Abstract
After multistage hydraulic fracturing of shale gas reservoir, a complex fracture network is formed near the horizontal wellbore. In postfracturing flowback and early-time production period, gas and water two-phase flow usually occurs in the hydraulic fracture due to the retention of a large amount of fracturing fluid in the fracture. In order to accurately interpret the key parameters of hydraulic fracture network, it is necessary to establish a production decline analysis method considering fracturing fluid flowback in shale gas reservoirs. On this basis, an uncertain fracture network model was established by integrating geological, fracturing treatment, flowback, and early-time production data. By identifying typical flow-regimes and correcting the fracture network model with history matching, a set of production decline analysis and fracture network interpretation method with consideration of fracturing fluid flowback in shale gas reservoir was formed. Derived from the case analysis of a typical fractured horizontal well in shale gas reservoirs, the interpretation results show that the total length of hydraulic fractures is 4887.6 m, the average half-length of hydraulic fracture in each stage is 93.4 m, the average fracture conductivity is 69.7 mD·m, the stimulated reservoir volume (SRV) is418×104 m3, and the permeability of SRV is5.2×10−4 mD. Compared with the interpretation results from microseismic monitoring data, the effective hydraulic fracture length obtained by integrated fracture network interpretation method proposed in this paper is 59% of that obtained from the microseismic monitoring data, and the effective SRV is 83% of that from the microseismic monitoring data. The results show that the fracture length is smaller and the fracture conductivity is larger without considering the influence of fracturing fluid.
Highlights
Due to the extremely low permeability of shale gas reservoirs, large-scale hydraulic fracturing treatment is often needed to achieve economic productivity
Many scholars have proposed complex fracture network inversion models for shale gas reservoirs, the existing gas-water two-phase dynamic analysis methods are mainly limited to early flowback simulations and cannot be used for long-term dynamic analysis
In this paper, based on the complex fracture network formed after hydraulic fracturing of shale gas reservoirs [10, 11], a gas-water two-phase flow model was established considering complex fracture network conditions and integrates geological-fracturing-production data
Summary
Due to the extremely low permeability of shale gas reservoirs, large-scale hydraulic fracturing treatment is often needed to achieve economic productivity. Due to the difficulty in solving the relationship between saturation and pressure, Zhang and Ayala [8] and Tabatabaie and Pooladi-Darvish [9] used the Boltzmann transformation method to obtain the self-model solution of the oil and gas two-phase seepage model These models are only applicable to the situation before the pressure reaches the boundary. Many scholars have proposed complex fracture network inversion models for shale gas reservoirs, the existing gas-water two-phase dynamic analysis methods are mainly limited to early flowback simulations and cannot be used for long-term dynamic analysis. Combining the analysis results of the flow stage and the automatic history matching correction fracture network model, a set of shale gas reservoir production decline analysis and fracture network inversion methods considering fracturing fluid flowback are proposed
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