Numerical simulation of water alternating gas flooding (WAG) using CO2 for high-salt argillaceous dolomite reservoir considering the impact of stress sensitivity and threshold pressure gradient

2021 ◽  
Author(s):  
Dan Wu ◽  
Eric Thompson Brantson ◽  
Binshan Ju
Keyword(s):  
Numerical Simulation ◽  
Pressure Gradient ◽  
Stress Sensitivity ◽  
High Salt ◽  
Threshold Pressure ◽  
Threshold Pressure Gradient ◽  
Water Alternating Gas ◽  
Gas Flooding ◽  
The Impact

scholarly journals Investigation of productivity decline in inter-salt argillaceous dolomite reservoir due to formation damage and threshold pressure gradient: Laboratory, mathematical modeling and application

2016 ◽  
Vol 35 (1) ◽  
pp. 33-53 ◽  
Author(s):  
Dan Wu ◽  
Binshan Ju ◽  
Shiqiang Wu ◽  
Eric Thompson Brantson ◽  
Yingkun Fu ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Effective Stress ◽  
Stress Sensitivity ◽  
Microscopic Model ◽  
Oil Well ◽  
Threshold Pressure ◽  
Threshold Pressure Gradient ◽  
Well Productivity ◽  
Sensitivity Experiments ◽  
The Impact

The inter-salt argillaceous dolomite reservoirs in the central region of China contain large abundance of oil resources with ultra-low permeability and porosity. However, the oil wells in this area show a very quick reduction with the decline of formation pressure. This article aims to investigate the main possible reasons that affect oil well productivity in the target oilfield. This study begins with analysis of capillary microscopic model, core stress sensitivity experiments, and non-Darcy percolation experiments. The impact of effective stress on permeability and porosity of the reservoir was revealed in this article. The novel productivity model and productivity evaluation model which couples stress sensitivity and threshold pressure gradient were proposed. The analysis of capillary microscopic model shows stress sensitivity of permeability to be much greater than that of porosity during the process of depressurization. The core stress sensitivity experiments results indicate that permeability and effective stress show index relationship while porosity and effective stress show binomial relationship. Damage rate and recovery rate of permeability and porosity were put forward to describe the degree of influence of stress sensitivity on permeability and porosity. The models were used to investigate the factors that affect single well productivity for the target oilfield. Application of the proposed model to this tight oilfield indicates that, the degree of influence of stress sensitivity is much greater than that of threshold pressure gradient. In addition, the greater the stress sensitivity coefficient and threshold pressure gradient are, the greater the productivity reduction will be.

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.

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.

scholarly journals Numerical Simulation of Microemulsion Flooding in Low-Permeability Reservoir

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Dongqi Wang ◽  
Daiyin Yin ◽  
Xiangzhu Gong
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Moisture Content ◽  
Pressure Gradient ◽  
Laboratory Experiments ◽  
Flow Equation ◽  
Low Permeability ◽  
Threshold Pressure ◽  
Threshold Pressure Gradient ◽  
Relative Errors

Based on the features of microemulsion flooding in low-permeability reservoir, a three-dimension three-phase five-component mathematical model for microemulsion flooding is established in which the diffusion and adsorption characteristics of surfactant molecules are considered. The non-Darcy flow equation is used to describe the microemulsion flooding seepage law in which the changes of threshold pressure gradient can be taken into account, and the correlation coefficients in the non-Darcy flow equation are determined through the laboratory experiments. A new treatment for the changes of threshold pressure and the quantitative description of adsorption quantity of surfactant and relative permeability curves are presented, which enhance the coincidence between mathematical model and experiment results. The relative errors of main development indexes are within 4%. A software is programmed based on the model to execute a core-level small-scale numerical simulation in Chaoyanggou Oilfield. The fitting relative errors of the pressure, flow rate, and moisture content are 3.25%, 2.71%, and 2.54%, respectively. The results of laboratory experiments and numerical simulation showed that microemulsion system could reduce the threshold pressure gradient by 0.010 MPa/m and injection pressure by 0.6 MPa. The biggest decline in moisture content reaches 33%, and the oil recovery is enhanced by 10.8%.

Numerical Simulation of Pressure Distribution between Injection and Production Well in Low Permeability Reservoir

2013 ◽  
Vol 807-809 ◽  
pp. 2554-2557
Author(s):  
Qi Han Zhang ◽  
Zi Yi Guo ◽  
Ji Peng ◽  
Ting Song Xiong ◽  
Shi Feng Xue
Keyword(s):  
Numerical Simulation ◽  
Pressure Gradient ◽  
Pressure Distribution ◽  
Low Permeability ◽  
Threshold Pressure ◽  
Production Well ◽  
Pressure System ◽  
Threshold Pressure Gradient ◽  
Low Permeability Reservoir ◽  
Pressure Sensitive

Considering the pressure-sensitive effect and threshold pressure gradient in low permeability reservoirs, a new mathematical model of the variable permeability for reservoir between injection and production well is established. The Garlerkin method is used to set up the finite element computation equations, and corresponding numerical simulation program is developed. The influence of Injection-production pressure, well spacing and hydraulic fracture are quantitative evaluation. The simulation results show that the pressure-sensitive effect and threshold pressure gradient has a strong influence on pressure distribution between injection and production wells. Establishing the effective driving pressure system is the key to improve well production of low permeability reservoir.

Productivity Analysis of Fractured Well in Tight Oil Reservoir

2014 ◽  
Vol 893 ◽  
pp. 712-715 ◽  
Author(s):  
Yong Gao Xu ◽  
Xian Wen Li ◽  
Rui Quan Liao ◽  
Dong Jin Xu
Keyword(s):  
Pressure Gradient ◽  
Stress Sensitivity ◽  
Tight Oil ◽  
Oil Well ◽  
Threshold Pressure ◽  
Productivity Analysis ◽  
Threshold Pressure Gradient ◽  
Reservoir Permeability ◽  
Fractured Well ◽  
The Mathematical Model

Hydraulic fracturing is an effective technique for increasing the productivity of wells producing from low permeability and tight oil formations (Reservoir permeability is less than 0.1mD). By establishing the seepage model of vertically fractured well, concerned on the threshold pressure gradient and stress sensitivity of the reservoir, the mathematical model has been solved and the productivity equation of vertically fractured well has been obtained in the paper. The productivity analysis shows that the bigger the threshold pressure gradient, the lower the productivity of oil well; the stronger the stress sensitivity, the lower the productivity, besides, the initial productivity of oil well increases with the increasing length of the fracture, but the increase rate tends small.

scholarly journals Numerical Simulation Study on Waterflooding Heavy Oil Based on Variable Threshold Pressure Gradient

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Fan Liu ◽  
Qingdong Ni ◽  
Chunguang Zhang ◽  
Wensheng Zhou ◽  
Jingqi Lin ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Pressure Gradient ◽  
Simulation Study ◽  
Heavy Oil ◽  
Fluid Viscosity ◽  
Threshold Pressure ◽  
Threshold Pressure Gradient ◽  
Variable Threshold ◽  
Oil Flow ◽  
Phase Mobility

The heavy-oil flow in porous media is characterized by non-Darcy law with variable threshold pressure gradient (TPG) due to the large fluid viscosity. However, available analytical and numerical models hardly consider this effect, which can lead to erroneous results. This paper is aimed at presenting an innovative approach and establishing a numerical simulator to analyze the heavy-oil flow behavior with waterflooding. The apparent viscosity of the oil phase and flow correction coefficient characterized by the TPG were applied to describe the viscosity anomaly of heavy oil. Considering the formation heterogeneity, the TPG was processed into a variable related to mobility and the directionality. The discretization and linearization of the mathematical model were conducted to establish a fully implicit numerical model; the TPG value on each grid node was obtained through oil phase mobility interpolation, and then, the Jacobi matrix was reassembled and calculated to solve pressure and saturation equations. The corresponding simulator was thus developed. The pre-/postprocessing module of the simulator is connected to ECLIPSE; then, an efficient algorithm is introduced to realize a fast solution. Results show that considering the TPG will not only reduce the waterflooding area but also reduce the oil displacement efficiency because of aggravating the nonpiston phenomenon and interlayer conflict. The numerical simulation study on the TPG of heavy oil provides theoretical and technical support for the rational development and adjustment of water-driven heavy oil.

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