RU2205434C1 - Method of geophysical prospecting to establish oil-and-gas productive types of geological section of variable thickness - Google Patents

Abstract

FIELD: oil geology. SUBSTANCE: given method is intended for optimization of arrangement of semi-wildcats on explored objects under conditions of varying thickness of oil-and-gas efficient rocks by complex of data of ground seismic prospecting, resistivity, radiation, acoustic, seismic logging, analysis of cores and tests of wells. Seismic prospecting operations are conducted, wells with core sampling are drilled, resistivity, radiation, acoustic, seismic logging is executed, wells are tested and cores are analyzed. Reference type-design practice with use of quantitative spectral-time parameters of results of geophysical examinations of wells is conducted by collection of drilling data. Reference model and experimental spectral-time images of oil-and-gas productive and other types of geological section are determined by data of ground seismic prospecting in area of wells. Six spectral-time parameters are determined and corrected for effect of analyzed seismic pulse variable in duration, they are compared with reference parameters which makes it possible to establish quantitatively oil-and-gas productive types of geological section of variable thickness in any point of interwell space. EFFECT: reduced expenses for drilling.

Description

 The invention relates to petroleum geology and can be used to optimize the location of exploratory and production wells at the studied object under conditions of varying thickness of oil and gas productive rocks based on a combination of ground seismic data, electrical, radioactive, acoustic, seismic logs, core studies and well tests.

 A known method of geophysical exploration for determining oil and gas productive types of a geological section, adopted as a prototype, including seismic exploration, drilling wells with coring, conducting electrical, radioactive and acoustic logging, well testing and judging by the data on oil and gas productive types of geological section of the studied object. Based on the totality of the drilling data, a standard sectional typification and determination of model reference spectral-temporal images (IAS) are carried out, and according to ground seismic data in the well area, reference experimental IES of oil and gas production and other types of geological section are determined based on the use of spectral-time analysis (SVAN) of seismic data in the target interval of recording and quantifying its results by determining the spectral-temporal parameters (SVP), which are the product of Nia specific frequency and time of the spectral density of the energy spectra in the frequency and time of their maximum or average values of frequency and time, as well as the ratio of the energy high and low frequencies, long and short times. Then, for all seismic profiles, continuously, in the target recording interval, SWAN and its quantitative spectral-temporal parameterization in frequency and time are carried out, and the results are compared with the reference ones, which allows quantitatively determining the oil and gas productive types of the geological section at any point in the interwell space.

The disadvantages of this method are:
- typification of a geological section based on a combination of drilling and well logging data without the use of SVAN and SVP;
- Conducting SWAN seismic data in one constant time interval and, accordingly, obtaining the NWO of various types of geological sections of constant thickness.

 Due to the indicated shortcomings of the prototype method, its application can lead to errors in determining the types of reference geological sections of wells, mainly by matching well standards with the resolution of seismic exploration, as well as when determining types of geological section of oil and gas productive rocks of variable thickness (for example, clinoforms ), according to seismic data, in connection with the forced division of the entire study area into separate zones with a constant thickness of the target deposits.

 A drawback of this approach is the fact that within separate zones with a constant thickness of productive rocks there may be no wells, which makes it impossible to map oil and gas productive types of sections throughout the study area.

 The task this proposal is aimed at is to provide a sharp reduction in the cost of drilling subsequent exploratory and production wells by determining with high accuracy the integrated geological characteristics (type of section) of oil and gas productive rocks of variable thickness at any point in the interwell space according to surface seismic exploration, linked to drilling results.

 The problem is solved in such a way that in a method that includes surface seismic exploration of MOGT, well drilling, electrical, radioactive, acoustic, seismic logging, well testing and core research, oil and gas production and other types of geological sections of variable thickness are determined integrally from the combination of drilling data: lithological and particle size distribution characteristics, features of the development of lithogenesis, the thickness of the target interval, the effective thickness of the reservoirs, their porosity, capacity and permeability permittivity, spectral and temporal parameters of results of geophysical studies of wells, water permeability and productivity.

 According to drilling data, including quantitative spectral-temporal parameters (SVP), obtained on the basis of spectral-time analysis (SVAN) of the results of geophysical surveys of wells, oil and gas production and other types of geological section of variable thickness are determined (see E.A. Taratyn, IA Mushin, V.Ya. Ptokhov, OG Belyaeva. "Spectral-temporal analysis of GIS data for their integration with seismic exploration", Applied Geophysics, vol. 128, M., Nedra, 1993, p. 137- 150; I.A. Mushin, L.Yu. Brodov, E.A. Kozlov, F.I. Khatyanov. "Structural and formation I am an interpretation of seismic data. "M., Nedra, 1990, 299 pp.).

 Based on the drilling and well logging data, model (synthetic) seismic traces are calculated, along which they carry out an SVAN and quantitative parameterization of its results in the form of the same SVP as the well logging. In this case, the SWAN time interval is taken constant, corresponding to the maximum thickness of the target deposits, and in all other cases, when the thickness of the target deposits decreases, only that part of the seismic record that corresponds to the changed (decreased) thickness of the target deposits remains in the same maximum time interval of the analysis, the rest of the record is reset to zero.

 Since the results of the SWAN of seismic data depend not only on the combination of physical properties of various types of geological section, but also on the pulse duration, correction factors are introduced into the SVP taking into account the inverse proportionality of the signal duration and the width of the spectrum (see A. Kharkevich "Spectra and analysis. M ., State publishing house of physical and mathematical literature, 1962, p. 235.).

 SWAN columns and SVPs of synthetic seismic traces form model spectral-temporal images (SVO) of oil and gas production and other types of geological section of variable thickness.

 According to the ground-based seismic surveys of the MOGT in the well area, experimental NWOs are determined in the same seismic recording intervals corresponding to the oil and gas productive types of geological section of variable thickness established by drilling data. In this case, the same correction coefficients are introduced into the SVPs as in the determination of model SVPs, taking into account the inverse proportionality of the signal duration and the spectral width.

 These experimental NEOs in the well area together with model NEOs with a cross-correlation coefficient (CEC) between them> 0.75 are seismic standards of various types of geological section.

 Based on a continuous SWAN of time sections along seismic profiles with a constant analysis time interval corresponding to the maximum thickness of oil and gas productive rocks and zeroed out in this maximum interval part of the seismic record that does not correspond to the target deposits when their thickness is reduced, the CBO of the target intervals of seismic recording in the interwell space is determined with correction factors for the SVP taking into account the inverse proportionality of the signal duration and the width of the spectra, and then Using the reference NWOs, oil and gas productive and other types of geological section of variable thickness are determined at any point of the studied object.

 The technical result is expressed in the mapping of oil and gas and other types of geological sections of variable thickness over the area and, thus, increasing the reliability and accuracy of the justification of the geological conditions for the laying of new exploration and production wells.

 A geophysical exploration method for determining oil and gas productive types of a geological section of variable thickness includes seismic exploration, well drilling, electrical, radioactive, acoustic, seismic logging, well testing and core research.

 According to drilling and well logging data, a section is typified, including the determination of oil and gas productive types of a geological section based on a combination of attributes at quantitative and qualitative levels — spectral-temporal parameters (SVP) of well logs, lithological facies and particle size characteristics, lithogenesis development features, target interval thickness, effective reservoir thickness , their porosity, capacity, permeability, hydraulic conductivity, well productivity. Moreover, the different types of the geological section identified have such physical properties that are displayed in various spectral-temporal images (NWO) of the GIS curves, i.e. qualitatively (visually) in the distribution of amplitudes on the SWAN column in terms of frequency-time coordinates, and quantitatively in spectral-temporal parameters (SVP) of energy frequency (along the frequency axis) and time (along the time axis) spectra.

 SWAN of well logs (SWAN logging) provides another fundamental feature of the typification of a well section - the correspondence of the number of types of cross-section of the resolution of seismic records based on its SWAN and quantitative parameterization by the same spectral-temporal parameters as well log data.

 According to the data of acoustic and radioactive logging, laboratory core tests, stiffness models are installed in the wells, synthetic seismic traces are calculated, model seismic sections are compiled, which are used to conduct SVAN and determine the model model SVOs, including oil and gas productive and other types of geological sections.

 Based on the SWAN-based MOGT seismic data, experimental standard water-based surveys are determined, including SVPs in the well area, corresponding to oil and gas production and other types of geological sections in target time intervals.

 Model and experimental SVO of oil and gas productive and other types of geological section, including SVP, should be similar with KVK> 0,75 that testifies the reasonable choice of reference SVO according to seismic data.

где К₁(f) и K₄(t) - отношение энергии высоких частот и больших времен к энергии низких частот и меньших времен; K₂(f) и K₅(t) - удельные спектральные плотности энергетического частотного и временного спектров, умноженные на средневзвешенные частоту и время; K₃(f) и K₆(t) - то же, умноженное на максимальные частоту и время; f₁ - начальная частота спектра, f₂ конечная частота спектра; Δf=f₂-f₁;

t₁, t₂, Δt, t_ср - то же по оси времен; A_i, A_j - текущие амплитуды спектров по оси частот и времен; f_i и t_j - текущие частота и время для A_i и A_j.The CBO is a SWAN column, which is characterized quantitatively along two axes and 6 (six) parameters (3 in frequency and symmetrically 3 in time):

where K ₁ (f) and K ₄ (t) is the ratio of the energy of high frequencies and large times to the energy of low frequencies and smaller times; K ₂ (f) and K ₅ (t) are the specific spectral densities of the energy frequency and time spectra multiplied by the weighted average frequency and time; K ₃ (f) and K ₆ (t) - the same, multiplied by the maximum frequency and time; f ₁ - the initial frequency of the spectrum, f _{2 the} final frequency of the spectrum; Δf = f ₂ -f ₁ ;

t ₁ , t ₂ , Δt, t _cf - the same along the time axis; A _i , A _j - the current amplitudes of the spectra along the axis of frequencies and times; f _i and t _j - current frequency and time for A _i and A _j .

The combination of six spectral-temporal parameters K ₁ -K ₆ quantitatively determines the reference NWO of oil and gas and other types of geological section of variable thickness, i.e. in an individual time interval for each SVO-standards. The difference in the CBO in this case, as already mentioned above, is due not only to the different types of section, but also to the variable magnitude of the studied pulse.

To take into account the influence of the variable SWAN interval, all SVPs (K ₁ -K ₆ ) are reduced to one interval - the maximum or minimum - as follows.

 It is known that the width of the spectrum (Δf) is inversely proportional to the duration of the function f (t), which in our case is equivalent to the time interval of the SWAN (Δt), which corresponds to the thickness of the target studied deposits, i.e. Δf × Δt = μ. For a rectangular pulse, μ = 1, triangular - 2, cosine - 1.5, and for a portion of a seismic path (Δt) undergoing SWAN, Δf × Δt = μ - the value is unknown, because the pulse of an arbitrary complex shape is analyzed.

для каждого из n эталонов типов разреза и m эталонных вариантов, в т. ч. при Δt_max, Δt_min и нескольких промежуточных значениях Δt_i. Для всего изучаемого объекта с числом типов разреза n находится или постоянное среднее значение

или принимается переменное μ, с постоянством для различных геологически однородных зон.The value of μ can be determined experimentally by SWAN of seismic recording in various time intervals corresponding to a variable thickness of oil and gas productive rocks in reference wells. Knowing Δt from the data of AK and ground-based seismic surveys of the MOGT (time sections) and determining Δf from SWAN, we find

for each of n standards of section types and m reference options, including at Δt _max , Δt _min and several intermediate values of Δt _i . For the entire object under study with the number of cut types n, a constant average value is found

or the variable μ is adopted, with constancy for different geologically homogeneous zones.

>1 для сложных сейсмических импульсов.Thus, the degree of inverse proportionality of the spectral width and the duration of the analyzed pulses is determined, i.e. SWAN intervals. This degree can be either simple (μ = 1) or different from the classical one with 1 <

> 1 for complex seismic pulses.

учитывающий разницу в ширине спектров - Δf - анализируемых сейсмических импульсов, возникшую не из-за разной формы импульсов (разных типах разреза), а по причине переменной их длительности - Δt.Knowing μ, we can determine the correction coefficient η for

taking into account the difference in the width of the spectra - Δf - of the analyzed seismic pulses, which arose not because of the different shape of the pulses (different types of section), but because of their variable duration - Δt.

For this, all comparisons are carried out either with Δf _min at Δt _max , or with Δ _max at Δt _min .

Любой другой импульс длительностью Δt_i имеет спектр с

Но это в том случае, когда μ=const в интервале сопоставления, т.е. это или весь изучаемый объект или его часть, в которой μ=const. Отсюда следует, что сопоставление спектра Δf_i со спектром, характеризующимся Δf_min (при Δt_max), для выяснения их разницы (или тождества), т. е. определения типа разреза, необходимо Δf_i разделить на

т. е. учесть разницу в Δf, обязанную не форме импульсов (типам разреза), а их длительности и, соответственно, интервалов СВАН. При выборе за основу Δt_min и, соответственно, Δf_max, необходимо Δf_i умножить на η. Таким образом, сопоставляются спектры с

или Δf = ηΔf_i.
Для временного спектра (по оси времен) его ширина прямо пропорциональна временному интервалу анализа. Предложенные СВП, количественно характеризующие результаты СВАН (K₁-K₆), учитывают изложенные выше трансформации ширины спектров в зависимости от длительности сейсмических импульсов (толщины целевых отложений).In the first case

Any other pulse of duration Δt _i has a spectrum with

But this is in the case when μ = const in the comparison interval, i.e. it is either the entire studied object or its part, in which μ = const. It follows that the comparison of the spectrum Δf _i with the spectrum characterized by Δf _min (at Δt _max ), in order to determine their difference (or identity), i.e., to determine the type of section, it is necessary to divide Δf _i by

i.e., to take into account the difference in Δf due not to the shape of the pulses (section types), but to their duration and, accordingly, the intervals of the SWAN. When choosing Δt _min and, accordingly, Δf _max , it is necessary to multiply Δf _i by η. Thus, the spectra are compared with

or Δf = ηΔf _i .
For the time spectrum (along the time axis), its width is directly proportional to the time interval of the analysis. The proposed SVPs, which quantitatively characterize the results of the SVAN (K ₁ -K ₆ ), take into account the above transformations of the spectral width depending on the duration of seismic pulses (thickness of the target deposits).

SVI K ₁ and K ₄ , which are the ratio of the spectral densities of the energy spectra of high and low frequencies, large and small times, do not change due to the symmetry of the expansion or contraction of the spectra, i.e. do not depend on the duration of seismic pulses; spectral density (at 1 Hz and 1 ms) is a constant value for any pulse duration, and the dependence of the weighted average or maximum frequency and time on the pulse duration is determined experimentally in exactly the same way as μ and η.

где α - степень обратной пропорциональности длительности импульса и средневзвешенной и максимальной частоты в формулах для K₂, K₃ и K₅, K₆, определяемая экспериментально.Thus, SVP K ₂ , K ₃ and K ₅ , K ₆ are compared: γ if Δt _max and Δf _{min are} taken as the basis and K ₂ , K ₃ and K ₅ , K ₆ , x γ if Δt _min is taken and Δf _max . Here γ is a correction coefficient equal to

where α is the degree of inverse proportionality of the pulse duration and the weighted average and maximum frequency in the formulas for K ₂ , K ₃ and K ₅ , K ₆ determined experimentally.

From the foregoing, it follows that the implementation of the method of geophysical exploration for determining oil and gas and other types of geological sections of variable thickness consists of the following steps:
- well drilling and well logging;
- terrestrial seismic surveys of the MOGT;
- typification of a section according to drilling with a quantitative characteristic (SVP) of section types based on SVAN of GIS curves;
- Creation of model and experimental reference SVO;
- determining the degree of inverse proportionality of the spectral width and pulse duration (μ);
- determination of the correction coefficient of the width of the spectrum, taking into account the duration of the pulses (η);
- determining the correction coefficient γ for the weighted average and maximum frequency of the SVP K ₂ , K ₃ and the weighted average and maximum time of the SVP K ₅ , K ₆ ;
- correlations of time sections along seismic profiles and determination of time intervals of the SWAN (Δt);
- conducting SWAN with a maximum Δt and zeroing of a part of the seismic record that does not correspond to oil and gas productive deposits with a decrease in their thickness;
- determination of SVP K ₁ -K ₆ using correction factors γ for SVP K ₂ , K ₃ and K ₅ , K ₆ ;
- determining the types of geological section from seismic profiles by comparing the reference and experimental SVP;
- building a map of the types of geological section.

Claims (1)

 A geophysical exploration method for determining oil and gas productive types of a geological section of variable thickness, including MOGT seismic exploration, drilling of wells with coring, electrical, radioactive, acoustic, seismic logging, well testing, core testing and judgment based on the data on oil and gas productive types of geological section of the studied object, characterized in that according to the totality of the drilling data conduct reference typification of the section using quantitative spectral-temporal parameters of the results of geophysical surveys of wells, which are the product of the specific frequency and time spectral densities of the energy frequency and time spectra by the maximum frequency and time, determined at the level of 0.7 of the spectrum maximum, or by the weighted average values of frequency and time, and also the ratio of the energy of high frequencies and large times to the energy of low frequencies and small times, according to surface seismic data in the area of the wells, determine the reference model and experimental spectral-temporal images of oil and gas productive and other types of geological section, characterized by spectral-temporal parameters of the results of geophysical surveys of wells, corrected for the influence of a variable duration of a seismic pulse corresponding to a variable thickness of the target deposits, then continuously over all seismic profiles in a constant maximum target interval of the seismic records corresponding to the maximum thickness of oil and gas mining Gorod, a spectral-temporal analysis is carried out with zeroing of that part of the record that does not correspond to the target deposits with a decrease in their thickness, which is revealed by correlation of the corresponding reflecting horizons in time sections, after which six spectral-time parameters are corrected for the influence of a variable in duration the analyzed seismic pulse and comparing them with the reference ones, which allows to quantify the oil and gas productive types of geological section a variable thickness anywhere interhole space.