What the Shale are We Talking About!

2021 ◽  
Author(s):  
Besmir Buranaj Hoxha ◽  
Claudio Rabe
Keyword(s):  
Failure Mechanism ◽  
Sedimentary Rocks ◽  
Formation Damage ◽  
Low Permeability ◽  
Wellbore Instability ◽  
The Past ◽  
In Situ Stresses ◽  
Different Types ◽  
Drilling Cost

Abstract Shale ‘stability’ has been extensively studied the past few decades in an attempt to understand wellbore instability problems encountered while drilling. Drilling through shale is almost inevitable, it makes up 75 percent of sedimentary rocks. Shale tends to be characterized as having high in-situ stresses, fissile, laminated, with low permeability. However, not all shale are the same, and the problem herein lies where they are all treated as such, in which most cases, has shown to be ineffective. Ironically, shale is predominantly generalized as being "reactive/swelling". Even though this can be true, it is not always the case because not all shale is reactive! In reality, there are many different types of shale: ductile, brittle, carbonaceous, argillaceous, flysch, dispersive, kaolinitic, micro-fractured etc. This study aims to clear many misconceptions and define different types of shale (global case scenarios) and their failing mechanisms that lead to wellbore instability, formation damage and high drilling cost. Afterwards, solutions will be offered, from a filed operation perspective, which will provide guidelines for stabilizing various shale based on their failure mechanism. Furthermore, we will define the symptoms for shale instability and propose industry accepted remedies.

In-Situ Stresses in Low-Permeability, Nonmarine Rocks

1989 ◽  
Vol 41 (04) ◽  
pp. 405-414 ◽  
Author(s):  
N.R. Warpinski ◽  
L.W. Teufel
Keyword(s):  
Low Permeability ◽  
In Situ Stresses

Interpretation of elastic – strain – recovery measurements near Elliot Lake, Ontario

1970 ◽  
Vol 7 (2) ◽  
pp. 576-578
Author(s):  
G. H. Elsbacher ◽  
H. U. Bielenstein
Keyword(s):  
Stress Field ◽  
Elastic Strain ◽  
Sedimentary Rocks ◽  
Lake Ontario ◽  
Strain Recovery ◽  
Tectonic Deformation ◽  
In Situ Stresses ◽  
Stress Environments ◽  
Mine Openings

In situ stresses obtained by measurements of elastic – strain – recovery in quartzose sedimentary rocks near Elliot Lake are interpreted in terms of two stress environments: one stress field induced by mining close to the mine openings and a remanent stress field preserved in the rocks from a time of tectonic deformation in the area.

A review of specific storage values from pore pressure response to passive in situ stresses: Implications for sustainable groundwater management

2020 ◽  
Author(s):  
Wendy A Timms ◽  
M Faysal Chowdhury ◽  
Gabriel C Rau
Keyword(s):  
Groundwater Management ◽  
Pore Pressure ◽  
Pressure Response ◽  
Earth Tides ◽  
Low Permeability ◽  
Specific Storage ◽  
Sustainable Groundwater Management ◽  
In Situ Stresses ◽  
Pore Pressure Response

<p>Specific storage (S<sub>s</sub>) values are important for analyzing the quantity of stored groundwater and for predicting drawdown to ensure sustainable pumping. This research compiled S<sub>s</sub> values from multiple available studies based on pore pressure responses to passive stresses, for comparison and discussion with relevant poroelastic theory and groundwater applications. We find that S<sub>s</sub> values from pore pressure responses to passive in situ stresses ranged from 1.3x10<sup>-7</sup> to 3.7x10<sup>-5</sup> m<sup>-1</sup> (geomean 2.0x10<sup>-6</sup> m-1, n=64 from 24 studies). This large S<sub>s</sub> dataset for confined aquifers included both consolidated and unconsolidated strata by extending two recent literature reviews. The dataset included several passive methods: Individual strains from Earth tides and atmospheric loading, their combined effect, and values derived from soil moisture loading due to rainfall events. The range of S<sub>s</sub> values spans approx. 2 orders of magnitude, far less than for hydraulic conductivity, a finding that has important implications for sustainable groundwater management. Both the range of values and maximum S<sub>s</sub> values in this large dataset were significantly smaller than S<sub>s</sub> values commonly applied including laboratory testing of cores, aquifer pump testing and numerical groundwater modelling. </p><p>Results confirm that S<sub>s</sub> is overestimated by assuming incompressible grains, particularly for consolidated rocks. It was also evident that Ss that commonly assumes uniaxial conditions underestimate S<sub>s</sub> that accounts for areal or volumetric conditions.  Further research is required to ensure that S<sub>s</sub> is not underestimated by assuming instantaneous pore pressure response to strains, particularly in low permeability strata. However, in low permeability strata S<sub>s</sub> could also be overestimated if based on total porosity (or moisture content) rather than a smaller free water content, due to water adsorbed by clay minerals. Further evaluation is also required for influences on S<sub>s</sub> from monitoring bore construction (ie. screen and casing or grouting), and S<sub>s</sub> derived from tidal stresses (undrained or constant mass conditions) that could underestimate S<sub>s</sub> applicable to groundwater pumping (drained or changing mass conditions). In summary, poroelastic effects that are often neglected in groundwater studies are clearly important for quantifying water flow and storage in strata with changing hydraulic stress and loading conditions. </p>

A Data-Driven Approach to Predict the Breakdown Pressure of the Tight and Unconventional Formation

2021 ◽  
Author(s):  
Zeeshan Tariq ◽  
Murtada Saleh Aljawad ◽  
Mobeen Murtaza ◽  
Mohamed Mahmoud ◽  
Dhafer Al-Shehri ◽  
...  
Keyword(s):  
Neural Network ◽  
Hydraulic Fracturing ◽  
Rock Properties ◽  
Breakdown Pressure ◽  
Rock Samples ◽  
In Situ Stresses ◽  
Fracturing Fluids ◽  
The Neural Network ◽  
Different Types

Abstract Unconventional reservoirs are characterized by their extremely low permeabilities surrounded by huge in-situ stresses. Hydraulic fracturing is a most commonly used stimulation technique to produce from such reservoirs. Due to high in situ stresses, breakdown pressure of the rock can be too difficult to achieve despite of reaching maximum pumping capacity. In this study, a new model is proposed to predict the breakdown pressures of the rock. An extensive experimental study was carried out on different cylindrical specimens and the hydraulic fracturing stimulation was performed with different fracturing fluids. Stimulation was carried out to record the rock breakdown pressure. Different types of fracturing fluids such as slick water, linear gel, cross-linked gels, guar gum, and heavy oil were tested. The experiments were carried out on different types of rock samples such as shales, sandstone, and tight carbonates. An extensive rock mechanical study was conducted to measure the elastic and failure parameters of the rock samples tested. An artificial neural network was used to correlate the breakdown pressure of the rock as a function of fracturing fluids, experimental conditions, and rock properties. Fracturing fluid properties included injection rate and fluid viscosity. Rock properties included were tensile strength, unconfined compressive strength, Young's Modulus, Poisson's ratio, porosity, permeability, and bulk density. In the process of data training, we analyzed and optimized the parameters of the neural network, including activation function, number of hidden layers, number of neurons in each layer, training times, data set division, and obtained the optimal model suitable for prediction of breakdown pressure. With the optimal setting of the neural network, we were successfully able to predict the breakdown pressure of the unconventional formation with an accuracy of 95%. The proposed method can greatly reduce the prediction cost of rock breakdown pressure before the fracturing operation of new wells and provides an optional method for the evaluation of tight oil reservoirs.

The Redox Environment of Deep Groundwaters Associated with the Tono Uranium Deposit, Japan

2002 ◽  
Vol 713 ◽  
Author(s):  
Randy Arthur ◽  
Teruki Iwatsuki ◽  
Katsuhiro Hama ◽  
Kenji Amano ◽  
Richard Metcalfe ◽  
...  
Keyword(s):  
Uranium Deposit ◽  
Sedimentary Rocks ◽  
Redox Potentials ◽  
Central Japan ◽  
Flow Models ◽  
The Past ◽  
Oxidation Reduction ◽  
Reversible Redox ◽  
Approximate Location

ABSTRACTAn unconformity underlying the Tono uranium deposit in central Japan represents the approximate location of a redox front separating relatively oxidizing groundwaters (Eh ≈0 mV) in the weathered, fractured Toki granite (TG) from strongly reducing pore fluids (Eh ≈-360 mV) in sedimentary rocks of the overlying Lower Toki Lignite-bearing Formation (TL). Uranium has been effectively immobilized in the TL during the past 10 million years. Stable and reversible redox potentials measured in-situ in boreholes penetrating the sedimentary rocks and granite appear to be controlled by the Fe(III)-oxyhydroxide – Fe2+ redox couple. A simplified analytical model of front migration suggests that chemical buffering by pyrite alone would limit the propagation velocity of the front into the TL to less than 8x10−6 m yr−1. The model is constrained by Darcy fluxes derived from groundwater flow models and relative 14C groundwater ages, average modal abundances of pyrite in the TL, and the analytical detection limit for dissolved oxygen in TG groundwaters (2 ppm). Model results also suggest that the redox buffering capacity of the TL would be exhausted within 10 million years if an upper bound O2(aq) concentration in TG groundwaters fixed by equilibrium with atmospheric O2(g) (8.5 ppm) is assumed. Immobilization of uranium in the TL is thus attributable to oxidation-reduction reactions that minimize O2(aq) concentrations primarily in the TG, and secondarily in the TL.

scholarly journals Raman Spectroscopy in Graphene-Based Systems: Prototypes for Nanoscience and Nanometrology

2012 ◽  
Vol 2012 ◽  
pp. 1-16 ◽  
Author(s):  
Ado Jorio
Keyword(s):  
Raman Spectroscopy ◽  
Carbon Nanostructures ◽  
External Factors ◽  
New Developments ◽  
One Dimensional ◽  
Resonance Effects ◽  
The Past ◽  
Different Types ◽  
Effect Of Disorder

Raman spectroscopy is a powerful tool to characterize the different types of sp2 carbon nanostructures, including two-dimensional graphene, one-dimensional nanotubes, and the effect of disorder in their structures. This work discusses why sp2 nanocarbons can be considered as prototype materials for the development of nanoscience and nanometrology. The sp2 nanocarbon structures are quickly introduced, followed by a discussion on how this field evolved in the past decades. In sequence, their rather rich Raman spectra composed of many peaks induced by single- and multiple-resonance effects are introduced. The properties of the main Raman peaks are then described, including their dependence on both materials structure and external factors, like temperature, pressure, doping, and environmental effects. Recent applications that are pushing the technique limits, such as multitechnique approach and in situ nanomanipulation, are highlighted, ending with some challenges for new developments in this field.

THE EFFECTS OF DRILLING FLUID-SHALE INTERACTIONS ON WELLBORE STABILITY

1995 ◽  
Vol 35 (1) ◽  
pp. 678 ◽  
Author(s):  
C.P Tan ◽  
E.M. Zeynaly-Andabily ◽  
S.S. Rahman
Keyword(s):  
Chemical Potential ◽  
Drilling Fluid ◽  
Wellbore Stability ◽  
Chemical Potential Difference ◽  
Wellbore Instability ◽  
Laboratory Techniques ◽  
In Situ Stresses ◽  
Physico Chemical ◽  
Mud Pressure

Wellbore instability, experienced mainly in shale sections, has resulted in significant drilling delays and suspension of wells in major Australian petroleum basins. These instabilities may be induced by either in-situ stresses that are high relative to the strength of the formations or physico-chemical interactions of the drilling fluid with the shales.This paper describes fundamental concepts of mud pressure penetration and flow of water between the wellbore and formation due to their chemical potential difference, and associated mud support changes as the drilling fluid interacts with shales. Due to the low permeability of shales, the penetration of the drilling fluid filtrate would result in an increase in pore pressure over a considerable distance from the wellbore. This instability mechanism strongly depends on properties of the drilling fluid filtrate and pore fluid, and the rock material composition.In addition to mud pressure penetration, water would be induced to either flow into or out of the formation depending on the relative chemical potential of the drilling fluid and the formation. A more stable wellbore condition could be achieved by optimising the chemical potential of drilling fluids.Drilling fluid and shale properties required for the models, which are determined using analytical and laboratory techniques, are presented herein. The effects of the time-dependent mechanisms on wellbore stability are demonstrated for a polyacrylamide, an ester-based and an oil-based mud. The results demonstrate that a more effective mud support can be obtained by optimising the adhesion and viscosity of the drilling fluid filtrate, and chemical potential of the drilling fluid.

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