SE Abu Dhabi Aptian 5 Shuaiba System: Understanding a Heterogeneous Reservoir Trend

The study area covers 1,300 km2 in southeastern Abu Dhabi and focuses on the Aptian (Apt.) 5 Upper Shuaiba progradational clinoform system. The Shuaiba Formation has been well-studied at the regional level, but with comparatively less focus on the Apt. 5 system. Studying depositional trends and shoal facies distributions within the Apt. 5 is critical for predicting reservoir presence and quality. Given the complexity of the Apt. 5 system, understanding the key controls over depositional environments, such as paleowind direction, is an important first step. This study combined regional context and geological understanding with previous studies to confirm existing clinoform interpretation, while also delineating four additional clinoform sequences using a reprocessed depth migrated 3-D seismic volume. Isochron maps were also used to group clinoforms into three packages distinguished by common morphologies possibly linked to their respective dominant reservoir facies. Preliminary observations suggest early clinoforms had more rudist build-ups, whereas the later clinoforms were dominated by narrow-shoal beaches. Coalescing clinoform shoal patterns, observed in the spectral decomposition and amplitude extraction maps, likely result from a combination of Bab Basin morphology, longshore current, and dominant paleowind direction during the Early to Middle Cretaceous. Existing interpretations of dominant paleowind direction vary significantly, ranging between E-W and S-N. Interpretations from this study are most consistent with prevailing paleowind out of the east-southeast. The Arabian plate was likely near the equator around 10°S latitude during the Aptian, which supports the southeast wind hypothesis when considering modern Coriolis patterns. Consistent wind influence on shallow water shoal environments would have winnowed mud and increased the proportion of grain-dominated sediment preserved relative to lower energy areas. The grain-dominated facies appear to be reflected in amplitude responses around the coalescing clinoforms, and in the amplitude variations along strike coincident with clinoform edges. Reservoir presence and quality uncertainty can be reduced if these observations can be confirmed. An improved understanding of the Apt. 5 clinoform system in southeast Abu Dhabi, and possible influences on reservoir distribution and quality, will help develop a better understanding of risk for prospect maturation.

Interdisciplinary approach for qualitatively monitoring coastline dynamics in North Java Coast, Case study: Karawang Regency Indonesia

The coast of north Java is the most rapid development area among other parts of Indonesia. Since the North Java Coast is dominated by mild slope, soft-loose quaternary sediment and provoked by the sea thus the vulnerability of it is the most challenging issue to be assessed. Karawang is the representative area to investigate the scientific reason of coastal dynamics. This study aims to reveal the coastline changing based on RBI (1210-211, 1210-212, 1210-221, 1210-542, 1210-543, 1210-544 and 1210-631) and LPI (1210-04 and 1209-01) maps, hydrodynamics simulation and field measurements associated with abrasion and accretion. The equalizing procedure has been applied for a benchmark of zero coastlines that LPI and RBI data were used to observe the back and forth of coastline changing throughout 2000 and 2018. The results show five districts, Tirtajaya, Pakisjaya, Cilebar, Cibuaya and Pedes have the highest abrasion with an average magnitude of 11.3 m/year, 9.1 m/year, 6.9 m/year, 5.1 m/year and 3.7 m/year respectively within a total 489 ha disappear area. By all integrated analysis data so we can conclude that the dominated monsoonal longshore current is east to west and working on the dominantly terrigenous coastal alluvium and intercalated by carbonatic marine sediment.

River Jets Versus Wave-Driven Longshore Currents at River Mouths

At river mouths, fluvial jets and longshore currents (LSCs) generated by waves interact hydrodynamically. This idealized numerical modeling study simulates a large number of hydro-morphodynamic conditions (650) to explore the emergent hydrodynamics determined by different mouth bar volumes and geometries, river discharge, wave heights, and directions and their potential stress on river-mouth development. We find that in the absence of a river-mouth bar (RMB), interactions are driven by momentum balances, expressed either as the balance of wave momentum flux (Mw) and jet momentum flux (Mj), or the balance of river jet discharge (QJet) and longshore current discharge (QLSC). When a RMB is present, the topography modifies the structure of the jet by spreading it, and we quantify this mechanism through the lateral jet transfer rate (LJT). Secondly, topography generates complex longshore wave-driven circulation as a result of the protruding shoreface which serves as a platform on which counter LSCs develop. The balance in QJet/QLSC may be used as an indication of the type of circulation. High and oblique waves favor longshore circulation and RMB bypass, whereas low waves and normal-to-coast angles generate diverging LSCs on the mouth bar crest which interrupts the longshore circulation. A quantification of the dynamic diversion is proposed in the form of the non-dimensional Dynamic diversion index (DyD), which scales with the product of Mj and Mw, and can account for the absolute strength of hydrodynamic interactions occurring at river mouths. RMB morphology can affect DyD in multiple ways by strengthening or by weakening the interactions. The DyD effect seems to increase with increasing RMB size, indicating that the RMB scale regulates the interplay of the wave-driven circulation and the river jet which further controls the adjacent topography changes.

Current Geodynamics and Evolutionary Trends of a Headland Bay Beach System in the Semi-Arid Coast of Chile

The Chilean coast is controlled by the tectonics and structure, generating an irregular coastal landscape, with bays, marine terraces, sandy and gravel beaches, sand dune fields and Andean slopes, forming some mega cliffs that are attacked by waves. The Chilean coastline is shaped by headland bay beaches, with a dynamic coast modeled by south-western winds and south–north longshore current. We analyzed the case of the Coquimbo mega headland bay beach, which consists of four headland bay beaches. A methodological study was carried out on the morphometric parameters of the shoreline and the types of beaches dominated by waves along with geomorphological analysis of the coastal zone. We observed a mass transfer process from south to north. The northern sections of the bays are the places with the densest sand dune fields. This concentration of dunes occurs in each bay individually and in the mega bay as well. The sedimentary supply comes from Andean catchments to the shoreline and is transported and reworked by the longshore current to the northern area, where a huge sand field dune has developed, 120 km away from the mouth of Limarí River, the most southern catchment in the study area. In the mega bay, the current trend is a continuous sedimentary supply, despite the semi-arid conditions and the extreme drought that has affected the area since 2011. The study area is also a popular destination in Chile for beach tourism and is a place of interest for the mining industry.

THE ROLE OF GEOTEXTILE TUBE AS LOW-CRESTED BREAKWATERS IN RESTORING SEVERE BEACH EROSION PROBLEM AT PEBUAHAN BEACH IN BALI ISLAND

Pebuahan Beach in Jembrana Regency, Bali has experienced severe beach erosion since the construction of the Nusantara Pengambengan fishing port, 10 km east of Pebuahan. Efforts to countermeasure the coastal problem has been carried out by many local residents, but failed due to strong longshore drift. Through a collaboration between the Research Center for Water Resources, the Bali Penida River Basin, and PT. Geotechnical Systemindo, the implementation of low-crested breakwaters (LCB) or PEGAR, made of Woven Geotextile Tubes was initiated. Four woven geotextile tubes C12.9 m with length varied from 20 m to 25 m were installed to form LCB with the length of 60 m, at distance to the coast of 50 m. The monitoring of shoreline changes was conducted over the 3 months after its installation, which shows the formation of a new shoreline with the amount of deposited sand of 185.8 m3. The breaking wave on LCB crest results in successfully controlling the longshore current, hence the longshore drift settles behind the LCB to form a new coastline. It is expected this field study can be treated as an additional input to improve LCB Guideline and to expand LCB effectiveness scope not only apply to shallow wave conditions and beaches such as on North coast of Java, but also can be applied more universally to a deeper coastal waters with high wave conditions.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/AFzvkvYY2Do

INVESTIGATING THE LITTORAL TRANSPORT OF SEDIMENT ALONG THE NASESE COASTLINE, SUVA, FIJI ISLANDS

The research investigated the current Nasese Coastline area from the impact of Littoral transport, a term used for the transport of non-cohesive sediments, i.e. mainly sand, along the foreshore and the shoreface of Nasese due to the action of the breaking waves and the longshore current. The littoral transport is also called the longshore transport or the littoral drift. The theoretical concept coastal sediment properties can be used to evaluate properties of sediment on site to avoid serve impacts towards the Suva Port in the future. The method used was on-site measurement by surveying to generate coastal profiles. Along with this, 1464 hours of wind data for the months of November and December 2019 were used to generate the frequency of the magnitude of Wind and the Direction using Wind Rose Plots for Meteorological Data. The movement of the sediments through the Beach Profiles agrees with the output generated Wind Directions. Therefore, Suva Port, may consider this situation in terms of the routine maintenance of dredging in order to sustain the acceptable depth of the Sea Port.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/vW05xoiNa_w

Investigasi Arus Sejajar Pantai (Longshore Current) di Daerah Abrasi Bengkulu Utara

The coastal area of Serangai Village is directly facing the open sea; as a result it is vulnerable to coastal abrasion. Longshore currents can accelerate the process of coastal abrasion. The study was aimed to determine the speed and direction of current as well as the existence of the longshore current at the Serangai. Field observation was conducted on 5-7 November 2018. The results showed that the frequency distribution of current at speed of 0-10 cm/s reached 69%, and at speed of 10-20 cm/s reached 25%. The highest speed of 20-30 cm/s has a frequency of 6 %. Moreover, the direction of the majority of ocean currents is to the southeast (120o-150o), showing that the current is more likely to be parallel to the shoreline called longshore current that can accelerate shoreline Serangai Village, Bengkulu. However, further research is needed to see variability of current associated with the season (monsoon). Wilayah pesisir Desa Serangai berhadapan langsung dengan laut lepas; sehingga rentan terhadap abrasi pantai. Arus sejajar pantai dapat mempercepat proses abrasi pantai. Penelitian bertujuan untuk mengetahui kecepatan dan arah arus serta keberadaan arus sejajar pantai di Serangai. Pengamatan lapangan dilakukan pada tanggal 5-7 November 2018. Hasil penelitian menunjukkan bahwa distribusi frekuensi arus pada kecepatan 0-10 cm/s mencapai 69%, dan pada kecepatan 10-20 cm/s mencapai 25%. Kecepatan tertinggi 20-30 cm/s memiliki frekuensi 6%. Selain itu, arah arus laut mayoritas ke arah tenggara (120o-150o), menunjukkan bahwa arus lebih cenderung sejajar dengan garis pantai yang disebut arus sejajar pantai yang dapat mempercepat garis pantai Desa Serangai, Bengkulu. Namun, penelitian lebih lanjut diperlukan untuk melihat variabilitas arus yang terkait dengan musim (monsun).