Reports: ND951041-ND9: Accurate Hydraulic Fracture Characterization Using Microseismic and Production/Welltest Data
Jingyi Chen, University of Tulsa
During this one-year extension period, we proposed a
new objective function is to accurately estimate the
microseismic event locations by using EnKF. Unlike previous applications
using the objective function of misfit between the theoretical traveltimes and
the observed traveltimes, the novel objective function consists of the
traveltime differences of P-wave first arrivals between seismic traces. The advantage
of
this method is to eliminate the effects of origin times of microseismic sources。A flat-layered 2D velocity model is used in this
test. A total of twelve geophones (inverted triangle) are placed in a vertical
monitoring well (Figure 1). The perforation shot (P) and other ten induced
microseismic events (S1-S10) are arranged in this model. The origin times of
the perforation shot and other ten microseismic events are set up as 100s and
150s, respectively. The P-wave first arrival times for perforation shot and
other microseismic sources are calculated by eikonal equation. We first used
EnKF to invert P-wave velocity structures of the model by using P-wave first
arrival traveltimes with Gaussian noise emitted from perforation shot. Then using
the velocity structures obtained above, we again implemented EnKF to invert the
locations of perforation shot and other ten microseismic events. Figure 1 shows
that the locations of perforation shot and microseismic events (cross) are very
close to the true locations (circle), which also indicates that our proposed
method is able to accurately predict microseismic source location.
Figure
1 Inverted locations of perforation shot and microseismic events
In addition, we also further calculated the porosity
and permeability distribution by assimilating both microseismic and welltest
data in heterogeneous case during the extension period.
This project has supported a graduate student to
earn Ph.D, and a master student. Two more graduate students were also involved
in this project as research assistant in a short time (one month). This project
proposed a new approach how we can take good use of two types of datasets:
Production data (well test) and microseismic data. As an important output of
this project, a paper has been accepted by SPE Journal.
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