Evaluation of damage mechanisms and skin factor in tight gas reservoirs

Dong

et al. 2018

RSC Adv.

Section: Thickening Property Of Siloxane In Comentioning

confidence: 99%

Effect of different factors on the yield of epoxy-terminated polydimethylsiloxane and evaluation of CO₂ thickening

Dong

et al. 2018

RSC Adv.

“…Low permeability shale reservoirs exhibited the same inclusiveness for hydraulic fracturing and CO 2 fracturing, and a proppant was employed to sustain these fractures in ultra-low permeability reservoirs [6]. In hydraulic fracturing stimulation, the low permeability reservoir would be damaged owing to the blockage of chemical additives and water [7,8]. Similarly, because of the low viscosity of pure CO 2 , the effectiveness of CO 2 fracturing is questioned.…”

Section: Introductionmentioning

confidence: 99%

Effect of a Modified Silicone as a Thickener on Rheology of Liquid CO2 and Its Fracturing Capacity

et al. 2019

Polymers

The low viscosity of pure liquid CO2 hindered the development of CO2 fracturing technology. A modified silicone polymer was prepared as a CO2 thickener to investigate the effect of temperature, pressure, shear rate and thickener content (wt.%) on the apparent viscosity and rheology of thickened liquid CO2. In addition, CO2 fracturing capacity was evaluated with the numerical simulation of extended finite element. The results displayed that an apparent viscosity of up to 1.3 mPa·s at 303 K and 18 MPa was attained over liquid CO2 using the thickener of 3 wt.% and Toluene of 9 wt.% as additives. Compared to the commercial linear polydimethylsiloxane, a better apparent viscosity was obtained from the mixture of this prepared thickener, Toluene and CO2. The apparent viscosity decreases with increasing temperature and shear rate. By contrast, an improving apparent viscosity was revealed with an increase in the pressure from 8 to 14 MPa and thickener content from 1 to 3 wt.%. The rheological index decreased with increasing thickener content with pressure but the rise in temperature led to an increasing rheological index. The mesh structure theory of the thickener, CO2 and Toluene molecules was in this paper gives a good explanation for the discrepancy between CO2 viscosity with the thickener content, temperature, pressure, or shear rate. Compared to pure CO2, the numerical simulation of CO2 fracturing demonstrated an excellent fracturing capacity by using the thickened CO2 fracturing fluid in shale reservoirs. This investigation could provide the basic reference for the development of CO2 fracturing technology.

“…With the refinement of exploration and production of oil and gas fields, the sensitive damage of reservoir is evaluated as one of the important factors influencing development effect, thus a lot of studies have been carried out on the formation mechanism, distribution characteristics and protective measures of reservoir sensitivity (Krueger, 1986;Zhang et al, 1996;Menouar et al, 2000;Civan, 2007;Alotaibi et al, 2009;Tian et al, 2015), with main focus on the evaluation and prediction of sensitivity effect and type, and its algorithm (Zhao Xingyuan, 1992;Peng Chunyao et al, 1999;Sun Jianmeng et al, 1999;Kang et al, 2000;Menouar et al, 2000;Zhao Dahua et al, 2002;Li Yonglin et al, 2003;Yin Xin, 2005;Zhao Xingyuan et al, 2005;Wang et al, 2006;Zhang Guanlong et al, 2006;Civan, 2007;Yuan Wenfang et al, 2014;Ma et al, 2016;Zhao Xiaohui et al, 2016). Several qualitative or semi quantitative prediction methods for the sensitivity of acid-sensitive minerals in the reservoir have been established gradually (Min et al, 2004;Zhang et al, 2007;Bahrami et al, 2011;Watheq et al, 2018). However, the current evaluation criterion of reservoir sensitivity is based on the damage rate of permeability in testing samples (absolute value of change rate of permeability) (Moghadasi et al, 2010;Habibi et al, 2012;Dou Honggen et al, 2016;Li et al, 2017), which masks the sensitization mechanism caused by different sensitivity effect, and could not benefit in restraining sensitivity effect in the reservoir (Yu et al, 2014;D...…”

Section: Introductionmentioning

confidence: 99%

Controls of Acid‐sensitive Minerals on Reservoir Sensitivity Testing: An Example from the Silurian Kepingtage Formation in Tazhong Area, Tarim Basin

Han

Acta Geologica Sinica (Eng)

et al. 2018

The Silurian Kepingtage Formation in Tazhong area is regarded as an acid‐sensitive hydrocarbon reservoir. However, formation mechanism of acid‐sensitive of the reservoir cannot be interpreted by the existing acid‐sensitive evaluation criterion based on damage rate. The contents of acid ‐sensitive minerals illustrated by bulk‐rock XRD, scanning electron microscopy and clay mineral composition analysis exert the dominant control on acid‐sensitive flow testing of the reservoir. The iron‐ bearing minerals (including pyrite cements and chlorite cements) mainly deteriorate reservoir quality, while the iron‐free minerals (including calcite cements and dolomite cements) mainly improve permeability. The permeability variation of the tested samples is controlled by the relative content of two acid‐sensitive minerals. On the basis of newly established sensitivity mechanism and its influence on permeability, the corresponding ion (Fe2+) stabilizer was added to the acidizing fluids during the acidification reconstruction, which inhibited the negative factors of acid‐sensitive minerals and improved the target layer quality effectively.