历年GRE考试真题精选系列五
The energy contained in rock within the earth’scrust represents a nearly unlimited energy source, but
until recently commercial retrieval has been limited to
underground hot water and/or steam recovery sys-
tems. These systems have been developed in areas of
recent volcanic activity, where high rates of heat flow
cause visible eruption of water in the form of geysers
and hot springs. In other areas, however, hot rock
also exists near the surface but there is insufficient
water present to produce eruptive phenomena. Thus a
potential hot dry rock (HDR) reservoir exists when-
ever the amount of spontaneously produced geother-
mal fluid has been judged inadequate for existing
commercial systems.
As a result of the recent energy crisis, new con-
cepts for creating HDR recovery systems—which
involve drilling holes and connecting them to artificial
reservoirs placed deep within the crust—are being
developed. In all attempts to retrieve energy from
HDR’s, artificial stimulation will be required to create
either sufficient permeability or bounded flow paths
to facilitate the removal of heat by circulation of a
fluid over the surface of the rock.
The HDR resource base is generally defined to
include crustal rock that is hotter than 150℃, is at
depths less than ten kilometers, and can be drilled
with presently available equipment. Although wells
deeper than ten kilometers are technically feasible,
prevailing economic factors will obviously determine
the commercial feasibility of wells at such depths.
Rock temperatures as low as 100℃ may be useful for
space heating; however, for producing electricity,
temperatures greater than 200℃ are desirable.
The geothermal gradient, which specifically deter-
mines the depth of drilling required to reach a desired
temperature, is a major factor in the recoverability of
geothermal resources. Temperature gradient maps
generated from oil and gas well temperature-depth re-
cords kept by the American Association of Petroleum
Geologists suggest that tappable high-temperature
gradients are distributed all across the United States.
(There are many areas, however, for which no tem-
perature gradient records exist.)
Indications are that the HDR resource-base is very
large. If an average geothermal temperature gradient
of 22℃ per kilometer of depth is used, a staggering
13,000,000 quadrillion B. T. U.’s of total energy are
calculated to be contained in crustal rock to a ten-
kilometer depth in the United States. If we conserva-
tively estimate that only about 0.2 percent is recover-
able, we find a total that is comparable to the esti-
mated resource base of all the coal remaining in the
united States. The remaining problem is to balance
the economics of deeper, hotter, more costly wells and shallower, cooler, less expensive wells against the value of the final product, electricity and/or heat.
历年GRE考试真题精选系列五
21.The primary purpose of the passage is to(A) alert readers to the existence of HDR’s as
an available energy source
(B) document the challenges that have been
surmounted in the effort to recover
energy from HDR’s
(C) warn the users of coal and oil that HDR’s
are not an economically feasible alternative
(D) encourage the use of new techniques for the
recovery of energy from underground hot
water and steam
(E) urge consumers to demand quicker devel-
opment of HDR resources for the
production of energy
22. The passage would be most likely to appear in a
(A) petrological research report focused on the
history of temperature-depth records in
the United States
(B) congressional report urging the conserva-
tion of oil and natural gas reserves in the
United States
(C) technical journal article concerned with the
recoverability of newly identified energy
sources
(D) consumer report describing the extent and
accessibility of remaining coal resources
(E) pamphlet designed to introduce home-
owners to the advantages of HDR
space-heating systems
23. According to the passage, an average geother-
mal gradient of 22℃ per kilometer of depth can
be used to
(A) balance the economics of HDR energy
retrieval against that of underground hot
water or steam recovery systems
(B) determine the amount of energy that will be
used for space heating in the United
States
(C) provide comparisons between hot water
and HDR energy sources in the United
States
(D) revise the estimates on the extent of
remaining coal resources in the United
States
(E) estimate the total HDR resource base in
the United States
24. It can be inferred from the passage that the
availability of temperature-depth records for
any specific area in the united States depends
primarily on the
(A) possibility that HDR’s may be found in
that area
(B) existence of previous attempts to obtain oil
or gas in that area
(C) history of successful hot water or steam
recovery efforts in that area
(D) failure of inhabitants to conserve oil or gas
reserves in that area
(E) use of coal as a substitute for oil or gas in
that area
历年GRE考试真题精选系列五
25. According to the passage, in all HDR recoverysystems fluid will be necessary in order to allow
(A) sufficient permeability
(B) artificial stimulation
(C) drilling of holes
(D) construction of reservoirs
(E) transfer of heat
26. According to the passage, if the average geother-
mal gradient in an area is 22℃ per kilometer of
depth, which of the following can be reliably
predicted?
Ⅰ.The temperature at the base of a 10-kilo-
meter well will be sufficient for the
production of electricity.
Ⅱ Drilling of wells deeper than 10 kilo-
meters will be economically feasible.
Ⅲ Insufficient water is present to produce
eruptive phenomena
(A) Ⅰ only
(B) Ⅱ only
(C) Ⅰ and Ⅱ only
(D) Ⅱ and Ⅲ only
(E) Ⅰ.Ⅱ. and Ⅲ
27. Which of the following would be the most ap-
propriate title for the passage?
(A) Energy from Waters Sources: The
Feasibility of Commercial System
(B) Geothermal Energy Retrieval: Volcanic
Activity and Hot Dry Rocks
(C) Energy Underground: Geothermal Sources
Give Way to Fossil Fuels
(D) Tappable Energy for America’s Future:
Hot Dry Rocks
(E) High Geothermal Gradients in the United
States: Myth or Reality?
28. INCENTIVE:
(A) agreement
(B) doubt
(C) deterrent
(D) complement
(E) negotiation
29. COMPASSION:
(A) indifference
(B) chastity
(C) sobriety
(D) timidity
(E) distress
30. AGGRAVATE:
(A) disperse
(B) alleviate
(C) heed
(D) render bland
(E) make equal
31. IMPLAUSIBLE:
(A) admirable
(B) believable
(C) controllable
(D) extremely practical
(E) carefully considered
32. ANTIPATHY:
(A) decorum
(B) benevolence
(C) proximity
(D) free will
(E) high spirits
历年GRE考试真题精选系列五
33. EXTRICATE:(A) complicate
(B) absorb
(C) induct
(D) entitle
(E) entangle
34. MORDANT:
(A) uninteresting
(B) supine
(C) genial
(D) given to silence
(E) highly emphatic
35. GLUT:
(A) dearth
(B) limit
(C) void
(D) supply
(E) drain
36. DISCRETE:
(A) continuous
(B) magnified
(C) tenuous
(D) contradictory
(E) ambivalent
37. PROPITIATE:
(A) arbitrate
(B) clarify
(C) seek refuge
(D) arouse hostility
(E) disagree violently
38. ENFRANCHISE:
(A) ensconce
(B) engage
(C) enfetter
(D) deflect
(E) depose </p>28.C 29.A 30.B 31.B 32.B 33.E 34.C 35.A 36.A 37.D 38.C
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