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Information Only
XI-26
The authigenic clays present within depositional pore space may affect
secondary recovery operations in two ways. First, they reduce penneability. Second,
some chlorites are sensitive to changes in the chemistry of formation waters (Walling
et a!., 1992); injection of water with a significant difference in pH from native
fonnation waters may cause retrogression of the chlorite and subsequent migration of
clays or fonnation of penneability-reducing gels.
These deleterious effects of water injection can be mitigated or even eliminated
by using Delaware fonnation waters for waterflood injection. These waters should be
approximately in equilibrium with reservoir mineralogy. Finally, the analogous
waterfloods that were used to derive a figure for ultimate secondary recovery are in
Delaware reservoirs and they have been successfully waterflooded. TIlls is a strong
indication that Brushy Canyon reservoifs in the vicinity of WIPP can be successfully
waterflooded. The recent initiation of a waterflood in the Avalon Brushy Canyon pool
and Worthington's (1994) calculation of a 100% increase in oil recovery at Shugart
East support the conclusion that waterflooding the Brushy Canyon in the vicinity of
WIPP will be technically possible and economically feasible.
The decision on whether or not to initiate waterfloods of Delaware oil pools in
the vicinity of WIPP will rest primarily with the operators that produce from these
pools. Many factors detennine whether or not an operator will initiate a waterflood.
These factors are mostly related to economics and include: 1) the ultimate secondary
recovery expected from a waterflood; 2) costs associated with a waterflood, including
the drilling of injection wells; 3) construction of surface facilities and injection
facilities; 4) the cost of obtaining and processing injection water; 5) the cost of brine
disposal, including the cost of drilling and equipping disposal wells; and 6) revenues
obtained from oil and gas production (detennined by production rates, oil prices, and
to a lesser extent gas prices).
Even if a waterflood project is expected to be economically successful, it may
not be initiated because of the limited financial resources that all operating companies
face. Expected return on investment from a watert100d project must be compared to
expected return on investment from other ventures; a waterflood will be initiated only
if expected return on investment is favorable. The technical and economic viability of
waterfloods in the vicinity of WIPP will be compared to the technical and economic
viability of Ventu1eS conducted elsewhere.
It must be emphasized that the oil estimated to be available through secondary
recovery (Tables 11-13) will be produced only 'if waterfloods are initiated while
primary production is in progress. Once wells that produce by primary methods have
been abandoned and plugged, then they will not be available for secondary recovery
operations. The high cost of reentering plugged wells, or of drilling replacement
wells, may render secondary recovery uneconomic. the presence of operable wells
used for primary recovery is essential for the economic viability of secondary