Net Identification: Techniques to Establish a Reliable Net to Gross Estimate

communication and quantification. Petrophysically, net has to be communicated in terms of permeability, the parameter which details a rock’s ability to flow gas. Permeability is the only parameter that comes close to describing the ability to flow gas or contribute energy. The more data available on permeability and net, the better the reservoir understanding will be and the easier it will be to explain reservoir processes. Net reservoir can be assessed by considering results from a number of investigative techniques. Important considerations include; over the life of the field will pressure from low permeable rocks contribute energy to the system, does the special core analysis data from drainage and the imbibition cycles indicate that there is movable fluid down to the permeability cut-off. It is important to quantify the impact of using a different cut-off on NtG. Consider if other traditional net indicators such as volume of shale or porosity either have uncertainty considered too large or are not representative of the permeable reservoir accurately. Net sensitivity can also be investigated by looking at the Equivalent Hydrocarbon Column (the sum of the product of porosity by gas saturation by net reservoir column). Consider the fraction of the reservoir rock that exists between specified permeability cut-offs. Investigate how sensitive the NtG is to the assigned permeability cut-off and assess the volume impact on recovery.