Pore structure characterization of tight sandstones via a novel integrated method: A case study of the Sulige gas field, Ordos Basin (Northern China)

An accurate description of fluid flow is critical for the prediction of the productivity of shale gas reservoirs. In this paper, we present the current advances and a systematic summary on the fluid flow in shale gas reservoirs. First, shale pore structures, consisting of organic pores and inorganic pores ranging from nanoscale to micro-scale, and reservoir fluids, including free gas, absorbed gas, and water, are systematically presented. Thereafter, multi-physics flow phenomena motivated by scale effects, such as continuum flow, slip flow, transition flow, free molecular flow, and surface diffusion for gas, as well as the effective viscosity and slip boundary condition for water, are carefully summarized. Meanwhile, these flow mechanisms are discussed with molecular dynamics (MD) simulations and theoretical analysis. Subsequently, on the basis of upscaling approaches, including capillary bundle models, the lattice Boltzmann method (LBM), and pore network models (PNMs), fluid flow through heterogeneous shale matrix is reviewed and the influences of scale effects and pore structures are clarified. Additionally, shale gas well performance is discussed by combining the multiple transport mechanisms and a fracturing-shut-in-flowback-production process. Our review concluded that the fluid flow behaviour in shale gas reservoirs is a complex multi-scale process accompanied by multi-physical phenomena and multi-fluid distributions. Keeping this in mind is helpful for predicting the shale gas production and recoverable gas resources. We expect this study can not only help by providing a better understanding of the fluid flow in shale reservoirs but also provide significant implications to address other multiphase flow processes. 

A comprehensive review on the flow behaviour in shale gas reservoirs: Multi‐scale, multi‐phase, and multi‐physics

Non-Darcy flows in layered porous media (LPMs) with contrasting pore space structures

An integrated model with stable numerical methods for fractured underground gas storage

The application of traditional well test interpretation methods cannot comprehensively consider characteristics of stress sensitivity and non-Darcy flow for low-permeability composite gas reservoirs, which makes it difficult to obtain real reservoir parameters. Based on the micro-mechanism analysis of stress sensitivity and non-Darcy flow in low-permeability gas reservoirs, the flow motion equation was improved. Thus, a mathematical model was established which belongs to the inclined well in the composite gas reservoir with a conventional internal zone and low-permeability external zone. Applying the finite element method to solve the flow model through Matlab programming, the equivalent pressure point was selected to research the pressure distribution of the inclined well. On this basis, the bottom hole pressure dynamic curve was drawn, the flow process was divided into seven stages, and the parameter sensitivity analysis was carried out. Finally, the advanced nature of the new model applied to the interpretation of the well test model is compared by conventional methods. The non-Darcy flow can cause the gradual upward warping of the bottom hole pressure dynamic curve in the later stage, and non-linear enhancement leads to an increase in the upturn through the simulation test. When the inclination angle is greater than 60°, early vertical radial flow and mid-term linear flow gradually appear. A decrease leads to a shorter duration of the pseudo radial flow in the internal zone and the radius of the internal zone. The conduction coefficients ratio of internal and external zones affects the pseudo pressure derivative curve slope in transition phase of pseudo radial flow in the internal and external zones. A comprehensive consideration of the low-permeability composite gas reservoir flow characteristics can improve the fitting degree of the pressure curves. Not only that, but it can also solve the strong diversification of reservoir parameters. Results have a guiding significance for low-permeability composite gas reservoir development and pressure dynamic evaluation in inclined wells.

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Well Test Analysis of Inclined Wells in the Low-Permeability Composite Gas Reservoir Considering the Non-Darcy Flow

Modeling transient flow behavior with the high velocity non-Darcy effect in composite naturally fractured-homogeneous gas reservoirs

QPG-dominated transient flow behavior of a well in a subsurface formation

Physical simulation of the nonlinear transient flow behavior in closed high-pressure gas reservoirs. Part I: Pressure-depleted flow experiments on matrix cores

The invention discloses a method for determining the single-well dynamic reserve of a non-conventional oil and gas reservoir multi-section fracturing horizontal well. The method includes the followingsteps of collecting basic parameters of an oil and gas reservoir, obtaining a well testing double-logarithmic curve through a well testing method, obtaining the first radial flow ending time, the second linear flow ending time and the stratum fluid pseudo-stable flowing time from the well testing double-logarithmic curve, calculating the non-crack section flowing time of stratum fluid on a shorthalf shaft and the non-horizontal well section flowing time of the stratum fluid on a long half shaft, calculating the short half shaft of a multi-section fracture horizontal well elliptic flow drainage area and the long half shaft of the multi-section fracture horizontal well elliptic flow drainage area through a formula, calculating the single-well flow drainage area of the oil and gas well, andfinally calculating the single-well dynamic reserve of the non-conventional oil and gas well through the data. By means of a modern well testing explanation method, the single-well flow drainage areaof the oil and gas well is obtained; in combination with a volume method formula, the single-well dynamic reserve of the non-conventional oil and gas well can be better, more conveniently and more accurately calculated.

Min Li

Papers

Modeling transient flow behavior with the high velocity non-Darcy effect in composite naturally fractured-homogeneous gas reservoirs

QPG-dominated transient flow behavior of a well in a subsurface formation

Physical simulation of the nonlinear transient flow behavior in closed high-pressure gas reservoirs. Part I: Pressure-depleted flow experiments on matrix cores

Method for determining single-well dynamic reserve of non-conventional oil and gas reservoir multi-section fracturing horizontal well