Productivity of Multiply Fractured Horizontal Wells in Tight Gas Reservoirs

Abstract

Abstract Horizontal wells can be stimulated by the creation of a number of hydraulic fractures along the wellbore. if the well is drilled in the direction of the minimum horizontal stress, a series of transverse hydraulic fractures will be induced. The limited communication between such transverse fractures and the wellbore creates a choking effect near the well and causes an apparent reduction in fracture conductivity. Methods to estimate the effect of the limited communication between the wellbore and the fracture based on Darcy flow of fluid in the fractures have been recently reported. Such methods, however, should not be applied to gas reservoirs since non-Darcy flow effects within the fracture may significantly influence well performance, particularly as the degree of communication performance, particularly as the degree of communication between the fracture and the wellbore is reduced. This study considers the effect that non-Darcy flow within the hydraulic fractures has on horizontal well productivity in tight gas reservoirs. Well performance was simulated with semi-analytical models and by numerical simulation. The effect of fracture and reservoir properties of gas well productivity is discussed, and various development productivity is discussed, and various development options for tight gas reservoirs are compared. Introduction The use of horizontal wells for exploiting oil and gas reservoirs is now firmly established within the industry. A survey of worldwide drilling activity reported plans for over 4500 horizontal wells in 1990. Although most of the horizontal well drilling to date has centred on oil reservoirs, interest in applying it to gas reservoirs is increasing. Horizontal gas wells in Alberta, Appalachian Basin (W. Virginia) and North Sea reservoirs have been recently reported. Of particularly interest are low-permeability gas reservoirs in which economic flow rates can normally be achieved only through hydraulic fracturing of the formation. Studies on the tight, naturally fractured Sole Pit area and tight gas reservoirs in general have Pit area and tight gas reservoirs in general have demonstrated that a horizontal well can outperform a hydraulically fractured vertical well. Furthermore, the orientation of the horizontal well can be controlled, whereas that of a hydraulic fracture depends on the stress prevalent regime present. prevalent regime present. Stimulation of a horizontal well in a low-permeability reservoir may further increase well productivity. Unlike a vertical well, a horizontal well may be fractured at more than one point along the well length. Multiply fractured horizontal wells (MFHWs) have been successfully applied by Maersk in oil reservoirs in tight chalk. The productivity increase resulting from multiple hydraulic fracture treatments along a horizontal well in a gas reservoir in naturally fractured shale can be 7 times greater than that achieved for stimulated vertical wells. The use of MFHWs in the development of coal-bed methane has also been recently studied. P. 133