Reliable prediction of the shale fracturing process is a challenging problem in exploiting deep shale oil and gas resources. Complex fracture networks need to be artificially created to employ deep shale oil and gas reserves. Randomly distributed minerals and heterogeneities in shales significantly affect mechanical properties and fracturing behaviors in oil and gas exploitation. Describing the actual microstructure and associated heterogeneities in shales constitutes a significant challenge. The RFPA3D (rock failure process analysis parallel computing program)-based modeling approach is a promising numerical technique due to its unique capability to simulate the fracturing behavior of rocks. To improve traditional numerical technology and study crack propagation in shale on the microscopic scale, a combination of high-precision internal structure detection technology with the RFPA3D numerical simulation method was developed to construct a real mineral structure-based modeling method. First, an improved digital image processing technique was developed to incorporate actual shale microstructures (focused ion beam scanning electron microscopy was used to capture shale microstructure images that reflect the distributions of different minerals) into the numerical model. Second, the effect of mineral inhomogeneity was considered by integrating the mineral statistical model obtained from the mineral nanoindentation experiments into the numerical model. By simulating a shale numerical model in which pyrite particles are wrapped by organic matter, the effects of shale microstructure and applied stress state on microcrack behavior and mechanical properties were investigated and analyzed. In this study, the effect of pyrite particles on fracture propagation was systematically analyzed and summarized for the first time. The results indicate that the distribution of minerals and initial defects dominated the fracture evolution and the failure mode. Cracks are generally initiated and propagated along the boundaries of hard mineral particles such as pyrite or in soft minerals such as organic matter. Locations with collections of hard minerals are more likely to produce complex fractures. This study provides a valuable method for understanding the microfracture behavior of shales.
Abstract Over-developed oilfields in East China have gone through suffering situations induced by high cost in recent years. The trend of resource deterioration is irreversible and the deterioration leads to the increasing difficulties in oil and gas exploration and development. The rate of return-on-investment continually decreases resulting from over-rapidly increasing properties, and ever-rising facility depreciation and damage. The space for increasing income and seeking profit is further narrowed by low oil price. These oilfields now move into the period that has huge obstacles to increase profit, confronted with more difficulties in obtaining economic reserves and profitable production. Now the development in over-developed oilfields has stepped into double-high phase, meaning that to avoid ineffective or poorly effective measures and control the fundamental indices like the rise of watercut, natural decline, and so on play the key role in improving development profit. It is necessary to accelerate the build-up of production capacity and enhance reserve, production, and the rate of return-on-investment by actively reforming techniques for the formation of a series of new ones on enhancing oil recovery, as well as advancing the four-unified-into-one management mode of merging production and management, investment and cost, reserve increase and production build-up, and research and production. The concept of focusing on reserve and production must be further switched, meanwhile profit must be realized in all the ingredients of exploration and development during their whole processes, and efficiencies must be maximized. The burden of production and management is relieved, and the focus is switched to profit in an overall and complete way by further recognizing that investment today is tomorrow's cost and strictly controlling property scale to prevent its excessive increase.
ABSTRACT Introduction Exposure to commercial marketing of cannabis vape products (CVPs) may encourage CVP use, yet little is known about how these products are marketed. This study examined marketing descriptions of CVPs’ functions and benefits in an online retail environment. Methods Product descriptions from a sample of 343 CVPs from 78 top-selling cannabis brands in 2023 were obtained from a large cannabis e-commerce website. Each description was thematically coded based on the promoted product features. Results The most frequently mentioned product feature was flavor profile and sensation (74.1%), including general and specific flavor descriptors (e.g., fruit flavors) and sensory experiences (e.g., sweet, spicy). Psychoactive effects were noted in 47.5% of the descriptions, detailing potency or effects such as feeling “high,” “stoned,” or “buzzed.” Product quality, such as “purity,” “natural,” or “organic,” was mentioned in 42.3% of the descriptions. Other product benefits described included mood enhancement (33.8%), reduced harm (24.2%), relaxation/tension reduction (23.9%), therapeutic effects (18.4%), focus/creativity (16.6%), convenience/discreetness (11.1%), socialization enhancement (6.7%), and physical performance enhancement (6.1%). Discussion Some frequently promoted product features of CVPs, such as flavor and sensation and psychoactive effects, may particularly appeal to younger consumers for non-medical use. Meanwhile, attributes surrounding high product quality and reduced harm may reduce individuals’ perceived risks of CVP use and may violate state restrictions on therapeutic claims. Additional research assessing the influence of exposure to marketed product features on product perceptions and use behaviors among priority populations is needed to inform regulations and enforcement.
Abstract The conductance sensor based water cut meter is usually used to measure content of the oil-water two phase mixed fluid for periodical well production logging. In order to solve the real-time monitoring problem of downhole water cut, this paper proposes an online water cut measurement system based on the conductance sensor technology. Through the newly developed system, the continuous and permanent water cut measuring can be realized. The system consists of two conductance sensors, one temperature sensor, sampling mechanism and control & storage unit. Due to different density of oil and water, the two conductors with cylindrical poles, equipped on the upside and downside of the fluid inlet respectively, sense the conductivity of the oil-water mixed fluid and the detached water. With the real-time sampled downhole temperature, the conductivity values are compensated to reflect the real characters of the two kinds of liquid. According to Maxwell's model of oil-water mixed fluid and the correction parameters from offline calibration, the water cut is deduced. Since all units are designed with low-power consumption and high protection level, the system can operate permanently and provide online monitoring values. The water cut measurement system is tested in a physical testing environment with different conditions of the oil-water mixing ratio, the mineralization degree of water, the liquid temperature and the flow rate. Testing results show that the water cut in oil-water mixed fluid and the sampled conductivity follow the Maxwell's model approximately, where the error between testing data and theoretical value is within 3% especially for the high water cut cases. When the temperature changes, the measured water cut value basically does not variate, although sampled conductivity of the two sensors change a lot with temperature. Different mineralization degree of water would affect the measured water cut result slightly, which should be due to the conflicts between the large conductance range and the sampling accuracy. The flow rate is another element to make the measured result fluctuation, but the water cut would be stable when using the average value within a period. In brief, the system provides real-time water cut measurement and the measuring accuracy can satisfy the requirements of petroleum production. The conductance sensor based water cut measurement system realizes real-time measuring of oil-water mixing ratio for oil production and can provide online parameters for optimizing production process rapidly. All electronic units are designed with low-power consumption, which ensure the system to run downhole permanently.
Shale oil of the Qingshankou Formation of the Gulong Sag, the northern Songliao Basin, represents the first attempt at large-scale development of pure-shale-type shale oil in China. By integrating the multi-scale refined reservoir characterization with macro-micro-scale mechanical testing, it is clarified that the Gulong shale is characterized by high clay mineral content, high rock plasticity, highly-developed bedding, and prominent mechanical anisotropy. A three-dimensional (3D) fracture propagation model of hydraulic fracturing was built for the Gulong shale, which fully captures the hydraulic fracture distribution pattern affected by the high bedding density, in-situ stress, and fracturing treatment parameters. Our research showed that due to influences of bedding, hydraulic fracturing in the Gulong shale forms a complex fracture morphology featuring the main fracture with multiple perpendicular branches that have different lengths (like the outdoor directional TV antenna); however, the vertical propagation of fractures is inhibited, and the fracture height is commonly less than 10 m. The limited stimulated reservoir volume (SRV) is the main problem facing the fracturing stimulation of the Gulong shale oil. Bedding density has vital effects on fracture morphology, so case-specific fracturing designs shall be developed for shale intervals with different bedding development degrees. For reservoirs with well-developed bedding, it is suggested to properly increase the perforation cluster spacing and raise the volume and proportions of viscous fluids of the pad, so as to effectively promote vertical fracture propagation and improve reservoir stimulation performance. This study integrates multi-scale fine reservoir characterization and macro-micro-scale mechanical testing, as well as the construction and numerical simulation of hydraulic fracturing models for high-density layered shale reservoirs, providing a new approach and methodological framework for the fracturing research of high-density layered shale reservoirs.
Abstract In this paper, Response Surface Methodology (RSM) was utilized as a robust and convenient predictive tool to establish the correlation between process parameters in in-situ laser-assisted machining and the surface roughness of single-crystal silicon. Based on the optimally designed diamond tool, a novel temperature field analysis method and RSM. The contribution rate of each process parameter on surface roughness was laser power > rotation speed > cutting depth > feed rate. The optimal process parameter combination is: rotation speed as 1001r/min, feed rate as 4.9μm/r, cutting depth as 7.55μm, and laser power as 28.81 W. Experimental validation of these optimal parameters compared surface roughness values obtained experimentally with those predicted. The surface roughness model showed a maximum relative error of 5.2%, with an average error of 4.8% across three experimental sets. These errors are within acceptable limits, indicating an alignment between predicted and experimental results.
Abstract Liquid CO2 fracturing is a novel stimulation technology, which helps realize multiple objectives such as conservation of water, sequestration of greenhouse gases and enhancement of single-well productivity and ultimate recovery. During operations, CO2 flows through storage tank, booster pump, blender, fracturing pump, and eventually into wellbore and production zone, generating a changing temperature and pressure distribution. CO2‘s phase state, density and viscosity properties change consequently, which influence significantly the reliability and stimulation effect. In a liquid CO2 fracturing field test for tight oil, temperature and pressure sensors are positioned at 12 critical nodes (including booster pump, blender, fracturing pump, wellhead and bottom hole) to monitor CO2 fluid. To ensure the reliability, CO2 is required to maintain in liquid state both on the surface and subsurface. Inlet, inside and outlet pressure of the blender should be concerned, because the blender utilizes non-mechanical pump, which requires sufficient motive flow to draw proppants into the main pipe, while the pressure difference directly impacts the flow rate of motive flow. The field test is successfully implemented with satisfactory result, 21 m3 proppants are added into the formation. The main conclusions are as follow. (1) In low-pressure fluid feeding stage, partial CO2 is gasified, which influences the stability of fluid feeding; In future a buffer vessel will be placed between storage tanks and booster pumps, which will provide adjustment for phase control; And a heat exchanger may help by further reduce the temperature of CO2.(2) Pressure difference among inlet, inside and outlet pressure of blender fluctuates during the whole process, with the probable reason of two additional static mixers, which create system pressure drop. (3) The temperature of CO2 is very low in low-pressure stage, and the pipes are frosted; When pumping pressure reaches 38MPa, the temperature gradually exceeds 0°C, and the pipes are defrosted. Phase evolution during liquid CO2 fracturing has been identified, and phase control method has been determined. This helps improvethe stability of fluid feeding and sand adding, and enhances the success ratio and stimulation result of fracturing.
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