Geofluids最新文献

Aiming at the characteristics of low shear resistance and high filtration loss of guar gum-fracturing fluid, a high-efficiency organic zirconium crosslinker was prepared. In addition, the effects of different factors on the filtration coefficient and apparent viscosity of fracturing fluid were studied, and this study explores the micro mechanisms of various factors affecting the filtration coefficient from a molecular dynamics perspective. The results show that the antifiltration ability of guar gum-fracturing fluid is inversely proportional to the fluid viscosity. The increase of crosslinker content and reservoir pressure is beneficial to improve the viscosity and antishear ability of guar gum-fracturing fluid. When the crosslinker content is 0.25% and pressure is 30 MPa, the fracturing fluid parameters are 145 mPa·s and 2.1 × 10⁻² m³ · min^1/2, respectively, while the increase of reservoir temperature and the shear rate reduces the rheology and shear resistance of guar gum-fracturing fluid, so that the viscosity and filtration coefficient of fracturing fluid at 180°C and 200 s^-1 are 123 mPa·s and 2.3 × 10^-2 m³·min^1/2, respectively. This work not only paves a new avenue for synthesizing organic zirconium as a crosslinker but also provides an efficient measure to reduce the filtration of guar gum-fracturing fluid on the oil and gas reservoirs.

Fractures in hot dry rock (HDR) reservoirs are the locations where heating fluid flows exchange heat with the HDR matrix. Cold shock with liquid nitrogen is one method for stimulating cracks. This study investigates the evolution law of fracture aperture under cold shock with liquid nitrogen. The real-time high-temperature triaxial servo control rock testing machine was used to conduct permeability experiments to examine the fracture aperture of single-fracture granite during liquid nitrogen shock cycles at various temperatures. The effects of pore pressure, temperature, and shocking cycles on the fracture aperture are analyzed, and the difference in fracture aperture variation under liquid nitrogen cooling and natural cooling modes is compared. The results showed that (1) during liquid nitrogen cooling, the fracture aperture expands as pore pressure rises; the effect of pore pressure on the fracture aperture becomes more robust as the number of liquid nitrogen shocking cycles and initial temperature increases; (2) under 1-2 soaking cycles, fracture aperture decreases as the temperature rises. Under two or more soaking cycles, the fracture aperture first increases and then decreases with increasing temperature; (3) when the initial temperature of fractured granite is 100°C, the fracture aperture is not significantly changed by repeated cold soaking cycles. However, with a higher initial temperature, the fracture aperture develops with more liquid nitrogen cold soaking cycles. The liquid nitrogen cooling method is more conducive to increasing the fracture aperture than natural cooling. The experimental results can provide primary experimental data for future research into controlling the evolution of granite cracks.

The Bou Azzer polymetallic Co-Ni-As±Au±Ag veins in the Central Anti-Atlas (Morocco) are significant sulfide ores hosted by Neoproterozoic ophiolites and are associated with felsic intrusive and subvolcanic phases. We report new mineralogical and fluid inclusion data to better understand mineralization’s formation processes and fluid evolution which are analyzed and merged with the existing published data. Gold-bearing sulfide-arsenide-quartz (±carbonate) veins in Bou Azzer exhibit mineralogical and fluid inclusion features similar to the epithermal and porphyry-style gold deposits. Modeling of widespread primary and pseudosecondary saline aqueous inclusions in the mineralized quartz veins suggests that circulating metalliferous brines, with estimated temperatures of ~275°C and pressures < 550 bars and salinity < 40%, precipitated sulfides in the veins. Gold was most likely transported as bisulfide complexes, and ore deposition was controlled by fluctuations in oxygen fugacity (ƒO₂) upon fluid cooling. The systematic decrease in temperatures and salinities from an early prearsenide stage to a late paragenetic arsenide and sulfide stage was likely linked with extensive mixing with meteoric waters in a shallow hydrothermal environment. Available sulfur, oxygen, and hydrogen stable isotope data for the Bou Azzer sulfide-arsenide-quartz veins indicate variable fluid sources, primarily magmatic and metamorphic fluids. The wide range of the estimated mineralization ages (from 680 Ma to 210 Ma) and the spatial association with major shear zones and felsic intrusive stocks imply a significant role of the regional tectonic activities or reflect complex and superimposed mineralization episodes, corresponding to orogenic events spanned the Pan-African cycle to the Atlasic orogenesis.

In response to the challenge posed by the limited capacity of postmining paste and original waste filling mining technology for small-scale waste rock treatment, which is incompatible with the requirements of modern high-yield mines producing millions of tons, fluidized filling mining technology in goaf presents a sustainable and environmentally friendly solution. This innovative method effectively addresses the balance between mining and filling operations while enabling large-scale waste rock management in coal mines. This article presents a model for predicting the spatial morphology of goaf and employs theoretical calculations to determine the residual space left after goaf caving. It unveils the fluidization filling approach for goaf caving, utilizing a “high- and low-level collaborative filling” strategy and taking advantage of various types of residual spaces within cavities and voids. Experimental investigations into gangue slurry diffusion in the goaf reveal insights into its diffusion patterns along three directions: horizontal, inclined, and vertical. The analysis also establishes correlations between porosity, space utilization rate, and the Talbol index. Furthermore, the research identifies the flow characteristics of fluidized filling slurry as consistent with the Bingham fluid behavior. A calculation formula for determining the diffusion radius of the filling slurry within cracks is provided. The study highlights four distinct flow stages in the process: stable laminar diffusion, transition from advection to turbulence, turbulence, and stoppage. To validate these findings, COMSOL simulation software is employed to simulate and analyze the diffusion patterns of gangue slurry within the goaf. The research outcomes offer valuable theoretical insights into the postgangue fluidization goaf filling technology and serve as a technical reference for the design of coal-based solid waste fluidization filling processes.

Improving the oil production from nonmain oil layers is crucial for the complex fault block oilfields during the late stage of high water cut development to ensure stable production and capacity expansion. However, the developing characterization of the nonmain layers and their remaining oil distribution is still inadequate. Developing an efficient mode of development remains a challenge. This paper presents a detailed characterization of the sedimentary microfacies and architecture of a nonmain reservoir based on core and logging data analysis. A flexible injection-production development strategy model was designed and applied in the Hetan oilfield, located in the southeast of Zhanhua Depression of Bohai Bay Basin as an example. The results show that the nonmain oil layer of the Hetan oilfield is composed of estuary bar microfacies sand bodies. Deposits of various shapes are formed on the side or in front of the main body of the estuary dam, which constitutes the nonmain oil reservoir. The lithology is fine, the sand body thickness is small, and the plane heterogeneity is strong. The distribution is banded, potato-shaped, and fragmented. The nonmain oil layer has a small oil-bearing area of 0.1-1.0 km² and a high oil saturation of over 58%. The Hetan oilfield has a significant amount of remaining oil enrichment and considerable potential for production digging. To optimize production, a flexible injection and production adjustment scheme is proposed, which includes designing multitarget horizontal wells and utilizing various methods such as optimizing well spacing, coupled injection, and cycle injection. Field tests conducted in the area have shown an increase in the recovery factor of nonmain oil layers from 16.7% to 28.5%. This indicates that identifying and characterizing nonmain oil layers through detailed analysis of sedimentary microfacies and reservoir architecture is useful in the late-stage development of complex fault block reservoirs to maintain sustainable and efficient oilfield development.

The management of rock mass deformation in high-stress roadways is a pivotal aspect of deep geotechnical engineering. Given the fruitful outcomes of research in rock mechanics regarding traditional confining pressure control methods, scholars have increasingly turned their attention to exploring pressure-relieving techniques, including borehole pressure relief and blasting pressure relief. However, there is limited research on pressure relief methods for deep-buried hard rock tunnels. This article commences with an overview of pressure relief in the roadway and conducts a detailed study on the parameters and methods of pressure relief in the roadway. To address safety and mining efficiency challenges, such as severe deformation leading to support failures, this study conducted a parameter analysis using the Sanshandao Gold Mine as a case study. Based on existing support methods, a strategy for arranging pressure relief roadways at varying distances from the main roadway is proposed, significantly enhancing the stress environment there. Numerical simulation software was employed to model two scenarios: (1) excavating the pressure relief roadway, main roadway, and maintenance roadway simultaneously and (2) first excavating the pressure relief roadway, followed by the main roadway and the maintenance roadway simultaneously. Simulation results indicated that the first pressure relief approach outperforms the second. The optimal position for both pressure relief roadways is 15 m from the main roadway, resulting in maximum deformation of the main roadway within 100 mm. These findings align with on-site stress monitoring data and satisfy safety production criteria. The research offers a theoretical foundation for similar pressure relief techniques in deeply buried, high-stress roadways.

Gas flaring (GasF) is an important aspect of the combustion mechanisms in the burning of related, undesirable, or surplus fluids (gases in particular) that are released during the ordinary or unexpected overpressuring process in several industrial activities, specifically in the petroleum resource (PTR) industries. It is also one of the major sources of greenhouse gas emissions which cause climate change (CMC). In addition to the generation of noise and heat, it makes substantial adjacent areas uninhabitable and, hence, causes detrimental consequences to the entire ecosystem as well as waste energy and results in economic losses. Reducing GasF is a critical issue due to its ensuing complications; consequently, there is a tenacious need to measure GasF via the study of its composition, distribution, and capacity, as well as the utilization of appropriate GasF recovery/removal procedures. The present review study will, thus, attempt to assess the impacts of GasF on the environment vis-à-vis the possible nexus between GasF/CMC using the perspective of the Niger Delta region of Nigeria which is rich in PTR, with relevant information drawn from existing publications. The roles of government, policymakers, and relevant stakeholders as well as suggestions and recommendations that will assist in the extenuation approaches and technologies of the influence of GasF on the environment are also discussed.