Analysis of Production Data from Multi-Fractured Shale Gas-Condensate Wells Coupled the Microscale Effects of Gas Transport
Authors: Bai Wenpeng , Cheng Shiqing , Cai Dingning , Guo Qiao , Guo Xinyang , Wang Yang 
Published: August 2024

ABSTRACT:
Analysis of early production data from shale condensate gas wells is crucial in assessing the effectiveness of reservoir fracturing processes. This paper presents a productivity prediction model for multistage fractured horizontal wells that considers slip flow, Knudsen diffusion, surface diffusion, and rock stress-dependent in shale condensate gas reservoirs. The model combines the multiphase material balance method and the constant component expansion test to accurately describe the phase behavior changes during the development process of condensate gas reservoirs. The results show that the microscale effect of gas transport gradually increases as the reservoir pressure decreases, and the new model predicts higher gas production and more accurate fracture parameters interpreted by history matching compared to the conventional model. In addition, the new model can predict production data for both linear and boundary dominated flow. Comparison of numerical simulation case and validation of filed case show the practicality of the proposed model, which is important for both productivity prediction and reserve assessment in shale condensate gas reservoirs.

1. INTRODUCTION
The development of multi-stage fracturing horizontal well drilling technology has become an important guarantee for the industrialized exploitation of unconventional oil and gas resources (Clarkson et al., 2020; Wang et al., 2020; Yan et al., 2024). There are many difficulties in the development of shale condensate gas reservoirs, such as the possible three-phase flow of oil, gas and water in the reservoir, the existence of a complex network in the stimulation area after large-scale fracturing, the need to consider the microscopic flow mechanism of the gas in shale nanopores, and the complexity of the fluid saturation and pressure relationship compared with that of the conventional condensate gas reservoirs.
Rate transient analysis (RTA) methods in unconventional oil and gas reservoirs can be used to analyze gas well production dynamic data, interpret reservoir and fracture parameters (Qanbari et al., 2017; Hamdi et al., 2018; Behmanesh et al. 2018), and assess the recoverable reserves of oil and gas reservoirs. In recent years, some scholars have developed analytical and semi-analytical transient production analysis methods to interpret parameters during linear flow in multiphase flow (Wu et al., 2023). Most scholars only consider a single flow regime in shale reservoirs (Clarkson and Qanbari, 2015; Williams-Kovacs and Clarkson, 2016), and seldom consider both linear flow and boundary control flow in the seepage equation for both oil and gas phases. Behmanesh et al. (2013) proposed a method for RTA analysis of tight condensate gas reservoirs, focusing mainly on transient linear flow regime. Miao et al. (2018) developed a rate transient analysis model considering multiple gas transport mechanisms of shale gas. They coupled gas slip flow, Knudsen diffusion of bulk gas and surface diffusion of adsorbed gas to pseudo-pressure and pseudo-time to obtain the analytical solution of gas production, but their model could not consider the two-phase flow mechanism of condensate gas. Luo et al. (2019) proposed a method for production data analysis in low-permeability volatile oil reservoirs, which includes transient linear flow and boundary-controlled flow, and they emphasized on the full-flow regimes analysis and proposed an empirical relationship between fluid saturation and pressure in volatile oil reservoirs through many numerical simulation studies. Zhang et al. (2021) Considering the microscopic flow mechanisms of gas-water two-phase flow in shale nanopores, a gas-water two-phase flow model during fracturing flowback of shale reservoirs is established. However, it requires many iterative calculations, and does not consider the oil-gas two-phase flow, and the actual application effect is poor. In summary, these methods are not applicable to the calculation of shale condensate production and their method does not consider the microscale gas transport mechanisms from shale nanopores, so new models need to be developed to predict the production of shale condensate wells.