ANALYSIS OF PRESSURE-DEPENDENT RELATIVE PERMEABILITY IN PERMEABILITY JAIL OF TIGHT GAS RESERVOIRS AND ITS INFLUENCE ON TIGHT GAS PRODUCTION

Tight-gas reservoirs have low permeability and significant damage. When drilling the tight formations, wellbore liquid invades the formation and increases water saturation of the near wellbore area and significantly deceases permeability of this area. Because of the invasion, the permeability of the invasion zone near the wellbore in tight-gas formations significantly decreases. This damage is mainly controlled by wettability and capillary pressure (Pc). One of the methods to improve productivity of tight-gas reservoirs is to reduce IFT between formation gas and invaded water to remove phase trapping. The invasion of wellbore liquid into tight formations can damage permeability controlled by Pc and relative permeability curves. In the case of drilling by using a water-based mud, tight formations are sensitive to the invasion damage due to the high-critical water saturation and capillary pressures. Reducing the Pc is an effective way to increase the well productivity. Using the IFT reducers, Pc effect is reduced and trapped phase can be recovered; therefore, productivity of the TGS reservoirs can be increased significantly. This study focuses on reducing phase-trapping damage in tight reservoirs by using reservoir simulation to examine the methods, such use of IFT reducers in water-based-drilled tight formations that can reduce Pc effect. The Pc and relative permeability curves are corrected based on the reduced IFT; they are then input to the reservoir simulation model to quantitatively understand how IFT reducers can help improve productivity of tight reservoirs.

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Liquid loading in wellbores and its effect on cleanup period and well productivity in tight gas sand reservoirs

The APPEA Journal ◽

10.1071/aj09033 ◽

2010 ◽

Vol 50 (1) ◽

pp. 559

Author(s):

Hassan Bahrami ◽

M Reza Rezaee ◽

Vamegh Rasouli ◽

Armin Hosseinian

Keyword(s):

Numerical Simulation ◽

Gas Production ◽

Production Performance ◽

Tight Gas ◽

Gas Reservoirs ◽

Liquid Loading ◽

Performance Modelling ◽

Well Productivity ◽

Tight Gas Reservoirs ◽

Tight Gas Reservoir

Tight gas reservoirs normally have production problems due to very low matrix permeability and significant damage during well drilling, completion, stimulation and production. Therefore they might not flow gas to surface at optimum rates without advanced production improvement techniques. After well stimulation and fracturing operations, invaded liquids such as filtrate will flow from the reservoir into the wellbore, as gas is produced during well cleanup. In addition, there might be production of condensate with gas. The produced liquids when loaded and re-circulated downhole in wellbores, can significantly reduce the gas production rate and well productivity in tight gas formations. This paper presents assessments of tight gas reservoir productivity issues related to liquid loading in wellbores using numerical simulation of multiphase flow in deviated and horizontal wells. A field example of production logging in a horizontal well is used to verify reliability of the numerical simulation model outputs. Well production performance modelling is also performed to quantitatively evaluate water loading in a typical tight gas well, and test the water unloading techniques that can improve the well productivity. The results indicate the effect of downhole liquid loading on well productivity in tight gas reservoirs. It also shows how well cleanup is sped up with the improved well productivity when downhole circulating liquids are lifted using the proposed methods.

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Using relative permeability curves to evaluate phase trapping damage caused by water- and oil-based drilling fluids in tight-gas reservoirs

The APPEA Journal ◽

10.1071/aj11048 ◽

2012 ◽

Vol 52 (1) ◽

pp. 595 ◽

Cited By ~ 1

Author(s):

Geeno Murickan ◽

Hassan Bahrami ◽

Reza Rezaee ◽

Ali Saeedi ◽

Tsar Mitchel

Keyword(s):

Capillary Pressure ◽

Relative Permeability ◽

Drilling Fluid ◽

Tight Gas ◽

Gas Reservoirs ◽

Tight Gas Reservoirs ◽

Water Based ◽

Tight Formations ◽

Relative Permeability Curves ◽

Tight Formation

Low matrix permeability and significant damage mechanisms are the main signatures of tight-gas reservoirs. During the drilling and fracturing of tight formations, the wellbore liquid invades the tight formation, increases liquid saturation around the wellbore, and eventually reduces permeability at the near wellbore zone. The liquid invasion damage is mainly controlled by capillary pressure and relative permeability curves. Due to high critical water saturation, relative permeability effects and strong capillary pressure, tight formations are sensitive to water invasion damage, making water blocking and phase trapping damage two of the main concerns with using a water-based drilling fluid in tight-gas reservoirs.Therefore, the use of an oil-based mud may be preferred in the drilling or fracturing of a tight formation. Invasion of an oil filtrate into tight formations, however, may result in the introduction of an immiscible liquid-hydrocarbon drilling or completion fluid around the wellbore, causing the entrapment of an additional third phase in the porous media that would exacerbate formation damage effects. This study focuses on phase trapping damage caused by liquid invasion using a water-based drilling fluid in comparison with the use of an oil-based drilling fluid in water-sensitive, tight-gas sand reservoirs. Reservoir simulation approach is used to study the effect of relative permeability curves on phase trap damage, and the results of laboratory experiments of core flooding tests in a West Australian tight-gas reservoir are shown, where the effect of water injection and oil injection on the damage of core permeability are studied. The results highlight the benefits of using oil-based fluids in drilling and fracturing of tight-gas reservoirs in terms of reducing skin factor and improving well productivity.

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Gas-Water Flow Behavior in Water-Bearing Tight Gas Reservoirs

Geofluids ◽

10.1155/2017/9745795 ◽

2017 ◽

Vol 2017 ◽

pp. 1-16 ◽

Cited By ~ 5

Author(s):

Renyi Cao ◽

Liyou Ye ◽

Qihong Lei ◽

Xinhua Chen ◽

Y. Zee Ma ◽

...

Keyword(s):

Water Saturation ◽

Flow Behavior ◽

Stress Sensitivity ◽

Gas Production ◽

Tight Gas ◽

Gas Reservoirs ◽

Threshold Pressure Gradient ◽

Tight Gas Reservoirs ◽

Gas Recovery ◽

Mobile Water

Some tight sandstone gas reservoirs contain mobile water, and the mobile water generally has a significant impact on the gas flowing in tight pores. The flow behavior of gas and water in tight pores is different than in conventional formations, yet there is a lack of adequate models to predict the gas production and describe the gas-water flow behaviors in water-bearing tight gas reservoirs. Based on the experimental results, this paper presents mathematical models to describe flow behaviors of gas and water in tight gas formations; the threshold pressure gradient, stress sensitivity, and relative permeability are all considered in our models. A numerical simulator using these models has been developed to improve the flow simulation accuracy for water-bearing tight gas reservoirs. The results show that the effect of stress sensitivity becomes larger as water saturation increases, leading to a fast decline of gas production; in addition, the nonlinear flow of gas phase is aggravated with the increase of water saturation and the decrease of permeability. The gas recovery decreases when the threshold pressure gradient (TPG) and stress sensitivity are taken into account. Therefore, a reasonable drawdown pressure should be set to minimize the damage of nonlinear factors to gas recovery.

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Simulation of Fracturing-Induced Formation Damage and Gas Production From Fractured Wells in Tight Gas Reservoirs

SPE Production & Operations ◽

10.2118/153255-pa ◽

2013 ◽

Vol 28 (03) ◽

pp. 246-258 ◽

Cited By ~ 3

Author(s):

Didier Yu Ding ◽

Hoel Langouët ◽

Laurent Jeannin

Keyword(s):

Gas Production ◽

Formation Damage ◽

Tight Gas ◽

Gas Reservoirs ◽

Tight Gas Reservoirs

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Effect of Geological Heterogeneity on the Production Performance of a Multifractured Horizontal Well in Tight Gas Reservoirs

Lithosphere ◽

10.2113/2021/4336062 ◽

2021 ◽

Vol 2021 (Special 1) ◽

Author(s):

Yue Peng ◽

Tao Li ◽

Yuxue Zhang ◽

Yongjie Han ◽

Dan Wu ◽

...

Keyword(s):

Horizontal Well ◽

Horizontal Wells ◽

Gas Production ◽

Production Performance ◽

Tight Gas ◽

Gas Reservoirs ◽

Gas Reservoir ◽

Tight Gas Reservoirs ◽

Reservoir Permeability ◽

Half Length

Abstract Multifractured horizontal wells are widely used in the development of tight gas reservoirs to improve the gas production and the ultimate reservoir recovery. Based on the heterogeneity characteristics of the tight gas reservoir, the homogeneous scheme and four typical heterogeneous schemes were established to simulate the production of a multifractured horizontal well. The seepage characteristics and production performance of different schemes were compared and analyzed in detail by the analysis of streamline distribution, pressure distribution, and production data. In addition, the effects of reservoir permeability level, length of horizontal well, and fracture half-length on the gas reservoir recovery were discussed. Results show that the reservoir permeability of the unfractured areas, which are located at both ends of the multifractured horizontal well, determines the seepage ability of the reservoir matrix, showing a significant impact on the long-term gas production. High reservoir permeability level, long horizontal well length, and long fracture half-length can mitigate the negative influence of heterogeneity on the gas production. Our research can provide some guidance for the layout of multifractured horizontal wells and fracturing design in heterogeneous tight gas reservoirs.

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Mitigation of Condensate Banking Using Thermochemical Treatment: Experimental and Analytical Study

Energies ◽

10.3390/en12050800 ◽

2019 ◽

Vol 12 (5) ◽

pp. 800 ◽

Cited By ~ 7

Author(s):

Amjed Hassan ◽

Mohamed Mahmoud ◽

Abdulaziz Al-Majed ◽

Ayman Al-Nakhli ◽

Mohammed Bataweel ◽

...

Keyword(s):

Relative Permeability ◽

Capillary Forces ◽

Co2 Injection ◽

Tight Gas ◽

Reaction Products ◽

Gas Reservoirs ◽

Tight Gas Reservoirs ◽

The Creation ◽

Chemical Activator

Condensate banking is a common problem in tight gas reservoirs because it diminishes the gas relative permeability and reduces the gas production rate significantly. CO2 injection is a common and very effective solution to mitigate the condensate damage around the borehole in tight gas reservoirs. The problem with CO2 injection is that it is a temporary solution and has to be repeated frequently in the field in addition to the supply limitations of CO2 in some areas. In addition, the infrastructure required at the surface to handle CO2 injection makes it expensive to apply CO2 injection for condensate removal. In this paper, a new permanent technique is introduced to remove the condensate by using a thermochemical technique. Two chemicals will be used to generate in situ CO2, nitrogen, steam, heat, and pressure. The reaction of the two chemicals downhole can be triggered either by the reservoir temperature or a chemical activator. Two chemicals will start reacting and produce all the mentioned reaction products after 24 h of mixing and injection. In addition, the reaction can be triggered by a chemical activator and this will shorten the time of reaction. Coreflooding experiments were carried out using actual condensate samples from one of the gas fields. Tight sandstone cores of 0.9 mD permeability were used. The results of this study showed that the thermochemical reaction products removed the condensate and reduced its viscosity due to the high temperature and the generated gases. The novelty in this paper is the creation of micro-fractures in the tight rock sample due to the in-situ generation of heat and pressure. These micro-fractures reduced the capillary forces that hold the condensate and enhanced the rock relative permeability. The creation of micro-fractures and in turn the reduction of the capillary forces can be considered as permanent condensate removal.

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Material constituents and mechanical properties and macro-micro-failure modes of tight gas reservoirs

Energy Exploration & Exploitation ◽

10.1177/0144598720913069 ◽

2020 ◽

Vol 38 (6) ◽

pp. 2631-2648

Author(s):

Zhaoyi Liu ◽

Ligang Zhang ◽

GR Liu ◽

Wei Li ◽

Shibin Li ◽

...

Keyword(s):

Mechanical Properties ◽

Failure Modes ◽

Gas Production ◽

Wellbore Stability ◽

Porous Polymer ◽

Tight Gas ◽

Tensile Shear ◽

Gas Reservoirs ◽

Tight Gas Reservoirs ◽

Triaxial Compressive Strength

In this work, a series of intensive laboratory tests are conducted to measure the material constituents, mechanical properties, and to examine macro-micro-failure modes of various types of rocks from tight gas reservoirs in the Da Qing oilfield in China. A set of key parameters are experimentally determined, including porosity, mineralogical compositions, microstructure, Young’s modulus, Poisson’s ratio, triaxial compressive strength, as well as macro- and micro-morphology failure modes. The relationships of these parameters are systematically analyzed, and the effects of the material constituents and microstructure characteristics such as cementation type, porosity, and mineral composition on rock mechanical properties are revealed as well as the patterns of micro- and macro-failures in types of rocks are investigated. The result shows that the micro-failure mainly exhibits features of transgranular and intergranular porous polymer fracture, and the macro-failure modes are mainly three types: shear-dominated, mixed shear–tensile and mixed tensile–shear. The mixed tensile–shear failure has mainly tensile fractures with branch fractures crossing each other, which forms a complex system fracture network. These findings are of importance for “sweet pot” evaluations, wellbore stability analysis, and hydraulic fracturing design for oil and gas production in tight gas reservoirs.

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Effect of liquid invasion damage and supercharging on wireline formation tester measurements in tight gas reservoirs

The APPEA Journal ◽

10.1071/aj11051 ◽

2012 ◽

Vol 52 (1) ◽

pp. 627 ◽

Cited By ~ 1

Author(s):

Joshua Andrews ◽

Hassan Bahrami ◽

Reza Rezaee ◽

Hamid Reza ◽

Sultan Mehmood ◽

...

Keyword(s):

Capillary Pressure ◽

Drilling Fluid ◽

Gas Production ◽

Tight Gas ◽

Formation Pressure ◽

Gas Reservoirs ◽

Reliable Determination ◽

Tight Gas Reservoirs ◽

Tight Gas Reservoir ◽

Measured Pressure

Wireline formation testing and measurement of true formation pressure can provide essential knowledge about the reservoir dynamic characteristics. In tight formations, a reliable determination of pressure and mobility gradients is challenging because of the tight nature of formation rock. Due to the very low reservoir permeability, the mud cake across wellbore is often ineffective in preventing filtrate invasion, thus causing the measured pressure to be higher than actual formation pressure as a result of supercharging effect. Wireline formation testing measurements are also influenced by the effects of filtrate invasion and capillary pressure, as the measured pressure is pressure of drilling fluid filtrate, the continuous phase present in the invaded region around wellbore. As a result, the measured pressure might be different to true formation pressure. This effect is more noticeable in tight gas reservoirs due to capillary pressure effect. This paper looks into estimation of true formation pressure and evaluates the effect of filtrate invasion damage and supercharging on wireline formation tester measurements in tight gas reservoirs. Numerical simulation approach is used to build the reservoir model based on data acquired from a tight gas reservoir. The model undergoes water injection followed by gas production from different testing points along the wellbore, and the corresponding pressure gradients are plotted to check for pressure matching with that of the formation fluid in the virgin region. The results indicate the significant effects of supercharging, reservoir characteristics, capillary pressure and liquid invasion damage on wireline formation pressure measurements in tight gas reservoirs.

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