(589f) Enhancing Oil Recovery from Shales: Reservoir-Specific and Economical Approach

Enhancing
Oil Recovery from Shales: Reservoir-Specific and Economical Approach

Harpreet Singh

National Energy Technology Laboratory, Morgantown,
WV

Ultra-tight hydrocarbon
reservoirs like shales present two major challenges to enhance oil recovery
from these formations: i) negligible fluid movement outside the fractures
limits the possibility of having an injection well to sweep the fluids towards
the production wells, ii) the wettability of these reservoirs tend to be
oil-wet that keeps the oil in the smallest pores compared to gas or water, making
it difficult to drive most of the oil out. Oil rates from these formations can
decline by a half in just first year due to their low permeability, which also leads
to large amount of oil remaining in smaller pores that is not able to move out.
Declining oil rates from oil-rich shales in a low oil-price environment would
benefit by enhancing the oil recovery from these formations if implemented in
an economically competitive way.

To solve this coupled
challenge of enhancing oil recovery while being economically prudent, this
study presents field scale simulations comparing the impact of miscible gas
injection and surfactant injection on enhancing oil recovery by a novel, but
economical, scheme of injection/production from the same well using different hydraulic-fractures.
This injection/production scheme has economical advantage over huff-n-puff scheme
such that there is no lag-period between injection and production. Oil recovery
by miscible gas injection or by surfactant injection follows different physical
mechanisms, where the former works by swelling the oil through miscibility and
the latter works by reducing the interfacial tension between oil and water. Suitability
of each method is based on reservoir-specific parameters such as pore pressure
and the in-situ brine salinity, besides the investment/infrastructure required
for each method. This study may help motivate further research in this area
that will benefit the shale industry by enhancing oil rates through an
economically competitive way.