Turymbetov T.A1., Aitkulov A.U1., Azhikhanov N.T2., Aimeshov Zh.A2.
1Caspian State
University of Technologies and Engineering named after Sh. Yessenov, Kazakhstan
2Kh.Yasavi
International Kazakh-Turkish University, Kazakhstan
Evaluation of a slight increase of
the well production rate in the application of technological operation to
improve the condition of fluid filtration
In the
process of oil production at operation of oil fields for increase production of
oil from wells used the most intensive methods of influence in the form of
hydraulic fracturing in the near-wellbore zone, by injecting fluids into the
formation to fracture the reservoir in order to create a specific canal, in the
form of cracks. Geological-based research in the fields of origin shows varying
degrees of technological efficiency due to the state of cracks in the near-wellbore
zone [1]. Efficiency created fractures substantiates value of the minimum well
production by fluid after hydraulic fracture. Therefore, before doing so, its
technological efficiency should be estimated [2]. In this regard, below given technology of calculation formulas for
determining the lower limit debit wells by liquid.
To determine the
lower limit debit wells use the following consideration. If in filtration flow,
which will be held in the reservoir (see Fig. 1a) in any way to put an
impenetrable barrier (see Fig. 1b), and the pressure drop Ðê-Ðñ remains
unchanged, then it leads to a reduction in flow rate or, in extreme cases when
the direction of the partition coincides with the direction of the streamlines,
flow rate will remain unchanged.
Fig. 1. Scheme flow in a reservoir with and without baffles.
In this
case, to determine the undersized debits (low flow rate) mentally put
impenetrable infinitely thin walls as shown in figure 2.
With
this arrangement of impermeable baffles, all the liquid will flow into the well
only through the horizontal cracks.
For
simplicity, we assume that the crack is located in the middle of the thickness
of the formation. Therefore, in view of the symmetry can be seen only half the
flow shown in figure 2.
In the
interval Rî≤r≤ Rê , fluid flow lines are directed horizontally. And
in the interval rñ ≤ r
≤ Rî streamlines
of fluid flow from the baffle until the crack are directed parallel to the
generators of the cone ÀÂÑD at cracks from
the reservoir until cone ÅÂÑF – parallel from
to the axis of the hole and the surface of the cone ÅÂÑF until borehole walls - horizontally (see fig. 3).
Fig. 3. Diagram of the cut half the thickness of the producing formation
with crack and are sloping septums
To
define the elementary (basic) inflow dq between two infinitely close
baffles (see fig. 3) [3]:
where
At that
Ðê,Ð1, Ð2, Ð3 and Ðñ – respectively the pressure
on the power supply contour, at the points indicated in figure 3 and the bottom
hole.
Substituting the values
of dq1, dq2, dq3, dq4
an obtaining fluid influx into the wellbore from the reservoir thickness
Practice shows that the fracturing, the
value of the crack opening δ, come much smaller
thickness the reservoir h, i.å. h>>δ. This allows without
(great) measure of accuracy to assume that the value debit (of the well flow)
shown in Figure 4 equal
where
Debit qî less than actual debits (flow rate)
of the well and in what follows we denote qî=qí (bottom boundary).
The relative increase qí compared to the debits (flow rate)
of the well qc before the formation of cracks is determined
by the following relationship
For existing wells Ñ=0. As indicated in the work [4], if Z2>5 formulas (4) and (5)
greatly simplified, as this
With allowance for
equality (6), the bottom boundary of debit the well qí and its relative increase φí are defined respectively by the following formulas:
The results of calculations for φí make sense, of course with φí≥1. Then the minimum
value of the relative increase well production (φí) according to the formula (8)
will have a value
The
average value of the research a parameter equal
Numerical calculations were carried out
and graphs depending φ on Ro
for different values of δ
the formation of horizontal cracks were built (Fig. 4).
Fig. 4. Relationship
between φí and φâ from
Ro by Ê1 = 0,25 mkm2
under conditions of the formation of horizontal cracks
From
the obtained results shown in figure 1, it could be seen that the change in
technological efficiency at formation of horizontal cracks depends on the
distribution radius and crack opening.
Therefore, among two factors, the degree of openness of horizontal cracks more
actively increases the production rate of the well. Increasing the radius of
the horizontal crack reduces the growth rate of increment in flow rate of the
well. It will be observed minimal change in flow rate of the well mostly
depends on the geometric dimensions of the horizontal cracks and parameters
filtration of the porous block and artificially formed horizontal cracks. Calculations
indicates that the permeability at pore space of 0.25 mkm2 and
respectively radius, and also discloses a horizontal crack 100 m and 1
mm minimally debit wells increases by 1.8 times.
References:
1. Bocharov B.A. On the joint development of oil reservoirs (in order
of discussion). Oil Industry. "2003. 11. p. 55-58.
2. Zhumagulov
B.T.,
Azhikhanov N.T.,
Kuatbekov B.N., Temirov B.M. Numerical solutions of the three-dimensional problem
of filtration in a nonhomogeneous porous medium // Series
of essential technical sciences. - 2005. 3. p.
221-224.
3. Shchelkachev
B.N. Fundamentals of application and theory of unsteady filtration. M .: Oil and Gas,
1995. Part
I. 586 p., Part II.- 493 p.
4. Aitkulov A.U. Fundamentals of underground hydromechanics and
development of oil fields. Almaty. 2003. 337 p.