Wellbore instability in shale gas wells drilled by oil-based fluids

You, Lijun; Kang, Yili; Chen, Zhangxin; Chen, Qiang; Yang, Bin

doi:10.1016/j.ijrmms.2014.08.017

Cited by 53 publications

(24 citation statements)

References 20 publications

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“…The HCl and NaOH solutions were selected as the acidic and alkali solutions in this paper. Suggested by the reports on the concentration of acid and alkali in FF and DF [4,5,7], the deionized water was used to adjust the HCl and NaOH solutions to pH 1, pH 3 and pH 11, pH 13, respectively. Additionally, to weaken the effect of shale hydration due to the clay swell, a 3 wt.% KCl solution was added into the HCl and NaOH solutions.…”

Section: Shale Sample and Acid-base Solutions Preparationmentioning

confidence: 99%

“…Generally, the work fluids (drilling fluids or fracturing fluids) are formulated with water or oil added by the alkalis, acids and other chemicals such as the surfactants, co-solvents and the scale inhibitors. According to the literatures in [4][5][6][7], the drilling fluids (DF) are usually formulated to be alkaline with high pH (pH = [11][12], and the fracturing fluids (FF) are formulated to be acidic with low pH (0.08-2.1% as acid volume).…”

Section: Introductionmentioning

confidence: 99%

“…Typically, under acidic conditions, the carbonates (e. g. dolomite) in shales are highly soluble owing to the combinations of H + and CO 3 2-or HCO 3 - [6][7][8][9]. Under alkaline conditions, the quartz (SiO 2 ) and montmorillonite in shale are easily corroded by OHto form the silicates and the colloidal ion clusters (e. g. Si(OH) 2 O 2 2and Si(OH)O 3 3-), respectively [4,5,10]. In addition, the albite in shale may undergo the albitization by the exchange of Na + and THERMAL SCIENCE: Year 2020, Vol.…”

Section: Introductionmentioning

confidence: 99%

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Effect of acid-base corrosion on the tensile strength of shale under different temperature

Liang

Hou

Zhai³

et al. 2020

Therm sci

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In this study, we mainly investigate the impact of the acid-base corrosion on the tensile strength of the shale under different concentration and water bath temperature of acid-base solutions. Based on the X-ray diffractometry, the SEM and Brazilian splitting tests, the changes of the composition, macro-surface morphology, micro-structure and tensile strength of shale before and after acid-base corrosion are systematically analyzed. The results show that acid-base corrosion would cause chemical damage to shale as a result of the removal of the high hardness minerals and the generation of the dissolved pores and microfractures, resulting in the reduction in its tensile strength. Meanwhile, higher concentration and water bath temperature can promote acid- or alkali-shale interactions and increase the weakening degree of the shale tensile strength.

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Section: Shale Sample and Acid-base Solutions Preparationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of acid-base corrosion on the tensile strength of shale under different temperature

Liang

Hou

Zhai³

et al. 2020

Therm sci

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“…Other heavy metals, such as cadmium and lead are highly poisonous. The high-pH drilling fluid has also been widely used in the drilling process, which would cause the alkali erosion of rock [9,10]. More importantly, Table 2.…”

Section: Introductionmentioning

confidence: 99%

A New Analysis Model for Potential Contamination of a Shallow Aquifer from a Hydraulically-Fractured Shale

Peng

Gao

et al. 2018

Energies

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Hydraulic fracturing (HF) is widely used in shale gas development, which may cause some heavy metals release from shale formations. These contaminants could transport from the fractured shale reservoirs to shallow aquifers. Thus, it is necessary to assess the impact of pollution in shallow aquifers. In this paper, a new analysis model, considering geological distributions, discrete natural fractures (NFs) and faults, is developed to analyze the migration mechanism of contaminants. Furthermore, the alkali erosion of rock caused by high-pH drilling of fluids, is considered in this paper. The numerical results suggest that both NFs and alkali erosion could reduce the time required for contaminants migrating to aquifers. When NFs and alkali erosion are both considered, the migration time will be shortened by 51 years. Alkali erosion makes the impact of NFs, on the contaminant migration, more significant. The migration time decreases with increasing pH values, while the accumulation is on the opposite side. Compared with pH 12.0, the migration time would be increased by 45 years and 29 years for pH 11.0 and 11.5, respectively. However, the migration time for pH 12.5 and 13.0 were found to be decreased by 82 years and 180 years, respectively. Alkali erosion could increase the rock permeability, and the elevated permeability would further enhance the migration velocity of the contaminants, which might play a major role in assessing the potential contamination of shallow aquifers.

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“…For deepwater drilling, platforms/floating vessels are required for the deepwater operations. More than 70% of all drilled formations (offshore & onshore) are shale formations and about 90% of wellbore stability problems occurred in these shale formations [1]. Shale formations with enormous organic matters are not the same with the conventional formations due to the characteristic of the source rocks, such as rich organic matter and developed fracture networks.…”

Section: Introductionmentioning

confidence: 99%

Wellbore Stability Problems in Deepwater Gas Wells

Aregbe¹

2017

WJET

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The analysis of wellbore stability in deepwater gas wells is vital for effective drilling operations, especially in deepwater remote areas and for modern drilling technologies. Wellbore stability problems usually occur when drilling through hydrocarbon formations such as shale, unconsolidated sandstone, fractured carbonate formations and HPHT formations with narrow safety mud window. These problems can significantly affect drilling time, costs and the whole drilling operations. In deepwater gas wells, there is also the possible of gas hydrate problems because of the low temperature and high pressure conditions of the environment as well as the coexistence of gas and water inside the wellbore. These hydrates can block the mud line, surface choke line and even the BOP stack if no hydrate preventive measures are considered. In addition, the dissociation of these hydrates in the wellbore may gasify the drilling fluid and reduce drilling mud density, hydrostatic pressure, change mud rheology and cause wellbore instabilities. Traditional wellbore stability analysis considered the formation to be isotropic and assumed that the rock mechanical properties are independent of in-situ stress direction. This assumption is invalid for formations with layers or natural fractures because the presence of these geological features will influence rock anisotropic properties, wellbore stress concentration and failure behavior. This is a complicated phenomenon because the stress distribution around a wellbore is affected by factors such as rock properties, far-field principal stresses, wellbore trajectory, formation pore pressure, reservoir and drilling fluids properties and time. This research work reviews the major causes of wellbore stability problems in deepwater gas wells and outlines different preventive measures for effective drilling operation, because real-time monitoring of drilling process can provide necessary information for solving any wellbore stability problems in a short time.

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Wellbore instability in shale gas wells drilled by oil-based fluids

Cited by 53 publications

References 20 publications

Effect of acid-base corrosion on the tensile strength of shale under different temperature

Effect of acid-base corrosion on the tensile strength of shale under different temperature

A New Analysis Model for Potential Contamination of a Shallow Aquifer from a Hydraulically-Fractured Shale

Wellbore Stability Problems in Deepwater Gas Wells

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