Well Testing Study Questions- PetroBowl

1. PETROBOWL- WELL TESTING
1. acidizing - The pumping of acid into the wellbore to remove near-
well formation damage and other damaging substances. This
procedure commonly enhances production by increasing the
effective well radius. When performed at pressures above the
pressure required to fracture the formation, the procedure is often
referred to as acid fracturing.
2. adjusted flow time - The approximated flow time used for a well-
test analysis when the flow rate varies before or during the test
period.
3. adjusted flow time - t = cumulative well production since the last
extended shut-in period divided by the flow rate just before a well
is shut in for a buildup test.
4. afterflow - The flow associated with wellbore storage following a
surface shut-in.
5. anisotropic formation - A formation with directionally dependent
properties.
6. annulus - The space between two concentric pipe strings, such as
between the production tubing and casing in a well.
7. average reservoir pressure - The pressure that would be obtained if
all fluid motion ceases in a given volume of reservoir. It also is the
pressure to which a well will ultimately rise if shut in for an
infinite period.
8. back flow - Fluid flow in the borehole from one zone into another
in response to pressure differences between the zones
9. bilinear flow - This flow regime is seen most commonly in tests of
hydraulically fractured wells and occurs for finite-conductivity
fracture where linear flow exists both in the fracture and to the
fracture plane. This flow regime is recognized as a 1/4 slope in the
pressure derivative on the log-log diagnostic plot.
10. bottomhole pressure - The pressure measured in a well at or
near the depth of the producing formation.
11. bottomhole shut in - A well shut in slightly above the
producing formation by use of special downhole tools containing a
valve that can be preprogrammed or controlled from the surface.

2. 12. boundary conditions - The flux (flow rate) or pressure states
assigned to the theoretical boundaries used in developing and
solving the differential equations that apply to well testing and in
specifying a model to match to pressure-transient data.
13. bounded reservoir - Reservoirs with sealed or apparent outer
boundaries that result in pressure depletion.
14. bubble point - The pressure and temperature conditions at
which the first bubble of gas comes out of solution in oil.
15. buildup test - The measurement and analysis of (usually)
bottomhole pressure data acquired after a producing well is shut in.
16. closed chamber testing - A type of drillstem testing
conducted with the drillstring in the hole and the surface valve
closed to create a closed chamber of known volume into which the
reservoir fluid can flow.
17. closed in well - A well with a valve closed to halt production.
18. To allow stabilization - Why are wells shut/closed-in prior to
build-up/drawdown testing?
19. commercial rate - A rate, or production volume, sufficient to
satisfy project economics.
20. commingled completion - A wellbore completed in two or
more reservoir zones that are not in hydraulic communication in
the reservoir. Backflow is common during rate cutbacks and
buildup tests on these types of completions.
21. compressibility - The relative change in fluid volume related
to a unit change in pressure. This is usually expressed as volume
change per unit volume of fluid per psi of pressure change.
22. condensate - Liquid phase occurring in gas condensate
reservoirs when the pressure is below the dewpoint pressure.
23. constant rate - A flow rate that does not change appreciably
during a test period
24. continuity equation - Material balance expressed in a
differential equation.
25. convolution - A mathematical operation that uses downhole
flow-rate measurements to transform bottomhole pressure

3. measurements distorted by variable rates to an interpretable
transient.
26. convolve - To mathematically transform bottomhole pressure
measurements distorted by variable rates to an interpretable
transient.
27. correcting pressure to a datum - A procedure for correcting
pressure measurements in a reservoir to a common datum level.
This is not required for calculating kh, permeability thickness, and
s, skin effect, but is required for determining average reservoir
pressures
28. cushion - A fluid column (usually water or nitrogen) put in
the drillstem to provide the desired backpressure at the start of a
drillstem test.
29. Darcy units - Units of atm, cm3/s, cp and D, as originally
used by Darcy in flow experiments.
30. atm, cm3/s, cp and D - List the units originally used by Darcy
in his flow experiments
31. datum level - The depth to which pressures are corrected to
adjust for differences in elevations at which pressure
measurements are made in different wells or at different times.
32. deconvolution - A mathematical operation that uses
downhole flow-rate measurements to transform bottomhole
pressure measurements distorted by variable rates to an
interpretable transient. This operation does not assume a particular
model for the pressure-transient response.
33. depletion - The drop in reservoir pressure or hydrocarbon
reserves resulting from production of reservoir fluids.
34. dew point - The pressure at which the first condensate liquid
comes out of solution in a gas condensate.
35. The formation of liquid hydrocarbons in a gas reservoir as
the pressure in the reservoir decreases below dewpoint pressure
during production. It is called retrograde because some of the gas
condenses into a liquid under isothermal conditions instead of
expanding or vaporizing when pressure is decreased. - For 20
points, explain what is meant by retrograde behavior

4. 36. diffusion equation - A fundamental differential equation
obtained by combining the continuity equation, flow law and
equation of state. Most of the mathematics of well testing were
derived from solutions of this equation, which was originally
developed for the study of heat transfer.
37. Permeability that varies with direction of flow through the
porous medium. - Define directional permeability
38. drainage area - The reservoir area or volume drained by the
well.
39. drainage volume - The portion of the volume of a reservoir
drained by a well.
40. drawdown test - The measurement and analysis of pressure
data taken after a well is put on production, either initially or
following an extended shut-in period.
41. drillstem test - Usually conducted with the drillstring still in
the hole these tests use a downhole shut-in tool that allows the well
to be opened and closed at the bottom of the hole with a surface-
actuated valve.
42. drillstem test - What does DST stand for?
43. DST pressure chart - The characteristic plot of pressure
versus time obtained from the mechanical recording of pressure
gauges in a DST tool.
44. dual completion - A wellbore with simultaneous production
of hydrocarbons, water or both from more than one producing
zone.
45. dual permeability reservoir - A dual-porosity reservoir in
which flow to the well occurs in both primary and secondary
porosity systems.
46. dual porosity reservoir - A rock characterized by primary
porosity from original deposition and secondary porosity from
some other mechanism, and in which all flow to the well
effectively occurs in one porosity system, and most of the fluid is
stored in the other.
47. early time transient data - The data observed before the start
of radial flow (middle-time transient data).

5. 48. effective wellbore radius - The value of wellbore radius that
produces equivalent results to those obtained using a skin factor of
zero.
49. equation of state - An equation that specifies fluid density as
a function of pressure and temperature.
50. fall off test - The measurement and analysis of pressure data
taken after an injection well is shut in.
51. final flow period - The final flow sequence in a drillstem test.
52. The production rate just prior to shut-in for a buildup test. -
In relation to well testing, what is meant by final flow rate?
53. final flowing pressure - The pressure determined at the
formation face just prior to shut-in for a buildup test. This value is
required to determine the skin effect.
54. final shut in period - The final buildup sequence in a
drillstem test.
55. finite conductivity fracture - A planar crack penetrated by a
well or propagated from a well by hydraulic fracturing with
nonzero pressure drop in the fracture during production.
56. finite wellbore solution - The solution to the diffusion
equation that results when the well (inner) boundary condition is
treated as a cylinder of finite radius instead of treating the well as a
line source.
57. flow after flow tests - Gas-well tests, often required by law,
in which one flow rate immediately follows another, with each
flow period reaching stabilized flow.
58. flow efficiency - The value that results when the actual
productivity index is divided by the productivity index predicted
from Darcy's law. Bonus: what value of flow efficiency indicates
damage/stimulation?
59. flow period - Part of a well test when the well is flowing. It is
usually specified prior to tests to ensure that a stable flow situation
has been reached or so that reservoir properties can be calculated
60. flow regime - The predominant flow geometry reflected in a
pressure-transient response that is most easily recognized in the
log-log presentation of the pressure-change derivative.

6. 61. Radial = flat derivative. Spherical = -ve 1/2 slope derivative.
Linear = +ve half slope derivative. Bilinear = +ve 1/4 slope
derivative. - Describe the characteristic shapes of radial, spherical,
linear and bi-linear flow on a log-log derivative plot
62. flow unit - A rock volume with identifiable fluid flow
characteristics that can be modeled, including heterogeneity or
anisotropy.
63. flowing pressure - The pressure determined at the formation
face during the flowing periods of a well test.
64. flowing well - A well in which the formation pressure is
sufficient to produce oil at a commercial rate without requiring a
pump.
65. fluid compressibility - The relative change in fluid volume
related to a unit change in pressure. This is usually expressed as
volume change per unit volume of fluid per psi of pressure change.
66. formation fracture pressure - Pressure above which injection
of fluids will cause the rock formation to fracture hydraulically.
67. fracture conductivity - Product of fracture permeability times
fracture width for a finite-conductivity fracture.
68. fracture gradient - The factor used to determine formation
fracturing pressure as a function of well depth in units of psi/ft.
69. fracture half-length - Radial distance from the wellbore to the
outer tip of a fracture penetrated by the well or propagated from
the well by hydraulic fracturing.
70. fractured well analysis - Analysis of a well that passes
through a natural fracture or that has been hydraulically fractured.
71. xf/2 (half the fracture half length) - Apparent wellbore radius
for a fractured well is equal to what?
72. free gas - Gas that exists in the reservoir in the gaseous phase
rather than in solution.
73. gas condensate - Hydrocarbon liquid dissolved in saturated
natural gas that comes out of solution when the pressure drops
below the dewpoint.

7. 74. The factor z, defined by the real (nonideal) gas equation of
state, pV = znRT. - What is gas deviation factor and in which
equation is it used?
75. gas formation volume factor - Gas volume at reservoir
conditions divided by gas volume at standard conditions.
76. gas gravity (molecular weight of air is 28.97g/cc) -
Hydrocarbon gas density expressed as the ratio of the molecular
weight of the gas to the molecular weight of air. Bonus: what is the
molecular weight of air?
77. gas oil ratio - The ratio of produced gas to produced oil,
commonly abbreviated GOR.
78. gas solubility factor - The volume of gas (at standard
conditions) liberated from a volume of oil (at standard conditions).
79. gas well - A producing well with natural gas as the primary
commercial product.
80. gas well deliverability - The calculated or measured rate a
gas well will produce for a given bottomhole or wellhead pressure.
81. heterogeneous formation - Formation with rock properties
changing with location in the reservoir
82. homogeneous formation - Formation with rock properties
that do not change with location in the reservoir.
83. Horner slope - The slope of the chosen straight-line section
of a Horner plot. It is used to determine permeability thickness, kh,
of the producing zone in the vicinity of the wellbore.
84. humping - The abnormal behavior in a buildup curve caused
by phase redistribution in a wellbore. This behavior is most
noticeable in oil wells producing a substantial amount of gas and
having a substantial skin effect. Analysis of buildup curves for
wells exhibiting this behavior can be difficult or impossible
85. hydrogen sulfide - An extraordinarily poisonous gas with a
molecular formula of H2S. At low concentrations, H2S has the
odor of rotten eggs, but at higher, lethal concentrations, it is
odorless
86. ideal gas - A gas defined by the fundamental equation of state
PV=nRT

8. 87. image well - A virtual well used to mathematically create the
effect of a flow barrier.
88. impermeable barrier - A single, impenetrable barrier to fluid
flow in a reservoir that causes a change of a factor of two in the
slope of buildup or drawdown curves.
89. infinite acting radial flow - Flow into the wellbore during a
well test, from a reservoir with no apparent outer boundary limit
affecting fluid flow during the test period
90. A reservoir with no apparent outer boundary limit affecting
fluid flow during a test period. - In relation to well testing, what is
an infinite acting reservoir?
91. infinite conductivity fracture - A planar crack penetrated by a
well or propagated from a well by hydraulic fracturing with zero
pressure drop in the fracture during production.
92. initial flow period - A short flow period at the beginning of a
drillstem test. This period is followed immediately by a longer
shut-in period to allow the pressure to closely approach initial
reservoir pressure.
93. initial reservoir pressure - The reservoir pressure measured in
a discovery well, usually referred to as pi. This value is necessary
for many reservoir engineering calculations, such as reserve
determination.
94. initial shut in period - The comparatively short shut-in period
following the initial flow period of a drillstem test.
95. injection well testing - The testing of wells in which fluid is
being injected into the reservoir. The most common type of test is
a falloff test, in which injection is halted and the pressure decline is
measured as a function of time.
96. interference testing - The pressure variation with time
recorded in observation wells resulting from changes in rates in
production or injection wells.
97. A multirate test designed as a series of drawdown and
buildup sequences at different drawdown flow rates, with each
drawdown of the same duration and each buildup reaching

9. stabilization at the same pressure as at the start of the test. - What
is an isochronal test?
98. isotropic formation - A type of formation whose rock
properties are the same in all directions.
99. Permeability that is the same in all directions. - What is
meant by sotropic permeability?
100. kh - permeability.thickness product - This product is the
primary finding of buildup and drawdown tests and is a key factor
in the flow potential of a well. It is used for a large number of
reservoir engineering calculations such as prediction of future
performance, secondary and tertiary recovery potential, and
potential success of well-stimulation procedures.
101. late time transient data - The portion of the pressure transient
occurring after radial flow. Analysis provides characterization of
outer boundaries such as faults or fluid contacts.
102. layer - A slab of reservoir rock bounded above and below by
another layer in vertical hydraulic communication.
103. layered reservoir testing - An advanced testing technique
using a combination of transient-rate and pressure measurements
and stabilized flow profiles to determine permeability and skin for
each of several layers commingled in a well.
104. limited entry - A completion with only a portion of the
productive interval open to flow, either by design or as a result of
damage. Results in partial penetration.
105. line source solution - The solution to differential equations
treating the well as a vertical line through a porous medium.
106. linear flow - A flow regime characterized by parallel flow
lines in the reservoir. This results from flow to a fracture or a long
horizontal well, or from flow in an elongated reservoir, such as a
fluvial channel, or as a formation bounded by parallel faults. It is
recognized as a +1/2 slope in the pressure derivative on the log-log
diagnostic plot. Its presence enables determination of the fracture
half-length or the channel or reservoir width, if permeability can be
determined independently.

10. 107. liquid level - The depth at which the first liquid is found in a
well.
108. material balance - An expression for conservation of mass
governed by the observation that the amount of mass leaving a
control volume is equal to the amount of mass entering the volume
minus the amount of mass accumulated in the volume.
109. middle time transient data - A common term for the infinite-
acting radial flow regime. This portion of the pressure-transient
response is between wellbore-dominated flow regimes in the early-
time transient data and boundary-dominated flow regimes in the
late-time transient data.
110. modified isochronal test - A type of deliverability test
conducted in gas wells to generate a stabilized gas deliverability
curve (IPR).
111. modified isochronal test - A multirate test designed as a
series of drawdown and buildup sequences at different drawdown
flow rates, with each drawdown and buildup of the same duration.
The purpose of the test is to determine well deliverability, and this
type of test is most commonly done in gas wells.
112. multiphase flow - The simultaneous flow of more than one
fluid phase through a porous medium.
113. False - well test analysis generally assumes single phase flow
- True or false - most well test analysis assumes multiphase flow?
114. multiple rate tests - Tests conducted at a series of different
flow rates for the purpose of determining well deliverability,
typically in gas wells where non-Darcy flow near the well results
in a rate-dependent skin effect.
115. naturally flowing well - A well in which the formation
pressure is sufficient to produce oil at a commercial rate without
requiring a pump.
116. non-Darcy flow - Fluid flow that deviates from Darcy's law,
which assumes laminar flow in the formation. Typically observed
in high-rate gas wells when the flow converging to the wellbore
reaches flow velocities exceeding the Reynolds number for laminar
or Darcy flow, and results in turbulent flow. Since most of the

11. turbulent flow takes place near the wellbore in producing
formations, the effect of this flow is a rate-dependent skin effect.
117. nonideal gas - A gas described by an equation of state of the
form pV = znRT, where z is the gas deviation factor dependent on
pressure, temperature and gas composition.
118. oil formation volume factor - Oil and dissolved gas volume at
reservoir conditions divided by oil volume at standard conditions.
119. oil well - A producing well with oil as its primary
commercial product.
120. partial completion - Completion of or flow from less than the
entire producing interval. This situation causes a near-well flow
constriction that results in a positive skin effect in a well-test
analysis.
121. partial penetration - An incompletely drilled portion of the
productive interval.
122. Henry Darcy - Who showed that the common mathematics of
heat transfer could be modified to adequately describe fluid flow in
porous media?
123. permeability thickness - This product is the primary finding
of buildup and drawdown tests and is a key factor in the flow
potential of a well.
124. phase redistribution - A pressure phenomenon caused in a
wellbore by rise of gas and fall of liquids trapped in a wellbore
after a surface shut-in. This phenomenon can cause a "hump" in
the buildup curve, and frequently leads to incorrect analysis of
buildup test results because the entire early portion of the transient
is adversely affected by this pressure response.
125. pore-pressure gradient - A change in pore pressure as a
function of distance. This can refer to radial change in pore
pressure with distance from the well (which can be calculated from
well-test analysis results) or to change in pore pressure with depth
126. porous medium - A rock or soil with interconnected pores
that permit flow of fluids through the medium.

12. 127. pressure - The force distributed over a surface, usually
measured in pounds force per square inch, or lbf/ in.2, or psi, in US
oilfield units.
128. pressure buildup - A rise in well pressure as a function of
time observed after a well is shut in or after the production rate is
reduced.
129. pressure depletion - The drop in average reservoir pressure
from fluid production.
130. pressure drawdown - The differential pressure that drives
fluids from the reservoir into the wellbore.
131. pressure falloff - The pressure decline after halting or
reducing fluid injection in a well.
132. pressure gauge - A device used to measure pressure.
133. pressure gradient - A change in pressure as a function of
distance. This can refer to radial change in pore pressure with
distance from the well (which can be calculated from well-test
analysis results), to change in pore pressure with depth (which can
be measured by formation tests, and implies formation fluid
density and/or fluid contacts) or to change in wellbore fluid
pressure with depth (which can be measured with production logs,
and implies wellbore fluid density).
134. pressure squared plot - A plot of p2 versus time function used
to analyze low-pressure gas-well drawdown and buildup tests. The
square term arises from substituting a gas-law equation into the
differential equations where required to account for fluid
compressibility. This allows an approximation for the differential
equations that approaches the linear form required to use the
classical solutions of the diffusion equation.
135. pressure transient analysis - The analysis of pressure changes
over time, especially those associated with small variations in the
volume of fluid.
136. pressure transient well tests - Well tests in which pressure is
recorded as a function of time and interpreted using various
analysis methods.

13. 137. pressure-drawdown analysis - The analysis of pressure-
transient behavior observed while the well is flowing. Results are
generally much less accurate than those from pressure buildup tests
138. production period - The flow period before a buildup. The
duration of the production period should be specified in the test
design to assure that a stable flow situation is reached
139. prorated well - A well in which the maximum production rate
is fixed by law. These laws were developed by producing states
primarily to control the market and avoid periodic price collapses.
140. pseudopressure plot - A plot of real gas pseudopressure
(pseudopotential) m(p) versus time function used to analyze gas-
well drawdown and buildup tests. The use of the real gas
pseudopressure linearizes the diffusion equation for gas flow. This
form enables rigorous analysis over all pressure ranges. The
pressure-squared plot can be used for low pressure (p < ~2000 psi),
and pressure can be used to analyze gas-well tests at high pressure
(p > ~3000 psi).
141. pseudosteady state - Behavior observed when a well reaches
stabilized production from a limited drainage volume. For
constant-rate production, under pseudosteady state, the difference
between the flowing wellbore pressure and the average reservoir
pressure in the drainage volume is constant, and the pressure
drawdown is a linear function of time, resulting in a unit slope in
the log-log pressure derivative. The late-time buildup pressure will
level off to the average reservoir pressure if the buildup duration is
sufficient long, resulting in a sudden drop in the log-log pressure
derivative. Pressure depletion occurs
142. pumping well - A well produced by use of some kind of
downhole pump.
143. pumping well tests - Testing that is accomplished by
measuring pressure in the annulus, or by pulling the pump and
running a pressure gauge in the hole.
144. radius of investigation - The calculated maximum radius in a
formation in which pressure has been affected during the flow

14. period of a transient well test. his may also be termed transient
drainage radius.
145. single phase flow - The flow of a single-phase fluid, such as
oil, water or gas, through porous media.
146. skin - A dimensionless factor calculated to determine the
production efficiency of a well by comparing actual conditions
with theoretical or ideal conditions.
147. skin - The zone of reduced or enhanced permeability around
a wellbore, often explained by formation damage and mud-filtrate
invasion during drilling or perforating, or by well stimulation.
148. skin effect - An increase or decrease in the pressure drop
predicted with Darcy's law using the value of permeability
thickness, kh, determined from a buildup or drawdown test. The
difference is assumed to be caused by the "skin." Skin effect can
be either positive or negative. The skin effect is termed positive if
there is an increase in pressure drop, and negative when there is a
decrease, as compared with the predicted Darcy pressure drop. A
positive skin effect indicates extra flow resistance near the
wellbore, and a negative skin effect indicates flow enhancement
near the wellbore.
149. skin factor - A numerical value used to analytically model the
difference from the pressure drop predicted by Darcy's law due to
skin.
150. spherical flow - A flow regime that occurs when the
predominant flow pattern in the reservoir is toward a point. This
flow occurs for partial penetration and limited-entry completions.
This flow regime is recognized as a -1/2 slope in the pressure
derivative on the log-log diagnostic plot. Its presence enables
determination of the spherical permeability. When spherical flow
is followed by radial flow, both horizontal and vertical
permeability can be quantified.
151. stabilization - A state that a producing well reaches when the
flow rate and well pressure are apparently constant for a reasonable
period of time, such as a few hours or a day or more.

15. 152. stabilized gas well - A gas well producing at a constant rate
in which wellhead pressure changes no more than a small amount
as a function of time.
153. static pressure - The pressure measured in a well after the
well has been closed in for a period of time, often after 24 or 72
hours. When a reservoir is first discovered, this pressure equals the
initial pressure. After production begins, this pressure approaches
the average reservoir pressure.
154. steady state behavior - Simultaneously constant pressure
(wellhead or bottomhole) and flow rate. This behavior can result
when there is pressure support, either naturally through an aquifer
or gas-cap drive, or artificially through water or gas injection.
155. subsurface pressure - Any pressure measured in a well below
the surface.
156. superposition - A mathematical technique based on the
property that solutions to linear partial equations can be added to
provide yet another solution. This permits constructions of
mathematical solutions to situations with complex boundary
conditions, especially drawdown and buildup tests, and in settings
where flow rates change with time.
157. superposition in space - A mathematical computation that
accounts for production from multiple wells. Image wells are used
to model the effect of impermeable barriers.
158. superposition in time - A mathematical computation that
accounts for the flow-rate history in analytical models generated to
match with pressure-transient test data.
159. surface pressure - The pressure measured at or near the
surface in a well. This measurement of pressure is usually
performed by inserting a gauge into the production string just
below the shut-in valve, and is also referred to as tubing-head
pressure.
160. surface shut-in - A well shut in at the surface, rather than
downhole. Most transient well tests are conducted in this manner
for convenience.

16. 161. three phase flow - The simultaneous flow of oil, free gas and
water into a wellbore. Stratified flow is the rule rather than the
exception.
162. transient drainage radius or radius of investigation - The
calculated maximum radius in a formation in which pressure has
been affected during the flow period of a transient well test. While
not absolutely accurate, the value has meaning in relation to the
total volume of reservoir that is represented by calculated reservoir
parameters, such as kh, the permeability thickness.
163. transient pressure - The change in pressure with time. In well
testing, this refers to the pressure measured as a function of time
after the test is initiated.
164. transient rate and pressure test analysis - The analysis of
transient rate and pressure data taken while a well is flowing at
variable rates. The analysis uses either deconvolution or
convolution to correct for the flow-rate variations and can
makedrawdown data interpretable. It has also been applied to
correct for afterflow during the buildup.
165. transient-pressure response - The pressure response resulting
from changes in a well's production rate.
166. two phase flow - he simultaneous flow of both oil and free
gas into a wellbore.
167. Type curves - Families of the paired pressure change and its
derivative computed from a model. T
168. type curve analysis - A method for quantifying well and
reservoir parameters such as permeability, skin, fracture half-
length, dual-porosity parameters, and others, by comparing the
pressure change and its derivative of the acquired data to reservoir
model curve families
169. Bourdet and Gringarten - that's a log-log type curve,
Gringarten et al, Ramey, McKinley, - Name as many type curves
as you can...
170. unitized production - Pooled production from wells or a
reservoir. The proceeds of this pooled production are distributed to
the participants according to an agreed-upon formula.

17. 171. units conversion factor - A constant provided in an equation
that applies only for a particular system of units.
172. variable rate - A condition that results when the flow rate
varies appreciably during a test period.
173. water formation volume factor - Water and dissolved gas
volume at reservoir conditions divided by water volume at
standard conditions. This value can often be neglected, since it is
always close to 1.0.
174. water influx - The replacement of produced fluids by
formation water.
175. well cleanup - That period when drilling debris and fluids are
still coming out of the formation and perforations. During this
time, the skin effect is changing and any well-test results may
reflect temporary obstruction to flow that will not be present in
later tests.
176. well interference - The change in pressure at one well caused
by production from one or more other wells.
177. well interference testing - The pressure variation with time
recorded in observation wells resulting from changes in rates in
production or injection wells.
178. well production rate - The volume of produced fluid per unit
of time
179. wellbore damage - Any restriction to flow from near-well
reductions in flow capacity. This damage is thought to result from
reductions in near-well permeability caused by perforating debris
or from the solids or mud filtrate invasion caused by the drilling
process.
180. wellbore fill up - Following a surface shut-in, the flow into a
well caused by the compressibility of the fluids in the wellbore.
Most of the flow occurs from compression of gas in the wellbore.
The practical result is that the sandface flow rate is not zero and,
therefore, not constant. This gives rise to one form of the wellbore-
storage effect.
181. wellbore-storage effects - Distortions in the reservoir
response due to wellbore storage. The characteristic trends are an

18. early unit slope trend with pressure change and the derivative
overlain on the log-log plot, followed by a "hump" in the pressure
derivative that gradually disappears as reservoir trends become
recognizable
182. wireline formation test - Test taken with a wireline formation
tester.
183. wireline formation tester - A tool run on an electric logging
cable that pushes a probe into the formation, which then allows
production into a small closed chamber. The tool is primarily used
to obtain formation pressures at chosen locations in an interval,
and, with an accurate quartz gauge, permeability estimates may be
obtained. Modern variations on this tool have been developed to
acquire formation-fluid samples.
184. zone - A slab of reservoir rock bounded above and below by
impermeable rock.
185. Related to shale gas production, name each of these lines. - 1.
Total Gas
186. 2. Free Gas -
187. 3. Adsorbed Gas -
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188. Name all the elements of the presented phase diagram. –
Phase 1: Solid
Phase 2: Liquid -
Phase 3: Gas -
Line 1: Vapor Pressure Line -
Line 2: Melting Point Line -
Line 3: Sublimation Line -
Point 1: Critical Point -
Point 2: Triple Point
189. In geophysics, what is the name of the following equation? -
The diffusion equation
190. Name all the different flow regimes.
1. Plug Flow
2. Wavy Stratified Flow -
3. Slug Flow -

19. 4. Dispersed Bubble Flow -
5. Stratified Flow -
6. Annular Flow