U.S. patent application number 11/762392 was filed with the patent office on 2007-12-27 for method of treating bottom-hole formation zone.
This patent application is currently assigned to Schlumberger Technology Corporation. Invention is credited to Dmitry Arefievich Chuprakov, Marc Jean Thiercelin.
Application Number | 20070295500 11/762392 |
Document ID | / |
Family ID | 38332207 |
Filed Date | 2007-12-27 |
United States Patent
Application |
20070295500 |
Kind Code |
A1 |
Chuprakov; Dmitry Arefievich ;
et al. |
December 27, 2007 |
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; Dmitry Arefievich;
(Moscow, RU) ; Thiercelin; Marc Jean; (Ville
d'Avray, FR) |
Correspondence
Address: |
SCHLUMBERGER-DOLL RESEARCH;ATTN: INTELLECTUAL PROPERTY LAW DEPARTMENT
P.O. BOX 425045
CAMBRIDGE
MA
02142
US
|
Assignee: |
Schlumberger Technology
Corporation
Cambridge
MA
|
Family ID: |
38332207 |
Appl. No.: |
11/762392 |
Filed: |
June 13, 2007 |
Current U.S.
Class: |
166/249 ;
166/308.1 |
Current CPC
Class: |
E21B 43/26 20130101 |
Class at
Publication: |
166/249 ;
166/308.1 |
International
Class: |
E21B 43/26 20060101
E21B043/26 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 22, 2006 |
RU |
2006122049 |
Claims
1. A method of treating a bottom-hole formation zone involving a
pulse generator to be tripped in a well followed by formation pulse
treatment distinguishing by the fact that negative pressure pulses
should be generated of amplitude higher than tensile formation
strength.
2. A method according to claim 1 distinguishing the fact that prior
to pulse action the pressure is built in a bottom-hole well zone
higher than the pore pressure in a far-field zone for the
formation.
3. A method according to claim 1 distinguishing the fact that in
case of hydraulic formation fracturing, pressure pulses should be
fed as a breaking fissure grows.
4. A method according to claim 2 distinguishing the fact that prior
to pulse action in the created fracture zone the pressure should be
built higher than the principle maximum stress in a far-field zone
for the formation.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority to Russian
Patent Application No. 2006122049 filed Jun. 22, 2006, which is
herein incorporated by reference.
FIELD OF THE INVENTION
[0002] This invention relates to the art of oil and gas well
production and can be used to treat a bottom-hole formation zone to
increase in well productivity and rocks 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 frequency pulses.
[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 a 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 propants 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.
[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 of magnitude of
several MPa 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. As an example let us consider an axisymmetric 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. + .rho. j = G .DELTA. u _ + .gradient. _ [ ( K + 1 3 G +
.alpha. 2 M ) ( .gradient. _ u _ ) + .alpha. M ( .gradient. _ w _ )
] , ( 1 a ) .rho. f + T .PHI. .phi. .rho. f + .mu. .kappa. =
.gradient. _ [ .alpha. M ( .gradient. _ u _ ) + M ( .gradient. _ w
_ ) ] . ( 1 b ) ##EQU00001##
[0010] 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 {right arrow over (u)} and {right
arrow over (w)}:
.sigma. ij = 2 Ge ij + .delta. ij ( ( K - 2 3 G + .alpha. 2 M ) e -
.alpha. M .zeta. ) , ( 2 a ) p = - .alpha. Me + M .zeta. . 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 . ( 2 b ) ##EQU00002##
[0011] At the interface between the well fluid and the porous
reservoir the following conditions are satisfied:
.sigma..sub.nm=-P, .sigma..sub.n.tau.=0, p=P (3)
[0012] 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 tg 2 ( .pi. 4 + .PHI. 2 ) - .sigma. 3 .gtoreq.
.sigma. c ( 4 b ) ##EQU00003##
[0013] 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.
[0014] Dynamic pulses P(t) applied are of negative amplitude, for
example, P(t)=-P-pulse exp.sup.-(-t.sup.2/T.sup.2 pulse), where,
P-pulse is the amplitude, and T-pulse is the pulse period.
[0015] Should the tensile formation strength T.sub.o 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. 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.
* * * * *