US 11,692,423 B1 · Method for realizing uniform stimulation for the oil and gas well by low-cost multi-stage fracturing

Abstract

The present invention discloses a method for realizing uniform stimulation for the oil and gas well by low-cost multi-stage fracturing, comprising the following steps: first calculate and predict the inlet widths of the fracture created in the planned hydraulic fracturing; then design the plugging scheme for blocking the fracture inlet after each fracturing treatment; the selected plugging particles are composed of filling particles and skeleton particles, with designed plugging scheme; after complete the design of plugging scheme, perform the fracturing treatment to create hydraulic fracturing in the reservoir; skeleton particles and filling particles are added into the fractures successively according to plan. The present invention provides a multi-stage single-cluster fracturing method, with the advantages of controllable fracture sizes and low cost. The present invention can realize a good uniformity of stimulation for the oil and gas wells.

A method for realizing uniform stimulation for an oil and gas well comprising a wellbore by multi-stage fracturing, comprising the following steps:

Step 1:
Calculating and predicting the inlet widths of a fracture wi created in a planned hydraulic fracturing treatment, with Equation (1);
w
i
=
2.18
[
Q
2
(
1
-
v
2
)
⁢
μ
E
⁢
h
]
⁢
0.2
t
0.2
(
1
)
Where:
wi is an inlet width of the fracture, in m;
E is Young's modulus of reservoir rock, in MPa;
Q is a pump rate of a fracturing fluid, in m3/s;
μ is a viscosity of the fracturing fluid, in MPa·s;
v is the Poisson's ratio of the reservoir rock, dimensionless;
h is a reservoir thickness, in m;
and t is a fracturing time, in s;
Step 2:
Designing a plugging scheme for blocking the fracture inlet after each fracturing treatment;
wherein selected plugging particles are composed of skeleton particles and filling particles;
the filling particles are a soluble fluid diverting agent, and the filling particles diameter is less than 1/3 of that of the skeleton particles;
the filling particles and the skeleton particles are respectively taken for fine screening to determine their particle diameter composition and classify as different kinds;
and calculating the harmonic mean of diameters for the particles according to Equation (2), as the average diameter of the plugging particles:
a
=
(
v
1
+
v
2
+
L
+
v
n
)
⁢
T
+
(
g
1
+
g
2
+
L
+
g
m
)
⁢
(
1
-
T
)
(
v
1
b
1
+
v
2
b
2
⁢
L
+
v
n
b
n
)
⁢
T
+
(
g
1
c
1
+
g
2
c
2
⁢
L
+
g
m
c
m
)
⁢
(
1
-
T
)
(
2
)
Where:
a is an average diameter of the plugging particles, in m;
bn is a particle diameter of n-th kind of skeleton particles, in m;
vn is a volume fraction of n-th kind of skeleton particles among all the skeleton particles, dimensionless;
cm is a particle diameter of m-th kind of filling particles, in m;
gm is a volume fraction of m-th kind of filling particles among all the filling particles, dimensionless;
and T is a volume fraction of the filling particles in the plugging particles, dimensionless;
Step 3:
Checking whether the average particle diameter a is greater than 1/5 of the inlet width of fracture calculated in Step 1:
a
>
1
5
⁢
w
i
(
3
)
If the conditions in Equation (3) are met, the average particle diameter a is selected as an optimized average particle diameter for plugging, and its corresponding particle composition is selected as an optimized particle composition;
if the conditions in Equation (3) are not met, larger skeleton particles will be reelected, and the average particle diameter of plugging particles will be recalculated according to Step 2 until the conditions in Equation (3) are met;
Step 4:
Calculating an optimized volume fraction Co of plugging particles required for blocking the fractures:
C
o
≥
3
1
⁢
0
⁢
(
1
-
1
2
⁢
e
-
w
o
3
.
3
⁢
a
)
⁢
(
1
-
a
w
i
)
2
(
4
)
Where:
α is the average diameter of plugging particles, in m;
and wi is the inlet width of fracture, in m;
Step 5:
Based on the optimized particle composition and the optimized volume fraction Co , using a hydraulic fracturing model to simulate a fracturing and plugging process and checking whether the volume fraction of particles in the fracture near the wellbore can reach 60%;
if the volume fraction fails to reach 60%, larger skeleton particles will be reelected, and Steps 2-5 are repeated until the volume fraction of particles in the fracture near the wellbore can reach 60% in the simulation;
Step 6:
After completing the design of the plugging scheme, performing the planned fracturing treatment to create hydraulic fracturing in the reservoir;
Step 7:
When the injection amount of fracturing fluid reaches 80-85% of the designed volume, pumping the plugging particles according to the optimized design to block the fracture;
After successful plugging, performing a next fracturing treatment for a subsequent perforation cluster;
Step 8:
Repeat Steps 1-7 until fracturing of all perforation clusters in the oil and gas well is completed;
Step 9:
If necessary, treatment fluid is injected into the wellbore to dissolve the filling particles at the fracture inlet to recover a flow channel between each fracture with the wellbore.

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Method for realizing uniform stimulation for the oil and gas well by low-cost multi-stage fracturing

Life of this patent

Method for realizing uniform stimulation for the oil and gas well by low-cost multi-stage fracturing

Life of this patent

Abstract

Claims6