(GP/GT) for Additional Water Supply in the Lower Rio Grande

1lI-18
Data for the injection flow rates and pressures and the receiving aquifer's performance need to be
assessed more completely. Data useful for estimating total quantity of fluids received by the reservoir
appear not to be generally available. However, secondary recovery data from the Railroad Commission
indicates that injection pressures vary from atmospheric to 2,400 psia at wellhead. Wellhead flow rates
in secondary recovery operations are reported to range from 75 to 10,000 BBLlDay with the majority
under 5,000 BBLlDay. Accumulated injection ranges up to 85 x 1(1 BBL injected since 1936. The
secondary recovery data indicates only what injection rates and accumulated storage volumes have been
achieved. As oil reservoir engineering will prevail, actual rates and storage volumes may be very far
from those achievable or optimum for fluid disposal. The pressures used may be more indicative of those
required for disposal, although the average porosities and permeabilities of the traps or structures, from
which petroleum production derives, may not be indicative of those properties in sand bodies in large
blocks.
The data available from oil and gas operations does not provide sufficient detail or evidence for assessing
the potential of subsurface disposal because most of these are proprietary.
SPECIALIST OPINION - SUBSURFACE DISPOSAL
Two specialist organizations have provided opinion concerning the potential for subsurface disposal. A
drilling and services organization considers that injection of 20,000 BBLlDay into 5 - 6,000 foot wells
of reasonable cost is possible. Such wells might inject up to 400,000 BBLlDay into a large reservoir
using 20 wells. If operated for 15 years, the receiving reservoir will need to store 2.2 x 1()I' BBL. (") A
second specialist organization notes that up to 1,000 gallons per minute (35,000 BBLlDay) can be injected
into a 5,000 to 6,OOO-foot well. Such a well would have a good-sized injection tubing terminating in a
gravel-packed, under-reamed injection section.
The latter organization pointed out that, in order to determine the potential for subsurface disposal, the
following steps are necessary:
(1) Geological mapping of the subsurface sands using well log data.
(2) Determination of porosity and permeability using core data and well log data.
(3) Reservoir engineering calculations.
(4) Preliminary design of injection wells and injection well surface equipment.
(5) Slim hole boring program with coring, reservoir fluid sampling, and production testing
programs.
(*) 2.2 Billion Barrels or Ca. 2,700,000 acre-feet.