Deepwater clastic sedimentation Research Papers (original) (raw)

“Whatever the Antients have said, the Black Sea has nothing Black in it, as I may say, beside the name.”
A quote from Joseph Pitton de Tournefort, royal botanist to Louis XIV, 1718
Indeed, the Black Sea represents a very colorful region, not only from a historical and cultural perspective, but also from a hydrocarbon exploration point of view. Located next to Europe, this region has seen a long history of geological and geophysical activities. For example, the Black Sea became the type example of an euxinic basin and the name was literally derived from its earliest ancient Greek name, Pontos Axeinos (the dark or somber sea). Strangely enough, at one point its Latin name became Pontus Euxinus (the welcoming sea).

Whereas there are offshore oil and gas fields in almost every sector of the Black Sea, the contribution of the entire region to the world’s petroleum production is relatively low. This is especially true comparing this basin to its much more successful neighbor, the Caspian Sea. In spite of many similarities between these two basins, for example sharing a critical source rock (Maykop), the Black Sea appears to be left behind.

One reason for the lack of an exploration breakthrough is the fact that, until recently, exploration efforts in the entire Black Sea were largely restricted to the shelf. Deepwater drilling technology can be brought into the area, but obviously at a higher cost and with extra technical challenges. Even though there are few wells which were drilled off the Black Sea shelf, the large area of the basin floor remains untested in spite of the significant exploration potential. This situation is about to change as several operators in the basin teamed up to make the first extended deepwater drilling campaign happen in 2010 and 2011. We do hope that several critical discoveries will be made. Success would elevate the status of the Black Sea from one of the last frontier deepwater basins to an emerging major petroleum province.

Due to the lack of well control in the deepwater, geophysical methods are key to effective hydrocarbon exploration and every paper in this special issue demonstrates the use of seismic technology. This holds true irrespective of the fact that we gathered a healthy mixture of academic and industry contributions.

The papers in this section illustrate the colorfulness of the geology and geophysics around the Black Sea following the coastline in a clockwise manner. The first three papers deal with the northern, Ukrainian sector of the Black Sea. Khriachtchevskaia et al. describe the current exploration understanding of the large Odessa Shelf area (NW Black Sea) where after four decades of exploration eight gas and gas-condensate fields have been found. Obviously, the remaining exploration potential is tremendous given the fact that there are a lot of undrilled structures in the area and 3D seismic technology typically have not been used, if at all.

Still in the area of the northwestern Black Sea, the paper by Naudts et al. shows stunning examples of different types of high-resolution reflection seismic data. The different seismic signatures of shallow free gas highlight the prospectivity of the broader Dnepr paleo-delta. The shallow gas and gas seep distribution in this part of the Black Sea could also serve as a template for other gassy deepwater basins around the world.

A very important recent offshore discovery was made offshore Ukraine, just SE of the Kerch Peninsula. Stovba et al. not only show critical data from the Subbotina discovery well, but also describes the different deepwater play types in this segment of the Black Sea. The huge potential seen on a regional 2D seismic grid highlights the need for large 3D seismic surveys in the area.

There are several very large structures known in the deepwater Black Sea. One of them, the Shatsky Ridge, for most part is located in offshore Russia. The paper by Meisner et al. gives a brief overview of the tectonic evolution of the Eastern Black Sea based on the interpretion of regional 2D reflection seismic data. The paper by Edwards et al. offers a different perspective on the formation of the Eastern Black Sea using long-offset seismic data offshore Turkey. Data were acquired using a combination of Ocean Bottom Seismometers (OBS), land seismometers and a marine air gun source, providing refracted and reflected energy recorded to offsets in excess of 100 km. The results provide significant constraints on the nature of the crust in this part of the Black Sea.

The overview of exploration play types in the western part of the Turkish Black Sea is presented by Menlikli et al. The accelerated exploration efforts of the last few years produced a vast 2D and 3D seismic data set in the southern part of the Western Black Sea resulting in the delineation of numerous exploration targets. The conjugate margin to this segment of Turkey lies in NE Bulgaria. The paper by Tari et al. highlights the untested deepwater potential of the Polskhov High and it also illustrates the critical improvement of the geological understanding of the prospectivity in this area going from 2D to 3D seismic data.

After many years of successful exploration on the Romanian shelf, the paper by Bega and Ionescu outlines the potential of extending some of the proven play types on the shelf into the adjacent deepwater areas. Their contribution also emphasizes the ultimate need for 3D seismic data in order to make this critical transition. Finally, the last paper by Duley and Fogg provides a detailed account of how modern geophysical methods and attention to details could deliver technical success in a mature area such as the shelf of the Romanian Black Sea.