Experimental study on production performance and reserves utilization law in carbonate gas reservoirs

Carbonate gas reservoirs in China are rich in reserves. In the development process, there are many reserves with low permeability, low efficiency and low recovery degree. It is difficult to stabilize gas well production and prolong its life cycle. Under the condition of original water saturation (Sw) of 0%, 20%, 40%, 55% and 65%, respectively, the physical simulation experiment of gas reservoirs depletion development was carried out by using long core multi-point embedded pressure measuring system. The long cores with average gas permeability of 2.300 mD, 0.485 mD and 0.046 mD (assembled from 10 carbonate cores) were used to carry out this experiment. During the experiment, the pressure dynamics at different positions inside the long core and the gas production dynamics at the outlet were recorded in real time to reveal the production performance and reserves utilization law of carbonate gas reservoirs. The results show that the stable production period of tight reservoir in carbonate gas reservoirs is short, and the low production period is relatively long. The stable production time and recovery rate of gas reservoir increase with the increase of reservoir permeability and decrease with the increase of water saturation. The production of tight carbonate gas reservoirs with permeability less than 0.1 mD is greatly affected by pore water, and the reservoir pressure distribution shows a steep pressure drop funnel, and the reserves far from well are rarely used. Therefore, the reserves far from well should be utilized by closing well to restore formation pressure balance, densifying well pattern or transforming reservoir. The variation range of water saturation in the development of carbonate gas reservoirs is influenced by reservoir permeability and water saturation, and closely related to formation pressure gradient in production process. It decreases with the increase of reservoir permeability and increases with the increase of original water saturation. The research results provide a theoretical basis for understanding the relationship between physical properties of carbonate gas reservoirs and production performance, reserves utilization law, and realizing balanced utilization, efficient development and long-term stable production of carbonate gas reservoirs.

Study on Water Injection Indicator Curve Model in Fractured Vuggy Carbonate Reservoir

Fractures and cavities are very well developed in fractured vuggy carbonate reservoirs in Tahe Oilfield, showing obvious constant volume or approximate constant volume characteristics, and the development of karst vuggy reservoirs is characterized by strong randomness, locality, heterogeneity, and discontinuous development, which has a great impact on oilfield development effect. The application of conventional reservoir engineering methods in this kind of reservoir has many limitations. The traditional water injection indication curve is mainly based on a sandstone reservoir, ignoring the elastic energy of the water body in a reservoir and the combination relationship of fracture and cavity, which can not meet the needs of the carbonate reservoir. According to the principle of volume balance of constant volume body and considering the elastic energy of original formation water, a new model of improved water injection indication curve and the original water-oil ratio of carbonate reservoir is proposed, and the chart of water injection indication curve is established. Compared with other methods, this method has the advantages of low cost and accurate identification results. The calculated reservoir parameters such as single well-controlled reserves, well-controlled water volume, and original water-oil ratio have high reliability, and the chart is easy to use. The model is applied to the Yuejin block of Tahe Oilfield, and the results show that the improved model is consistent with the results of other test methods, such as high-precision seismic combined with fracture cavity carving technology, which indicates that the model has strong reliability.

PENGARUH KADAR AIR TERHADAP BESARNYA PENURUNAN PADA UJI KONSOLIDASI

Clay soil is a cohesive soil with low bearing capacity and low shear strength where the load on it will be limited. The addition of water content in clay soil will result in changes in soil volume that will affect the strength of the soil. The research aims to know how much water content affects the values of consolidation settlement. A consolidation test was carried out three times with variations of the original soil sample, 35% water content and 30% water content. The results obtained a settlement of 0,1864 cm for original water content, 0,1677 cm for 35% water content, and 0,1414 cm for 30% water content.

Digital centralized water meter using 433 MHz LoRa

The local water supply corporation in Indonesia only uses analog water meter so that the monitoring of water usage information was conducted by officers manually. Officers must physically monitor the value in the customer's water meter that can lead to unreliable reading and ineffectiveness of process. Smart meter is one of the smart city metrics which could overcome this problem. This research uses the flow sensor to design and incorporate automated water meters. The measured value is then passed via the 433 MHz LoRa, a low-power wide-area network protocol, to the local hub, then forwarded to the server via the internet based cellular network. Results show that our proposed system's accuracy hit 97.31% at an ideal distance of 200 meters from customer to the local hub. The customer's water usage could be tracked in real time with our proposed system. Furthermore, the original water meter need not to be replaced which may minimize capital costs for this system.

Thresholds, Timing, and Teleconnections: A coupled water-power-economic analysis

Previous studies have failed to capture critical dynamics stemming from overlapping hydrological, power, and economic networks when assessing the economic impacts of future water stress on the power system. In this paper, we employ a coupled water-power-economy model to capture these important interactions. We identified three channels that are key to assessing economic impacts – thresholds, teleconnections, and timing. We find that not all reductions in reserve electricity generation capacity result in impacts (thresholds), and that when they occur, intermittent interruptions in electricity supply occurring at critical times of the day, week, and year account for most of the economic impacts (timing). Lastly, we find that impacts may be in different locations from the original water stress (teleconnections). This work underscores the importance of a coupled modeling approach that captures interactions across systems while retaining spatial, temporal, and sectoral detail.

Reducing the residual error of multibeam sounding data through empirical mode decomposition based on cubic Bessel interpolation

The systematic residual errors present in multibeam echo-sounding data cause the areas of overlap between adjacent swaths to become distorted. A method is proposed in this paper to reduce the residual error of multibeam sounding data through empirical mode decomposition (EMD) based on cubic Bessel interpolation. Numerical experiments confirm that the discrepancy in the overlap between two swaths is significantly reduced after applying EMD improved by cubic Bessel interpolation compared with both the original water depth data and with data processed using conventional EMD based on cubic spline interpolation. The mean square error of the improved method is decreased by 67% and 29% compared with that of the original and conventional EMD cases, respectively. Therefore, EMD with cubic Bessel interpolation can efficiently reduce the residual error of multibeam echo-sounding data.

Source of Oxygen Fed to Adventitious Roots of Syzygium kunstleri (King) Bahadur and R.C. Gaur Grown in Hypoxic Conditions

Syzygium kunstleri, a woody plant species, adapts to hypoxic conditions by developing new adventitious roots. Here, we investigate its morphological adaptation to long-term water level changes and the sources and pathways of O2 supplied to its adventitious roots. Cuttings were cultivated in hydroponic and agar media, and then, the water level was increased by 6 cm following adventitious root emergence; afterward, O2 partial pressure changes were measured using a Clark-type O2 microelectrode. O2 concentrations in the adventitious roots decreased when N2 was injected, regardless of the presence of light, indicating that the O2 source was not photosynthetic when bark was removed. New adventitious roots developed near the surface when the water level increased, and O2 conditions above the raised water level influenced O2 concentrations in adventitious roots. O2 concentrations in adventitious roots that developed before the water level increased were lower than in the newly developed adventitious roots but increased when the O2 concentrations above the original water level increased. Our study highlights morphological changes, such as the development of adventitious roots, as environmental adaptation mechanisms. By revealing O2 sources in S. kunstleri under hypoxic environments, we offer insights into the challenges of long-term adaptation to changing environments in woody plants.

Budyko’s framework to estimate Runoff sensitivity for the Indian sub-continental river basins

<p>Indian rivers are an inevitable part of the nation’s economy and society due to which it is necessary to understand the water budget for Indian sub-continental river basins. The available water and energy both play a prominent role in the runoff generation. However, the sensitivity of precipitation and temperature in runoff estimates are not well-explored. Here, we estimate the total runoff using  Budyko’s original water balance model for 220 sub-basins that are selected based on the major discharge stations in India. The Budyko’s total runoff is well correlated with the Variable Infiltration Capacity (VIC) simulated total runoff. Further, we estimate the precipitation elasticity and potential evaporation (PET) sensitivity of total annual runoff using the second-degree linear relation. We find that runoff is more sensitive towards the change in precipitation rather than the change in temperature in Cauvery, South Coast, Pennar, East Coast and Krishna basins. However, Indus and Brahmaputra basins show the contrasting pattern.  </p>