First Look-Ahead VSP Guided Salt Dome Island Exploration Well Drilling in the UAE

An exploration well offshore UAE, which was the first of it's kind, was planned to be drilled from an island and within salt dome. Well planning was based on a structural model that was estimated using coarse 2D surface seismic (with no line crossing planned well location) and gravity measurements. This model, therefore, had a large uncertainty as to the salt location and geometry. Concerns of potential drilling hazards associated with salt required utilizing the ability of borehole seismic to look-ahead of bit to image salt and direct the well such that it would be sufficiently far away from salt face. Pre-job survey planning was first made assuming salt face to the northwest (based on gravity data) of wellhead and that the well would remain outside the salt. To ensure the well remains close, but not too close, Vertical Seismic Profile (VSP) was planned to include Salt Proximity Survey. Just prior to spudding, a surface core indicated salt was, in fact, southeast of wellhead, thus changing the objectives of VSP from locating how far away the well was from salt, to how soon will it exit salt. After survey modeling for four possible scenarios, Look-ahead Zero-Offset and Offset VSPs were acquired using vibroseis at the island, at each of four casing points and rapidly processed to guide drilling next sections. In the 26" section, the well started drilling in salt and there was concern that there would be problems with casing design if the well did not exit salt before 4000 ft. A Zero-Offset and Offset VSP were shot for reflection imaging off the salt face. The survey indicated the salt face was approaching the well but at low rate (due to dip) to ensure an exit before 4000 ft. The well was deviated southeast and it exited the salt at 3620 ft. In the 17.5" section, a second run of Zero-Offset and Offset VSP were acquired indicating the salt face was still moving away from the well toward the northwest. In the 12.25" section, a third set of Zero-Offset and Offset VSP was shot. This survey confirmed the salt face was moving continually northwest and it was suggested the well deviate northwest to remain closer to salt. A large reverse fault was also clearly imaged and confirmed by drilling. In the 8.5" section, the well was drilled northwest at high angle as could be tolerated until it was TDed below target formation "A". The final set of Zero-Offset and Offset VSP results showed the salt was, at the level of formation "A", farther northwest than could be imaged by these VSP. There has been little to no experience of drilling salt dome islands in Abu Dhabi. This paper demonstrated how look-ahead VSP guided exploration well drilling in the salt dome island. Out-of-the-box survey design and rapid turnaround processing successfully aided in imaging location of the salt face and allowed casing points to be made without having to plug back and sidetrack. Once out of the salt, VSP allowed the well to be drilled closer to salt without re-entering it.

List of Analogues for Highly Productive Rocks Around Salt Domes

In the Dnipro-Donets depression, the Devonian salt during Carboniferous time became movable and created salt domes in the Permian, moving to the sea bottom and flowing therewith, forming bodies visible today as salt canopies and overhangs. These features are clear pieces of evidence of salt exposure on the surface, especially considering belts of reservoirs around salt domes. These reservoirs can be extremely prolific in some wells. Previous exploration targeting such deposits was driven mainly by drilling wells within the areas of known deep fields such as Medvedivske, Zakhidno-Khrestyschenske and others in the central part of the DDB. These reservoirs are composed of poorly sorted coarse material of wide variety of rocks including sandstones, carbonates, dolomites, igneous rocks of deep (granites), and shallow (diabases) formations. Currently, with the availability of 3D seismic surveys, these deposits become visible as bright spots and flat spots. Although it is not a 100% indicator due to fact that shallow salt canopies and lithology changes of rocks around salt domes may also interpret seismic reflections. It is good to mention that the Permian is an aridic environment with gradually losing water influx to the basin from base to top within the thickness of more than 1-2 kilometers. It could be utilized as boundary analogues to cover most of the possible intermediate scenarios in three areas. The first analogue is the outcropped salt dome in Solotvyno village in Carpathian mountains in western Ukraine close to the Romania border. This salt dome is an important example of showing the current deposition of transported coarse material from depth around salt domes. The second one is salt domes exposed as mountains of the Oman desert where it is possible to follow the material path approaching the salt uplift. And the third example is the Death Valley in Arizona, USA. The valley is an example of fans mostly deposited by gravity rather than permanent water flows. It good to mention that there are more examples that could be treated as direct analogues (the Zagros mountains in Iran) but they are not easily accessible for field trips if needed. For recognizing real targets vs artifacts, applying the knowledge of current deposition examples around the world would help dramatically (Western Ukraine, Oman, Death Valley in Arizona).

Improving Participation in the German Search for a Nuclear Waste Repository Site: a WebGIS as a Transdisciplinary Approach to Support Dialogue?

The political and social debate on nuclear energy in Germany has been characterized for many decades by a high potential for conflict and dissatisfaction. In particular, the controversies surrounding the Gorleben salt dome achieved international attention and altered the relationship between the population and political decision makers at the local up to international levels. With the Site Selection Act from 2013 (StandAG, first revision 2017) a new approach was selected in order to find a participative, inclusive and transparent search process for the best possible site of a repository for highly radioactive waste in Germany. In connection with this a self-learning process was proclaimed, based on a white (unprejudiced) map, which aimed to give the general public an active role; however, even the first interim report of the Federal Company for Radioactive Waste Disposal (BGE) and the publication of the multicolored map, in which geologically suitable areas were extensively shown, revealed a massive potential for conflict. Many citizens and activists, who had already protested against the Gorleben salt dome, in this early phase of the process criticized the lack of transparency and opportunities to voice an opinion on possible site regions. In order to counter these criticisms, the possibilities for a web geographic information system (WebGIS) application (interactive map) as an online platform were analyzed (Walkobinger and Tauch, 2018; Brown and Kyttä, 2018). The aim was to virtualy present available geodata (Chwalisz, 2021), which enabled people to contribute to spatial information (geological, superficial) and therefore to achieve an interaction and participation option with respect to the possible site regions. For this, available geodata relevant for the site search process, such as subareas (BGE, 2020), nuclear power stations (active/inactive, research stations etc.), storage facilities (repository, central, intermediate storage etc.), historically relevant sites (sites of protest, uranium-enrichment and preparation plants etc.) and basic data on orientation were used. Based on this, two possibilities for participative interaction were analyzed: (1) the inclusion of spatially located notes that contain own experiences or local knowledge (e.g. reports, concerns, suggestions, own expert opinions) and (2) the initiation of a platform for a spatially located discussion. Against the background of transdisciplinary research, the aim was to evaluate the participative value of this application in an iterative process, in which the research process is supported by an accompanying group from civil society. For this panel we want to present our results from the transdisciplinary research process. In addition to testing the suitability of such a participation mode, we want to analyze where problems arise and which information is necessary or can lead to conflicts (Griffin, 2020). Finally, we want to gain information on how such participation modes influence the quality of the dialogue and how they contribute to an overall perception of a legally acceptable process (Rzeszewski and Kotus, 2019).

Acquisition/Processing: Machine learning-based deblending: Dispersed source array data example

Machine learning (ML) has proven its value in the seismic industry with successful implementations in areas of seismic interpretation such as fault and salt dome detection and velocity picking. The field of seismic processing research also is shifting toward ML applications in areas such as tomography, demultiple, and interpolation. Here, a supervised ML deblending algorithm is illustrated on a dispersed source array (DSA) data example in which both high- and low-frequency vibrators were deployed simultaneously. Training data pairs of blended and corresponding unblended data were constructed from conventional (unblended) data from another survey. From this training data, the method can automatically learn a deblending operator that is used to deblend for both the low- and the high-frequency vibrators of the DSA data. The results obtained on the DSA data are encouraging and show that the ML deblending method can offer a good performing, less user-intensive alternative to existing deblending methods.