U.S. patent application number 15/849713 was filed with the patent office on 2018-06-21 for method for determining an inflow profile in a multilayer well.
The applicant listed for this patent is SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to Lev Andreevich Kotlyar, Vyacheslav Pavlovich Pimenov, Valery Vasilievich Shako.
Application Number | 20180171780 15/849713 |
Document ID | / |
Family ID | 61258818 |
Filed Date | 2018-06-21 |
United States Patent
Application |
20180171780 |
Kind Code |
A1 |
Shako; Valery Vasilievich ;
et al. |
June 21, 2018 |
METHOD FOR DETERMINING AN INFLOW PROFILE IN A MULTILAYER WELL
Abstract
A bottomhole temperature and a bottomhole pressure in a well are
measured by means of sensors mounted on a perforation string below
all perforation intervals. The measurements are made prior to
perforating the well and after perforating the well until a
temperature of a produced fluid returns to an initial reservoir
temperature. Then the temperature of the produced fluid is measured
by means of temperature sensors mounted on the perforation string
above each perforation interval and a total production rate of the
well is estimated. An excessive thermal energy of the produced
fluid is calculated for each temperature sensor mounted on the
perforation string above the perforation intervals and production
rates of the individual perforation intervals are determined based
on the calculated excessive thermal energies of the produced fluid
and the known number of perforating charges in each perforation
interval.
Inventors: |
Shako; Valery Vasilievich;
(Moscow, RU) ; Pimenov; Vyacheslav Pavlovich;
(Moscow, RU) ; Kotlyar; Lev Andreevich; (Moscow,
RU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHLUMBERGER TECHNOLOGY CORPORATION |
Sugar Land |
TX |
US |
|
|
Family ID: |
61258818 |
Appl. No.: |
15/849713 |
Filed: |
December 21, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 47/07 20200501;
E21B 41/0092 20130101; E21B 47/10 20130101; E21B 47/06
20130101 |
International
Class: |
E21B 47/06 20120101
E21B047/06; E21B 41/00 20060101 E21B041/00; E21B 47/10 20120101
E21B047/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 2016 |
RU |
2016150448 |
Claims
1. A method for determining a fluid inflow profile in a multilayer
well, the method comprising: measuring a bottomhole temperature and
a bottomhole pressure in a well by means of sensors mounted on a
perforation string below all perforation intervals, wherein the
measurements are made prior to perforating the well and after
perforating the well until a temperature of a produced fluid
returns to an initial reservoir temperature, measuring the
temperature of the produced fluid by means of temperature sensors
mounted on the perforation string above each perforation interval,
estimating a total production rate of the well, calculating an
excessive thermal energy of the produced fluid for each temperature
sensor mounted on the perforation string above the perforation
intervals, and determining production rates of the individual
perforation intervals based on the calculated excessive thermal
energies of the produced fluid and the known number of perforating
charges in each perforation interval.
2. The method of claim 1, wherein the total production rate of the
well is determined by measuring a flow rate at the surface or in
the well.
3. The method of claim 1, wherein the total production of the well
is determined by calculating a flow rate based on the change in the
bottomhole pressure.
4. The method of claim 1, wherein the total production of the well
is determined by calculating a flow rate using the bottomhole
pressure and numerically simulating the multilayer exploitation
well.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to Russian Application No.
2016150448 filed Dec. 21, 2016, which is incorporated herein by
reference in its entirety.
BACKGROUND
[0002] The disclosure relates to the field of geophysical
exploration of oil and gas wells, namely to determination of an
inflow profile of a produced fluid in multilayer wells with several
perforation intervals.
[0003] Determination of an inflow profile from a multilayer well is
an important problem. Determination of a production rate of
individual perforation intervals is necessary, in particular, for
making a decision on the need for acid treatment, repeated
perforation, etc.
[0004] Determination of an inflow profile is performed usually
during production logging of an exploitation well using mechanical
flow meters (see, for example, Hill, A.D., Production
Logging--Theoretical and Interpretive Elements, SPE Monograph
Series., 2002, p. 61). The main drawbacks of this method are the
need to conduct a special well logging (in addition to the
operations carried out in the well during perforation and well
testing) and difficulty in determining production rates of
low-yield formations.
[0005] The contribution of different perforation intervals can also
be estimated using the temperature logging data of the exploitation
well (see Cheremensky G. A., Applied Geothermy, M. Nedra, page 181)
or basing on the analysis of non-stationary temperature data
obtained by changing flow rate of a well (see Chekalyuk, E. B.,
Thermodynamics of the oil reservoir, Moscow, 1965, page 88, or
Ramazanov, A., Valiullin, R. A., Shako, V., Pimenov, V.,
Sadretdinov, A., Fedorov, V., Belov, K., 2010. Thermal Modeling for
Characterization of Near Wellbore Zone and Zonal Allocation, SPE
136256-MS). The drawbacks of these methods include the need to
analyze relatively small temperature signals and the need to
conduct special loggings of the well or to mount the special
equipment in the well.
SUMMARY
[0006] In accordance with the proposed method, a bottomhole
temperature and a bottomhole pressure measurements are made by
means of sensors mounted on a perforation string below all
perforation intervals and by means of temperature sensors mounted
on the perforation string above each perforation interval.
[0007] The temperature and bottomhole pressure measurements are
made prior to perforating the well and after perforating until a
temperature of the produced fluid returns to an initial reservoir
temperature. A total production rate of the well is estimated and
an excessive thermal energy of the produced fluid is calculated for
all temperature sensors mounted on the perforation string above the
perforation intervals, and then the production rate of the
individual perforation intervals is determined based on the
calculated excessive thermal energy of the produced fluid and the
known number of perforating charges in each perforation
interval.
[0008] In accordance with one embodiment of the disclosure, the
total production rate of the well is determined by measuring a flow
rate at the surface or in the well.
[0009] According to another embodiment of the disclosure, the total
production rate of the well is determined by calculating a flow
rate based on the change in the bottomhole pressure.
[0010] In accordance with another embodiment of the disclosure, the
total production rate of the well is determined by calculating a
flow rate using the bottomhole pressure and numerically simulating
the multilayer exploitation well.
BRIEF DESCRIPTION OF DRAWINGS
[0011] The disclosure is illustrated by the drawings, where FIG. 1
shows a schematic diagram of a well with two perforation intervals,
FIG. 2 shows an example of the bottomhole pressure P.sub.0(t) and
temperatures of the produced fluid T.sub.1(t) and T.sub.2(t) above
the perforation intervals, FIG. 3 shows a production rate of the
well calculated for the pressure shown in FIG. 2, FIG. 4 shows
total excessive thermal energy of the produced fluid (calculated
from temperature T.sub.2, solid line) and the corresponding energy
calculated from the temperature T.sub.1, FIG. 5 shows the algorithm
for determining the inflow profile using numerical simulation of
the multilayer exploitation well.
DETAILED DESCRIPTION
[0012] The disclosure proposes to determine the inflow profile in
wells having several perforation intervals using well pressure
measurement results and temperature measurement results by means of
sensors mounted on a perforation column. The temperature should be
measured above each perforation interval and at the bottom of the
well, below all perforation intervals.
[0013] The method comprises measuring a bottomhole pressure
P.sub.0(t) and a bottomhole temperature T.sub.0(t), which
determines an average rock temperature in a depth interval under
consideration. The measurements are made by means of sensors
mounted on the perforation string in the well below all perforation
intervals and also by measuring the temperature T.sub.i(t) of the
produced fluid (i=1, 2, . . . , m, m is a number of the perforation
intervals) by means of temperature sensors mounted on the
perforation string above each perforation interval.
[0014] The measurements of the pressure P.sub.0(t) and temperature
T.sub.i(t) (i=0, 1, . . . , m) start before perforation (which
allows to determine formation pressure and geothermal temperature)
and the measurements continue for several hours after the
perforation, until the temperature of the produced fluid, heated by
the energy of the perforation explosion, returns to an initial
reservoir temperature. When perforating charges are exploded, part
of the energy is spent on evaporation of the well fluid and on the
energy of the cumulative jet, but most of the energy is spent on
heating the perforation string, a casing pipe and the rock near the
well. Heating of the produced fluid occurs when it comes into
contact with these bodies.
[0015] The total production rate of the well Q(t) is then evaluated
using one of the following methods: [0016] measurement of a flow
rate at the surface or in the well, [0017] calculation of the flow
rate by changing the bottomhole pressure P.sub.0(t) (if the
produced fluid does not reach the surface), [0018] calculation of
the flow rate using the bottomhole pressure P.sub.0(t) and
numerical simulation of the multiplayer exploitation well.
[0019] The parameters (permeability and skin factors) that
determine the productivity of individual formations are assumed to
be equal to the mean values, which are determined by the
traditional hydrodynamic exploration of the well.
[0020] The excessive thermal energy of the produced fluid for each
temperature sensor is calculated
E.sub.i=.rho..sub.flc.sub.fl.intg.Q(t)[T.sub.i(t)-T.sub.f](i=1, . .
. ,m),
where T.sub.f is an average rock temperature in the considered
depth interval (determined by T.sub.0(t) and practically equal to
it), .rho..sub.flc.sub.fl is a volumetric heat capacity of the
fluid.
[0021] Production rate of individual perforation intervals is
calculated from the values E.sub.i and the known amounts of
perforating charges in each perforation interval.
[0022] Let us consider the case of a low-rate well, when during the
first hours after the perforation there is no flow of the produced
fluid onto the surface.
[0023] A schematic diagram of the well with a perforation string, a
packer and two perforation intervals is shown in FIG. 1, which
depicts a packer--1, a valve--2, a temperature sensor T.sub.2--3, a
temperature sensor T.sub.1--4, a bottom-hole temperature sensor and
a pressure sensors T.sub.0, P.sub.0--5, a second inflow zone--6, a
first inflow zone--7, a second perforation interval--8, a first
perforation interval--9.
[0024] FIG. 2 shows a synthetic example of the bottomhole pressure
P.sub.0(t) and temperatures of the produced fluid T.sub.1(t) and
T.sub.2(t) above the perforation intervals. The thick curve
corresponds to the bottomhole pressure, which is .about.50 bar
before perforation and increases to the pressure of the formation
(about 85 bar) during production in accordance with the fact that
the fluid level rises in the production pipe. In this case, it is
assumed that the perforation intervals have the same length and the
same number of perforating charges.
[0025] If there is no flow of the produced fluid onto the surface,
the total production rate of the well Q(t) can be calculated from
the bottomhole pressure P.sub.0(t):
Q ( t ) = .pi. r ti 2 .rho. fl g dP 0 dt ##EQU00001##
where r.sub.t is the internal radius of the pipe, g=9.81 m/s.sup.2
is gravity acceleration, .rho..sub.fl--density of fluid.
[0026] FIG. 3 shows the production rate of the well calculated by
this formula for the pressure shown in FIG. 2 (for .rho..sub.fl=850
kg/m.sup.3, r.sub.t=0.038 m). The calculated production rate is
then used to determine the inflow profile.
[0027] In the event that the total production rate of the well was
measured in the well or at the surface, this production rate is
directly used for determining the inflow profile.
[0028] The charts of temperature T.sub.1 and T.sub.2 (FIG. 2) show
that immediately after the perforation, the flow temperature of the
produced fluid is much greater (in this case by .about.20 C) than
the temperature of the rocks T.sub.f (points in FIG. 2). This
temperature is determined by heating the well fluid during
explosion and by heating the formation fluid when it comes into
contact with the hot rock, the casing string and the perforation
string. It should be noted that the temperature of the rock can be
estimated from the results of measuring the temperature in the well
before perforation.
[0029] The flow of reservoir fluid cools the near-wellbore rock,
casing string and perforation string and in several hours
(t.sub.p=5/10 hours) after the perforation, the temperatures
measured in the well approach the unperturbed rock temperature
(FIG. 2). This means that the thermal part E.sub.m, of the
explosion energy of the perforating charges was transformed into
the excessive thermal energy of the produced fluid.
[0030] In this case m=2 and E.sub.m.ident.E.sub.2. Using the
temperature T.sub.2, measured by the sensor, which is located above
all perforating intervals, and the production rate of the well
Q(t), this energy can be calculated by the formula:
E 2 ( t ) = .rho. fl c fl .intg. 0 t Q ( t ) [ T 2 ( t ) - T f ] dt
##EQU00002##
[0031] The solid line in FIG. 4 shows the excessive thermal energy
of the produced fluid for the data shown in FIG. 2. It is seen that
in .about.3 hours after the perforation E.sub.2 reaches its highest
value E.sub.2.apprxeq.16.5 MJ.
[0032] The total energy of the perforation explosion, calculated
based on the specific energy of the explosion and the mass of the
explosive, in this case is E.sub.e.apprxeq.28 MJ. This means that
approximately .delta.=60% of the explosion energy was converted
into the thermal energy of the rock, the casing string and the
perforation string:
E.sub.m=.delta.E.sub.e
[0033] The remaining part of the explosion energy (about 40%) was
spent on rock destruction, generation of shock waves in the rock
and in the well, or it was quickly moved beyond the considered
interval with the gaseous products of the explosion.
[0034] The procedure for calculating the production rate of the
individual perforation intervals, proposed in the present
disclosure, is based on the following assumptions: [0035] the value
.delta. is the same for different perforation intervals, [0036]
fluids entering the well from different perforation intervals have
the same volumetric heat capacities, [0037] a distance between the
perforation intervals is small and the loss of fluid thermal energy
to the surrounding rocks between the perforation intervals can be
neglected, [0038] production duration after perforation and the
production rate of the well are large enough so that the fluid
temperature measured by the sensors is reduced to the temperature
of the unperturbed rocks.
[0039] Let m is a number of perforation intervals,
Q.sub.i is a production rate from an i.sup.th interval,
Q = j = 1 m Q j ##EQU00003##
is a total production rate of the well,
.gamma. i = 1 Q j = 1 i Q j ##EQU00004##
is a production rate of the well from the lower i perforation
intervals, referred to the total production rate of the well
(.gamma..sub.m=1), n.sub.i is a number of perforating charges in
the i.sup.th perforation interval,
N = j = 1 m n j ##EQU00005##
is a total number of perforating charges in the well,
b i = 1 N j = 1 i n j ##EQU00006##
a number of charges in the lower i perforation intervals, referred
to the total number of perforating charges in the well (b.sub.m=1),
T.sub.i(t) is the fluid temperature measured by the temperature
sensor located above the i.sup.th perforation interval.
[0040] The production rate of the individual perforation intervals
(at the initial stage of the value .gamma..sub.i) is calculated
using the energy conservation law, which is recorded for all
intervals (i=1, 2, . . . m):
b i .rho. fl c fl .intg. 0 t Q ( t ) [ T m ( t ) - T f ] dt = .rho.
fl c fl .intg. 0 t Q ( t ) .gamma. i [ T i ( t ) - T f ] dt
##EQU00007## or ##EQU00007.2## .gamma. i = b i E m ( t ) E i ( t )
##EQU00007.3##
[0041] where i=1, 2, . . . m,
E i ( t ) = .rho. fl c fl .intg. 0 t Q ( t ) [ T i ( t ) - T f ] dt
##EQU00008##
[0042] The required relative productivity
y i ( y i = O i / Q , i = 1 m y 1 = 1 ) ##EQU00009##
of the individual perforation intervals is calculated by the
formulas:
y.sub.1=.gamma..sub.1
y.sub.2=.gamma..sub.2-.gamma..sub.1
y.sub.3=.gamma..sub.3-.gamma..sub.2
[0043] In the case of two perforation intervals (m=2) and the same
number of perforating charges in the intervals (b.sub.1=0.5) the
calculated energy E.sub.1(t) is shown in FIG. 4 by the dotted
line.
[0044] The calculated value of the dimensionless production rate
.gamma..sub.1(t) is approximately constant value after .about.3
hours after perforation: .gamma..sub.1=y.sub.1.apprxeq.0.7.
[0045] In general, non-stationary well production rate Q(t) can be
calculated using the measured bottomhole pressure P.sub.0(t) and
the numerical model of a multilayer exploitation well, which
includes the permittivity {k.sub.i} and skins {s.sub.i} of the
productive formations as free parameters. The values of these
parameters can be found using an iterative procedure, the algorithm
of which is shown in FIG. 5.
[0046] An initial set of parameters characterizing the productive
intervals, {k.sub.i,s.sub.i} is determined by the conventional
hydrodynamic study (HDS) of the well under the assumption that all
formations have the same properties. For these parameters using the
measured bottomhole pressure P.sub.0(t) the total production rate
of the well Q(t) and the relative production rates {y.sub.k.sub.i}
of the individual perforation intervals are calculated. Then, using
the found production rate Q (t) and the temperatures measured by
the sensors mounted above the production layers using the procedure
described above the relative production rates {y.sub.Q.sub.i} are
found and the two obtained sets of numbers describing the inflow
profile are compared, for example, the value of the discrepancy S
is calculated:
S = i = 1 m ( y Qi - y ki ) 2 ##EQU00010##
[0047] If S is less than the specified value of the discrepancy
.epsilon.:S<.epsilon., then this set of parameters is adopted as
the solution of the task. Otherwise, the values of the parameters
{k.sub.i,s.sub.i} are changed, and the calculations continue until
the vectors {y.sub.k.sub.i} and {y.sub.Q.sub.i} coincide with a
given accuracy.
* * * * *