US2013322209A1PendingUtilityA1
Methods and Systems for Microseismic Mapping
Est. expiryApr 8, 2029(~2.7 yrs left)· nominal 20-yr term from priority
G01V 1/40G01V 2210/123G01V 1/303G01V 1/288
48
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Claims
Abstract
Methods and systems for the detection and localization of microseismic events are proposed which operate in real-time. Hypocenters in three spatial dimensions are provided along with an estimate of the event origin time. Sensor positions may be distributed in 3D space, and are not confined to linear arrays in vertical wells. A location of the event is approximated and a grid search, based on the approximate location of the event, is used to derive a residual function over a finer sampling followed by a gradient search of the residual function to optimize the location of the event.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1 . A method of detecting and locating a microseismic event, comprising:
acquiring waveform data from microseismic events with an array of seismic sensors distributed in a non-vertical configuration in one or more wellbores traversing subterranean formations; determining signal-to-noise ratio (SNR) data; detecting a microseismic event by generating a first map based on the SNR data; and when a maximum value of the first map exceeds a predetermined value, locating the event by generating a second map based on an origin time and origin time uncertainty of the detected event, and utilizing direction of incoming signals at each seismic sensor of the non-vertically distributed array.
2 . A method according to claim 1 , further comprising:
applying a gradient search to refine the location of the microseismic event.
3 . A method according to claim 2 , wherein:
the gradient search comprises applying a Geiger search algorithm.
4 . A method according to claim 1 , further comprising:
determining direction of incoming signals at each seismic sensor of the distributed array by using a probability function based on a continuously estimated P-wave polarization vector and uncertainty associated with the polarization vector.
5 . A method according to claim 1 , wherein:
detecting the event comprises determining for each time sample, t, and grid node, (x,y,z), a value of the product of SNR for P-waves, SNRP r (t), and SNR for S-waves, SNRS r (t), at modeled arrival times for P-waves, tp r (x,y,z), and S-waves, ts r (x,y,z), over all receivers, r.
6 . A method according to claim 5 , wherein:
locating the event by generating the second map comprises utilizing:
Loc
(
x
,
y
,
z
)
=
1
σ
t
o
∑
t
=
t
o
-
σ
t
o
2
t
o
+
σ
t
o
2
+
1
Det
(
t
,
x
,
y
,
z
)
PDF
pol
(
x
,
y
,
z
)
,
wherein:
the origin time, t 0 , is the time of the maximum value of the first map, Det(t,x,y,z);
the origin time uncertainty, σt 0 , is the time range where maxima of the first map around the origin time, t 0 , exceed 50% of a maximum at an estimated origin time; and
PDF
pol
(
x
,
y
,
z
)
=
∏
r
=
1
nr
∏
i
=
1
3
1
2
π
σ
ri
(
t
)
-
[
vm
ri
(
t
)
-
vp
ri
(
x
,
y
,
z
)
2
σ
ri
(
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)
]
2
,
wherein:
{right arrow over (vm r )}(t) denotes a continuously estimated P-wave polarization vector with associated uncertainty, {right arrow over (σ)} r (t);
{right arrow over (vp)} r (x, y, z) denotes a modeled P-wave polarization vector; and
index, i, is one component of three components of the polarization vectors.
7 . A method according to claim 1 , wherein:
at least one wellbore is a deviated well.
8 . A method according to claim 1 , wherein:
at least one wellbore is a horizontal well.
9 . A method according to claim 1 , wherein:
the one or more wellbores comprise a plurality of wells.Join the waitlist — get patent alerts
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