Research Challenges of Unconventional Shale Reservoirs

Daniel T. Georgi (Aramco Services Company)

In addition to the low, near zero permeability of unconventional organic rich shales reservoirs, that by definition require stimulation, the identification, evaluation and performance prediction are challenging. The challenges include:

• Identification of sweet spots (location of best places to drill)

• Quantification of gas in place

• Rock characterization (especially for successful stimulation)

• Prediction of Initial production, flow rates and ultimate recovery.

The industry has well defined, reasonably successful approaches for exploration and production of conventional reservoirs. Generally, Original Oil or Initial Gas In Place (OOIP or IGIP) are computed by measuring water saturation and computing the associated hydrocarbon saturation by subtracting Sw from unity (e.g. SH = 1 - Sw ). Sw is computed with an empirical equation and works well for most conventional reservoirs. However, the Archie equation is challenged in shaly-sand reservoirs, when the shale content exceeds 10 to 20%. In organic rich shales, it is difficult to measure even porosity and, hence, even if we could estimate the water saturation the hydrocarbon saturation cannot be computed by subtracting the volume of water from the total pore space. However, even if the water saturation is not relevant to the IGIP it does influence the mechanical properties of the clays and shale.

Knowing the gas in place is vital from an economic and reservoir engineering point of view. Hence, we are utilizing high resolution micro- and nano-CT as well as NMR and dielectric measurements to characterize the Organic Rich Shales. From the detailed pore level description, and point-by point wettability we need to estimate the gas in place, water saturation and matrix permeability. These data measured on the nano and micron scales need to be up-scaled to estimate the initial flow rates, production versus time and the ultimate recovery.

Back to Seminar Home Page

Last modified 22-November-2013 by website owner: NCNR (attn: )