The Use of An Integrated Approach in Estimation of Water Saturation and Free Water Level in Tight Gas Reservoirs: Case Studies

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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New Methods to Calculate Water Saturation in Shale and Tight Gas Reservoirs

Open Journal of Yangtze Oil and Gas ◽

10.4236/ojogas.2018.33019 ◽

2018 ◽

Vol 03 (03) ◽

pp. 220-230

Author(s):

Arash Kamari ◽

James J. Sheng

Keyword(s):

Water Saturation ◽

Tight Gas ◽

Gas Reservoirs ◽

Tight Gas Reservoirs ◽

New Methods

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Seismic Characterization of Tight Gas Reservoirs; An Integrated Approach

AAPG/EAGE tight reservoirs in the Middle East Workshop ◽

10.3997/2214-4609.20131813 ◽

2013 ◽

Author(s):

Jalal Khazandehdari

Keyword(s):

Integrated Approach ◽

Tight Gas ◽

Gas Reservoirs ◽

Tight Gas Reservoirs ◽

Seismic Characterization

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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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Secondary formation damage of low-pressure layer during commingled production in multilayered tight gas reservoirs

Scientific Reports ◽

10.1038/s41598-019-53940-6 ◽

2019 ◽

Vol 9 (1) ◽

Author(s):

Jingchen Ding ◽

Changhui Yan ◽

Yongming He ◽

Changcheng Wang

Keyword(s):

Water Saturation ◽

Low Pressure ◽

Working Fluid ◽

Formation Damage ◽

Tight Gas ◽

Gas Reservoirs ◽

Back Flow ◽

Tight Gas Reservoirs ◽

Secondary Formation ◽

Tight Gas Reservoir

AbstractThis paper experimentally investigates fluid back-flow behavior and formation damage during commingled production in multilayered tight gas reservoirs. The development of fluid back-flow in commingled tight gas reservoirs was simulated using a newly designed experimental platform. The results indicate that when there is a pressure difference between different layers during commingled production from tight gas reservoir, water produced from the high-pressure layer will invade the low-pressure layer along with gas back-flow and will accumulate in the near-wellbore area. This will lead to an increase in water saturation and a decline in permeability in the low-pressure layer and result in a significant reduction in ultimate recovery. The outcomes of these experiments demonstrate that as well as the formation damage caused by the working fluid during drilling and fracturing, “Secondary Formation Damage” also occurs during commingled production in multilayered tight gas reservoirs. This secondary formation damage mainly occurs in the near-wellbore area of low-pressure layers and is more severe with greater proximity to the wellbore. Through further experimentation to assess the factors influencing secondary formation damage, it is shown that the degree of secondary formation damage increases with decreasing original formation pressure, original water saturation, and permeability in the lower-pressure layer.

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An Integrated Approach to Evaluate the Further Development of the Changbei Unconventional Tight Gas Reservoirs

10.2523/16770-abstract ◽

2013 ◽

Author(s):

Kuifu Du ◽

Susanne Schaeftlein ◽

Glenn Mahiya ◽

Matthias Thum ◽

Roy Marden ◽

...

Keyword(s):

Integrated Approach ◽

Tight Gas ◽

Gas Reservoirs ◽

Tight Gas Reservoirs ◽

Further Development

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Experimental Study on Reducing Water Phase Trapping in Tight Gas Reservoirs

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.295-298.3293 ◽

2013 ◽

Vol 295-298 ◽

pp. 3293-3297

Author(s):

Hao Zhang ◽

Xiao Ning Feng ◽

Ji Ping She ◽

Fu You Huang ◽

Guan Fang Li

Keyword(s):

Water Saturation ◽

Water Phase ◽

Tight Gas ◽

Prevention Measures ◽

Gas Reservoirs ◽

Reservoir Water ◽

Tight Gas Reservoirs ◽

Western Sichuan ◽

Water Based ◽

Western Sichuan Basin

This document explains and demonstrates how to reduce water phase trapping in tight gas reservoirs during drilling. The water phase trapping laboratory device and experiment method has been studied, through the experiments on reservoir water phase trapping of western Sichuan Basin in China, Knowing that the damage is very serious, water self absorption experiments with different periods show that porosity and permeability of cores are basically above 50%. for the reason, the high capillary pressure and low water saturation are the main factors. Water phase trapping damage prevention measures has been put forward, including avoiding using water-based operating fluid as much as possible, minimizing or even avoiding the invasion of water-based operating fluid, and reducing interfacial tension and promote smooth operating fluid flow back.

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