US 10,761,241 B2 · Methods for optimizing bunch distance of fractured horizontal wells of shale gas

Abstract

The present disclosure provides a method for optimizing bunch distance of fractured horizontal wells of shale gas, which relates to the technical field of oil exploration. The method comprises first establishing a stress field distribution model for a single fracture; then establishing an induced stress distribution model of segmented single-bunch fracturing for a horizontal well; later establishing an induced stress distribution model of segmented multi-bunch fracturing for a horizontal well; last optimizing fracturing parameters and fracture distance according to the distribution pattern of the induced stress difference. The method considers the stress barrier, stress interference effects, and the variation of the effective net pressure during the synchronous expansion of fractures, so the calculation model is more in line with the actual working conditions, has higher precision, and can provide more accurate theoretical guidance for the optimization design of segmented multi-bunch fracturing of a horizontal well.

A method for optimizing bunch distance of fractured horizontal wells of shale gas, characterized in that, the method comprises

establishing a stress field distribution model for a single fracture;
establishing an induced stress distribution model of multi-segment single-bunch fracturing for a horizontal well;
establishing an induced stress distribution model of multi-segment multi-bunch fracturing for a horizontal well;
calculating the induced stress outside a fracture in a segment adjacent to a previous segment;
calculating the induced stress between fractures inside a segment;
calculating the induced stress outside a fracture in a segment adjacent to a next segment;
calculating the horizontal induced stress difference of segmented multi-bunch fracturing for a horizontal well;
and
determining a bunch distance, as an optimal bunch distance, at which the horizontal induced stress difference is at a maximum;
and
forming the horizontal well having the optimal bunch distance;
wherein establishing the induced stress distribution model of multi-segment multi-bunch fracturing for a horizontal well comprises calculating an effective net pressure of the first fracture in the segment relative to the previous segment, calculating an effective net pressure of each fracture in the segment relative to neighboring fractures in the segment, and calculating an effective net pressure of the last fracture in the segment relative to the next segment;
wherein each segment has three bunches of fractures, wherein the three bunches of fractures of the Nth segment are sequentially recorded as fractures N 1, N2, and N3, fracture N1 is the fracture nearest the (N-1)th segment, fracture N3 is the fracture the furthest away from the (N -1)th segment, fracture N2 is the fracture between fracture N1 and fracture N3;
wherein the effective net pressure of fracture N1 relative to the previous segment is
Peni(N1)=Pn−σh(n−1)3(N1)
wherein σh(n−1)3(N1) is an induced stress in a minimum horizontal geostress direction generated by the third fracture of the (N−1)th segment to fracture N1;
wherein the induced stress generated at any point between fracture N1 and fracture N2 is
{
σ
e
⁢
n
⁢
h
⁡
(
N
1
,
N
2
)
=
P
n
⁢
sin
⁢
β
n
⁢
1
2
⁢
(
2
⁢
l
n
⁢
1
r
n
⁢
2
)
3
2
-
P
n
[
r
n
⁢
1
⁢
cos
⁢
β
n
⁢
1
(
r
n
⁢
1
⁢
r
n
⁢
2
)
1
2
-
1
]
σ
e
⁢
n
⁢
H
⁡
(
N
1
,
N
2
)
=
2
⁢
v
⁢
P
n
[
r
n
⁢
1
⁢
cos
⁢
β
n
⁢
1
(
r
n
⁢
1
⁢
r
n
⁢
2
)
1
2
-
1
]
wherein σenh(N1, N2) is the induced stress in the minimum horizontal geostress direction generated by fracture N1 to fracture N2;
βn1 is an angle of fracture N1 to a point in the next segment;
ln1 is a total length of fracture N1;
rn1 is a half length of Fracture N1;
rn2 is a half length of fracture N2;
σenH(N1, N2) is the induced stress in the maximum horizontal geostress direction generated by fracture N1 to fracture N2;
wherein the relationship between fracture N2 and fracture N3 is
{
σ
e
⁢
n
⁢
h
⁡
(
N
2
,
N
3
)
=
P
n
⁢
sin
⁢
β
n
⁢
2
2
⁢
(
2
⁢
l
n
⁢
2
r
n
⁢
3
)
3
2
-
P
n
[
r
n
⁢
2
⁢
cos
⁢
β
n
⁢
2
(
r
n
⁢
2
⁢
r
n
⁢
3
)
1
2
-
1
]
σ
enH
⁡
(
N
2
,
N
3
)
=
2
⁢
v
⁢
P
n
[
r
n
⁢
2
⁢
cos
⁢
β
n
⁢
2
(
r
n
⁢
2
⁢
r
n
⁢
3
)
1
2
-
1
]
wherein σenh(N2, N3) is the induced stress in the minimum horizontal geostress direction generated by fracture N2 to fracture N3;
βn2 is an angle of fracture N2 to a point in the next segment;
ln2 is a total length of fracture N2;
rn2 is a half length of Fracture N2;
rn3 is a half length of Fracture N3;
σenH(N2, N3) the induced stress in the maximum horizontal geostress direction generated by fracture N2 to fracture N3;
wherein the effective net pressure of Fracture N3 relative to the next segment is
p
enr
⁡
(
N
3
)
=
p
n
-
∑
i
=
1
N
-
1
⁢
σ
h
i
⁢
3
⁡
(
N
3
)
wherein Penr(N3) is the effective net pressure of fracture N3 relative to the next segment.

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Methods for optimizing bunch distance of fractured horizontal wells of shale gas

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Methods for optimizing bunch distance of fractured horizontal wells of shale gas

Life of this patent

Abstract

Claims7