The Effects of Fracture Penetration Ratio and Fracture Conductivity on the Performance of Hydraulic Fractured Vertical Wells in Gas Reservoirs

Abstract

Predicting the effects of the fracture penetration ratio and fracture conductivity in hydraulically-fractured vertical wells in dry-gas and wet-gas reservoirs is important in determining the well performance in a given formation. A fracture length and conductivity which provide the highest ultimate gas recovery factor at the earliest time to reach abandonment conditions is the proper fracture type which has to be selected for developing the reservoir.

A three dimensional reservoir simulation model is used to evaluate the performance of hydraulic fractured vertical wells as a function of fracture penetration ratio and fracture conductivity. Accurate determination of initial gas reserves, average reservoir pressure at abandonment time, and the time to reach abandonment conditions is very important to the petroleum industry. Material balance technique and volumetric method, currently used in the petroleum industry to determine the reserves, which do not consider well performance and, as a result, predict a very high recovery factor at abandonment pressure for hydraulic fractured vertical wells in volumetric dry-gas and wet-gas reservoirs.

Well performance in hydraulic fractured vertical wells depends on fracture penetration ratio and fracture conductivity. A comparison with horizontal wells of same penetration ratio is also provided in this paper as an alternative to hydraulic fracturing. A number of simulation runs were performed on a square shape reservoir of horizontal permeability 0.01 md, 0.1 md and 1 md with a penetration ratio of 0.2, 0.4 and 0.8. Our results quantify and show that the ultimate recovery factor and abandonment time are function of fracture penetration ratio regardless of fracture conductivity. In addition, our results shows that in low permeability reservoirs a hydraulic fractured vertical well of similar penetration ratio to a horizontal well perform twice in terms of recovery factor and abandonment time.  The effects of formation thickness, well parameters and reservoir rock properties on the average reservoir pressure at abandonment time and on the time to reach the economic limit are also presented in this paper.  Based on the results of fracture penetration ratio and fracture conductivity in volumetric dry-gas and wet-gas reservoirs, this paper presents recommendations regarding the proper well type with which the reservoir should be developed.