Loading Criteria and Deposit Layer Characteristics as Causes of Sediment Settlement in an Estuary

Sediment compaction due to the extraction of groundwater and self-weight consolidation, and monitoring land settlement of the river delta using geodetic measurement has been executed in several studies, while sediment settlement in the estuary is hypothesized due to dynamic loads. The present study aimed to observe clues for the occurrence of sediment settlement due to loading variation and deposit layer characteristics in the estuary. This research was based on four loading data for examination, i.e., hydraulic head pressure, sediment transport rate, sediment deposition, and water density. Two years of previous research simulations, including the rainy and dry seasons, were recalculated to gain the load pressure and were considered to assess the maximum load prediction. This review found evidence that dynamic loads predominated in maximum pressure changes in boreholes (BH2) and (BH3), and were due to river discharge and tidal occurrence, respectively. The dynamic load of sediment in BH2 contributed more than in BH3, where it was almost nonexistent. Observing the sediment layer characteristics, both settled for almost a month and two weeks, respectively, showed sediment settlement of more or less than 2 and 8 mm. Despite insignificant loading changes, these findings can further our understanding of loading criteria and settlement in different geometric locations.

Analysis of water distribution system at Alang-Alang Lebar

Municipal Waterworks Tirta Musi manages and supplies clean water to Palembang city. The distribution network system of Municipal Waterworks Tirta Musi is expected to distribute water sufficiently to all customers in the 18 districts this Municipal Waterworks serves. However, it was found that in Alang-alang Lebar service unit water was not delivered sufficiently. Moreover, Alang-alang Lebar service unit plans to improve the service so that the system will serve increasing customers until the next 20 years. This study aims to analyze the water distribution system to find the cause of insufficient water in Alang-Alang Lebar; predicting the number of customers in the next 20 years, and propose some improvements in the distribution system. A computer program EPANET was used to conduct the simulations on pipe networks. Data required for hydraulic analysis using EPANET was obtained from Municipal Waterworks Tirta Musi. The result shows that head pressure was the main problem in Alang-Alang Lebar. Adding discharge of pump reservoir, enlarging pipe diameters in some parts will improve the distribution performance. The proposed design of the distribution system will be able to deliver water for the next 20 years with an increasing number of the customer.

Front-End Integrated Production System Modelling for Production Optimization – Experience from a Niger Delta Field

The M001 project involved the hook-up of 12 wells (17 conduits) which were drilled and completed between year 2000 and 2005 but were closed-in for operational reasons, until year 2019 when the first seven (7) conduits on cluster MX1 were cleaned up successfully. The seven conduits (Well-A, Well-B, Well-C, Well-D, Well-E, Well-F & Well-G) were expected to flow via three 8" bulk lines. Post well open-up and handover to production, significant bulking / backing out effects were observed. An average Flow Line Pressure (FLP) of ∼22 bar was recorded on the flowlines, hence limiting the capacity to bulk the wells, [FLP increases towards Flowing Tubing Head Pressure (FTHP) hence, pushing the well out of the critical flow envelope as FTHP<<1.7FLP]. Due to this challenge, total production from Cluster MX1 was sub-optimal with only five (5) conduits out of seven (7) able to flow due to bulking and backing out effect. The sub-optimal performance from the conduits were investigated using the Integrated Production System Model (IPSM) / PIPESIM models. Four different scenarios were run in the model and the calibrated IPSM model indicated all 7 conduits should flow if there are no surface restrictions. The model identified pressure, mass and rate imbalances in the integrated system and suggested the presence of a restriction at the manifold, causing sub-optimal production from the wells. The model outcome triggered an onsite investigation / troubleshooting from the wellhead to the manifold at the facilities end where an adjustable choke was identified in the ligaments of the manifold. In line with process safety requirements, a risk assessment was carried out and a Management of Change (MOC) raised to remove the adjustable choke at the manifold. Post implementation of the intervention, all the seven (7) conduits produced without any bulking effect. Total production realized from the seven (7) conduits post execution of the recommended action is ca. 9.3 kbopd against 5.2 kbopd pre-intervention. A total of ca. 4.1 kbopd production gain was realized and 10 mln USD proposed for additional bulkline was saved.

Effects of Surge Tank Geometry on the Water Hammer Phenomenon: Numerical Investigation

A surge tank, as one of the most common control facilities, is applied to control head pressure level in long pressurized pipelines during the water hammer occurrence. The cost-effective operation of surge tank is highly affected by its characteristics (i.e., surge tank diameter and inlet diameter of surge tank) and can effectively reduce the repercussion of water hammer. This investigation utilized the method of characteristics (MOC) in order to simulate the behavior of transient flow at surge tank upstream and head pressure fluctuations regime for hydraulic system of a hydropower dam. The various types of boundary conditions (i.e., sure tank, reservoir, branch connection of three pipes, series pipes, and downstream valve) were applied to numerically investigate the simultaneous effects of the surge tank properties. In this way, all the simulations of water hammer equations were conducted for nine various combinations of surge tank diameter (D) and inlet diameter of surge tank (d). Results of this study indicated that, for the surge tank design with D=6m and d=3.4m, head pressure fluctuations reached minimum level in the large section of pipeline here is surge tank upstream. Additionally, occurrence of water hammer phenomenon was probable at the initial section of pipeline.

Energy Efficiency Improvement of Debutanizer Column, for NGL Separation

Compared to other petroleum, the natural gas combustion remains the cleanest and the one showing less CO2 emission. These reasons make the natural gas combustion one of the important issues to study. The separation of NGL is energy intensive. This operation is performed through a series of column including the debutanizer column. The present work is devoted to optimize the energy consumption at the level of the debutanizer column. The response surface technique and deploying a central composite numerical design is followed makes use of available data from a refinery. Using a multiple linear regressions, the optimization method leads us to three reliable models. Each of the three models takes as input the reflux ratio and the head pressure in order to predict the condenser heat duty, the reboiler heat duty and the purity of the produced butane. Suggested mathematical models were validated and their reliability was assessed via a set of statistical analyses. The optimization aims to simultaneously minimize the energy consumption of the condenser and reboiler, and maximize the purity of the ejected Butane. This optimization step allowed us to define the optimal values of reflux ratio and head pressure, with desirability function equal to 99 %. Under the determined optimal values, operating energy and cost of the industrial process were reduced by 38 % and 37 %, respectively, and besides, a high purity of butane was noticed reaching 99 %. From an economic point of view, separation NGL with optimal values of pressure and reflux ratio, may contribute to a decrease of CO2 emission and increases the energy efficiency.

A Reversible Cytotoxic Lesion of the Corpus Callosum Developing after a Rapid Alteration in Cerebrospinal Fluid Pressure/Volume in a Patient with New Daily Persistent Headache

A case is presented of a woman with a history of daily persistent head pressure and dizziness who developed a cytotoxic lesion of the splenium of the corpus callosum after an acute withdrawal of chronic acetazolamide treatment and then, in quick succession, a CSF pressure/volume drop with a lumbar puncture. This is the first documentation that rapid alterations of CSF pressure/volume may trigger cytotoxic lesions in the central nervous system.

An Innovative Well Intervention for Production Optimization in Depleted Gas Reservoirs Thru Coil Tubing

Coil Tubing operated in NL wells, South Sumatera because of depleted reservoir pressure. Objective of coiled tubing operation are sand clean-out and acid stimulation to restore well productivity. Previously in NL wells has used a snubbing unit in intervention well but the results were not good. Formation damage was suspected due to packer fluid introduced into formation during snubbing job. Production optimization in brownfield is required to extend the economic producing life of the field using cost-effective and low-risk technologies. Well stimulation is generally proposed to enhance well productivity by acidizing treatment. Acidizing in sandstone applied in Medco to improve well productivity. But loss problem got in conventional rig operation during killing well in low reservoir gas well. Coiled tubing (CTU) can solve the problem and can operate without killing the well. Recipe acid HCl 15% get optimum in solubility test around 28-31%. Coiled Tubing Operation applied pulsonic method to get optimum result. After CTU Job (clean sand out & acidizing), well productivity improved refer to gas rate and flowing well-head pressure (FWHP) monitoring. Initial gas gain was more than 2.5 MMSCFD from 2 wells (NL-X1 and NL-X2) that were treated with CTU acid stimulation. Gas cumulative is around 176 MMSCF (3 months production) and still counting. Further evaluation will be conducted by performing complete well test (transient analysis). As conclusion, coiled tubing operation has proven to become effective well intervention in depleted gas wells to improve production optimization and open the opportunity to unlock potential in other wells which experiencing similar challenges. This paper shares case study, how to develop acid stimulation strategy covering guideline in acid selection and deploy acid without killing well in South Sumatra.

On Similarity of Seismo Magnetic Power Density and Pressure Head Fractal Dimension for Characterizing Shajara Reservoirs of the Permo-Carboniferous Shajara Formation, Saudi Arabia

The quality and assessment of a reservoir can be documented in details by the application of seismo magnetic power density. This research aims to calculate fractal dimension from the relationship among seismo magnetic power density, maximum seismo magnetic power density and wetting phase saturation and to approve it by the fractal dimension derived from the relationship among inverse pressure head * pressure head and wetting phase saturation. Two equations for calculating the fractal dimensions have been employed. The first one describes the functional relationship between wetting phase saturation, seismo magnetic power density, maximum seismo magnetic power density and fractal dimension. The second equation implies to the wetting phase saturation as a function of pressure head and the fractal dimension. Two procedures for obtaining the fractal dimension have been utilized. The first procedure was done by plotting the logarithm of the ratio between seismo magnetic power density and maximum seismo magnetic power density versus logarithm wetting phase saturation. The slope of the first procedure = 3- Df (fractal dimension). The second procedure for obtaining the fractal dimension was determined by plotting the logarithm (inverse of pressure head and pressure head) versus the logarithm of wetting phase saturation. The slope of the second procedure = Df -3. On the basis of the obtained results of the fabricated stratigraphic column and the attained values of the fractal dimension, the sandstones of the Shajara reservoirs of the Shajara Formation were divided here into three units