Disclosed herein are optical swell meters and methods for creating a swelling strain profiles of shale specimens. The optical swell meters can measure fine-scale variations and capture the role of small-scale heterogeneity in the swelling behavior of the shale specimens.
Interaction of clay-rich formations with fluids occurs during drilling, hydraulic fracturing, and enhanced oil recovery operations. During these operations, clay swelling can cause conductivity damage by impeding hydrocarbon flow. The degree to which damage induced by swelling of the clays prevails, is dependent upon the mineralogy of the rock, composition of fracturing and reservoir fluids, and fluid access to different zones of the fracture network. In the case of wellbore drilling operations for petroleum exploration or extraction, water-based drilling fluids are often used instead of oil- or synthetic-based alternatives due to their environmental effects. Water, however, can react with clays and lead to their hydration and subsequent swelling. This, in turn, may have a negative impact on well costs, and can impede the drilling process.
To minimize the adverse effects of clay swelling during these operations, it is crucial to monitor and understand the mechanisms behind the process. Past research has conducted measurements of swelling in shale when immersed in water. These studies used conventional measurement techniques like linear variable differential transformer (LVDT) sensors and strain gauges, which provided average strain values, but did not investigate fine-scale variation in the deformation of the shale specimens.
Consequently, there is need for new systems and methods for measuring fine-scale variations of shale, capturing the role of small-scale heterogeneity in their swelling.
Provided herein are optical swell meters and methods for using them to provide a swelling strain profile of samples during interaction with a fluid. In a specific embodiment, the system can include a glass imbibition chamber containing a specimen, where an imbibition fluid is located within the glass inhibition chamber and at least partially covering the specimen; a digital camera set a distance away from the chamber and facing chamber; and at least one light source, where the light source illuminates the specimen.
In another specific embodiment, a method for creating a swelling strain profile can include: applying a random intensity speckle pattern to at least one face of a specimen, the specimen being capable of deformation due to contact with a fluid; placing a specimen within a glass chamber and filling the glass chamber with an imbibition fluid; illuminating the specimen; capturing a plurality of images of the specimen over time using a digital camera and thereby creating digital images; and using digital image correlation to analyze the digital images to generate a strain map across the specimen surface.
The present disclosure can be better understood by referring to the following drawings. The drawings constitute a part of this specification and include exemplary embodiments of the optical swell meters, which can be embodied in various forms.
The optical swell meters can include, but are not limited to: one or more glass chambers, one or more digital camera, and one or more light emitting diode lights. The method of using the optical swell meters can include providing a swelling strain profile of shale samples during interaction with a fluid. The shale specimen to be tested can be painted to generate a random speckle pattern. Then, the shale specimen can be placed in a glass chamber containing a fluid of interest. The digital camera can be used to capture the deformation process as the submerged sample swells. The digital images can be analyzed using a digital image correlation technique to generate strain maps across the specimen surface for every image captured during the swelling process. The strain map can include a collective of strains measurements at thousands of points on the sample surface and, therefore, can provide valuable information about strain distributions and strain localization. The crack formation and propagation during the swelling can also be observed from the strain maps.
The method of using the optical swell meter can include applying a random intensity speckle pattern to the front face (the face towards the camera) of the specimen by using flat white spray paint. The specimen can be placed on a brass wire mesh, which can be attached to the base of the imbibition chamber thus allowing an all-face-open imbibition configuration. The speckle pattern on the specimen can be illuminated using two LED lights. The digital camera can be used to capture images of the swelling of the specimen over time. The captured images can be analyzed using digital image correlation. The digital image correlation enables the visualization and quantification of full-field deformation. Full-field monitoring helps measure the strain distribution and localization, as well as the evolution of strain field with time. The strain localization is influenced by the distribution of the minerals in the specimen. The results provide a better understanding of strain development during imbibition in comparison to traditional linear variable differential transformer-based measurements that give only an average strain value. The results from the study show large strains get localized along a few select laminations. These laminations showed a large tensile strain in the direction perpendicular to the bedding plane.
The optical swell meters and methods for using them allow for measuring fine-scale variations thereby capturing the role of small-scale heterogeneity in the swelling behavior of shale specimens. The optical swell meters provide a means for investigating the swelling deformation of shale upon immersion in water using digital image correlation. The digital image correlation is a non-contact measurement technique developed for capturing deformations over the surface as a function of time.
The optical swell meters can measure the deformation of clay-rich geologic rocks in contact with water using camera associated with digital image correlation techniques. The optical swell meters can capture the full-field deformation of shale compared to the average values provided with the linear variable differential transformer methods, thus the optical swell meter can be more representative of heterogeneous nature of shale formation (democratization of deformation) with shales being anisotropic in nature (behave differently in different directions). The optical swell meters can provide swelling measurements in the direction of lamination versus perpendicular to lamination. To represent the complex nature of shale formation for improved engineering designs, the optical swell meters can provide the full-field deformation of shale due to water interaction. The optical swell meters can support geothermal, hydrocarbon and carbon dioxide companies to mitigate wellbore collapse, carbon dioxide leakage, and more informed decisions on field development.
In an embodiment, the method of using the optical swell meters can include a digital image correlation technique as a non-contact method for full-field measurement of microscopic shale deformation in interaction with water. A speckle pattern is applied to the specimen and then the deformation of the specimen during imbibition is captured using a digital camera. The images are analyzed using a 2D-digital image correlation image processing software to obtain displacements and strains. The method of using the optical swell meters can yield measurements of deformation that evolve over time, showing the role of each lamina on deformation.
To provide a better understanding of the foregoing discussion, the following non-limiting examples are offered. Although the examples can be directed to specific embodiments, they are not to be viewed as limiting the invention in any specific respect. Examples of the graft copolymers of dextran and polyacrylamide and reaction conditions for making them are shown in Tables 1-6.
Tuscaloosa Marine Shale samples with 35% to 52% clay are tested in interaction with water. Implementation of digital image correlation technique to capture deformation during the imbibition process and the impact of clay content on fine-scale deformation and consequent fracturing of clay-rich shales.
The digital image correlation can capture the specimen deformation during imbibition as shown in
A 6.3 MP monochrome digital camera (Blackfly S) was used to capture the deformation images while the specimen in submerged in DI water. The images were taken at 5-minute interval for the first 2 hrs and then 30-minute interval for 4 days. The images were analyzed using commercial DIC software (ARAMIS 2019). The DIC analysis was conducted using a subset size of 45 pixels and a step size of 15 pixels.
A calibration study was conducted to evaluate the accuracy of the underwater 2D-DIC system. A non-deforming flat aluminum target plate with a random speckle pattern was placed underwater in the location of the specimen for the experiment. The aluminum target was given precise in-plane (in the image plane—perpendicular to the optical path) and out-of-plane (along optical path) displacements using a micrometer. Images of the aluminum target plate were captured at different displacements and then a deformation analysis was conducted using DIC to quantify the effect of prescribed translation on pseudo-DIC stain. The strains observed in the calibration study are shown in
The two specimens for this example were selected from different depths of a single well in TMS formation. X-ray diffraction analysis was conducted on selected samples to identify mineralogy. The results are presented in Table 1.
Both the selected specimens were rich in clay, with a weight percentage of 34.4 in specimen S1 and 52.2 in S2. Quartz was the other major constituent with S1 having 58.2 and S2 having 37.7 wt %.
For this example, shale samples were cut into cuboid shape with bedding planes oriented horizontally, and nominal specimen size of 38 mm width, 25 mm height and 25 mm depth. The DIC system allowed the monitoring of deformation over the entire speckled surface of the specimen and evaluation of the deformation as a function of location and time.
Both the specimens exhibited large swelling in the vertical direction.
Horizontal normal strains (εxx) in S2 at 0.096 hrs and 0.367 hrs are shown in
Average normal vertical strain and average normal horizontal strain were calculated for the specimens to compare their swelling behavior as a function of time. The average strain in each specimen was calculated by tracking the average displacement of sections at specimen boundaries.
The evolution of average vertical strains in the two specimens is shown in
The results show that the swelling deformation in specimens, when exposed to deionized water, is not uniform. Large numbers of high swelling sites were observed in the specimens (
To understanding the optical swell meter, references are made in the text to exemplary embodiments of an optical swell meter, only some of which are described herein. It should be understood that no limitations on the scope of the invention are intended by describing these exemplary embodiments. One of ordinary skill in the art will readily appreciate that alternate but functionally equivalent components, materials, designs, and equipment may be used. The inclusion of additional elements may be deemed readily apparent and obvious to one of ordinary skill in the art. Specific elements disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to employ the present invention.
Although the invention has been described with reference to the above examples, it will be understood that modifications and variations are encompassed within the spirit and scope of the invention. Accordingly, the invention is limited only by the following claims.
This application claims the benefit of priority under 35 U.S.C. § 119(e) of U.S. Ser. No. 63/223,331, filed Jul. 19, 2021, the entire contents of which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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63223331 | Jul 2021 | US |