- Home
- Conferences
- Conference Proceedings
- Conferences
Sixth EAGE Shale Workshop
- Conference date: April-May 28-01, 2019
- Location: Bordeaux, France
- Published: 28 April 2019
21 - 40 of 67 results
-
-
Early & Late Diagenetic Mineral Development within the Upper Jurassic Haynesville-Bossier Shale, USA
More LessSummaryDespite recent advances, diagenetic processes in fine-grained sediments remain relatively poorly understood. Key questions still to be resolved include how mineral cements develop in low porosity and permeability systems and the extent of element mobility during the diagenesis of fine-grained sediments. This study uses petrographic, mineralogical and geochemical data from the Haynesville-Bossier Shale identify early and late diagenetic mineral development. On the basis of grainsize and mineralogy five facies are designated: (i) silica-rich argillaceous mudstones, (ii) argillaceous siliceous mudstones, (iii) mixed siliceous mudstones, (iv) mixed mudstones and (v) cemented mudstones. The diagenetic development of the Haynesville-Bossier Shale can be divided in to early and late diagenesis. Ferroan and non-ferroan dolomite, framboidal pyrite, and microfossil pore-filling kaolinite cements all formed during early diagenesis. Late diagenetic cements include microcrystalline calcite, euhedral pyrite, replacive and displacive chlorite, calcite-replacive albite, and replacive and/or displacive quartz. Late diagenetic cements would have required a wide range of geochemically mobile elements, (bed scale); illitisation of smectite during late diagenesis is a potential source for these elements. The work impacts porosity and permeability evolution and fracture susceptibility in unconventional shales.
-
-
-
Mineral Diagenetic Control On Hydrocarbon Expulsion in Organic-Rich Mudrocks, Bakken Formation, North Dakota, U.S.A.
Authors K. Milliken and T. ZhangSummaryAn indicator of expulsion efficiency obtained from gases extracted from mudstone correlates with the degree of microquartz cementation. Cemented samples have stronger retention of hydrocarbons. The strongest degrees of expulsion are observed in samples that lack cements and have diagenesis dominated by compaction. This suggests that mudrock compaction remains an active process in the zone hydrocarbon generation.
-
-
-
The Elastic Anisotropy of the Whitby Mudstone Formation at Varying Water Saturations
Authors L. Douma, J. Dautriat, J. Sarout, D. Dewhurst and A. BarnhoornSummaryMudstones are characterized by their tight matrix and are therefore of interest in various industries, including the petroleum and underground repository industry. These clay-rich rocks often show dynamic elastic anisotropy, which causes significant problems in geophysical interpretations. In addition, pore water has a significant effect on the bulk properties of mudstones. However, the degree of saturation is often not reported in the literature. This study investigates the impact of water saturation on the elastic anisotropy of the Whitby Mudstone. Four core plugs with different water saturations were deformed until failure and tested ultrasonically at effective confining pressure conditions of 25 MPa. P-wave and S-wave velocities were monitored along the symmetry axis, across the core diameter, and at ~49˚ to the horizontal bedding plane to calculate the full elastic tensor and subsequently the Thomsen anisotropy parameters. The degree of saturation highly affects the rock strength and static elastic properties and leads to significant changes in the elastic anisotropy parameters.
-
-
-
Experimental Assessment of the Impact of Partial Saturation On the Mechanical Properties of Gas Shales
Authors A. Minardi, A. Ferrari, R. Ewy and L. LalouiSummaryThe impact of partial water saturation on the mechanical behaviour of clays and claystones has been widely proved. This work aims at demonstrating that also for gas shales partial water saturation has a significant influence on their stiffness and strength properties although they have different characteristics compared to other clayey materials. Samples extracted from two different unconventional shale gas reservoirs are tested. An experimental methodology and a testing device are developed to perform uniaxial compressive tests and unloading-reloading cycles at different total suction values. The control of total suction with the vapour equilibrium technique is used to equalize specimens to different water saturation conditions and assess the consequent impact on mechanical properties. The obtained outcomes clearly demonstrate that partial water saturation cannot be neglected to characterize the mechanical properties of gas shales. A reduction of uniaxial compressive strength of 22 % is observed in the total suction range between 150 and 10 MPa. Regarding the elastic stiffness, a decrease up to 50% is exhibited when the material is wetted from 150 MPa to 0 MPa of total suction.
-
-
-
Mineralogy and Mechanical Properties of Mudrocks Before and After Stepwise Ageing in sCO2
Authors D. Dewhurst, M. Raven, S. Salwani Bt Md Shah, S. Syareena Bt Md Ali, A. Giwelli and S. FirnsSummaryTwo mudrock seals from a site being evaluated for geological storage of CO2 were tested to understand their geomechanical properties, mineralogical composition and geochemical make up before and after immersion in super-critical CO2 (sCO2) at high pressure and temperature (150°C and 4200 psi) representing close to in situ conditions. Physico-chemical properties such as cation exchange capacity and specific surface area were also evaluated. Samples for mineralogy, geochemistry and physico-chemical properties were tested stepwise from their initial state through to 1, 4 and 6 months immersion in sCO2. Samples for geomechanical testing were compared in their initial preserved state and after ageing for 6 months in sCO2. No change in composition was noted for either mineralogy or major element geochemistry and the physico-chemical properties measured were also unchanged. However, geomechanical properties did change, with compressive strength, tensile strength, friction coefficient and elastic stiffness all increasing after exposure to sCO2. As there was no change in mineralogy or geochemistry, it is most likely that the loss of water during exposure to sCO2 resulted in the strength increase observed in these mudrocks.
-
-
-
Measuring the Anisotropic Dynamic and Static Moduli of the Duvernay Shale
Authors L. Shen, D.R. Schmitt, W. Li and X. ChenSummaryWe measure the anisotropic static and dynamic moduli of a calcareous shale from the Duvernay unconventional hydrocarbon reservoir. The full set of the five stiffness, following the assumed Transverse Isotropy for earth materials, needed to describe the complete elastic behaviour of the test sample are obtained by measuring the acoustic wave velocities on a sample cut into the shape of prism allowing Piezoelectric wafers to be attached to its surface and receive/emit waves in different angles. Measurements are taken at different confining pressures up to 180 MPa. Static loading tests are performed on the cylindrical plugs cored at different angles using the Hoek Cell. We observed that Young's modulus at the direction parallel to the direction of symmetry axis (E3) is highly pressure-dependent for both dynamic (20 – 30 GPa) and static (12 – 37 GPa) measurements. Lesser pressure dependence is observed for the dynamic (34–36 GPa) and static (~26 GPa) E1,2 . Static and dynamic Poisson's ratios demonstrate pressure dependence too. Generally speaking, the static moduli are more prone to pressure change compared with their dynamic counterparts.
-
-
-
Assessment of stress dependent elastic and permeability anisotropy using small cubic shale samples
Authors J. Dautriat, M. Cauchefert, Y. Kovalyshen, J. Sarout, A. Giwelli and D.N. DewhurstSummaryAssuming transverse anisotropy, elastic properties and anisotropy of rock formations at depth are usually determined in the laboratory using a cylindrical rock sample, preferably plugged orthogonal to the symmetry plane. Such anisotropy is usually caused by bedding or laminations when present. On the other hand, permeability anisotropy evaluation requires a pair of companion samples cored along and orthogonal to the bedding plane. Shaly cores recovered from the well often experience drying, desiccation and stress-relief fracturing when not properly preserved, which makes it difficult to sub-sample standard-size cylindrical plugs. Therefore, we developed a new laboratory approach to test relatively small cubic rock samples without modifying existing pressure vessel equipment designed for standard cylindrical samples. This approach is tested on the Opalinus Clay and validated by comparing the elastic anisotropy results, in term of Thomsen's parameters, obtained on a parent specimen and three cubes extracted from it. We demonstrate that elastic anisotropy parameters inferred from the cubes are accurate as long as a small, homogeneous and representative samples of the formation can be recovered. If this condition is fulfilled, permeability anisotropy can also be successfully determined from small cubic samples using a dedicated permeameter designed for tight and low permeability cylindrical rock samples.
-
-
-
Chemo-Mechanical Coupling in Fine-Grained Soils and Sedimentary Rocks
Authors I. Bourg, F. Carrillo, X. Shen and T. UnderwoodSummaryFine-grained sedimentary rocks such as shale or mudstone are ubiquitous in sedimentary basins and play important roles as caprocks, host rocks, or source rocks in many energy technologies including carbon capture and storage, nuclear waste storage, and hydrocarbon extraction. Fine-grained soils are equally ubiquitous and play important roles in soil carbon storage and food security. Accurate predictive models of the hydrologic properties of these media remain elusive, however, because of the significant experimental challenges posed by their low mechanical strength, ultra-low permeability, and sensitivity to geochemical and geomechanical alteration. An even greater challenge is that nanoscale interactions between clay particles give rise to strong couplings between the chemistry, mechanics, and hydrology of these media. Our research aims to gain fundamental insight into these interactions and couplings by using computational fluid dynamics, discrete element model, brownian dynamics, and atomistic-level simulations of water-clay-salt-(organic) systems.
-
-
-
Determination of Thermal Conductivity Variations within Oil Shale Reservoirs Using Integration of Thermal Core Logging and Standard Well Logging Data
Authors A. Shakirov, E. Chekhonin, E. Popov, R. Romushkevich and Y. PopovSummaryContinuous vertical variations of thermal conductivity were registered using optical scanning technique at 847 full-size core samples of the oil field located in West-Siberia. Target interval is highly heterogeneous and anisotropic oil-source rock – the Bazhenov formation. Thermal core logging and well logging data were integrated for shale reservoirs thermal conductivity prediction. Correlation analysis between neutron porosity and thermal conductivity was performed. The vertical resolution of the corresponding logging tool was considered. The obtained regression equation was used for thermal conductivity prediction. Mean absolute percentage error is 8 %. For shale oil thermal conductivity prediction volumetric mineralogical model from standard well logs was constructed. Using different mixing rules including the Liechtenecker equation vertical variations of thermal conductivity were predicted. Mean absolute percentage error is 6.6 %.
-
-
-
Ekofisk Time-Lapse Seismic Monitoring of Injection in Shale
More LessSummaryCutting re-injection operations in overburden shale formations at the Ekofisk field, has started since 1997. High fidelity time-lapse seismic data (Life of Field Seismic, LoFS) are a critical tool to monitor development of pressure around the injected area. Time-strain data in particular can provide robust pressure and fracture development information. The data also efficiently assist in quantitative pressure estimation around the injected interval. This study has implications for unconventional shale reservoirs where time-lapse seismic are employed.
-
-
-
Yield characteristics of caprocks: a criticial state mechanics approach
Authors C.C. Graham, J.F. Harrington, R.C. Cuss and K. DanielsSummaryThe yield behaviour of both clay soils and reservoir materials can effectively be assessed using critical state mechanics. Nevertheless, this approach has been relatively unused, in relation to caprock materials and the shape of the yield envelope is poorly-constrained in comparison. In this study, we present experimental data on the hydromechanical behaviour of caprocks and their associated critical state yield envelopes. The degree of uncertainty in the form of the yield surface is considered, before the likely consequences of various stress path scenarios is examined. The potential for permeability enhancement versus reduction is also considered and the influence of stress history is found to be key. This approach demonstrates the potential for yield to be reached during some depletion scenarios, though this deformation is often compactive and permeability-reducing in nature. As such, the critical state approach represents an effective tool for assessing performance of caprocks under a range of potential stress paths.
-
-
-
Improving Anisotropic Velocity Model Calibration in Microseismic Data From the Woodford Shale
Authors P.J. Usher and J. HuangSummaryThis study demonstrates a workflow of anisotropic velocity calibration for microseismic monitoring. We search for a layered P and S velocity, along with Thomsen parameters, that minimises travel time residuals with our calibration shots. Due to the limited calibration shots, the travel time residual was minimised for a set of early microseismic events from each stage. The velocity models varied from isotropic, to constant non-zero Thomsen parameters, layered Thomsen parameters that are proportional to 1/VP and finally to a general layered vertical transversely isotropic velocity model. We showed that different levels of model complexity effect event location in the Woodford Shale. With increasing complexity, the event locations become more accurate, cluster around the injection points, and have less artefacts and systematic biases. The calibrated anisotropic model can later be used to characterise the fractures and mineral content of the shale and thus add value to microseismic monitoring. This process can be automated to help remove biases, to quantify velocity model error, and as step towards joint inversion for layered anisotropic velocity and event locations.
-
-
-
Analysis of Cretaceous Shales in the Rovuma Basin, Offshore Mozambique
Authors O. Nhabanga, P. Ringrose and R. HoltSummaryAcoustic log data are important and have been widely used in the petroleum industry to detect fractures in the formation, the fluids and to check the quality of the cementation process in the wellbore. In present study, we used the acoustic log data to detect the overpressured Cretaceous shale units, by contrasting P- and S-waves, under mechanical and chemical compactions.
-
-
-
Characterization of Shale-Gas Reservoir Based On An Anisotropic AVO Inversion and Quantitative Seismic Interpretation
More LessSummaryA well log penetrating the Lower Silurain shale (S1l) in the south of the Sichuan Basin shows that this shale formation represents strong VTI (vertically transverse isotropy) properties. Anisotropy has significant influence on the seismic amplitude variation with offset (AVO) response, so AVO analysis and inversion ignoring the influence of anisotropy can be inaccurate. In this parper, an anisotropic AVO inversion is introduced based on a modified approximation of the PP-wave reflection coefficient for VTI media. Three attributes including the acoustic impedance (attribute A), the shear modulus weighted by an anelliptical anisotropy parameter (attribute B), and the approximated horizontal P-wave velocity (attribute C) can be simultaneously inverted by using a Bayesian-framework-based inversion scheme. A statistical rock-physics workflow is then applied to the inverted attributes for quantitative seismic interpretation. The field-data application on a lower Silurian-age shale-gas reservoir shows the feasibility of both approaches. The shale formation can be discriminated from surrounding formations by using the combination of the attributes A and C, and the gas-bearing shale can be identified through the combination of the attributes A and B.
-
-
-
Time-Lapse Analysis on Repeated Well Logs: A Focus On Shales
Authors A. Jaramillo, M.D. Mangriotis and C. MacBethSummaryShales play a significant role controlling fluid flow and seismic-wave propagation due to their low permeability and anisotropic structure. Field observations indicate that during production, pore pressure reduction in the reservoir generates strain deformation in the overburden that varies with lithology and stress path. 4D seismic is a primary source of spatial information on these geomechanical effects. For this purpose, a physical model that links the velocity perturbations to the vertical strain via a factor R is widely used. This study aims at computing R factors from a repeated well log analysis. The combination of seismic with petrophysics is key to understand the physics of the lithology-dependent R. We performed the analysis on two Jurassic shales from Central North Sea to calculate R factors in the overburden shales based on the existing pore-related model proposed by Hatchell and Bourne (2005) . The petrophysical analysis of repeated wireline logs has shown that R-factors of around 5 are appropriate for both the Heather and Kimmeridge clay based on an HBR model using log-derived time-lapse porosity values. This range is in agreement with most published overburden R-values from seismic data, and can be explained by porosity deformation.
-
-
-
AVO Modelling Considering Various Caprock and Reservoir Scenarios for Potential CO2 Storage in Smeaheie Area, Northern North Sea
Authors M. Fawad and N.H. MondolSummaryUnlike a hydrocarbon accumulation where we are sure of a working reservoir and the caprock integrity, the CO2 storage has many unknowns before the gas is injected and placed there. To reduce this risk it is imperative to model all the possible scenarios before taking a major decision for CO2 storage. To evaluate subsurface reservoirs and caprocks for CO2 sequestration, the CO2 plume movement while injection and subsequent changes in the elastic properties at the reservoir-caprock interface are important. The AVO method might provide us with a tool to detect the position and level of saturation of CO2 in a reservoir while and after injection. The upper Jurassic Sognefjord Formation is a potential CO2 storage formation overlain by the Heather and Draupne Formations considered to be the cap rocks in the Smeaheie area within the northern North Sea. In this study we considered two different reservoir-caprock cases with five different saturation, pressure and temperature scenarios for each case to check the sensitivity of the AVO method in this area. These findings will help understanding the change in elastic properties at the reservoir-caprock interface as a function of CO2 saturation, facilitating detection of its migration and possible phase changes.
-
-
-
Phase and Group Velocities in TI and ORT Media
By A. StovasSummaryPhase and group velocity approximations are important to characterize the anisotroopic matherial. We develop simple and very accurate velocity approximation with simple parameter estimation. Approximations are tested for TI and ORT models.
-
-
-
Estimation of Unconventional Reservoir Matrix Permeability and Pore Volume Using Rate-Transient Analysis Techniques: Method Refinements
Authors C. Clarkson, A. Vahedian, A. Ghanizadeh and C. SongSummaryA core analysis procedure based on rate-transient analysis theory has been successfully tested in the lab. Two permeability estimates and one pore volume estimate are possible using this technique, with the results being achieved faster than conventional testing (e.g. pulse-decay test). Refinements in one permeability estimation method, based on the distance of investigation, were illustrated. The combination of the rate-normalized pseudopressure derivative, used to identify the end of linear flow, and a new expression for DOI, yielded permeability values very close to the pulse-decay method.
-
-
-
Laboratory- and Simulation-Based CO2 Storage Resource Estimates for the Bakken Unconventional Tight Oil Formation
Authors J. Sorensen, S. Hawthorne, N. Azzolina, B. Kurz and V. HerdegenSummaryThe Bakken Formation in North America includes two organic rich shale units that serve as oil source rocks with an intermediate tight, silty carbonate unit that serves as the target reservoir. The juxtaposition of a need to improve Bakken oil productivity with a desire to manage carbon dioxide (CO2) emissions from power plants has led to an interest in the injection of CO2 for enhanced oil recovery (EOR) and associated CO2 storage. Characterization methods, including micro-x-ray computer tomography imaging, field emission and focused ion beam scanning electron microscopy, and CO2 sorption isotherm measurement, were applied to quantify the petrophysical factors that control CO2 interactions and oil mobility in the Bakken. Laboratory experiments investigated the ability of CO2 to permeate Bakken rocks and mobilize oil. Modeling was performed to history match experiments, and simulate injection scenarios. These efforts resulted in the development of a refined method for estimating the potential CO2 storage resource of the Bakken. Application of the refined method indicates that the range of storage resource estimates for the Bakken shale units is 5.8 to 26.3 kg CO2/m3 rock. Estimates of storage resource for the nonshale Bakken member ranged from 1.9 to 12.4 kg CO2/m3 rock.
-
-
-
Detailed profiling organic carbon content of oil shales with thermal core logging technique
Authors E. Popov, Y. Popov, R. Romushkevich, M. Spasennykh and E. KozlovaSummaryThe development of a thermal core logging technique as a field-scale geophysical technique presented new possibilities for multiphysical testing of shales, e.g. preparation of representative databases of the thermal properties for basin modeling and hydrodynamic modeling for thermal methods of EOR, and practical application of correlations between shale thermal conductivity and total organic carbon. The technique of determination of oil shale total organic carbon from the thermal core logging data was developed that provides detailed continuous high-resolution profiling total organic carbon of oil shales along wells. The technique was studied and tested on more than 11 500 oil shale samples from Bazhenov and Domanic Formations when more than 1250 shale samples were also tested for total organic carbon content with Rock-Eval pyrolysis. The data on shale total organic carbon obtained from the measurements with pyrolysis allow to calibrate and control the results of total organic carbon determinations from the thermal core logging. Continuous profiling total organic carbon from continuous thermal core logging provides reasonable selection of shale samples for future investigations and are basis for basin modeling and calculation of reserves
-