Abstract
ABSTRACTThe channel fracturing technique has been proven to provide much higher conductive fracture networks by placing discontinuously proppant inside fracture packs. Despite the great success of this new fracturing technique, there is still a lack of models and methods to characterize non-uniform placement of fracture proppant and heterogeneous permeability distribution within stimulated-reservoir-volume (SRV). In this article, a dual-porosity model is coupled with the tri-linear flow model to quantify the production performance of channel fractured horizontal wells. As a consequence of channel fracturing, the non-uniform distribution of fracture networks, and the heterogeneities of both matrix/fracture porosity and permeability are characterized using fractal theory. By implementing the Bessel Function and Laplace transform techniques, analytical solutions are derived by integrating fluid flow across primary hydraulic fractures, SRV and unstimulated reservoir matrices. Through quantitative comparisons of well bottom-hole pressure history, a synthetic fine-grid numerical simulation example is implemented to verify the accuracy of analytical solutions. Sensitivity analysis of fractal dimension, fractal connectivity-index and primary fracture conductivity is carried out to quantify the temporal and spatial consequences of channel fracturing on both reservoir/facture heterogeneity and well productivity throughout well life.
Highlights
In recent years, shale oil and gas have greatly contributed to the US energy portfolio and are expected to be the main source of energy within the 20 years
The results indicated that the enhancement of fracture conductivity by a non-uniform proppant cluster is several orders of magnitude larger than that of a 20/40-mesh sand proppant pack with even distribution (Figure 2)
With the increase of fractal dimensions, the average values of fracture permeability increase, which means the enhancement of the conductivity of average hydraulic fractures
Summary
Shale oil and gas have greatly contributed to the US energy portfolio and are expected to be the main source of energy within the 20 years. The proppant pack serves as a mechanical support to open hydraulic fractures, which form a highly conductive porous medium for fluid flow. Fractal theory is combined with the tri-linear flow model in a dual-porosity matrix-fracture system to present the production of multistage fractured horizontal wells. 2. Fracture conductivity with open channels The objective of the channel fracturing technique is to introduce a heterogeneous fracture structure with open channels inside fractures instead of the conventional homogenous distribution of proppant pack to enhance the flow capacity of reservoir fluids. This article extends the fractal theory to demonstrate the non-uniform distribution of proppant pack inside both primary fractures and SRV caused by the channel fracturing technique, as shown in Equations (1–6): km(y) = km y bf dm−θm−2.
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