Neftegaz.RU #3-17 ENG

OFS
nine-points development pattern
with the pattern arrangement 25
and 16 hectares/well. Transversal
fractures orientation for lowpermeability
reservoirs is preferred:
it provides higher productivity of
the production wells, provides more
extensive coverage of a reservoir,
helps to bring into development
multicompartment beds. But based
on the results of the variants analysis
the preference has been given to
longitudinal fractures orientation
due to the lowest risks for this
system implementation and because
of the complexity related to the
waterflooding pattern arrangement
for the system with transversal
fractures orientation of hydraulic
fracturing [1].
Based on the hydrodynamic fluid
simulation results, implementation
of HW with multi-stage hydraulic
fracturing on the experimental
plot will allow not only ORF
increasing by 5 percent but also
reducing development period by
more than two times as compared
with the basic variant. The use
of hydrodynamic fluid simulation
models is one of the main means
for designing; but notwithstanding
its high accuracy, it is impossible
to be confined with only these
models applying for the purposes
of development variants calculation
due to availability of a large number
of such variants and long time
period required for the calculations
performing. Under such conditions
the reasonable approach is to
use two-stage simulation, when
preliminary calculations allowing
reducing a number of variants and
evaluating degree of impact of
each parameter on oil production
levels are performed at the first
stage using analytical models, and
adjustments with a help of numerical
hydrodynamic calculations and
selection of the best variant are
performed at the second stage.
The paper [2] proposes the following
model for calculation of flow rate
of horizontal well with multi-stage
hydraulic fracturing and transversal
fractures arrangement:
(1)
The given equation consists of two
parts, the first term of the equation
describes fluid inflow to the fracture
space border excluding external
parts of the outermost fractures
draining areas.
External parts of the outermost
fractures draining areas are
accounted by the following equation
where
(2)
– fracture total area;
– half the length of a fracture from
hydraulic fracturing;
– distance to external boundary.
Pressure at the border of
interfracturing space:
where ,
TABLE 2. Input data
(3)
Name of the indicator
– length of a horizontal well;
– number of fractures from
hydraulic fracturing.
Let us calculate flow rate of
horizontal well with multi-stage
hydraulic fracturing drilled under
conditions of the producing bed
АС11. The bed net oil pay thickness
14 m. Rock pressure is 26 MPa,
bottom-hole pressure is 5 MPa,
average permeability of the bed
is 3.5 · 10 -3 μm 2 . The input data for
calculations are given in the table 2.
One of the applied model
disadvantages is the fact that fluid
inflow to horizontal well having no
fractures is not considered in the
fluid flow rate calculations. Resulting
uncertainty can be relevant when
there is small number of fractures.
But when number of fractures grows
subsequently the error significantly
decreases as far as the main part of
the flow goes to the fractures. In this
regard we do not consider HW with
less than four fractures.
The calculation results for fluid flow
rate and pressure at the fracture
space border are given in the
Value
Permeability of the bed k, 10 -3 μm 2 3.5
Well length L, m 700
Viscosity μ, mPa · s 1.4
Rock pressure P rock , MPa 26
Bottom-hole pressure P bh , MPa 5
Half the length of a fracture x f , m 50
Bed thickness h, m 14
Distance to external boundary , m 300
Volume factor b 1.2
TABLE 3. The calculation results for fluid flow rate depending on hydraulic fractures number
Hydraulic fractures
number
4 5 6 7 8 9 10 11 12 13 14 15
P 0 , MPa 24.0 18.5 14.8 12.4 10.7 9.5 8.7 8.0 7.5 7.1 6.8 6.6
Q, m 3 /day 148.0 186.9 212.7 230.1 241.9 250.3 256.4 260.9 264.4 267.1 269.2 271.0
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