Webcast – Rock Pore Typing a Tight Gas Sand Reservoir

Emerson Paradigm provided us the opportunity to present a live webcast on the 19th April 2018. This topic was first presented at the New Zealand Petroleum Conference 2018 and featured in the recent Virtual Petrophysics technical post, VPPS Byte 8. This Virtual Lecture Series webcast is now available for on demand viewing via GoToWebinar. You will be asked to complete registration information which then passes you through to the webcast.

ABSTRACT

Pore Typing A Tight Gas Sand Reservoir – The Mangahewa

Scott Dodge, Virtual Petrophysics Director and Principal

Rock pore typing technology is developed for the tight gas sand Mangahewa reservoirs in the Taranaki basin to predict reservoir flow performance. The technology of rock pore typing provides the means to accurately predict permeability and well producibility in these highly modified diagenetic sandstones that show no correlation of porosity and permeability.

This diagenesis adversely modifies the pore system creating quartz cementation that reduces primary porosity as well as additional micro porosity associated with diagenetic clays and leached feldspar grains. Thus, a complex pore system is created owing to mineral diagenesis accelerated by abnormal pressures and temperatures.

Characterising the pore system is performed using laboratory MICP (Mercury Injection Capillary Pressure) and NMR (Nuclear Magnetic Resonance) on core plugs. MICP measures the pore volumes accessible by pore restrictions and NMR measures the surface to volume relationship, or pore sizes that are accessed by MICP. The fundamental physics allow us to describe the pore system in terms of permeability as a function of pore size. Pore typing is accomplished without the need for lithology or mineralogy information to develop the permeability model.

This work shows that the laboratory NMR pore size distribution provides similar information as MICP and is used in a Darcy permeability model to quantify the distribution of reservoir permeability. Discrete pore types are identified to build a Petrophysical rock pore type catalogue for this reservoir. The pore type model is applied to the NMR wireline log to provide a continuous measure of pore types in wellbores.