PERENCANAAN SPILLWAY MORNING GLORY PADA BENDUNGAN SEMANTOK NGANJUK

Bangunan spillway adalah salah satu bagian komponen suatu bendungan yang berfungsi untuk melindungi tubuh bendungan dari bahaya pelimpasan (overtopping) pada saat banjir. Bendungan Semantok yang menjadi objek pada perencanaan ini, direncanakan menggunakan spillway tipe morning glory. Spillway ini merupakan suatu struktur yang digunakan untuk mengendalikan pelepasan air yang mengalir dari bendungan ke daerah hilir, berbentuk menara/cerobong yang sangat efektif untuk bendungan yang tidak memiliki ruang yang cukup untuk pelimpah jenis lainnya. Perencanaan ini terdiri dari analisis yang meliputi : analisis hidrologi, hidrolika, analisis stabilitas, dan analisa struktur. Adapun bendungan yang direncanakan memiliki periode ulang 1000 tahun dengan luas DAS sebesar 14,30 km2 dan panjang sungai 7,44 km serta data hujan harian sebanyak 25 tahun. Dari hasil kajian yang diperoleh elevasi puncak bangunan spillway adalah +128.00 Mdpl dengan debit banjir maksimum 125,16 m3/det pada elevasi +129.30. Tinggi bangunan 30,5 meter dengan diameter puncak 6 meter dan diameter konduit 4 meter. Panjang terowongan konduit 182,70 meter. Serta tebal dinding 0,40 meter dengan tulangan horisontal & vertikal D22-150 mm. ========== The spillway construction is one of the components of a dam which has function to protect the dam from overtopping during a flood. Semantok dam is the object on this plan, it is planned to use the type of morning glory spillway. The spillway is a structure that is used to control the release of water flowing from the dam to the downstream areas, shaped tower / funnel which is very effective for dams that do not have sufficient space for the overflow of other spillway types. This plan consists several analysis such as: analysis of hydrology, hydraulics, stability analysis, and structural analysis. The planned dam has a period of 1000 years with a watershed area of 14.30 km2 and length of the river 7.44 km as well as the daily rainfall data as much as 25 years. From the results of the study obtained that spillway top elevation is +128.00 MASL with maximum flood discharge 125.16 m3 / sec at an elevation of +129.30. The structure height 30.5 meters with the peak of diameter is 6 meters and a diameter of conduit is 4 meter. The lenght of the tunnel conduit is 182.70 meter. As well as the wall thickness of 0.40 meters with a reinforcement horizontal and vertical D22-150 mm

Impact of Wet Supercritical CO2 Injection on Fly Ash Geopolymer Cement Under Elevated Temperatures for Well Cement Application

An alternative cement system created through geopolymerization of fly ash offers favorable properties such as able to resist acidic fluids and possess high compressive strength. However, the application of fly ash geopolymer as wellbore cement under carbon dioxide (CO2) environment at elevated temperature is not well recorded in the literature. This paper character- izes the fly ash-based geopolymer cement and experimentally investigates its mechanical and microstructure changes after exposed to CO2 under elevated temperature. Microstructure identification on the altered cement paste was conducted by the analysis of XRD and SEM. In this study, fly ash-based alkali-activated cement was made using 8 molal sodium hydroxide and sodium silicate as alkali activators. The results found that crystal-like shape identified as calcium carbonate was formed at the surface of spherical fly ash particle after carbonation formation. The strength of geopolymer cement was found not to be decreased although carbonation process was occurred. Microstructure analysis revealed that zeolite was formed during CO2 acid exposure for geopolymer cement which contributes to the strength development

The suitability of fly ash based geopolymer cement for oil well cementing applications: A review

The increase in awareness towards global warming has prompted the research of alternatives to the conventional ordinary Portland Cement (OPC). In addition, studies have demonstrated that the use of geopolymer cement slurries resulted in lower carbon emission and superior cement properties compared to the ordinary Portland cement. In this study, the factors which affect the wellbore integrity in regards to cementing were identified and a comparison between Class G cement and Fly Ash Geopolymer (FAGP) cement pertaining to the identified factors were made. In addition, a thorough analysis on the factors affecting the properties of geopolymer in regards to its application in oil well cementing was performed. The results enable the finding of optimum parameters required to produce geopolymer cements for oil well applications. The FAGP cement achieved higher compressive strengths compared to Class G cement for all curing temperatures above 36⁰C. At optimum curing temperatures, for all curing time FAGP cement achieved higher compressive strengths in comparison Class G cement. Moreover, FAGP cement was found to be more susceptible to marine environment whereby curing medium of brine water resulted in higher compressive strengths. In addition, FAGP cement has lesser carbon footprint, superior chemical durability, lower permeability and higher crack propagation threshold in comparison the Class G cement. In addition, key variables which influence the compressive strength of FAGP cement such as type of activating solution, concentration of activating solution alkaline liquid to fly ash ratio, aging duration and water to binder ratio were identified and the corresponding optimum values in achieving highest compressive strength were suggested. The conclusion supports the usage of geopolymer cement for oil well cementing whereby it has an edge over conventional Portland cement for better short term and long term performance to ensure wellbore integrity throughout the producing life span of the well, with less hazards imposed on the environment

Conventional and intelligent models for detection and prediction of fluid loss events during drilling operations: a comprehensive review

Fluid loss to subsurface formations is a challenging aspect during drilling operations in petroleum industry. Several other drilling issues such as fluid influx and pipe sticking can be triggered in such scenarios, posturing a significant risk to rig personnel, environment, and economical drilling. Therefore, prediction and early detection of lost circulation events are required for safe and economic drilling operation. Several theoretical studies have been performed to detect and predict fluid loss event during hydrocarbon extraction. This paper reviews the existing conventional and intelligent models developed for early detection and prediction of lost circulation events. These predictive and detecting models comprise of Artificial Intelligence (AI) algorithms that require improvements for data reduction, universal prediction and compatibility. The review also covers several sensor-based techniques, different geostatistical-based models and Pressure-While-Drilling (PWD) tools for their applications in early loss circulation detection. In addition, loss circulation zones types, severity level, scenario and common preventive measures are also included in this review. This study aims to provide a systematic review of the published literature from the last forty years on the developed conventional and intelligent models for detection and prediction of fluid loss events and emphasizes on increasing AI involvement for precise results

Application of machine learning to determine the shear stress and fltration loss properties of nano‑based drilling fuid

A detailed understanding of the drilling fuid rheology and fltration properties is essential to assuring reduced fuid loss during the transport process. As per literature review, silica nanoparticle is an exceptional additive to enhance drilling fuid rheology and fltration properties enhancement. However, a correlation based on nano-SiO2-water-based drilling fuid that can quantify the rheology and fltration properties of nanofuids is not available. Thus, two data-driven machine learning approaches are proposed for prediction, i.e. artifcial-neural-network and least-square-support-vector-machine (LSSVM). Parameters involved for the prediction of shear stress are SiO2 concentration, temperature, and shear rate, whereas SiO2 nanoparticle concentration, temperature, and time are the inputs to simulate fltration volume. A feed-forward multilayer perceptron is constructed and optimised using the Levenberg–Marquardt learning algorithm. The parameters for the LSSVM are optimised using Couple Simulated Annealing. The performance of each model is evaluated based on several statistical parameters. The predicted results achieved R2 (coefcient of determination) value higher than 0.99 and MAE (mean absolute error) and MAPE (mean absolute percentage error) value below 7% for both the models. The developed models are further validated with experimental data that reveals an excellent agreement between predicted and experimental data

DEVELOPMENT OF PREDICTIVE EQUATIONS FOR PERMEABILITY AND STRENGTH OF OIL WELL CEMENT USING ELECTRICAL IMPEDANCE

Oilwell cement plays an important role either to seal-off the casing or to isolate the formation layers from the fluids infiltration that might cause a well bore damage. A cautious evaluation of cement after displacement is coming to be crucial to secure the long-term durability and integrity of wellbore. This work in turn is focused on the utilization of electrical properties for predicting the permeability and compressive strength of oil well cement. At present work, an electrical impedance measurement has been used to detect the conductivity evolution of oil well cement during early hydration. It was then followed by an examination towards the potential existence of interface conductivity along with its effects on various water cement ratios, curing temperature and also pressure. In analyzing the interface conductivity, the evaluation of the electrical responses in the form of conductivity dispersion characteristics has been done. Together with porosity data, conductivity data consisting of bulk and pore solution conductivity were examined to study several composite conductivity models to describe certain changes in the electrical conductivity of oil well cement system. Several empirical equations for predicting the permeability and compressive strength of oilwell cement based on its electrical properties response have been proposed. To validate the result, the proposed equations were experimentally compared to other cement samples with different water cement ratios and curing conditions. A comparison has also been made to the equation proposed by Katz�Thompson and Johnson's and also data from literatures. A good agreement between the proposed equation and measured data then shows that it is feasible to obtain the cement's strength and permeability in place using these electrical properties. Permeability and compressive strength in mature stage, furthermore, can be predicted by the proposed equations