Fast Evaluation of Caprock Strength Sensitivity to Different CO2 Solutions Using Small Sample Techniques

Abstract

The Draupne shale is a rock formation functioning as overburden for gas reservoirs in the Norwegian Sea and potentially as caprock for future CO2 storage locations as well. In this paper, the Draupne shale was exposed to several fluids: CO2 gas, supercritical CO2, CO2 gas dissolved in brine, supercritical CO2 dissolved in brine, as well as brine and dry air. The motivation for the exposure tests was to investigate whether injected CO2 in a reservoir coming into contact with the caprock could change the caprock’s mechanical properties and increase the risk for leakage of the stored CO2. In addition, a systematic exposure study will provide more insight into the various processes susceptible of altering the shale’s shear strength and acoustic velocity, such as clay hydration, mineral dissolution, and capillary forces. Due to the low permeability of the shale, experiments were conducted on mm-sized disk samples, reducing fluid diffusion into the shale, and allowing for many repeated tests on disks close by in the original core. The punch method, where a small circle is punched out of the shale, was used to assess shear strength, while continuous wave technique was used to assess ultrasonic velocity. Results show that the shale is not noticeably sensitive to CO2, in the sense that no additional weakening is observed in the presence of CO2 as compared to brine exposure. This last weakening effect is probably due to poor matching between pore fluid salinity and exposure brine strength.

Effect of Core Muscle Strength Training Combined with Taijiquan on Bone Mineral Density Measured by Quantitative CT Scanning in the Elderly

“…It can pass through the cancellous bone and excessively separate the bone mineral and bone marrow in the bone tissue, so as to obtain a separate calcium map or bone marrow map, so as to realize the quantitative measurement of BMD. In this study, dual-energy CT scanning was used to measure BMD by using dual-energy material separation technology, and the BMD of the vertebral body was measured by comparing with single-energy QCT to evaluate the application value of DECT in the measurement of bone mineral density [ 4 ].…”

Geo-mechanical and geo-morphology characterisation of the cap rocks in the Niger Delta for potential carbon capture and storage

“…Kaolinite was only found in the bottom cap rock of the Upper Delta (UDCB) region and the upper caprock of the Deep Offshore (DOCT) depo belt is devoid of Garnet see Table 1 . The ratio of the tectosilicate and phyllosilicate minerals indicate that the cap rock in all three regions is silicate shale as suggested by Edvardsen et al [ 21 ], Ubani et al [ 41 ] and Du et al [ 44 ]. The silicate shale samples have the requisite mineralogy and characteristic low permeability and porosity to serve as cap rocks for the depleted reservoirs.…”

“…Espinoza et al [ 20 ] suggests that sedimentary formations were chosen because it has been proven that natural carbon dioxide accumulates in them where pore pressure varies from hydrostatic pressure to lithostatic pressure, however, it is essential that the chosen basins be characterized. To seal off the carbon dioxide, a sealing caprock is essential [ 21 , 22 ]. The caprock sealing the reservoir formation also needs to be characterized to ascertain its integrity.…”

“…The induced seismic events may cause faulting and or fault reactivation. According to Edvardsen et al [ 21 ], the strength of rocks and other porous materials is degraded when effective stresses surpass the material's intrinsic resistance, whether in tension or compression. With these narratives, the integrity of the silicate shale caprocks must be studied to ensure that the caprocks will not fail and release carbon dioxide.…”

Combined Effects of CO2 Adsorption-Induced Swelling and Dehydration-Induced Shrinkage on Caprock Sealing Efficiency

“…In this conceptual model, the CO 2 –brine water two-phase flow is observed only in the fracture network. However, due to the interaction between the shale caprock and CO 2 , the CO 2 adsorbs into the matrix and water is then produced due to the dehydration [ 37 ]. The matrix is subjected to the two actions of both the CO 2 adsorption-induced swelling and dehydration-induced shrinkage (see Figure 2 ).…”