scholarly journals The effect of fluid compressibility and elastic rock properties on deformation of geothermal reservoirs

2019 ◽  
Vol 217 (1) ◽  
pp. 122-134 ◽  
Author(s):  
D Juncu ◽  
Th Árnadóttir ◽  
H Geirsson ◽  
G Gunnarsson
Keyword(s):  
Rock Properties ◽  
Geothermal Reservoirs ◽  
Elastic Rock ◽  
Fluid Compressibility

Cementation exponent as a geometric factor for the elastic properties of granular rocks

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. MR341-MR349
Author(s):  
Tongcheng Han ◽  
Zhoutuo Wei ◽  
Li-Yun Fu
Keyword(s):  
Elastic Properties ◽  
Geophysical Methods ◽  
Effective Medium ◽  
Geometric Factor ◽  
Rock Properties ◽  
Modeling Approaches ◽  
The Earth ◽  
Elastic Rock ◽  
Effective Medium Models ◽  
Electromagnetic Surveys

A geometric factor properly describing the microstructure of a rock is compulsory for effective medium models to accurately predict the elastic and electrical rock properties, which, in turn, are of great importance for interpreting data acquired by seismic and electromagnetic surveys, two of the most important geophysical methods for understanding the earth. Despite the applications of cementation exponent for the successful modeling of electrical rock properties, however, there has been no demonstration of cementation exponent as the geometric factor for the elastic rock properties. We have developed a workflow to model the elastic properties of clean and normal granular rocks through the combination of effective medium modeling approaches using cementation exponent as the geometric factor. Based on the dedicated modeling approaches, we find that cementation exponent can be adequately used as a geometric factor for the elastic properties of granular rocks. Further results highlight the effects of cementation exponent on the elastic and joint elastic-electrical properties of granular rocks. The results illustrate the promise of cementation exponent as a geometric link for the joint elastic-electrical modeling to better characterize the earth through integrated seismic and electromagnetic surveys.

scholarly journals Hydraulic and Mechanical Impacts of Pore Space Alterations within a Sandstone Quantified by a Flow Velocity-Dependent Precipitation Approach

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3100 ◽  
Author(s):  
Maria Wetzel ◽  
Thomas Kempka ◽  
Michael Kühn
Keyword(s):  
Flow Velocity ◽  
Power Law ◽  
Elastic Moduli ◽  
Rock Properties ◽  
Local Flow ◽  
Mineral Growth ◽  
Macro Scale ◽  
Elastic Rock ◽  
The Impact ◽  
Flow Velocities

Geochemical processes change the microstructure of rocks and thereby affect their physical behaviour at the macro scale. A micro-computer tomography (micro-CT) scan of a typical reservoir sandstone is used to numerically examine the impact of three spatial alteration patterns on pore morphology, permeability and elastic moduli by correlating precipitation with the local flow velocity magnitude. The results demonstrate that the location of mineral growth strongly affects the permeability decrease with variations by up to four orders in magnitude. Precipitation in regions of high flow velocities is characterised by a predominant clogging of pore throats and a drastic permeability reduction, which can be roughly described by the power law relation with an exponent of 20. A continuous alteration of the pore structure by uniform mineral growth reduces the permeability comparable to the power law with an exponent of four or the Kozeny–Carman relation. Preferential precipitation in regions of low flow velocities predominantly affects smaller throats and pores with a minor impact on the flow regime, where the permeability decrease is considerably below that calculated by the power law with an exponent of two. Despite their complete distinctive impact on hydraulics, the spatial precipitation patterns only slightly affect the increase in elastic rock properties with differences by up to 6.3% between the investigated scenarios. Hence, an adequate characterisation of the spatial precipitation pattern is crucial to quantify changes in hydraulic rock properties, whereas the present study shows that its impact on elastic rock parameters is limited. The calculated relations between porosity and permeability, as well as elastic moduli can be applied for upscaling micro-scale findings to reservoir-scale models to improve their predictive capabilities, what is of paramount importance for a sustainable utilisation of the geological subsurface.

AN INTEGRATED PETROPHYSICAL WORKFLOW TO GENERATING FLUID SUBSTITUTED LOGS FOR AVO CHARACTERISATION—GIPSY AND NORTH GIPSY FIELDS CASE STUDY, NORTH WEST SHELF, AUSTRALIA

2002 ◽  
Vol 42 (1) ◽  
pp. 477
Author(s):  
D.L Clarke ◽  
A.P Clare
Keyword(s):  
Field Study ◽  
Water Saturation ◽  
Integrated Approach ◽  
Rock Properties ◽  
Intrinsic Permeability ◽  
North West ◽  
Consistent Model ◽  
Original Field ◽  
Elastic Rock

As part of a multi-well field study an integrated petrophysical workflow was developed to include the generation of fluid substituted logs for AVO characterisation.The workflow relied upon the construction of a multimineral model that best approximated the actual mineral content of the reservoir. Any limitations or assumptions were noted and taken into account when creating the multi-mineral model. Other petrophysical results were derived from the same model to validate its consistency such as intrinsic permeability, porosity, water saturation, etc. Iteration between the model and the results was required until a consistent model was achieved.The estimation of an intrinsic permeability log was based upon the k-Lambda method that uses the multimineral model and porosities.The estimation of a shear slowness log and the fluid substituted logs was based upon elastic rock properties derived from the multi-mineral model and the acquired compressional slowness log and bulk density log. This integrated approach provides a higher confidence in the derived results, which are then used as input into the reservoir model, thereby improving the reserve calculations.The interdependence of each derived result on the same input multi-mineral model ensures consistency and predictability in a complex geological environment, which captures all available information.The method is demonstrated with the Gipsy–1 and North Gipsy–1 wells, which were part of the original field study.

Digital rock physics: Segmentation of sub-resolution features

2020 ◽  
Author(s):  
Martin Balcewicz ◽  
Erik H. Saenger
Keyword(s):  
Computed Tomography ◽  
High Resolution ◽  
Rock Physics ◽  
Rock Properties ◽  
X Ray ◽  
Digital Rock Physics ◽  
Tomography Image ◽  
X Ray Computed ◽  
Computed Tomography Image ◽  
Elastic Rock

<p>Digital rock physics (DRP) became a complementary part in reservoir characterization during the last two decades. Deriving transport, thermal, or effective elastic rock properties from a digital twin requires a three-step workflow: (1) Preparation of a high-resolution X-ray computed tomography image, (2) segmentation of pore and grain phases, respectively, and (3) solving equations due to the demanded properties. Despite the high resolution µ-CT images, the numerical predictions of rock properties have their specific uncertainties compared to laboratory measurements. Missing unresolved features in the µ-CT image might be the key issue. These findings indicate the importance of a full understanding of the rocks microfabrics. Most digital models used in DRP treat the rock as a heterogeneous, isotropic, intact medium which neglect unresolved features. However, we expect features within the microfabrics like micro-cracks, small-scale fluid inclusions, or stressed grains which may influence the elastic rock properties but have not been taken into account in DRP, yet. Former studies have shown resolution-issues in grain-to-grain contacts within sandstones or inaccuracies due to micro-porosity in carbonates, this means the micritic phase. Within the scope of this abstract, we image two different sandstone samples, Bentheim and Ruhrsandstone, as well as one carbonate sample. Here, we compare the mentioned difficulties of X-ray visualization with further analytical methods, this means thin section and focused ion beam measurements. This results into a better understanding of the rocks microstructures and allows us to segment unresolved features in the X-ray computed tomography image. Those features can be described with effective properties at the µ-scale in the DRP workflow to reduce the uncertainty of the predicted rock properties at the meso- and fieldscale.</p>

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