CARBONATE reservoirs contain a significant proportion of the world’s remaining oil&gas reserves and therefore their relative importance is expected to dramatically increase during the first half of this century.
However, the highly complex structure of these reservoirs presents major technical challenges.
ITF, the Aberdeen-based technology facilitator, has issued a call for proposals that it hopes will help to improve the industry’s understanding of carbonate reservoirs and, consequently, allow production from them to be maximised.
Some sources estimate that more than 60% of the world’s remaining oil and 40% of gas reserves in place are located in carbonate reservoirs – for example, offshore Mauritania, where early drilling into carbonate reefs has both frustrated and tantalised exploration licence holders.
Carbonate reservoirs are a more complex proposition than their sandstone counterparts, principally because of their more heterogeneous nature.
This heterogeneity can occur at the micron/pore-space scale, through rock grain and texture to heterogeneity measured in terms of kilometres.
It is a result of a number of factors, including the chemical and biological origin of the material and its depositional environment, as well as the subsequent geological processes such as compaction, and faulting and fracture formation.
Carbonates are also readily susceptible to chemical change following their deposition, which increases their complexity.
Explaining the background to the call, ITF’s subsurface technology analyst, Colin Sanderson, said: “Although carbonate reservoirs make a big contribution to global hydrocarbon supply – many of the big Middle Eastern fields are carbonate in nature – they present different challenges in comparison to sandstone reservoirs, where recovery factors are generally higher.
“Because they account for such a large proportion of remaining reserves, it will become increasingly important that the industry has a better understanding of carbonate reservoirs if we are to maximise production from them and meet future energy demand.”
The ITF’s call invites proposers to focus on one or more of eight aspects of improved understanding of carbonate reservoirs: rock typing and upscaling; permeability prediction; microporosity; seismic characteristics of carbonates; dolomite geometries; fractures; chalk, and reservoir engineering.
Sanderson, said: “Carbonate reservoirs occur all around the world, so this is a topic of fundamental importance to the industry.”
