In a mature province
The Danish part of the North Sea is a mature area seen from an oil industrial perspective. The first well, A-1, was drilled in 1966 and first oil was produced from a Danish field in 1972. This means that Denmark has seen oil and gas activities for more than 50 years. A recent assessment of the remaining potential in the Danish part of the North Sea estimates that approx. 3 billion barrels of oil equivalent are still remaining – this corresponds to more or less the total production from the Danish sector up until now.
Several decades with exploration has resulted in a high subsurface understanding gained through the collection of a wide range of data e.g. seismic surveys and wells. Particularly in the Central Graben area, where most of the producing fields are located, valuable knowledge about the subsurface has been gathered through significant investments by oil companies. Through the years extensive exploration activity has been carried out through mapping and evaluation of potential accumulations with increasingly more advanced investigation and interpretation methods.
Are large amounts of data always an advantage?
Is access to large amounts of data in a mature region always an advantage? Could we become to detail orientated over time in mature regions and forget to step back and look at the larger regional perspective? The risk of giving already completed studies and interpretations to much emphasis is present.
Exploration in mature regions benefits from constantly looking at the available data from a new perspective. Experience gained from different hydrocarbon provinces, basins and plays can help foster new ideas and lead to new exploration approaches and methods in a mature region. New perspectives and approaches have time and again shown that a mature region can continuously reveal surprises.
The larger perspective
The most common approach to exploration in immature regions is to obtain an understanding of the geological and structural trends based on the available data at hand.
Geological deposits that contain accumulations of oil and gas may be limited to regionally small areas but can also be found in regionally large areas covering many hundreds of kilometres.
When oil companies initiate the exploration for hydrocarbons in new frontier regions, a useful approach is to ”zoom out” and look at the subsurface deposits in a larger, regional perspective across geological structures and national borders. In this way, they will screen for the most prolific areas with the highest potential of yielding oil and gas discoveries.
This screening approach can easily be transferred to mature regions where it can be combined with the knowledge of prospective deposits as well as the location of discoveries and producing fields within the region. In this way, it will be possible to identify trends and thereby the potential for new exploration opportunities.
Like pearls on a string
There has through the years been great activity in the Danish part of the North Sea. This means that it must be possible to identify overall patterns in e.g. the presence of reservoir rock, the location of the discoveries and the producing fields. Hence analysis and better understanding of the controlling factors behind these existing oil or gas discoveries may lead to the potential for locating new.
By closely studying a map of wells and discoveries in the Danish part of the Central Graben, one will notice areas with sparse wells and discoveries as well as areas with a dense accumulation of wells and discoveries. It can be noticed that the discoveries and fields are located along north-west/south-eastward lines. These lines reveal a trend of oil and gas accumulations almost like pearls on a string across several geological layers.
When including data of discoveries and wells from surrounding countries such as Norway, Germany and England one will get a clearer understanding of these trends. An obvious observation to make along these regional trend lines is noticing areas where wells have not been drilled and discoveries made. These gaps may indicate previously overlooked areas along the trend lines which are worth exploring in more detail.
In some cases, these underexplored areas are close to national borders where discoveries have been made in close proximity on one side of the border but not on the other. As we all know geology does not depend on international offshore borders, so underexplored areas close to borders could become exciting exploration goals.
The dotted lines illustrates trends ind fields and discoveries in Danish area.
Trend lines in a regional perspective. By zooming out you see, that there are unexplored areas along the trend lines. The areas are marked with red circles.
New ways call for experience and courage
Exploration in a mature area like the Danish part of the North Sea requires lots of experience but also the courage to implement new and different approaches.
After the awarding of licences in the 7th round in 2016 and through acquisitions in 2017, several new players – both large and small companies – are active in Denmark. These companies can bring much needed “new eyes” to oil and gas exploration in Denmark.
The study of regional trends in mature regions with large amounts of available data is maybe what will inspire to continued exploration and create renewed interest in an upcoming 8th licensing round in the Danish part of the North Sea.