U.S. patent application number 12/906557 was filed with the patent office on 2011-05-12 for method of treating bottom-hole formation zone.
This patent application is currently assigned to Schlumberger Technology Corporation. Invention is credited to Arefievich Dmitry Chuprakov, Gisele Thiercelin, Marc Jean Thiercelin.
Application Number | 20110108268 12/906557 |
Document ID | / |
Family ID | 43973287 |
Filed Date | 2011-05-12 |
United States Patent
Application |
20110108268 |
Kind Code |
A1 |
Chuprakov; Arefievich Dmitry ;
et al. |
May 12, 2011 |
METHOD OF TREATING BOTTOM-HOLE FORMATION ZONE
Abstract
The invention relates to the methods of treating a bottom-hole
formation zone to increase in well productivity and rocks
permeability. According to this method a pulse generator should be
tripped in a well and the formation pulse treatment should be
conducted by generating negative pressure pulses of amplitude
higher than the tensile formation strength. The method provides the
high fissuring rate by breaking formation fluid-bearing permeable
rocks around a wellbore.
Inventors: |
Chuprakov; Arefievich Dmitry;
(Kirov, RU) ; Thiercelin; Marc Jean; (US) ;
Thiercelin; Gisele; (Dallas, TX) |
Assignee: |
Schlumberger Technology
Corporation
Cambridge
MA
|
Family ID: |
43973287 |
Appl. No.: |
12/906557 |
Filed: |
October 18, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11762392 |
Jun 13, 2007 |
|
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12906557 |
|
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Current U.S.
Class: |
166/249 |
Current CPC
Class: |
E21B 43/003
20130101 |
Class at
Publication: |
166/249 |
International
Class: |
E21B 43/00 20060101
E21B043/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 22, 2006 |
RU |
2006122049 |
Claims
1. A method of treating a bottom-hole formation zone, the method
comprising the steps of: tripping a pulse generator in a well;
pressurizing a bottom-hole zone higher than the pore pressure or
the principle maximum stress in a far-field zone of the formation;
generating at least one negative pressure pulse with magnitude
higher than ultimate tensile formation strength and duration less
than a character time of diffusion of a fluid in a reservoir.
2. The method of claim 1 wherein the at least one negative pressure
pulse is applied in a process of hydraulic fracturing during a
fracture propagation.
3. The method of claim 1 wherein the at least one negative pressure
pulse has magnitude of 5 MPa.
4. The method of claim 1 wherein a duration of the at least one
negative pressure pulse is 0.01 s.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of application
Ser. No. 11/762,392, filed Jun. 13, 2007.
FIELD OF THE INVENTION
[0002] The subject disclosure relates to oil and gas well
production and can be used to treat a bottom-hole formation zone to
increase well productivity and rock permeability.
BACKGROUND OF THE INVENTION
[0003] At present, various methods of treating a bottom-hole
formation zone are directed to the increase in oil recovery
coefficient. These are reactant treatments of the producing
formations involving the injection of different processing media
based on organic and non-organic matters to a well, pulse methods
combined with mechanical; thermal and chemical effect, and
hydraulic fracturing of the formation, being a better-known well
stimulation of hydrocarbons through increase in permeability of the
bottom-hole zone of the producing formation due to fissuring.
[0004] The methods of treating a bottom-hole zone involving
pressure pulses are based on elastic wave/pressure wave excitation
in rock formation. The pressure wave effect was proposed more than
40 years ago as an alternative procedure resulting in higher
efficiency of the standard methods. This method has not found a
wide application yet despite some beneficial results in practice
(e.g. flow rate increase and/or oil recovery coefficient). The
central problem is the lack of reliable field data and theoretical
reasoning too. Particularly, it is impossible to predict or
stimulate what is the effect (positive or negative) of pressure
pulses on production. Nevertheless, some equipment has been
developed, among them surface vibrators and downhole tool (pressure
pulse excitation tool, sparkers, magnetostrictive and piezoceramic
sources), which results a wide range of pulse frequency.
[0005] A most close analog to a method applied is a method of
treating a bottom-hole zone involving the trip of a pulse generator
in a well followed by the formation pulse treatment specified in
patent RU 2105874, 1998.
SUMMARY OF THE INVENTION
[0006] The present invention provides a method of treating a
bottom-hole zone that provides high fissuring rate by breaking
formation fluid-bearing permeable rocks around a wellbore. This
method increases the rock permeability through the generation of
formation microfractures or the regeneration of earlier fissures;
and combined with the hydraulic fracturing provided that fractures
propagate and reach the surface of the hydraulic fracturing
fissures the pressure pulses form rock lumps that do away with the
fissure surface and become proppants themselves.
[0007] In the present invention a provision is made for the method
of treating a bottom-hole zone involving the trip of a pulse
generator in a well followed by the formation pulse treatment to
generate the negative pressure pulses of amplitude higher than
tensile formation strength and with duration less than the
character time of diffusion of fluid in reservoir. If the
characteristic diffusion time of fluid in a reservoir is T, then
the duration of a pulse can be set as 1/100 of T which is
sufficient. The diffusion time for fluid in a reservoir is
estimated as T=R 2/D, where R is the radius of a wellbore and D is
the coefficient of diffusion of a fluid. For example, if the
character diffusion time is T=1 sec, then the duration of a pulse
can be set at 0.01 sec.
[0008] In case of hydraulic formation fracturing, pressure pulses
are fed as a breaking fissure grows. Moreover, prior to pulse
action the pressure is built in a bottom-hole well zone higher than
pore pressure in a far-field zone for the formation; or in case of
hydraulic fracturing the pressure is built in the created fracture
higher than principle maximum stress in the far-field zone for the
formation.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The invention is carried out as follows. A pulse generator
should be tripped in a well and negative pressure pulses be
generated around oil-bearing formation of amplitude higher than the
tensile formation strength. A short and power pulse with magnitude
of several MPa and duration less than the character time of
diffusion of fluid in reservoir can initiate fissuring near a
wellbore and in a created fracture (in case of hydraulic
fracturing). Each next negative pressure pulse should make
formation fissures grow. In case of hydraulic formation fracturing,
pressure pulses can be fed as a breaking fissure grows. To create
ruptures prior to pulse action the pressure is built in a
bottom-hole well zone higher than pore pressure in a far-field zone
for the formation; or in case of hydraulic fracturing the pressure
is built in the created fracture higher than the principle maximum
stress in the far-field zone for the formation.
[0010] As an example let us consider an axisymmentric well of
radius R being drilled straight, and the hydraulic fracturing
(straight and vertical) of L long is in a permeable rock formation.
The well cavity and the hydraulic fracturing are filled with fluid
at a certain pressure P.sub.w. For a well P.sub.w>p.sub.0, for
hydraulic fracturing P.sub.w>-.sigma..sub.1.sup.(f), where,
p.sub.0 is the pore pressure in the far-field zone (e.g. 5 MPa),
and .sigma..sub.1.sup.(f) is the principle maximum stress in the
far-field zone (e.g. 8 MPa) (it is taken that the tensile stress is
positive). The pressure P.sub.w has been applied for the set time
to build up excessive pressure in the formation (i.e. fluid
diffusion process). Elastic motion in the fluid-bearing pore medium
is described by the following equations for a medium displacement
vector u and a relative fluid displacement vector w:
.rho. u .fwdarw. + .rho. f w .fwdarw. = G .DELTA. u .fwdarw. +
.gradient. .fwdarw. [ ( K + 1 3 G + .alpha. 2 M ) ( .gradient.
.fwdarw. u .fwdarw. ) + .alpha. M ( .gradient. .fwdarw. w .fwdarw.
) ] , ( 1 a ) .rho. f u .fwdarw. + T .phi. .phi. .rho. f w .fwdarw.
+ .mu. .kappa. w .fwdarw. . = .gradient. .fwdarw. [ .alpha. M (
.gradient. .fwdarw. u .fwdarw. ) + M ( .gradient. .fwdarw. w
.fwdarw. ) ] . ( 1 b ) ##EQU00001##
[0011] Where, p is the total mass density of the saturated rock,
p.sub.f is the pore fluid mass density, G is the shear modulus, K
is the bulk modulus under drainage, M is the BioH modulus, .alpha.
is the elastic pore medium coefficient, .phi. is the porosity, T
.phi. is the rock pore tortuosity coefficient, .mu. is the fluid
viscosity, k is the rock permeability, and a point is the time
derivative. Stress components and the pore pressure are in the form
of the first space derivative and w:
.sigma. ij = 2 G e ij + .delta. ij ( ( K - 2 3 G + .alpha. 2 M ) e
- .alpha. M .zeta. ) , ( 2 a ) p = - .alpha. M e + M .zeta. . ( 2 b
) ##EQU00002##
[0012] Where,
e ij = 1 / 2 ( .differential. u i / .differential. x j +
.differential. u j / .differential. x i ) , e = i .differential. u
i / .differential. x i , .zeta. = - i .differential. w i /
.differential. x i . ##EQU00003##
[0013] At the interface between the well fluid and the porous
reservoir the following conditions are satisfied:
.sigma..sub.nn=-P, .sigma..sub.n.tau.=0, p=P (3)
[0014] Where, the left-hand side of the equations has normal
stress, shear stress and pore pressure, respectively, and
P=P.sub.w+P(t) is the total pressure of the well fluid. Solving a
problem (1) of the boundary conditions (3) for the wellbore and
hydraulic fracturing gives the space stress and pore pressure
distribution. The use of the below known criteria of the tensile
failures and the failures according to a Mohr-Coulomb law is the
possibility of estimating the tensile rock failure and the failure
by shear fractures:
g TC .ident. .sigma. 1 eff = .sigma. 1 + p > T 0 , ( 4 a ) g MC
.ident. .sigma. 1 t g 2 ( .pi. 4 + .PHI. 2 ) - .sigma. 3 .gtoreq.
.sigma. c , ( 4 b ) ##EQU00004##
[0015] Where, g.sub.TC and g.sub.MC are the function of fissure
flow for ruptures and shear fractures, respectively, being analyzed
to predict rock fracturing; T.sub.0 and .sigma..sub.c are the
tensile strength and the crushing strength of the rock,
respectively.
[0016] Dynamic pulses P(t) applied are of negative amplitude, for
example, P(t)=-P-pulse exp(-t.sup.2/T.sup.2pulse), where, P-pulse
is the amplitude, and T-pulse is the pulse period.
[0017] Should the tensile formation strength T.sub.0 is 1 MPa, the
amplitude P-pulse is rather powerful, e.g. 5 MPa, and the T-pulse
duration for rock permeability k equal to 10.sup.-3 is rather
short, e.g. 0.01 s; ruptures and shear fractures occurring around
wellbore and created fractures.
[0018] A fissure propagation direction can be predicted by the
nature of the fissures themselves, i.e. ruptures or shear
fractures. With pressure reduced, a maximum tensile component is
radial relative to a wellbore wall and normal relative to a fissure
direction at the surface of the fracturing. Therefore, ruptures
propagate in parallel to the wellbore boundary or a created
fracture. Shear fractures, if any, are inclined at an angle
.psi..sub.c=.pi./4-.phi./2 to the direction of principle minimum
stress, where, .phi. is the rock friction angle.
* * * * *