A New Method for Providing Increased Fracture Conductivity and Improving Stimulation Results
Authors: Tinsley J.M. , Williams J.R. 
Published: December 2007

The effectiveness of the propping agent has a great bearing on the success of a fracturing treatment. A proppant bed with low intergranular permeability results in poor well performance. This paper presents a method for creating a propped fracture where the performance is dependent on the flow channels between spaced beds of proppant.

Introduction

The success of a fracturing stimulation treatment is dependent on the strength and distribution of the propping agent used to prevent the created fracture from closing after the treatment. A method is presented in which the proppant is distributed in a planned spaced manner throughout the fracture separated by stages of flush fluid. In this periodic propped method, the proppant stages function as periodic propped method, the proppant stages function as pillars to hold the fracture surfaces apart so the fluid pillars to hold the fracture surfaces apart so the fluid may flow between the proppant beds. The flow capacity of an open crack is several orders of magnitude greater than that of a bed of proppant. The design of the staging is discussed and the mathematical model it is based on is given. Treatments in the field are discussed and results are given for three areas. Significant production-increase values have been realized.

Background

It is generally accepted that increased productivity resulting from hydraulic-fracturing stimulation treatments is dependent on the effectiveness of the propping agent used. The vertical fracture Aces are held apart during the fracturing treatment by the friction pressure caused by the flow of the fracturing fluid. However, when the treatment ends and this friction pressure is no longer present, the fracture opening closes under the influence of the tectonic stresses. In fracturing treatments, some type of granular propping agent, such as sand, is transported into the propping agent, such as sand, is transported into the fracture to hold the faces apart. The proppant bed that fills the fracture may have a fluid conductivity hundreds of times greater than the formation. This proppant-filled channel serves to increase the effective drainage radius of the wellbore and increase the well's producing rate. A number of authors have discussed the importance of the conductivity of the fracture with respect to the production improvement realized. production improvement realized. The ratio of fracture conductivity to formation permeability (C/ki) generally should be greater than permeability (C/ki) generally should be greater than 10,000:1 if the full benefit of the propped fracture is to be realized. The effect of fracture conductivity on the production increase may be illustrated by the curves in Fig. production increase may be illustrated by the curves in Fig. 1. For a well on 40-acre spacing with rw = 0.33 ft, the constant on the abscissa (RCF) would be 0.006. Thus, a C/ki ratio of 10,000:1 will result in RC (relative capacity) = 60, and the Jfs/Ji values are near maximum for any L/re value. If the formation permeability (ki) was 0.1 md, a fracture flow capacity of 1,000 md-ft would be needed for C/ki = 10,000. Fig. 2, the flow capacity of 20-40 sand, shows that such a flow capacity could be obtained at concentrations above 1,000 lb/1,000 sq ft of propped area. However, if the formation permeability was much greater than 0.1 md, it would be necessary to use a proppant with much higher flow capacity. This generally proppant with much higher flow capacity. This generally means a larger grain size, which increases the probability of grain crushing and sand-out. At some higher formation permeability it might not be possible to obtain sufficient conductivity using possible to obtain sufficient conductivity using conventional propping methods and materials.

JPT

P. 1319