Numerical Well-Testing Model of Fractured-Well in Low Permeability Reservoir Based on Mutative Permeability Effect

2013 ◽  
Vol 433-435 ◽  
pp. 1984-1987
Author(s):  
Yu Chen Zhang ◽  
Jiu Ning Zhou ◽  
Jing Wen Cui
Keyword(s):  
Low Permeability ◽  
Well Testing ◽  
Upward Movement ◽  
Threshold Pressure ◽  
Algebraic Equations ◽  
Pressure Derivative ◽  
Threshold Pressure Gradient ◽  
Well Model ◽  
Numerical Well Testing ◽  
Fractured Well

At present, threshold pressure gradient method is usually used for describing fluid flow in low-permeability media. However, it is only an approximate approach. In this paper, a 2-D fractured-well model for numerical well-testing considering non-darcy mutative-permeability effect was established, and PSOR iterative algorithm was used for solving the sets of algebraic equations. Based on this model, the typical curves of pressure and pressure derivative were drawn with different sets of parameters. When considering mutative-permeability effect, the pressure derivative curves move upward in each flowing period compared with darcy flowing model. In addition, the range of upward movement is larger as the non-darcy effect is more notable.

scholarly journals A New Method for Research on Unsteady Pressure Dynamics and Productivity of Ultralow-Permeability Reservoirs

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Kun Wang ◽  
Li Li ◽  
Xiao Chen ◽  
Wei Liang ◽  
Yong Yang ◽  
...  
Keyword(s):  
Stress Sensitivity ◽  
Low Permeability ◽  
Threshold Pressure ◽  
Test Interpretation ◽  
Well Test ◽  
Pressure Derivative ◽  
Threshold Pressure Gradient ◽  
The Real ◽  
Skin Factor ◽  
Low Permeability Reservoirs

In the numerous low-permeability reservoirs, knowing the real productivity of the reservoir became one of the most important steps in its exploitation. However, the value of permeability interpreted by a conventional well-test method is far lower than logging, which further leads to an inaccurate skin factor. This skin factor cannot match the real production situation and will mislead engineer to do an inappropriate development strategy of the oilfield. In order to solve this problem, key parameters affecting the skin factor need to be found. Based on the real core experiment and digital core experiment results, stress sensitivity and threshold pressure gradient are verified to be the most influential factors in the production of low-permeability reservoirs. On that basis, instead of a constant skin factor, a well-test interpretation mathematical model is established by defining and using a time-varying skin factor. The time-varying skin factor changes with the change of stress sensitivity and threshold pressure gradient. In this model, the Laplace transform is used to solve the Laplace space solution, and the Stehfest numerical inversion is used to calculate the real space solution. Then, the double logarithmic chart of dimensionless borehole wall pressure and pressure derivative changing with dimensionless time is drawn. The influences of parameters in expressions including stress sensitivity, threshold pressure, and variable skin factor on pressure and pressure derivative and productivity are analyzed, respectively. At last, the method is applied to the well-test interpretation of low-permeability oil fields in the eastern South China Sea. The interpretation results turn out to be reasonable and can truly reflect the situation of low-permeability reservoirs, which can give guidance to the rational development of low-permeability reservoirs.

scholarly journals Multi-Scale Insights on the Threshold Pressure Gradient in Low-Permeability Porous Media

Symmetry ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 364 ◽  
Author(s):  
Huimin Wang ◽  
Jianguo Wang ◽  
Xiaolin Wang ◽  
Andrew Chan
Keyword(s):  
Porous Media ◽  
Pressure Gradient ◽  
Water Saturation ◽  
Flow Behavior ◽  
Low Permeability ◽  
Threshold Pressure ◽  
Threshold Pressure Gradient ◽  
Linear Flow ◽  
Multi Scale ◽  
Non Linear

Low-permeability porous medium usually has asymmetric distributions of pore sizes and pore-throat tortuosity, thus has a non-linear flow behavior with an initial pressure gradient observed in experiments. A threshold pressure gradient (TPG) has been proposed as a crucial parameter to describe this non-linear flow behavior. However, the determination of this TPG is still unclear. This study provides multi-scale insights on the TPG in low-permeability porous media. First, a semi-empirical formula of TPG was proposed based on a macroscopic relationship with permeability, water saturation, and pore pressure, and verified by three sets of experimental data. Second, a fractal model of capillary tubes was developed to link this TPG formula with structural parameters of porous media (pore-size distribution fractal dimension and tortuosity fractal dimension), residual water saturation, and capillary pressure. The effect of pore structure complexity on the TPG is explicitly derived. It is found that the effects of water saturation and pore pressure on the TPG follow an exponential function and the TPG is a linear function of yield stress. These effects are also spatially asymmetric. Complex pore structures significantly affect the TPG only in the range of low porosity, but water saturation and yield stress have effects on a wider range of porosity. These results are meaningful to the understanding of non-linear flow mechanism in low-permeability reservoirs.

A Novel Model for Well Production Performance Estimate in Low-Permeability and Tight Reservoirs Considering Stress Sensitivity

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Mingda Dong ◽  
Xuedong Shi ◽  
Jie bai ◽  
Zhilong Yang ◽  
Zhilin Qi
Keyword(s):  
Pressure Gradient ◽  
Effective Stress ◽  
Stress Sensitivity ◽  
Production Performance ◽  
Low Permeability ◽  
Threshold Pressure ◽  
Threshold Pressure Gradient ◽  
Vertical Well ◽  
Tight Reservoirs ◽  
Rock Compressibility

Abstract Stress sensitivity phenomenon is an important property in low-permeability and tight reservoirs and has a large impact on the productivity of production wells, which is defined as the effect of effective stress on the reservoir parameters such as permeability, threshold pressure gradient, and rock compressibility change accordingly. Most of the previous works are focused on the effect of effective stress on permeability and threshold pressure gradient, while rock compressibility is critical of stress sensitivity but rarely noticed. A series of rock compressibility measurement experiments have been conducted, and the quantitative relationship between effective stress and rock compressibility is accurately described in this paper. In the experiment, the defects in previous experiments were eliminated by using a new-type core holder. The results show that as the effective stress increases, the rock compressibility becomes lower. Then, a stress sensitivity model that considers the effect of effective stress on rock compressibility is established due to the experimental results. The well performance of a vertical well estimated by this model shows when considering the effect of effective stress on the rock compressibility, the production rate and recovery factor are larger than those without considering it. Moreover, the effect of porosity and confining pressure on the productivity of a vertical well is also studied and discussed in this paper. The results show that the productivity of a vertical well decreases with the increase in overburden pressure, and increases with the increase in the porosity.

A New Unsteady-State Model for Calculating Oil-Water Relative Permeability of Low-Permeability/Ultra-Low Permeability Reservoirs

2012 ◽  
Vol 616-618 ◽  
pp. 964-969 ◽  
Author(s):  
Yue Yang ◽  
Xiang Fang Li ◽  
Ke Liu Wu ◽  
Meng Lu Lin ◽  
Jun Tai Shi
Keyword(s):  
Porous Media ◽  
Pressure Gradient ◽  
Capillary Pressure ◽  
Relative Permeability ◽  
Oil Reservoirs ◽  
Flow In Porous Media ◽  
Low Permeability ◽  
Threshold Pressure ◽  
Flow Process ◽  
Threshold Pressure Gradient

Oil and water relative permeabilities are main coefficients in describing the fluid flow in porous media; however, oil and water relative permeability for low - ultra low perm oil reservoir can not be obtained from present correlations. Based on the characteristics of oil and water flow in porous media, the model for calculating the oil and water relative permeability of low and ultra-low perm oil reservoirs, which considering effects of threshold pressure gradient and capillary pressure, has been established. Through conducting the non-steady oil and water relative permeability experiments, oil and water relative permeability curves influenced by different factors have been calculated. Results show that: the threshold pressure gradient more prominently affects the oil and water relative permeability; capillary pressure cannot influence the water relative permeability but only the oil relative permeability. Considering effects of threshold pressure gradient and capillary pressure yields the best development result, and more accordant with the flow process of oil and water in low – ultra low perm oil reservoirs.

Threshold Pressure Gradient in Ultra-low Permeability Reservoirs

2008 ◽  
Vol 26 (9) ◽  
pp. 1024-1035 ◽  
Author(s):  
F. Hao ◽  
L. S. Cheng ◽  
O. Hassan ◽  
J. Hou ◽  
C. Z. Liu ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Low Permeability ◽  
Threshold Pressure ◽  
Threshold Pressure Gradient ◽  
Low Permeability Reservoirs

scholarly journals Pressure Performance of Highly Deviated Well in Low Permeability Carbonate Gas Reservoir Using a Composite Model

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5952
Author(s):  
Qinwen Zhang ◽  
Liehui Zhang ◽  
Qiguo Liu ◽  
Youshi Jiang
Keyword(s):  
Pressure Gradient ◽  
Stress Sensitivity ◽  
Composite Model ◽  
Darcy Flow ◽  
Low Permeability ◽  
Threshold Pressure ◽  
Gas Reservoir ◽  
Threshold Pressure Gradient ◽  
Effects Of Stress ◽  
Deviated Wells

It is commonly believed that matrix and natural fractures randomly distribute in carbonate gas reservoirs. In order to increase the effective connected area to the storage space as much as possible, highly deviated wells are widely used for development. Although there have been some studies on the composite model for highly deviated wells, they have not considered the effects of stress sensitivity and threshold pressure gradient in a dual-porosity gas reservoir. In this paper, a semi-analytical composite model for low permeability carbonate gas reservoir was established to study the effect of non-Darcy flow. By employing source function, Fourier transform and the perturbation method, the pressure performance and typical well test curves were obtained. Eight flow regimes were identified, and their characteristics were discussed. As a result, it can be concluded that the effects of stress sensitivity and threshold pressure gradient would make pseudo-pressure and derivative curves rise, which is the characteristic of non-Darcy flow to determine whether there is stress sensitivity or threshold pressure gradient.

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