ASCAPE: A Flexible and Efficient Analytical Tool to Evaluate Aquifer Storage Capacity for CO2 Sequestration

In recent years, carbon neutrality has emerged as an important social and political focus globally, where carbon sequestration plays a key role. The present work is aimed at introducing ASCAPE (Aquifer Storage CAPacity Evaluation tool), a fast and flexible tool useful in case of CO2 aquifer sequestration to preliminarily evaluate the required storage capacity as a function of the maximum allowable pressure increment. ASCAPE is based on the volumetric method included in SPE "Guidelines for Applications of the CO2 Storage Resources Management System" (SPE, 2020) for aquifer sequestration. The analytical formula was integrated to include additional physical phenomena as CO2 solubility in water, pressure control through water production, effect of gas pools connected to aquifer. The tool, implemented in Excel/VBA environment, allows to easily obtain a theoretical Pressure increment vs. Aquifer Volume curve useful to estimate the required aquifer volume to store a given quantity of CO2. ASCAPE results were validated comparing to a simplified 3D model simulated by a compositional commercial dynamic simulator. The validation showed a very good alignment with the 3D dynamic simulation results under several conditions. Many tests were performed with and without the CO2 solubility model, demonstrating that this phenomenon acts as pressure increment reducer. The original volumetric model can be therefore considered slightly conservative, since it neglects this physical contribution, which allowed to improve the reliability of the proposed analytical model. The proposed methodology is a general-purpose application being not related to a specified candidate and, therefore, it can be tailored on the specific scenario to be evaluated. ASCAPE was developed for preliminary screening of CO2 sequestration concepts in greenfield development areas, where the absence of brown or exhausted fields makes the storage in aquifer the only viable solution. Different aquifers were compared under certain assumptions of carbon to be stored with and without water production, allowing a preliminary evaluation that will be used to rank the concepts in terms of technical/economic feasibility.

Batch Production: A Success Story to Improve Oil Production in Mature Fields in Medco E&P, South Sumatera

X and Y fields are mature fields with almost 400 wells have been drilled since 1996. Many wells have been shut-in for a long time due to producing below economical limit of 10 BOPD. Several reasons are due to depleted reservoir pressure, watered out, and low reservoir quality. Long shut-in time allows the reservoir pressure to build up and improve. On the other side, good waterflood and pressure maintenance efforts also improved the reservoir pressure and oil recovery potential. Many wells become potential for reactivation. In 2018, 5 (five) wells were reactivated after a long period of shut-in. However, the initiatives were not entirely effective due to lack of established method for candidates selection and prioritization applied. Not all wells can be monitored and reviewed thus resulting in lacking of reactivation candidates. In 2019, a more comprehensive method named “Batch Production” is introduced. It is an end-to-end selection process which consists of 5 (five) lenses: well screening, reservoir aspect review, operational aspect review, prioritization, and execution and monitoring. After implementing “Batch Production” method in 2019, we successfully reactivated 35 (thirty five) wells in 2019 – 2020 with total initial gain of 1062 BOPD, which are significantly higher than 2018 result of 5 (five) wells with 184 BOPD gain. Telisa reservoir has higher initial oil gain compared to Baturaja reservoir which were mostly driven by reservoir pressure increment. This result proves how “Batch Production” method is effective and covers all the important aspects in well reactivation. It also helps the operation team by streamlining the process of reactivating a well. No additional cost such as rig intervention or well stimulation is needed in this method, making this initiative as cost-effective yet very profitable for mature fields.

A New Mechanistic Model for Emulsion Rheology and Boosting Pressure Prediction in Electrical Submersible Pumps (ESPs) under Oil-Water Two-Phase Flow

Summary As the second most widely used artificial lift method in the petroleum industry, electrical submersible pumps (ESPs) maintain or increase flow rates by converting the kinetic energy to hydraulic pressure. As oilfields age, water is invariably produced with crude oil. The increase of water cut generates oil-water emulsions due to the high-shearing effects inside a rotating ESP. Emulsions can be stabilized by natural surfactants or fine solids existing in the reservoir fluids. The formation of emulsions during oil production creates a high viscous mixture, resulting in costly problems and flow assurance issues, such as increasing pressure drop and reducing production rates. This paper, for the first time, proposes a new rheology model to predict the oil-water emulsion effective viscosities and establishes a link of fluid rheology and its effect with the stage pressure increment of ESPs. Based on Brinkman's (1952) correlation, a new rheology model, accounting for ESP rotational speed, stage number, fluid properties, and so on, is developed, which can also predict the phase inversion in oil-water emulsions. For the new mechanistic model to calculate ESP boosting pressure, a conceptual best-match flow rate (QBM) is introduced. QBM corresponds to the flow rate whose direction at the ESP impeller outlet matches the designed flow direction. Induced by the liquid flow rates changing, various pressure losses can be derived from QBM, including recirculation losses, and losses due to friction, leakage, sudden change of flow directions, and so on. Incorporating the new rheology model into the mechanistic model, the ESP boosting pressure under oil-water emulsion flow can be calculated. To validate the proposed model, the experimental data from two different types of ESPs were compared with the model predictions in terms of ESP boosting pressure. Under both high-viscositysingle-phase fluid flow and oil-water emulsion flow, the model predicted ESP pressure increment matches the experimental measurements well. From medium to high flow rates with varying oil viscosities and water cuts, the prediction error is less than 15%.

Mechanical Model of the Initial Leg Pressure Increment of the Shield and Its Application to Monitor Roof Load in Longwall Panels

The shield pressure cannot always be used to represent the upper load of longwall panels, since its value is steady or even decreases by the yielding action. However, the leg pressure increment of the shield (LPIS) at the initial stage is not influenced by yielding and could therefore be an important factor to judge the state of overlying loads. In this study, a mechanical model is established to analyze the relationship between the overlying loads of the main roof and LPIS after cutting. There is a linear positive correlation between leg pressure increment and overlying loads and a second-order relationship between leg pressure increment and length of main roof cantilever in the proposed model. Therefore, it can be used to determine the magnitude of roof weighting strength in different periods as well as the length of the main roof cantilever in a period. Finally, the mine pressure difference between the period of fully mechanized mining and the period of fully mechanized caving mining in the MinDong-1 coal mine serves to verify the rationality of the proposed model.

Hubungan Tingkat Pengetahuan Lansia Tentang Hipertensi Dengan Kepatuhan Diet Hipertensi Di Panti Sosial Tresna Werdha Jara Mara Pati Buleleng

Background: Hypertension is a disease with the condition of arterial blood pressure increment above normal, the systolic pressure ≥140 mmHg and diastolic ≥85 mmHg. The disease can be prevented and cured with proper hypertension diet and can be done with sufficient knowledge. Purposes: To identifying the sufferers’ knowledge regarding hypertension, hypertension diet obedience, and to analyze the correlation between the knowledge and diet obedience. Methodology: A correlational descriptive research with Cross Sectional approach. Research subjects are the elderly above 60 (sixty) years old. Spearman Rank Correlation Statistic test are applied with 5% degree of error and p value under 0,05. Result: Respondent possess 59,71% of a good knowledge, 30,77% of enough knowledge and 9,62% of less knowledge of hypertension. Obedience level shows that 51,92% respondent are obedient, 34,62% are enough obedient and 13,46% less obedient to hypertension diet. Spearman Rank statistic test shows 0,887 of value and p-value of 0,000 which mean a positive correlation between knowledge and diet obedience of hypertension. Summary: The more educated respondent regarding hypertension are correspond to the obedience to consuming hypertension diet.

Personalysis: Personality and Stress Analysis of Students

Stress is a mental condition that decreases the quality of life and influences almost every feature of life. Stress is a significant issue these days, particularly among students. The age that was once assumed to be the most cheerful phase of life is currently under a lot of pressure. Increment in levels of stress these days’ prompts to numerous issues like misery, suicide, coronary episode, and stroke. In this paper, we are ascertaining the stress levels of students during their B. Tech degree. Our goal is to examine stress in the students at various focuses in his life. The impact that semester exam or placement tests has on student often goes unnoticed. The fact of understudy being in a relationship is not taken into account as a prime factor in calculating stress levels. In this research paper, we have considered that factor also. For calculating stress levels, students were asked some basic questions about how they feel, and what comes into mind when they see a picture and some personal questions based on their relationship status.

Effects of CO2, H2O and N2 Dilutions on Emission Characteristics and Partially Premixed Combustion of Shale Gas

Environmental constraints of countries on hazardous emissions promote the usage of gas fuels in combustion systems for energy production. The shale gas recently shines out as one of the promising gas fuels of the future owing to its wide reserves discovered in the different gas fields of countries. This study numerically focuses on the emission characteristics and turbulent adiabatic combustion of partially premixed shale gas and humid air with dilution effects of CO2, H2O, and N2 under different pressures. Ansys codes are used for the numerical computations of computational fluid dynamics on 2D model of a co-axial type combustor to find out the emissions and flame speeds during the combustion of shale gas and air. Based on the results, the maximum NO mass fractions are obtained at 1.42, 1.44, and 1.4 equivalence ratios for Barnette, New Albany, and Haynesville. The increasing equivalence ratio raises the mass fractions of CO and turbulent flame speeds. The rising CO2 dilution into the additional air diminish the flame speeds, NO and CO fractions. The growing H2O addition decreases NO and CO mass fractions. On the contrary, it augments the flame speeds. The enhancing N2 dope decreases NO and rears CO mass fractions. The rising pressure with 15% CO2 dilution fades up the turbulent flame speeds, NO and CO fractions. The pressure increment with 15% H2O dope reduces CO and the flame speeds. But, it lightly relieves NO fractions. The growing pressure with 15% N2 addition abates the mass fractions of CO and turbulent flame speeds.

Elastic-Plastic Threshold and Rational Unloading Level of Rocks

During loading and unloading test, various rocks manifest different stress values of elastic-plastic transformation. This study proposes to include axial pressure increment ratio in the conventional triaxial compression test to evaluate different variables (nominal elastic modulus, nominal Poisson’s ratio, strain, and energy). The relationships among various factors including variables, the stress level of initial confining stress and axial pressures, were analyzed by analyzing the stress–strain plot record obtained from testing various rocks. The extreme value point of the deformation parameter, also known as the elastic-plastic threshold, was analyzed. In addition, the elastic-plastic thresholds were later used as unloading points during the unloading tests. Under the same confining condition, different rocks demonstrated different unloading levels. Furthermore, a linear correlation was observed between unloading levels and changing confining pressures, and the gradient is mainly related to the types of rocks. During the unloading tests of rocks, the rational unloading level is recommended to be no higher than the stress level at the elastic-plastic threshold under the corresponding confining pressure.

Effects of Cap Bottom Elevation on Wave Loads on the Piles Under the Cap

High-rise pile cap foundations are generally used to support offshore wind turbines or sea-crossing bridges. They endure complex wave loads due to the interaction of free surface and the cap. An additional pressure increment has been found under the cap when free surface impinges the cap bottom. This additional pressure changes the wave loads on the piles under the cap compared with the case without the cap. In the present paper, we investigate the effects of the cap bottom elevation on the wave loads of the piles under the cap by using fully nonlinear numerical simulations. Based on parameters of waves and the structure used in Donghai Bridge Wind Farm, China, we simulate a number of cases with different cap bottom elevation to explore its influence on wave loads of the piles under the cap. We find that the influence is of significance and requires enough attention.