Smectite to illite transformation of Gulf of Mexico -Eugene Island (GoM-EI) mudrock

Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2016.Cataloged from PDF version of thesis.Includes bibliographical references (pages 93-94).Predicting pore pressure is an important job in the petroleum industry. Standard methods for estimating pressure do not apply to the basin where overpressure is often observed. Compaction disequilibrium and clay mineral diagenesis are recognized as potential contributors to overpressure generation. My research aims to look at the relationship between smectite-to-illite transformation and overpressure generation. The proposed research has two phases. Phase one objective is to study the reaction rate and the conditions such as temperature, time, KCl concentration that induce smectite-to-illite transformation. Phase two study objective is to investigate the change in compressibility and permeability of resedimented GoM-EI mudrock due to smectite-to-illite transformation. This thesis presents the results of phase one study. In phase one study, we have successfully transformed smectite to illite in laboratory environment using GoM-EL as starting material. Based on mineral composition results of cooked samples, it is clearly that illitization goes through three stages. The first stage is that a highly smectitic clay is represented by randomly ordered illite-smectite mixed layer phase (I/S). With increasing reaction, randomly ordered I/S are transformed into regularly interstratified structures. The third stage is that the ordered I/S reacts to a final discrete illite. Additional thermal gravimetric analysis (TGA) study on cooked samples confirms that the transformation is releasing water. However, we are unable to determine the volume change of the sample using mineral study.by Chunwei Ge.S.M

Damage Detection by Acoustic Emission

Mentor: J. F. LabuzAcoustic emission (AE) is microseismic signal generated by microcracks in brittle material such as concrete or rock. AE signals carry information about the source, including location and magnitude. Therefore, it is useful tool in evaluating deterioration of a structure. The growth of damage and potential failure can be identified by monitoring AE. It was observed that AE rate increased during the peak. Besides, detailed analysis showed that the locations of AE events coincide with the location of damage. The experimental results also showed damaged material had higher AE rate than “healthy” material.This research was supported by the Undergraduate Research Opportunities Program (UROP).Ge, Chunwei. (2012). Damage Detection by Acoustic Emission. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/123070

Compression behavior of smectitic vs. illitic mudrocks

Thesis: Ph. D. in the field of Geotechnical and Geoenvironmental Engineering, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2019Cataloged from PDF version of thesis.Includes bibliographical references (pages 165-168).Overpressure or fluid pressure in excess of hydrostatic pressure has been observed globally in many deep water sedimentary basins. One of the possible mechanisms for overpressure is the smectite-to-illite (S-I) transformation. During the transformation, the basal spacing of the smectite layer reduces. The interlayer water is released into pore space, causing an increase in pore pressure. This thesis investigates the compression and permeability behavior change due to S-I transformation. Uniaxial compression testing was performed on smectitic and illitic mudrocks. The original Gulf of Mexico - Eugene Island (GoM-EI) mudrock sets the baseline for smectitic mudrock in order to compare with illitic mudrocks. Two methods were used to create illitic mudrock from the GoM-EI sediment.The illitic mudrock A was cooked in a high temperature constant rate of strain (CRS) device with effective stress applied (200 °C and 30 days); the illitic mudrock B was cooked in a hydrothermal cooker in a slurry state (250 °C and 18 days). The multi-functional high temperature CRS device was designed from scratch to tackle the challenge of measuring the mechanical properties of a mudrock and transforming the clay minerals. Although the methods of inducing S-I transformation are different, similar degrees of illitization for the illitic mudrock A and B was achieved by selecting the right temperature and time combination. The mineral transformation does not greatly alter the compressibility of the mudrocks. However, both the illitic mudrock A and B sit higher in porosity space than the smectitic mudrock at low stress level.As effective stress increases, the illitic mudrock A converges with the smectitic mudrock, while the illitic mudrock B reverses order with the smectitic mudrock at 30 MPa. The permeability of the smectitic mudrock ranges over five orders from 10⁻¹⁶ to 10⁻²⁰ m² from a porosity of 0.58 to 0.23. The permeability of the mudrocks are greatly increased by the mineral transformation. The permeability ratio of the illitic mudrocks over the smectitic mudrock increases from 2 to 12 as porosity decreases. The creep rate (C[subscript alpha]) at room temperature and elevated temperature were measured during the transformation stage of the illitic mudrock A. C[subscript alpha] at elevated temperature increases by 50 % compared with that at room temperature. The increase in rate is caused by mineral transformation. Using the difference in rate, a model is proposed to estimate the effective stress reduction or overpressure generation based on the degree of mineral transformation.by Chunwei Ge.Ph. D. in the field of Geotechnical and Geoenvironmental EngineeringPh.D.inthefieldofGeotechnicalandGeoenvironmentalEngineering Massachusetts Institute of Technology, Department of Civil and Environmental Engineerin

Application of measurement and control technology in deep and normal pressure shale gas exploration and development

Deep and normal-pressure shale gas is the key field of shale gas exploration and development of SINOPEC. At present, this type of shale gas is faced with difficulties in the beneficial development. In order to increase the productivity of single well and further reduce cost and increase efficiency, higher technical requirements are put forward for wellbore measurement and control technology. In order to accurately evaluate shale gas reservoirs, quantitative characterization of reservoir micro-characteristics, prediction of pore pressure coefficient, calculation of gas content, evaluation of low-resistivity shale, and compressibility evaluation of shale gas reservoirs have been carried out, forming a relatively mature shale gas "double sweet spots" fine evaluation technology. In order to improve the drilling rate of deep high-quality shale, a working model integrating directional drilling, mud logging, logging and steering is created. Based on multi-attribute geological modeling and well-to-seismic integration, the geosteering technology for horizontal wells in complex structural areas is formed. According to the difference of geological characteristics in different blocks, the application scopes of the two drilling speed improvement technologies, namely rotary steering and screw + MWD, are defined, thus realizing targeted measures for speed improvement. To meet the requirements of large-scale volumetric fracturing, a number of technologies such as multi-stage perforating bridge plug combined operation, equal aperture perforation, high temperature underground microseismic monitoring and "tractor + DAS fiber" fracturing monitoring have been developed and applied. The shale gas "double sweet spots" fine evaluation technology, the technology for improving reservoir drilling rate, and the technology for increasing drilling speed and fracturing performance have been widely used in deep and normal-pressure shale gas field, which well support the exploration and development of deep and normal-pressure shale gas. Next, SINOPEC will give full play to its advantages in the technology integrating directional drilling, mud logging, logging and steering, continue to promote measurement and control technology innovation, and continue to solve key problems in the interpretation and evaluation technology of new formations/new types of shale gas, the development of high-temperature measurement and control instruments and tools, and the acquisition of basic data, so as to fully guarantee the high-quality exploration and cost-effective development of deep and normal-pressure shale gas

Stress Response and Damage Characteristics of Local Members of a Structure due to Tunnel Blasting Vibrations Based on the High-Order Local Modal Analysis

Damage characteristics and dynamic stress response of aging masonry structures for blast-induced ground motion were performed using high-order local modal analysis method. A complete investigation of damage types and locations of aging masonry buildings due to tunnel blasting vibration were performed by on-site survey. A typical 2-storey aging masonry building located above a tunnel was selected for dynamic response analysis. The experimental dynamic characteristics of the structure were determined by using the operational modal analysis (OMA) method. Finite element models for the masonry structures were updated by modifying material parameters based on OMA results. The first five natural frequencies of the updated finite element models ranged from 8.80–24.99 Hz, and the first five modes were global modes. The sixth to twentieth natural frequencies ranged from 26.10–36.34 Hz, and the sixth to twentieth modes were local modes whose deformation was greater than the global deformation. Since the principal frequencies of the tunnel blast vibration were mostly higher than the natural global modes’ frequencies and were much closer to the natural frequencies of local members, local members experienced more intensive vibrations compared to the main body structure. The principal compressive stress (PCS) and principal tensile stress (PTS) of local members were several times greater than that of the main body structure. Therefore, local members of the masonry building suffered most from the tunnel blasting vibration. Corners due to stress concentration, the contact area between brick and concrete, local members, and precast floor seams are prone to damage during tunnel blasting. With the vibration velocity increasing, the PCS and PTS of local members gradually increase. But, the PTS ratio of local members decreases with the increase of peak particle velocities. The dynamic response analysis result and the damage locations using high-order local modal analysis method are in accordance with the damage found at the site

Environmental controls on seasonal ecosystem evapotranspiration/potential evapotranspiration ratio as determined by the global eddy flux measurements

Abstract. The evapotranspiration/potential evapotranspiration (AET/PET) ratio is traditionally termed as crop coefficient (Kc) and has been gradually used as ecosystem evaporative stress index. In the current hydrology literature, Kc has been widely used to as a parameter to estimate crop water demand by water managers, but has not been well examined for other type of ecosystems such as forests and other perennial vegetation. Understanding the seasonal dynamics of this variable for all ecosystems is important to project the ecohydrologcial responses to climate change and accurately quantify water use (AET) at watershed to global scales. This study aimed at deriving Kc for multiple vegetation cover types and understanding its environmental controls by analyzing the accumulated global eddy flux (FLUXNET) data. We examined monthly AET/PET data for 7 vegetation covers including Open shrubland (OS), Cropland (CRO), Grassland (GRA), Deciduous broad leaf forest (DB), Evergreen needle leaf forest (ENF) and Evergreen broad leaf forest (EBF), and Mixed forest (MF) across 81 sites. We found that, except for evergreen forests (EBF and ENF), Kc values had large seasonal variation across all land covers. The spatial variability of Kc was best explained by latitude suggesting site factors has a major control on Kc. Seasonally, Kc increased significantly with precipitation in the summer months. Moreover, Leaf Area Index (LAI) significantly influenced monthly Kc in all land covers except EBF. During the peak growing season, forests had the highest Kc values while Croplands (CRO) had the lowest. We developed a series of multi-variatelinear monthly regression models for a large spatial scale Kc by land cover type and season using LAI, site latitude and monthly precipitation as independent variables. The Kc models are useful for understanding water stress in different ecosystems under climate change and variability and for estimating seasonal ET for large areas with mixed land covers. </jats:p

Stress Response and Damage Characteristics of Local Members of a Structure due to Tunnel Blasting Vibrations Based on the High-Order Local Modal Analysis

Damage characteristics and dynamic stress response of aging masonry structures for blast-induced ground motion were performed using high-order local modal analysis method. A complete investigation of damage types and locations of aging masonry buildings due to tunnel blasting vibration were performed by on-site survey. A typical 2-storey aging masonry building located above a tunnel was selected for dynamic response analysis. The experimental dynamic characteristics of the structure were determined by using the operational modal analysis (OMA) method. Finite element models for the masonry structures were updated by modifying material parameters based on OMA results. The first five natural frequencies of the updated finite element models ranged from 8.80–24.99 Hz, and the first five modes were global modes. The sixth to twentieth natural frequencies ranged from 26.10–36.34 Hz, and the sixth to twentieth modes were local modes whose deformation was greater than the global deformation. Since the principal frequencies of the tunnel blast vibration were mostly higher than the natural global modes’ frequencies and were much closer to the natural frequencies of local members, local members experienced more intensive vibrations compared to the main body structure. The principal compressive stress (PCS) and principal tensile stress (PTS) of local members were several times greater than that of the main body structure. Therefore, local members of the masonry building suffered most from the tunnel blasting vibration. Corners due to stress concentration, the contact area between brick and concrete, local members, and precast floor seams are prone to damage during tunnel blasting. With the vibration velocity increasing, the PCS and PTS of local members gradually increase. But, the PTS ratio of local members decreases with the increase of peak particle velocities. The dynamic response analysis result and the damage locations using high-order local modal analysis method are in accordance with the damage found at the site.</jats:p