By Luke Stoeckel with edits by Tom Sturman, Richard Yeomans

In order to evaluate reservoir properties we need to use the information and methods shown in collaboration to get an accurate representation of the reservoir system and the subsurface. We can physically test the properties of the rock with core logging and lab tests. It is possible to 'ground-truth' these results we see in the petrophysical logs and correlate with similar observations in other wells without core only petrophysical logs. We use empirical relationships with information from the petrophysical logs to evaluate porosity, density, and quality of hydrocarbons. The petrophysical logs are also used to visually estimate the depths at which hydrocarbons occur and the content of hydrogen they contain giving indication of they’re saturation. When correlated correctly accurate representations of the subsurface can be constructed and modelled which reduces the risk of producing a well with possible flow impedances or reduced quality of hydrocarbon.

Even though it is accepted that physical core samples are very accurate we need to understand they are very expensive to acquire and take a lot of drilling time. This is why geophysical logs are run because they are faster, cheaper and the understanding that we now have of rock properties we can accurately use the information to construct a subsurface model. Even though geophysical logging is very efficient and relatively quick there is always the need to increase logging speed and resolution to reduce the cost of logging whilst still maintaining the accuracy need to model the reservoir. In coring there is also development of quicker retrieval times of the core sample. One way of doing this is by using a slick line that attaches to the core barrel then pulls the core barrel up and out of hole, negating the need to pull the entire drill string every time we wish to get the sample. Another way of increasing the speed of retrieving core that is being developed at the moment is spiralled inserts inside the drill string which essentially spirals the core up the drill string to the surface. However this is in the very early stages of development.