Method for characterizing gas-bearing reservoir based on logging constraint

Patent metadata

Field	Value
Publication number	US-10802170-B2
Application number	US-201916690050-A
Country	US
Kind code	B2
Filing date	Nov 20, 2019
Priority date	Nov 21, 2018
Publication date	Oct 13, 2020
Grant date	Oct 13, 2020

Abstract

The invention relates to petroleum seismic exploration, and more specifically to a method for gas-bearing reservoir characterization using logging information. In the method, logging information is used as a constraint to indirectly characterize the distribution range of the gas-bearing reservoir by determining the upper and lower boundaries. In addition, this method enables the automatic determination of the optimal calculation parameters according to the characteristics of input data, allowing for more accurate results.

First claim

What is claimed is:

1. A method for gas-bearing reservoir characterization based on logging constraint, comprising:
(1) inputting a seismic record of a 3D seismic data set, and smoothing two ends of the seismic record to obtain a smoothed seismic record x(t);
(2) substituting the smoothed seismic record x(t) to

FB
=

[

∂

SP
opt

∂

ω
opt

]

2

;

to obtain an optimal fluid mobility interface curve FB;
wherein ω opt is optimal frequency parameter, and SP opt is energy of optimal instantaneous amplitude spectrum;
calculating SP opt according to
SP opt =[real( S opt )] 2 +[imag( S opt )] 2 ;

wherein S opt is optimal instantaneous amplitude spectrum; real(g) represents the real part of S opt , imag(g) represents the imaginary part of S opt ;
calculating S opt according to

S
opt

=

ift
⁡

[

X
×

exp
⁡

(

-

2
⁢

π
2

⁢

f
2

α
opt
2

⁢

ω
opt

2
⁢

⁢

β
opt

)

]

;

wherein X is derived from a Fourier transform of x(t); f is a vector constructed by index numbers of sampling points; α opt and β opt are optimal adjustment parameters, ift(g) represents an inverse Fourier transform;
setting a one-dimension vector ω=[4, 5,L,ω u ], wherein ω u is an upper limit frequency; setting a one-dimension vector α=[0.5,0.6,L,1.5]; and setting subscripts of elements in the vector α to be i=1, 2,L,11; and determining optimal parameters ω opt , α opt and β opt according to the following steps:
a) for α(i), setting subscripts of elements in the vector ω to be j=1,2,L,n, and establishing an objective function T(α(i), ω(j))=−(f 1 +f 2 ) for each element ω(j) of ω;
wherein f 1 =sum(fb n ), f 2 =sum(−g), sum(g) represents a summation operation;
finding out β, which maximizes the value of objective function T(α(i), ω(j)), by using a one-dimension grid search method; storing β into β(j) of a one-dimensional vector β, and storing the value of the objective function into T(j) of a one-dimension vector T;
b) finding out a maximum value T(maxid) of T, and finding out ω(maxid) and β(maxid) at a location of subscript (maxid); and storing T(maxid), ω(maxid), α(i) and β(maxid) into an i-th row of a two-dimension vector Ω with eleven rows and four columns;
c) setting i=i+1, if i>12, performing step d), otherwise repeating step a) and step b) again;
d) finding out a maximum value in a first column of Ω to obtain last three values in a row corresponding to a subscript of the maximum value in the first column of Ω, wherein the obtained last three values are the optimal frequency parameter ω opt and the optimal adjustment parameters α opt and β opt , respectively;
in the objective function, setting fb n as a normalization of the fluid mobility interface curve fb, and calculating fb according to

fb
=

[

∂
SP

∂

ω
⁡

(
i
)

]

2

;

wherein SP is energy of instantaneous amplitude spectrum;
calculating SP according to
SP =[real( S )] 2 +[imag( S )] 2 ;

wherein S is instantaneous amplitude spectrum, and is calculated according to

S
=

ift
⁡

[

X
×

exp
⁡

(

-

2
⁢

π
2

⁢

f
2

α
⁡

(
i

Assignees

• Univ Chengdu Technology

Inventors

• Chen Xuehua
• Zhang Jie
• Luo Xin
• Jiang Wei
• Zhou Chen
• Xiang Wei

Classifications

• G01V1/50 Primary

  Analysing data · CPC title

• G01V1/307

  for determining seismic attributes, e.g. amplitude, instantaneous phase or frequency, reflection strength or polarity · CPC title

• G01V2210/6161

  Seismic or acoustic, e.g. land or sea measurements · CPC title

• G01V2210/624

  Reservoir parameters · CPC title

• G01V1/306 Primary

  for determining physical properties of the subsurface, e.g. impedance, porosity or attenuation profiles · CPC title