US2025052152A1PendingUtilityA1
Method for evaluating productivity of vertically heterogeneous gas reservoir considering interlayer crossflow
Assignee: HAINAN BRANCH OF CHINA NAT OFFSHORE OIL CHINA CO LTDPriority: Aug 7, 2023Filed: Aug 23, 2024Published: Feb 13, 2025
Est. expiryAug 7, 2043(~17 yrs left)· nominal 20-yr term from priority
E21B 49/087E21B 49/0875
44
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Claims
Abstract
A method for evaluating productivity of a heterogeneous gas reservoir considering interlayer crossflow is disclosed in the invention, and includes: (1) dividing a heterogeneous gas reservoir into multiple reservoir sections along the depth of the heterogeneous gas reservoir; (2) obtaining the productivity of each reservoir section according to data obtained through wireline formation test; (3) superimposing the productivity of all reservoir sections based on the water-electricity similarity principle to obtain the superimposed productivity of the heterogeneous gas reservoir; and (4) using an interlayer crossflow correction coefficient considering influence caused by the interlayer crossflow to obtain the corrected productivity of the heterogeneous gas reservoir.
Claims
exact text as granted — not AI-modified1 . A method for evaluating corrected comprehensive productivity of a heterogeneous gas reservoir along its depth considering interlayer crossflow, comprising the following steps:
(1) dividing a heterogeneous gas reservoir into multiple reservoir sections along the depth of the heterogeneous gas reservoir; (2) obtaining the productivity of each reservoir section according to data obtained through wireline formation test and laboratory test, wherein the productivity of each of the reservoir sections is calculated based on a calculation formula (1):
q
sc
=
-
A
+
A
2
-
4
B
(
ψ
(
p
wf
)
-
ψ
(
p
e
)
)
+
C
2
B
where
,
A
=
6.367
×
10
-
4
Te
(
-
b
(
p
e
-
p
_
)
)
K
0
h
ln
(
r
e
r
w
)
B
=
1.0795
×
10
-
10
γ
g
Te
(
-
b
(
p
e
-
p
_
)
)
K
1.5
h
2
μ
_
(
1
r
w
-
1
r
e
)
C
=
λ
(
p
e
+
p
wf
2
)
(
r
e
-
r
w
)
e
(
-
b
(
p
e
-
p
_
)
)
μ
_
Z
_
q sc is the gas production rate under standard conditions, m 3 /d;
ψ
(
p
)
=
∫
p
0
p
pe
(
-
b
(
p
e
-
p
_
)
)
μ
Z
is the pseudo-pressure function of single-phase gas;
T is reservoir temperature;
p e , p , p wf , and p are respectively original reservoir pressure, mean reservoir pressure, bottom hole flowing pressure, and pressure at any point in formation, MPa;
K and K 0 are respectively reservoir permeability at pressure of p and permeability at the original reservoir pressure p e , mD;
h is reservoir thickness, m;
r e and r w are respectively reservoir radius and wellbore radius, m;
γ g is the relative density of natural gas;
b is a stress sensitivity coefficient, MPa −1 ;
μ and μ are respectively natural gas viscosity and mean natural gas viscosity, mPa·s;
λ is starting pressure gradient, MPa/m; and
Z and Z are respectively a deviation coefficient and a mean deviation coefficient;
(3) superimposing the productivity of all the reservoir sections to obtain the superimposed productivity of the whole heterogeneous gas reservoir,
wherein the superimposed productivity of the gas reservoir is that of all the reservoir sections, namely:
Q
tol
=
∑
i
=
1
n
q
i
Q
m
=
α
*
Q
tol
Where Q tol is the superimposed productivity of the gas reservoir;
q i is the productivity of the i(th) reservoir section;
α is the correction coefficient of the interlayer crossflow; and
Q m is the corrected comprehensive productivity of the gas reservoir,
calculating corresponding flow coefficients (kh/μ) of various reservoir sections according to the permeability (k), effective thickness (h), and gas viscosity (μ) of various heterogeneous gas reservoirs; arranging the flow coefficients into a sequence from small to large; calculating the cumulative percentages of flow coefficients and effective thicknesses of the various reservoir section, respectively; plotting Lorenz curve on a rectangular coordinate paper;
calculating a ratio of an envelope area S ADCA to a triangle area S ABC as a flow variation coefficient β; using a relation curve of an interlayer interference coefficient γ and a flow variation coefficient β to calculate the interlayer interference coefficient γ due to good correlation between them; and then calculating the interlayer crossflow correction coefficient according to formula α=1−γ=1−β; and
(4) using an interlayer crossflow correction coefficient considering influence caused by the interlayer crossflow to obtain the corrected comprehensive productivity of the whole heterogeneous gas reservoir.
2 . The method according to claim 1 , wherein Step (1) comprises dividing the reservoir into several different reservoir sections according to permeability obtained through logging data, wherein each of the reservoir sections is a relatively homogeneous reservoir section.
3 . The method according to claim 1 , wherein Step (1) comprises arranging a first wireline formation tester at a first depth and a second wireline formation tester at a second depth, changing the pumping speed of the first wireline formation tester, observing the pressure variation of the probe of the second wireline formation tester in another layer, then determining whether an adjacent layer pertains to a same reservoir section according to the pressure variation of the probe of the second wireline formation tester.
4 . The method according to claim 3 , wherein the determining whether an adjacent layer pertains to a same reservoir section according to the pressure variation of the probe of the second wireline formation tester comprises:
if pressure measured by the second wireline formation tester is changed along with that measured by the first wireline formation tester, the two layers pertain to the same reservoir section; or if pressure measured by the second wireline formation tester is not changed along with disturbance, the two layers are two independent reservoir sections.
5 . The method according to claim 1 , wherein Step (2) comprises using static permeability K s obtained through the wireline formation test and permeability K g (1−Sw) obtained through core displacement test to establish a conversion function relation K g (1−Sw) =f (K s ), and obtaining effective permeability K g (1−Sw) based on the data obtained through the wireline formation test.
6 . The method according to claim 1 , wherein Step (2) comprises establishing a conversion relation of measured productivity Q i and effective permeability K g (1−Sw) according to the measured productivity relation of the reservoir section.
7 . The method according to claim 6 , wherein the conversion function relation is Q i =a*K b g (1−Sw) +c, wherein a, b, and c are fitting coefficients.
8 . The method according to claim 7 , wherein the conversion function relation is validated and corrected using DST ((Drill stem testing).Join the waitlist — get patent alerts
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