scholarly journals Physical Simulation and Mathematical Model of the Porous Flow Characteristics of Gas-Bearing Tight Oil Reservoirs

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3121
Author(s):  
Yuan Rao ◽  
Zhengming Yang ◽  
Yapu Zhang ◽  
Zhenkai Wu ◽  
Yutian Luo ◽  
...  
Keyword(s):  
Oil Reservoirs ◽  
Tight Oil ◽  
Production Well ◽  
Porous Flow ◽  
Bubble Point ◽  
Bubble Point Pressure ◽  
Point Pressure ◽  
Tight Oil Reservoirs ◽  
Gas Bearing ◽  
Solution Gas

The separation of solution gas has great influence on the development of gas-bearing tight oil reservoirs. In this study, physical simulation and high-pressure mercury intrusion were used to establish a method for determining the porous flow resistance gradient of gas-bearing tight oil reservoirs. A mathematical model suitable for injection–production well networks is established based on the streamline integral method. The concept of pseudo-bubble point pressure is proposed. The experimental results show that as the back pressure decreases from above the bubble point pressure to below the bubble point pressure, the solution gas separates out. During this process, the porous flow resistance gradient is initially equal to the threshold pressure gradient of the oil single-phase fluid, then it becomes relatively small and stable, and finally it increases rapidly and exponentially. The lower the permeability, the higher the pseudo-bubble point pressure, and the higher the resistance gradient under the same back pressure. For tight reservoirs, the production pressure should be maintained above the pseudo-bubble point pressure when the permeability is lower than a certain value. When the permeability is higher than a certain value, the pressure can be reduced below the pseudo-bubble point pressure, and there is a reasonable range. The mathematical results show that after degassing, the oil production rate and the effective utilization coefficient of oil wells decline rapidly. These declines occur later and have a flat trend for high permeability formations, and the production well pressure can be reduced to a lower level. Fracturing can effectively increase the oil production rate after degassing. A formation that cannot be utilized before fracturing because of the blocked throats due to the separation of the solution gas can also be utilized after fracturing. When the production well pressure is lower than the bubble point pressure, which is not too large, the fracturing effect is better.

scholarly journals Influence of reservoir lithology on porous flow resistance of gas-bearing tight oil reservoirs and production forecast

2021 ◽  
Author(s):  
Yuan Rao ◽  
Zhengming Yang ◽  
Lijing Chang ◽  
Yapu Zhang ◽  
Zhenkai Wu ◽  
...  
Keyword(s):  
High Pressure ◽  
Flow Resistance ◽  
Oil Production ◽  
Oil Reservoirs ◽  
Tight Oil ◽  
Dissolved Gas ◽  
Porous Flow ◽  
Bubble Point Pressure ◽  
Point Pressure ◽  
Gas Bearing

AbstractThe release of dissolved gas during the development of gas-bearing tight oil reservoirs has a great influence on the effect of development. In this article, the high-pressure mercury intrusion experiment was carried out in cores from different regions and lithologies of the Ordos Basin and the Sichuan Basin. The objectives are to study the microscopic characteristics of the porous throat structure of these reservoirs and to analyze the porous flow resistance laws of different lithology by conducting a resistance gradient test experiment. A mathematical model is established and the oil production index is corrected according to the experiment results to predict the oil production. The experimental results show that for tight reservoirs in the same area and lithology, the lower the permeability under the same back pressure, the greater the resistance gradient. And for sandstone reservoirs in different areas, the resistance gradients have little difference and the changes in the resistance coefficients are similar. However, limestone under the same conditions supports a much higher resistance gradient than sandstone reservoirs. Furthermore, the experimental results are consistent with the theoretical analysis indicating that the PVT (pressure–volume-temperature) characteristics in the nanoscale pores are different from those measured in the high-temperature, high-pressure sampler. Only when the pressure is less than a certain value of the bubble point pressure, the dissolved gas will begin to separate and generate resistance. This pressure is lower than the bubble point pressure measured in the high-temperature and pressure sampler. The calculation results show that the heterogeneity of limestone reservoirs and the mismatch of fluid storage and flow space will make the resistance, generated by the separation of dissolved gas, have a greater impact on oil production.

scholarly journals Porous flow characteristics of solution-gas drive in tight oil reservoirs

Open Physics ◽  
2018 ◽  
Vol 16 (1) ◽  
pp. 412-418
Author(s):  
Xiao Qianhua ◽  
Wang Zhiyuan ◽  
Yang Zhengming ◽  
Liu Xuewei ◽  
Wei Yunyun
Keyword(s):  
Flow Resistance ◽  
Material Balance ◽  
Oil Reservoirs ◽  
Tight Oil ◽  
Porous Flow ◽  
Drainage Radius ◽  
Solution Gas Drive ◽  
Tight Oil Reservoirs ◽  
Gas Drive ◽  
Solution Gas

Abstract The variation of porous flow resistance of solution-gas drive for tight oil reservoirs has been studied by designing new experimental equipment. The results show that the relation between the porous flow resistance gradient and pressure is the exponential function. The solution-gas driving resistance is determined by a combination of factors, such as the gas-oil ratio, density, viscosity, permeability, porosity and the Jamin effect. Based on the material balance and the flow resistance gradient equation, a new governing equation for solution-gas drive is established. After coupling with the nonlinear equation of elastic drive, the drainage radius of solution-gas drive is found to be very small and decreases rapidly when the bottom-hole pressure approaches the bubble-point value. Pressure distribution of the solution-gas drive is non-linear, and the values decrease sharply as it approaches the well bore. The productivity is rather low despite being strongly influenced by permeability. Therefore, stimulated reservoir volume (SRV) is the essential measure taken for effective development for tight oil reservoirs.

scholarly journals Experimental Investigation of Oil Recovery from Tight Sandstone Oil Reservoirs by Pressure Depletion

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2667 ◽  
Author(s):  
Wenxiang Chen ◽  
Zubo Zhang ◽  
Qingjie Liu ◽  
Xu Chen ◽  
Prince Opoku Appau ◽  
...  
Keyword(s):  
Oil Recovery ◽  
Oil Reservoirs ◽  
Oil Reservoir ◽  
Reservoir Pressure ◽  
Dissolved Gas ◽  
Tight Sandstone ◽  
Bubble Point ◽  
Bubble Point Pressure ◽  
Pressure Depletion ◽  
Point Pressure

Oil production by natural energy of the reservoir is usually the first choice for oil reservoir development. Conversely, to effectively develop tight oil reservoir is challenging due to its ultra-low formation permeability. A novel platform for experimental investigation of oil recovery from tight sandstone oil reservoirs by pressure depletion has been proposed in this paper. A series of experiments were conducted to evaluate the effects of pressure depletion degree, pressure depletion rate, reservoir temperature, overburden pressure, formation pressure coefficient and crude oil properties on oil recovery by reservoir pressure depletion. In addition, the characteristics of pressure propagation during the reservoir depletion process were monitored and studied. The experimental results showed that oil recovery factor positively correlated with pressure depletion degree when reservoir pressure was above the bubble point pressure. Moreover, equal pressure depletion degree led to the same oil recovery factor regardless of different pressure depletion rate. However, it was noticed that faster pressure drop resulted in a higher oil recovery rate. For oil reservoir without dissolved gas (dead oil), oil recovery was 2–3% due to the limited reservoir natural energy. In contrast, depletion from live oil reservoir resulted in an increased recovery rate ranging from 11% to 18% due to the presence of dissolved gas. This is attributed to the fact that when reservoir pressure drops below the bubble point pressure, the dissolved gas expands and pushes the oil out of the rock pore spaces which significantly improves the oil recovery. From the pressure propagation curve, the reason for improved oil recovery is that when the reservoir pressure is lower than the bubble point pressure, the dissolved gas constantly separates and provides additional pressure gradient to displace oil. The present study will help engineers to have a better understanding of the drive mechanisms and influencing factors that affect development of tight oil reservoirs, especially for predicting oil recovery by reservoir pressure depletion.

ELECTROKINETIC COUPLING MODEL FOR POROUS FLOW IN TIGHT OIL RESERVOIRS

2017 ◽  
Vol 8 (4) ◽  
pp. 295-305
Author(s):  
Qianhua Xiao ◽  
Zhengming Yang ◽  
Xiangui Liu ◽  
Xiong Wei ◽  
Yanzhang Huang
Keyword(s):  
Coupling Model ◽  
Oil Reservoirs ◽  
Tight Oil ◽  
Porous Flow ◽  
Tight Oil Reservoirs

Development of a New Correlation for Bubble Point Pressure in Oil Reservoirs using Artificial IntelligenceTechnique

2017 ◽  
Author(s):  
Salaheldin Elkatatny ◽  
Rami Aloosh ◽  
Zeeshan Tariq ◽  
Mohamed Mahmoud ◽  
Abdulazeez Abdulraheem
Keyword(s):  
Oil Reservoirs ◽  
Bubble Point ◽  
Bubble Point Pressure ◽  
New Correlation ◽  
Point Pressure

Development Features of Cold Production with Horizontal Wells in a Foamy Extra-Heavy Oil Reservoir

2021 ◽  
Author(s):  
Zhaopeng Yang ◽  
Xingmin Li ◽  
Xinxia Xu ◽  
Yang Shen ◽  
Xiaoxing Shi
Keyword(s):  
Heavy Oil ◽  
Horizontal Wells ◽  
Oil Field ◽  
Production Performance ◽  
Oil Reservoirs ◽  
Bubble Point ◽  
Foamy Oil ◽  
Bubble Point Pressure ◽  
Heavy Oil Reservoirs ◽  
Point Pressure

Abstract The block M as a foamy extra-heavy oil field in the Carabobo Area, the eastern Orinoco Belt, has been exploited by foamy oil cold production utilizing horizontal wells. The early producing area of block M has been put into production more than 10 years. And the development features of cold production in foamy extra-heavy oil reservoirs are different from the conventional oil field. It is necessary to investigate the development features of this kind reservoir and analyze its influence factors. Combining the production data with the reservoir geological characteristics of the research area, the cold production features of foamy extra-heavy oil using horizontal wells are analyzed. Then numerical simulations were adopted to study the influence factors of cold production performance. In the early stage of cold production, the oil production rate is high and the producing GOR is low. With the process of cold production, the reservoir pressure decreases gradually, the producing GOR increases gradually, and the oil production rate decreases gradually. When the bottom hole flowing pressure drops to below the bubble point pressure, the flow of extra-heavy oil in the reservoir can be divided into two zones: far well zone and near well area. In the far well zone, the pressure is higher than the bubble point pressure. The flow of oil is a single-phase flow, and the displacement mode is elastic driving. In the near well area, the pressure is lower than the bubble point pressure, and the oil flow is foamy oil flow, and the displacement mode is the dissolving gas drive driven by foamy oil. There exists many factors that influence the cold production performance of foamy extra-heavy oil, including reservoir depth, reservoir thickness, reservoir physical property and heterogeneity. The oil recovery factor per unit pressure drop can evaluate the cold production performance of foamy extra-heavy oil reservoirs. The effectiveness of cold production is closely related to reservoir parameters. Larger reservoir thickness, deeper reservoir depth and greater reservoir permeability will enhance the performance of cold production. Closer, larger and more interlayers above the horizontal well will hinder the performance of cold production. This research provides certain guidance and reference for further development adjustment and new project evaluation for foamy extra-heavy oil reservoirs in the Eastern Orinoco Belt.

Committee Machine-Ensemble as a General Paradigm for Accurate Prediction of Bubble Point Pressure of Crude Oil

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Sina Rashidi ◽  
Mohammad Khajehesfandeari
Keyword(s):  
Crude Oil ◽  
Phase Region ◽  
Accurate Prediction ◽  
Oil Reservoirs ◽  
Accurate Estimation ◽  
Two Phase ◽  
Committee Machine ◽  
Bubble Point ◽  
Bubble Point Pressure ◽  
Point Pressure

Abstract Bubble point pressure (BPP) not only is a basic pressure–volume–temperature (PVT) parameter for calculation nearly all of the crude oil characteristics, but also determines phase-type of oil reservoirs, gas-to-oil ratio, oil formation volume factor, inflow performance relationship, and so on. Since the measurement of BPP of crude oil is an expensive and time-consuming experiment, this study develops a committee machine-ensemble (CME) paradigm for accurate estimation of this parameter from solution gas-oil ratio, reservoir temperature, gas specific gravity, and stock-tank oil gravity. Our CME approach is designed using a linear combination of predictions of four different expert systems. Unknown coefficients of this combination are adjusted through minimizing deviation between actual BPPs and their associated predictions using differential evolution and genetic algorithm. Our proposed CME paradigm is developed using 380 PVT datasets for crude oils from different geological regions. This novel intelligent paradigm estimates available experimental databank with excellent accuracy i.e., absolute average relative deviation (AARD) of 6.06% and regression coefficient (R2) of 0.98777. Accurate prediction of BPP using our CME paradigm decreases the risk of producing from a two-phase region of oil reservoirs.

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