In the past 5 years many news accounts exclaimed the riches of Lebanese offshore hydrocarbon resources. While some made the adequate warnings about the numbers being broad estimates, others published those numbers as though they were proven resources. For the sake of clarity, let’s go back to an interview from October 2013: “the current estimate, under a probability of 50 percent, for almost 45 percent of our waters has reached 95.9 trillion cubic feet of gas and 865 million barrels of oil”. That was stated by Gebran Bassil, the Minister of Energy at the time. Let’s first try to break down what this statement means and second, try to shed some light on how these estimates are usually carried out in oil and gas exploration.
Starting with the statement, it is clear that the study was partial and covered around 45 percent of Lebanon’s waters leaving 55 percent unassessed and hence, maybe, some additional resources. As for the volumes, these are announced under a probability condition which translates into 1/2 chances of having more volume of what was announced and 1/2 chances of having less volume of what was announced. As for the gas volumes, they are substantial for a country such as Lebanon; as a comparison, Egypt’s annual gas consumption is around 1.8 trillion cubic feet. But for the oil this is a relatively small amount in the deep offshore context.
Let’s move on to trying to explicit how these volumes might have been estimated. Firstly, and to be clear, what follows will be an assumption based on standard industry workflows; no detailed technical information has been made available to LOGI and hence, we are in no position to express any quality judgment on the work that has been done.
In the case of Lebanon it started by acquiring seismic data which means making some kind of ultrasound scan of the earth. Using this data, geoscience professionals come up with maps of underground structures that could trap hydrocarbons. Then they need to estimate two sets of parameters: the so-called petroleum system parameters which will basically translate in the chances of actually having trapped hydrocarbons in the structure and then the so-called reservoir parameters which will mainly translate into the volume of hydrocarbons (oil or gas) that could be trapped within the mapped structures. To put it simply: 1) what are my chances of getting hydrocarbons in the trap I mapped; and, 2) if hydrocarbons are present, what’s the amount I can expect? And given that there is no direct measurements, estimates are made based on previous experience in similar contexts combined with statistical and probabilistic approaches. That is why, in the statement, the announced volumes are associated to a probability.
Unfortunately, and without any relationship with the quality of the work, this can only be considered as a “best technical guess” based on available data and not as proof. In the world of geoscientists that carry out exploration work, “certainty” is almost never reached; when wells are drilled they only measure data at the well location. So field volumes and reservoir parameters will be narrowed down through time with the amount of wells drilled on any given field. Finally, as an order of magnitude, a well compared to the size of a field is like an apple compared to a skyscraper and you need to estimate what’s in the skyscraper from the information provided by the apple. Food for thought.