simple derivation of the mathematical expressions of skin formulations presented here.