Abstract
Triple-porosity model is usually adopted to describe reservoirs with multiscaled pore spaces, including matrix pores, natural fractures, and vugs. Multiple fractures created by hydraulic fracturing can effectively improve the connectivity between existing natural fractures and thus increase well deliverability. However, little work has been done on pressure transient behavior of multistage fractured horizontal wells in triple-porosity reservoirs. Based on source/sink function method, this paper presents a triple-porosity model to investigate the transient pressure dynamics and flux distribution for multistage fractured horizontal wells in fractured-vuggy reservoirs with consideration of stress-dependent natural fracture permeability. The model is semianalytically solved by discretizing hydraulic fractures and Pedrosa’s transformation, perturbation theory, and integration transformation method. Type curves of transient pressure dynamics are generated, and flux distribution among hydraulic fractures for a fractured horizontal well with constant production rate is also discussed. Parametric study shows that major influential parameters on transient pressure responses are parameters pertinent to reservoir properties, interporosity mass transfer, and hydraulic fractures. Analysis of flux distribution indicates that flux density gradually increases from the horizontal wellbore to fracture tips, and the flux contribution of outermost fractures is higher than that of inner fractures. The model can also be extended to optimize hydraulic fracture parameters.
Highlights
The concept of dual-porosity media was first proposed by Barenblatt et al [1] to describe naturally fractured media
This study develops a semianalytical model based on source/sink function theory for analyzing transient pressure responses and flux distribution of naturally fractured-vuggy reservoirs, in which the reservoir itself is conceptualized as triple-porosity media and the interaction between hydraulic fractures and reservoir is considered
Based on the mathematical model and discussion in this paper, the following conclusions can be warranted: (1) A mathematical model is presented for investigating transient pressure dynamics as well as flux distribution of multistage fractured horizontal wells in stress-sensitive triple-porosity reservoirs
Summary
The concept of dual-porosity media was first proposed by Barenblatt et al [1] to describe naturally fractured media. In most existing models for fractured horizontal wells in triple-porosity reservoirs three porous media denote hydraulic fractures, natural fractures, and matrix pores, which means the reservoir itself is considered as a dual-porosity medium. This study develops a semianalytical model based on source/sink function theory for analyzing transient pressure responses and flux distribution of naturally fractured-vuggy reservoirs, in which the reservoir itself is conceptualized as triple-porosity media and the interaction between hydraulic fractures and reservoir is considered. The model presented here can completely reflect transient pressure characteristics during all the possible flowing period as well as flux distribution among multiple fractures This model takes into account the stress-sensitivity of permeability caused by closure of natural fractures during production. We first studied the transient pressure responses caused by a continuous line-sink in triple-porosity reservoirs and adopted the line-sink solution with superposition principle to obtain the pressure transient dynamics and flux distribution of multistage fractured horizontal wells in triple-porosity reservoirs
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