The Effect of Fracturing Fluid Saturation on Natural Gas Flow Behavior in Tight Reservoirs

Mianmo Meng,Yang Wu,Hongkui Ge,Yinghao Shen,Xiaosong Xu

doi:10.3390/en13205278

Mianmo Meng, Yang Wu + Show 3 more

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https://doi.org/10.3390/en13205278

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Abstract

Hydraulic fracturing becomes an essential method to develop tight gas. Under high injection pressure, fracturing fluid entering into the formation will reduce the flow channel. To investigate the influence of water saturation on gas flow behavior, this study conducted the gas relative permeability with water saturation and the flow rate with the pressure gradient at different water saturations. As the two dominant tight gas-bearing intervals, the Upper Paleozoic Taiyuan and Shihezi Formations deposited in Ordos Basin were selected because they are the target layers for holding vast tight gas. Median pore radius in the Taiyuan Formation is higher than the one in the Shihezi Formation, while the most probable seepage pore radius in the Taiyuan Formation is lower than the one in the Shihezi Formation. The average irreducible water saturation is 54.4% in the Taiyuan Formation and 61.6% in the Shihezi Formation, which indicates that the Taiyuan Formation has more movable water. The average critical gas saturation is 80.4% and 69.9% in these two formations, respectively, which indicates that the Shihezi Formation has more movable gas. Both critical gas saturation and irreducible water saturation have a negative relationship with porosity as well as permeability. At the same water saturation, the threshold gradient pressure of the Taiyuan Formation is higher than the one in the Shihezi Formation, which means that water saturation has a great influence on the Taiyuan Formation. Overall, compared with the Shihezi Formation, the Taiyuan Formation has a higher median pore size and movable water saturation, but water saturation has more influence on its gas flow capacity. Our research is conducive to understanding the effect of fracturing fluid filtration on the production of natural gas from tight reservoirs.

Highlights

A tight sand formation attracts a lot of attention due to its great natural gas-bearing property [1], and hydraulic fracturing is regarded as an effective way to exploit its resources [2,3]
The main purpose of our study focused on the effect of fracturing fluid filtration on the exploitation of natural gas from tight reservoirs
A tight reservoir is an important formation to hold a large amount of natural gas, and hydraulic fracturing is necessary to exploit the resources

Summary

Introduction

A tight sand formation attracts a lot of attention due to its great natural gas-bearing property [1], and hydraulic fracturing is regarded as an effective way to exploit its resources [2,3]. Under the effect of high injection pressure, capillary force and osmotic effect, and so on [4,5,6], fracturing fluid filtrates into the formation. This behavior can reduce the gas flow channel, and cause aqueous phase trapping (APT), which will influence the natural gas exploitation [7,8]. Bennion et al [16] proposed two important parameters to evaluate APT damage, including initial water saturation and permeability

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Conclusion