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Prominent Activity and
Technology Trends
Stimulation of Watered-out
Inactive/Marginal Wells in Louisiana with Dual
Completions
The concept and
technology for revaluation of marginal and inactive
wells associated with considerable reserves but
non-productive due to water problems in reservoirs with
strong water drive are considered prominent topics for
Louisiana. The technology is presently being developed
at LSU and the program’s information is in the process
of being transferred to oilfield operators in the State.
The program’s ultimate goal is successful deployment of
a novel technology for re-building productivity
potential of aging oilfield infrastructure in the State.
There are
reportedly 34,355 inactive wells in Louisiana. A great
number of these wells are marginal producers and they
are idling, not because the resources have been
depleted, but because they have become unprofitable due
to excessive water production. For small operators in
Louisiana, produced water is the single most important
factor controlling economics of their business.
Excessive water production makes the whole economics of
reservoir/well management vulnerable to ever fluctuating
crude oil prices. In the past, in response to low oil
prices, numerous low-producing wells have been shut-in
as they became uneconomical. Recent dramatic increase of
world oil prices and steadily growing demand for energy
require revaluation of the whole aging infrastructure of
wells in the state and potential for recuperating their
productivity after recompleting the wells with downhole
water drainage (water sink) installations. A dual well
completion technique with downhole water sink (DWS) has
been explained and discussed in past workshops. The
technique has been field tested in vertical wells and
extensively studied for various applications. It has
potential for producing oil from wells that have been
severely damaged by water. It may also produce oil from
thin oil pay zones underlain by a strong water column -
unrecoverable by conventional wells.
Case studies have shown
that combination of water flooding with DWS may improve
sweep efficiency and recovery without changing the size
or pattern of floods, i.e. without drilling new wells.
Production of water-drive reservoirs in Louisiana has
left considerable petroleum reserves un-recovered due to
various mechanisms commonly known as reservoir
compartmentalization, by-passing caused either by
mobility or gravity contrasts, under-running, coning,
channeling, and viscous fingering. The resulting
by-passed oil may range from 40 to 90 percent of the oil
in place dependent upon fluid properties and thickness
of the pay zone. Workshops regarding this situation have
help operators understand how the oil remains
unrecovered in reservoirs with bottom or side-water
drive. Simulation models show that the combined effect
of water underrunning, salient and coning may cause
by-passing of large volumes of oil while making a well
inactive due to high water cut. Additional studies also
addressed the critical problem of identifying reserves
that can be recovered without drilling new wells, i.e.
the reserves that can be produced by existing shut-in
wells or marginal active wells. Although this work is
still in progress a method and software for preliminary
screening well/reservoir candidates has been developed.
The method employs expert system technique and search
analysis software coupled with the Louisiana oilfield
data base SONRIS.
Conasauga Shale Gas Play In
Alabama
Development of the Conasauga shale gas play in northeast
Alabama continues. With the exception of one well, all
development has been in St. Clair County. The Alabama
Oil & Gas Board (Board) established the Big Canoe Creek
Field, the first shale gas field in Alabama, on 320-acre
drilling units. Dominion Black Warrior Basin, Inc.
(Dominion) has drilled 13 wells there, ranging in depth
from 3,412 feet to 9,023 feet. Initial gas flow rates
reported to the Board have ranged from 26 – 233 Mcfd.
Dominion continues to drill. Drilling in the field has
been challenging due to unique geologic conditions
encountered. Problems include lost circulation, swelling
of clays, and well bore drift.
There has been other Conasauga Shale drilling. Energen
Resources Corporation drilled a couple wells in 2006 in
St. Clair County outside the boundaries of the Big Canoe
Creek Field and one in Etowah County. Two of the three
wells were plugged and abandoned, one due to drilling
problems. No test results have been reported for the
third well.
Rock units are highly folded and faulted, making
geologic interpretations difficult. Thrust faults, which
are low angle reverse faults, are the principle faulting
mechanism. These faults can cause an exaggerated
thickness of the Conasauga as a result of stacking of
faulted strata.
View full article on website of Alabama Geological
Survey/Alabama Oil & Gas Board (http://www.gsa.state.al.us/documents/misc_ogb/Overview_jun2007.pdf).
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