A study of the mechanism of nonuniform production rate in shale gas based on nonradioactive gas tracer technology

Abstract

The performance of horizontal wells in shale gas is controlled by multiple factors, and there is a difference in gas production rate between different fracturing stages. However, the mechanism of the nonuniform gas production rate is still not clear. In this paper, a typical shale gas well in the Longmaxi formation was selected to conduct the performance evaluation based on the nonradioactive gas tracer technology. The gas production profile was obtained, and the production feature of each stage was analyzed. On this basis, the production differences between fracturing stages were compared in four aspects: reservoir physical properties, distribution of natural fracture, parameters of fracturing operation, and technology of temporary plugging re‐orientation. The effect of various factors on the contribution of each stage was analyzed. And then, the mechanism of the nonuniform gas production rate was clarified. Finally, relevance analysis was performed to determine the main controlling factors, and a mathematical model for characterizing the nonuniform gas production rate feature was established by adopting the nonlinear regression method. This study provides a reliable basis for optimal fracturing designing and reasonable production planning.

Distribution Characteristics and Backflow Flow Pattern of a Slickwater Fracturing Fluid in Shale Based on Low-Field Nuclear Magnetic Resonance

“…In this case, the goal is to compare the relative effects of multiple independent variables on the dependent variable. Therefore, standardized regression coefficients are used. , Typically, a significance value below 0.05 is considered statistically significant, indicating that the linear regression is valid. Due to operational errors and uncontrollable physicochemical influencing factors in practical experiments, it is challenging to achieve ideal experiment results.…”

“…Additionally, most shale gas areas in China are located in mountainous regions, which significantly increases investment costs. 3,4 As shale gas reservoirs are considered unconventional reservoirs, hydraulic fracturing is a necessary technique for industrial extraction. After hydraulic fracturing operations, well soaking measures are typically applied before commencing production to allow for the backflow of fracturing fluids from the reservoir.…”

“…Compared to shale plays in North America, shale gas reservoirs in China are more structurally complex and deeper and present greater technical challenges for extraction. Additionally, most shale gas areas in China are located in mountainous regions, which significantly increases investment costs. , As shale gas reservoirs are considered unconventional reservoirs, hydraulic fracturing is a necessary technique for industrial extraction. After hydraulic fracturing operations, well soaking measures are typically applied before commencing production to allow for the backflow of fracturing fluids from the reservoir. − During the fracturing process, fracturing fluids can easily enter the shale gas reservoir and become trapped under capillary pressure, leading to significant impacts on the reservoir properties and productivity.…”

“…Yang et al found through shale soaking experiments that a large amount of a high-salinity water film is attached between the crystal layers of shale clay minerals. When low-salinity fluids from the outside invade the shale reservoir, the high-salinity water film on the surface of the clay minerals will quickly dilute. , There are three main mechanisms for the hydration of clay minerals in shale after encountering water, − namely, surface hydration, ion hydration, and osmotic hydration. The distribution of fracturing fluids in shale pores is closely related to factors such as minerals, ion concentration in the aqueous phase, and the external environment .…”

Transient Interporosity Flow in Shale/Tight Oil Reservoirs: Model and Application

“…However, in well test models or numerical simulation models, the dual-porosity model is still widely used to compromise between accuracy and computational efficiency. To overcome the high in situ stress and horizontal stress difference and to improve the complexity of the fracture, multicluster fracture with tight cutting has been used in recent years . The flow between the perforation tunnel and matrix can also be characterized by the dual-porosity model, which can provide the possibility to optimize the number of perforation clusters.…”