Rock Thickness Identification by XGBoost with Logging Data

Based on research on the response mechanism of rock formations and reservoirs to logging curves, 12 logging curves selected by combining the depth characteristics of formations are proposed to identify rock formations and reservoirs using four algorithms: logistic regression (LR), support vector machine (SVM), random forest (RF) and XGBoost. Out of 60 wells in the study block, 57 wells were selected for training and learning, and the remaining 3 wells were used as prediction samples for testing the algorithm. The recognition of rock formations and reservoirs is performed by each of these four machine learning algorithms, and predictive knowledge is obtained separately. It was found that the accuracy of the 4 algorithms for rock formation and reservoir layer identification reached over 90%, but the XGBoost algorithm was found to be the best in terms of the 4 scoring criteria of F1-score, precision, recall and accuracy. The accuracy of rock formation identification could reach over 95%, and the correlation analysis between the logging curve and rock formation could be performed on this basis. The results show that the RMN, RLLD and RLLS have the most obvious responses to the sandstone layer, off-surface reservoir and effective thickness layer, and the CAL has the least effect on the formation and reservoir identification, which can provide an effective reference for the selection and dimensionality reduction of the subsequent logging curves.

Parametric assessment of hydrochemical changes associated to underground pumped hydropower storage

Underground pumped hydropower storage (UPHS) using abandoned mines is an alternative to store and produce electricity in flat regions. Excess of electricity is stored in form of potential energy by pumping mine water to a surface reservoir. When the demand of electricity increases, water is discharged into the mine (i.e., underground reservoir) through turbines producing electricity. During the complete operational process of UPHS plants, hydrochemical characteristics of water evolve continuously to be in equilibrium successively with the atmosphere (in the surface reservoir) and the surrounding porous medium (in the underground reservoir). It may lead to precipitation and/or dissolution of minerals and their associated consequences, such as pH variations. Induced hydrochemical changes may have an impact on the environment and/or the efficiency (e.g., corrosions and incrustations affect facilities) of UPHS plants. The nature of the hydrochemical changes is controlled by the specific chemical characteristics of the surrounding porous medium. However, the magnitude of the changes also depends on other variables, such as hydraulic parameters. The role of these parameters is established to define screening criteria and improve the selection procedure of abandoned mines for constructing UPHS plants.This work evaluates the role of the main hydrogeological factors for three different chemical composition of the porous medium. Results are obtained by means of numerical reactive transport modeling. Potential impacts on the environment (mainly on groundwater and surface water bodies) and on the efficiency of the UPHS plants vary considerably from a hydraulic parameter to another showing the need for a detailed characterization before choosing locations of future UPHS plants.

Underground Pumped-Storage Hydropower (UPSH) at the Martelange Mine (Belgium): Interactions with Groundwater Flow

Underground pumped-storage hydropower (UPSH) is a promising technology to manage the electricity production in flat regions. UPSH plants consist of an underground and surface reservoirs. The energy is stored by pumping water from the underground to the surface reservoir and is produced by discharging water from the surface to the underground reservoir. The underground reservoir can be drilled, but a more efficient alternative, considered here, consists in using an abandoned mine. Given that mines are rarely waterproofed, there are concerns about the consequences (on the efficiency and the environment) of water exchanges between the underground reservoir and the surrounding medium. This work investigates numerically such water exchanges and their consequences. Numerical models are based on a real abandoned mine located in Belgium (Martelange slate mine) that is considered as a potential site to construct an UPSH plant. The model integrates the geometrical complexity of the mine, adopts an operation scenario based on actual electricity prices, simulates the behavior of the system during one year and considers two realistic scenarios of initial conditions with the underground reservoir being either completely full or totally drained. The results show that (1) water exchanges may have important consequences in terms of efficiency and environmental impacts, (2) the influence of the initial conditions is only relevant during early times, and (3), an important factor controlling the water exchanges and their consequences may be the relative location of the natural piezometric head with respect the underground reservoir.

Long-term (1870-2018) drought reconstruction in India

<p>Droughts in India affect food production, gross domestic product (GDP), livelihood, and socio-economic condition of a large population associated with agriculture. Recent drought (2015-2018) caused groundwater depletion and affected about one-fourth of the Indian population. However, it remains unclear if the drought of 2015-2018 was among the most severe droughts that occurred in India. Here we use a long-term (1870-2018) data to identify the top five ("deadly") meteorological/hydrological droughts based on overall severity score in the last century and half period. Out of a total of 18 meteorological droughts, the deadly droughts occurred in 1899, 1876, 2000, 1918, and 1965. Similarly, the deadly hydrological droughts occurred in 1899, 2000, 1876, 1965, and 1918 during 1870-2018. All the five deadly droughts were associated with the positive phase of El Nino Southern Oscillations (ENSO). Results show that the relationship between ENSO and monsoon (June to September) precipitation in India has weakened while the role of Indian and Atlantic Oceans has strengthened during the recent decades. Notwithstanding the longest (41 months) duration, the 2015-2018 drought did not feature among the deadly droughts. The 2015-2018 drought affected surface (reservoir storage) and groundwater availability in both southern and northern parts of India and was linked to El-Nino and Indian Ocean Dipole. Droughts and rapidly declining groundwater together can pose serious challenge to ensure fresh water security in India.</p>

Evaluating Historical Impacts of Surface Reservoir Storage on Catchment Memory Across the US

<p>Today there are tens of thousands of storage structures in the US ranging from Hoover Dam, with a capacity more than 34 million cubic meters, to small structures less than 2 m tall.  While there exists a myriad of water management tools that capture storage operations for local to regional systems, national and global scale hydrologic models struggle to incorporate this storage. Large scale earth system simulations generally exclude management operations or rely on generic operating policies due to lack of data.  Reservoir storage capacity is much more easily obtained and can tell us about the potential for regulation of a system, but without evaluating actual operations we can’t capture the actual influence of human storage on catchment dynamics.  Here we use the National Inventory of Dams to evaluate the evolution of total storage capacity across the US over the last century. Consistent with previous work we show spatial trends in storage volume relative to streamflow and storage purpose (i.e. flood control as opposed to water supply). To quantify the actual impact of operations on hydrologic regimes though, reservoir capacity is not sufficient. Therefore, we also assemble a dataset of reservoir inflows, outflows and changes in storage focusing on large reservoirs in the western US.  Using these timeseries we can isolate the historical regulation imposed by reservoirs and their impact catchment memory. Furthermore, we compare our historical observations to generic operating policies to evaluate how well storage dynamics are captured by existing models and the potential for these tools to over or underestimate reservoir impacts.</p>

Qualitative interpretation method of water flooding in independent off surface reservoir of Lamadian Oilfield

With Lamadian Oilfield entering the late stage of ultra-high water cut, the number of thick layers in water drive is becoming less and less, so it is imperative to study the remaining oil in thin difference reservoir. For the thin difference reservoir, the independent off surface reservoir has naturally become an important research object [1]. It is necessary to study the waterflooding condition of the independent outer surface reservoirs to find out the producing law of the thin difference reservoirs at present. In this paper, we mainly use thewater washing data of independent outer surface reservoir and core data of sidewall of coring well to find the water flooding interpretation law of independent outer surface reservoir.This paper focuses on the analysis of the characteristics of the electric logging curve of the independent off surface reservoir after water flooding, and summarizes a set of qualitative interpretation methods suitable for the independent off surface reservoir of Lamadian oilfield. This method can improve the accuracy of waterflooded layer interpretation and meet the needs of remaining oil potential tapping in the later stage of ultra-high water cut.

Magmatic carbon outgassing and uptake of CO2 by alkaline waters

Much of Earth's carbon resides in the “deep” realms of our planet: sediments, crust, mantle, and core. The interaction of these deep reservoirs of carbon with the surface reservoir (atmosphere and oceans) leads to a habitable surface environment, with an equitable atmospheric composition and comfortable range in temperature that together have allowed life to proliferate. The Earth in Five Reactions project (part of the Deep Carbon Observatory program) identified the most important carbon-bearing reactions of our planet, defined as those which perhaps make our planet unique among those in our Solar System, to highlight and review how the deep and surface carbon cycles connect. Here we review the important reactions that control the concentration of carbon dioxide in our atmosphere: outgassing from magmas during volcanic eruptions and during magmatic activity; and uptake of CO2 by alkaline surface waters. We describe the state of our knowledge about these reactions and their controls, the extent to which we understand the mass budgets of carbon that are mediated by these reactions, and finally, the implications of these reactions for understanding present-day climate change that is driven by anthropogenic emission of CO2.