An Offshore Benign WBM System Can Prevent Hard, Brittle Shale Instability

Peng, Chengyong; Yan, Juntao; Feng, Wenjie

doi:10.1080/10916460903030433

Cited by 5 publications

(3 citation statements)

References 1 publication

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“…Brittle failure is due to: 1) shales becomes weaken due to hydration of micro fracture surfaces, and bedding planes, 2) clay fail when surrounded by a quartz and feldspar matrix which are non-swelling minerals. Brittle shales usually contain a high percentage of kaolinite, illite and chlorite which may become unstable in a high pH environment (Peng et al, 2010). Borehole failure and shape of cuttings, on these occasions, might be very severe depending on the degree of rock anisotropy and the direction of drilling with respect to the lamination (bedding planes) dip, which is also known as the attack angle.…”

Section: Brittle Shalesmentioning

confidence: 99%

A review on borehole instability in active shale formations: Interactions, mechanisms and inhibitors

Gholami

Elochukwu

Fakhari

et al. 2018

Earth-Science Reviews

202

106

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Shale formations are known for their chemical interactions with water based muds which may result in swelling, bit balling or even closure of the wellbore. As a result, eco-friendly water based fluids with inhibitive characteristics are required for drilling through shale formations. The aim of this study is to provide a deeper insight into drilling through shale formations by providing few approaches for different circumstances. Many inhibitors developed so far are introduced with their mechanism of shale inhibition presented. It appears that silicate based muds and thermally activated mud emulsion (TAME) are the best option to mitigate shale related issues, but more studies are required to provide a permanent solution for this very complicated issue, especially under HPHT conditions.

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Section: Brittle Shalesmentioning

confidence: 99%

A review on borehole instability in active shale formations: Interactions, mechanisms and inhibitors

Gholami

Elochukwu

Fakhari

et al. 2018

Earth-Science Reviews

202

106

View full text Add to dashboard Cite

show abstract

“…Previous studies evidenced that over 90% of wellbore instability issues were caused by the reduction in shale strength that stemmed from hydration swelling and dispersion of shale formation during the drilling process . In particular, it should be noted that deep hard and brittle shale, which is mainly rich in Illite and develops microscale pores or fractures, is more prone to hydration dispersion, resulting in accidents such as cuttings disintegration, wellbore collapse, and pipe sticking in deep intervals, where high-pressure, high-temperature (HPHT) conditions prevail. , Thus, drilling fluids have attracted more attention from scientists and engineers owing to the growing drilling issues related to elevated temperatures and wellbore instability.…”

Section: Introductionmentioning

confidence: 99%

In Situ Shale Wettability Regulation Using Sophisticated Nanoemulsion to Maintain Wellbore Stability in Deep Well Drilling

Wang

et al. 2022

Langmuir

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Wettability alteration of the shale surface is a potential strategy to address wellbore instability issues arising from shale hydration. In this study, we have explored an oil-in-water (o/w) nanoemulsion, in which soluble silicate (lithium silicate and potassium methyl silicate) as the aqueous phase and organosilanes (3-methacryloxypropyltrimethoxysilane (KH570) and n-octyltriethoxysilane (n-OTES)) as the oil phase, as a shale inhibitor via forming a hydrophobic “artificial borehole shield” in situ on shale surfaces to maintain wellbore stability in high-temperature drilling operations. The shale dispersion test showed the highest shale recovery of nanoemulsion was up to 106.4% compared to that of water (20%), and recovered shale cuttings remained at the original integrity after hot rolling at 180 °C, indicating superior inhibition performance and resistance to elevated temperatures. Moreover, recovered shale cuttings manifested water repellency upon reimmersion in water, ascribed to the hydrophobic film, preventing water from permeating into the shale. The results of the contact angle measurement elucidated that the film wettability, from hydrophilic to superhydrophobic (ranging from 9.6–154°), can be achieved by altering the n-OTES-to-KH570 weight ratio from 0.2 to 2.25, and the film with the highest hydrophobicity (154°) and the lowest surface energy (3.17 mJ·m–2) can be obtained at a ratio of 1.3. Scanning electron microscopy images demonstrated that the superhydrophobic film was composed of tightly stacked reticulate nanofilaments with a diameter of 7–17 nm and several micrometers in length and overlapped well-distributed nanospheres with a diameter of 30 nm. X-ray diffraction and Fourier transform infrared spectroscopy confirmed the film was crystalline silica grafted with long-chain alkylsiloxane. It is assumed that the unique micronanostructure combined with the siloxane modification contributed to the hydrophobicity. Consequently, this study provides a potential alternative solution for wellbore stabilization in deep well drilling engineering by employing nanoemulsion as a shale hydration inhibitor via forming a protective film with controllable wettability. Furthermore, it can be conferred a practical application due to easily available, less hazardous, and cost-effective materials.

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“…Mechanical and physicochemical mechanisms were introduced to explain the shale instabilities of the wellbore; however, the studies on wellbore instability mechanisms in shale gas wells are still not clear. Shale swelling is the main instability mechanism for expansive shale, which consists of mainly smectite and illite–smectite mixed layers. − Different from the conventional shale, organic-rich shale is characterized by a high content of brittle minerals, weak-swelling clay minerals, and naturally developed fractures. − Clay minerals of gas shale formation are mainly illite, kaolinite, and chlorite, which are weak expansive and weak dispersive minerals. , So, the inhibition of gas shale hydration is important for maintaining shale stability, but it is not sufficient. In addition, even when drilled with OBDFs, wellbore instability problems are still not completely resolved.…”

Section: Introductionmentioning

confidence: 99%

Wellbore Instability Induced by the Coupling of High-pH Fluid–Shale Reaction and Fracture Surface Sliding in Shale Gas Wells: Experimental and Field Studies

2020

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The wellbore stability in shale gas reservoir is the key factor for safe drilling and effective development of shale gas. However, the instability mechanism remains unclear in shale gas wells. In this work, the wellbore instability mechanism was studied by conducting experimental and field case studies in Longmaxi shale. A high-pH condition strengthened clay mineral hydration by increasing the absolute ζ-potential of the shale clay minerals. Alkali-soluble minerals (clay minerals, quartz, feldspar, etc.) were eroded greatly in a high-pH fluid, resulting in a large number of dissolution pores and weakening the microstructure of the shale. The high-pH fluid further reduced the difficulty of shale frictional sliding by lubricating the shale surface and weakening the asperity strength of the surface. Adjusting the pH value of drilling fluids and plugging lost circulation channels became key jobs to maintain the wellbore stability in shale gas wells. This study provides theoretical guidance for drilling fluid optimization used in shale gas wells.

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An Offshore Benign WBM System Can Prevent Hard, Brittle Shale Instability

Cited by 5 publications

References 1 publication

A review on borehole instability in active shale formations: Interactions, mechanisms and inhibitors

A review on borehole instability in active shale formations: Interactions, mechanisms and inhibitors

In Situ Shale Wettability Regulation Using Sophisticated Nanoemulsion to Maintain Wellbore Stability in Deep Well Drilling

Wellbore Instability Induced by the Coupling of High-pH Fluid–Shale Reaction and Fracture Surface Sliding in Shale Gas Wells: Experimental and Field Studies

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