CN-121995524-A - Mudstone compaction extrapolation applicability judging method based on acoustic wave and density logging

CN121995524ACN 121995524 ACN121995524 ACN 121995524ACN-121995524-A

Abstract

The invention belongs to the technical field of basin simulation, and particularly relates to a mudstone compaction extrapolation applicability judging method based on sound waves and density logging. 1. Selecting continuous mudstone sections, sampling data points, taking the value of acoustic time difference Deltat ma of a rock skeleton, drawing a casting point relation graph, 2, identifying stratum interfaces with different convergence trends of acoustic time difference data of upper and lower stratum mudstone sections according to convergence trends of discrete distribution of the data points, 3, acquiring fitting straight lines of upper and lower data point groups of each data point group section or a target unconformity surface, 4, making difference between the corresponding burial depth of the base line value Deltat 0 in the fitting curve and the corresponding burial depth of the studied unconformity surface, acquiring assumed stratum recovery erosion quantity H, 5, obtaining a functional relation rho' (Z) of the density of the target stratum group section relative to the burial depth through logarithmic fitting, 6, calculating recovery pressure P b and present pressure P x , and comparing the numerical values of the recovery pressure P b and the present pressure P x .

Inventors

ZHANG ZHIKAI
ZHANG YUNFENG
YU XUNTAO
Zhu Suihang
LI ZHONGTANG
ZHANG YU

Assignees

东北石油大学

Dates

Publication Date: 20260508
Application Date: 20251222

Claims (5)

1. A mudstone compaction extrapolation applicability judging method based on acoustic wave and density logging is characterized by comprising the following steps: Firstly, taking a single well point as a basic working unit, selecting a continuous mudstone section for data point sampling based on acoustic time difference logging data, taking a value of acoustic time difference Deltat ma of a rock framework, and drawing a point throwing relation diagram of the buried depth and acoustic time difference logging under a Z-ln (Deltat-Deltat ma ) coordinate system; Step two, taking stratum group sections as basic research units, marking the acoustic wave time difference data of the mudstone sections in a segmented mode according to the burial depth, and identifying stratum interfaces, namely unconformity surfaces, with different convergence trends of the acoustic wave time difference data of the upper and lower stratum mudstone sections according to the convergence trends of discrete distribution of data points; Dividing data point group sections formed by single-layer group sections or integrated contacted multi-layer group section mudstone section acoustic wave time difference data points by taking an unconformity surface as a boundary, and obtaining a fitting straight line of each data point group section or upper and lower data point group sections of the unconformity surface to be researched, wherein Z-ln (delta t-delta t ma ) adopts a semi-logarithmic coordinate system, and a mathematical model formula of the fitting straight line is as follows: ln(Δt-Δt ma )＝-CZ+ln(Δt 0 -Δt ma ) (1); Wherein Deltat ma is the acoustic time difference value of the rock skeleton, the unit is us.m -1 ;Δt 0 is the initial deposition acoustic time difference base value, the unit is us.m -1 , C is the slope of a compaction trend line, the unit is m -1 , Z is depth, and the unit is m; Step four, taking the value of the initial sedimentary acoustic wave time difference Deltat 0 of the destination group section below the destination unconformity surface, extrapolating the data point group section fitting curve below the destination unconformity surface to the initial sedimentary acoustic wave time difference value, namely Deltat 0 , by using an extrapolation method, and taking the difference between the buried depth H Δt0 corresponding to the baseline value Deltat 0 in the fitting curve and the buried depth H m corresponding to the studied unconformity surface to obtain the assumed stratum recovery ablation quantity H, wherein the calculation formula is as follows: Setting an initial density rho 0 of a destination group section below the non-integrated destination surface, and combining a known density log of the destination group section with the stratum recovery degradation H assumed in the fourth step, and obtaining a functional relation rho' (Z) of the density of the destination group section relative to the buried depth z through logarithmic fitting, wherein a fitting formula is as follows: ρ′(Z)=f(Z) (3); Step six, calculating the recovery pressure P b generated by the assumed formation recovery erosion amount H on the destination group section by utilizing the functional relation rho' (Z) in the step five, wherein the recovery pressure P b takes an absolute value, calculating the present pressure P x generated by the destination group section by the target non-integrated surface overburden formation by utilizing the known density logging curve rho (Z) of the target non-integrated surface overburden Z depth and the present pressure P x of the target non-integrated surface overburden formation, and comparing the value of the recovery pressure P b with the present pressure P x , wherein if P x ＜P b shows that the original formation deposition rule is not destroyed, and if P x ＜＜P b shows that the formation may be influenced by complex factors; The calculation formula of the recovery pressure P b is as follows: Wherein ρ' (Z) is a continuous mudstone segment data point set obtained by sampling a target non-integrated subsurface target formation segment, and is used for representing the assumed density function relation of the degraded stratum with the depth; the calculation formula for the pressure P x nowadays is as follows: where ρ (Z) is a known density log of the present-day subsurface formation for characterizing the differential relationship of density and depth of the real-world subsurface formation.
2. The method for determining the suitability of mudstone compaction extrapolation based on acoustic and density logging as claimed in claim 1, wherein in step five, the density fitting function ρ' (z) is in the form of natural logarithms.
3. The method for determining the suitability of mudstone compaction extrapolation based on acoustic 2 wave and density logging as claimed in claim 1, wherein in the sixth step, the pressure integral is in absolute unit Pa.
4. The method for determining suitability of mudstone compaction extrapolation based on acoustic and density logging as claimed in claim 1, wherein in step six, ρ' (Z) is fitted together with an initial density-depth coordinate point (ρ 0 , Z-H) consisting of an initial density ρ 0 of a group of formations of the order below the set-purpose unconformity and a hypothetical formation recovery ablation amount H.
5. The method of determining the suitability of mudstone compaction extrapolation based on acoustic and density logging as claimed in claim 1, wherein in step six, if P x ＜P b indicates that the original formation deposition rule is not destroyed, if P x ＜＜P b indicates that the formation may be affected by a complex factor.

Description

Mudstone compaction extrapolation applicability judging method based on acoustic wave and density logging Technical Field The invention belongs to the technical field of basin simulation, and particularly relates to a mudstone compaction extrapolation applicability judging method based on acoustic time difference logging and density logging. Background Recovery of formation erosion is a key element in basin modeling, and mudstone compaction extrapolation is one of the common recovery methods. The method estimates the ablation amount by extrapolation of a fitted curve based on the relationship between the mudstone acoustic wave time difference and the buried depth. However, in practical application, due to factors such as formation complexity, change of deposition environment, logging data errors and the like, the applicability of the mudstone compaction extrapolation method is often difficult to accurately judge, so that a great deviation exists in the recovery result of the degraded amount, and the accuracy of basin simulation and the reliability of oil and gas exploration are affected. Disclosure of Invention In order to solve the problems of the background technology, the invention provides a method for judging the applicability of a mudstone compaction extrapolation based on acoustic wave and density logging, which aims to solve the problems of lack of objective basis and easy misjudgment in the prior art for judging the applicability of the mudstone compaction extrapolation, and improve the accuracy and reliability of recovery of the degraded amount. The invention adopts the following technical scheme that the method for judging the applicability of the mudstone compaction extrapolation based on acoustic wave and density logging comprises the following steps: Step one, taking a single well point as a basic working unit, selecting a continuous mudstone section for data point sampling based on acoustic time difference logging data, taking a value of acoustic time difference Deltat ma of a rock framework, and drawing a point throwing relation diagram of the buried depth and acoustic time difference logging under a Z-ln (Deltat-Deltat ma) coordinate system. And secondly, taking the stratum group section as a basic research unit, marking the acoustic wave time difference data of the mudstone section in a segmented mode according to the burial depth, and identifying stratum interfaces, namely unconformity surfaces, with different convergence trends of the acoustic wave time difference data of the upper and lower stratum mudstone sections according to the convergence trend of the discrete distribution of the data points. Dividing data point group sections formed by single-layer group sections or integrated contacted multi-layer group section mudstone section acoustic wave time difference data points by taking an unconformity surface as a boundary, and obtaining a fitting straight line of each data point group section or upper and lower data point group sections of the unconformity surface to be researched, wherein Z-ln (delta t-delta t ma) adopts a semi-logarithmic coordinate system, and a mathematical model formula of the fitting straight line is as follows: ln(Δt-Δtma)＝-CZ+ln(Δt0-Δtma) (1)。 Wherein Deltat ma is the rock skeleton acoustic wave time difference value, the unit is us.m -1;Δt0 is the initial deposition acoustic wave time difference base value, the unit is us.m -1, C is the slope of compaction trend line, the unit is m -1, and Z is depth, and the unit is m. Step four, taking the value of the initial sedimentary acoustic wave time difference Deltat 0 of the destination group section below the destination unconformity surface, extrapolating the data point group section fitting curve below the destination unconformity surface to the initial sedimentary acoustic wave time difference value, namely Deltat 0, by using an extrapolation method, and taking the difference between the buried depth H Δt0 corresponding to the baseline value Deltat 0 in the fitting curve and the buried depth H m corresponding to the studied unconformity surface to obtain the assumed stratum recovery ablation quantity H, wherein the calculation formula is as follows: Setting an initial density rho 0 of a destination group section below the non-integrated destination surface, and combining a known density log of the destination group section with the stratum recovery degradation H assumed in the fourth step, and obtaining a functional relation rho' (Z) of the density of the destination group section relative to the buried depth z through logarithmic fitting, wherein a fitting formula is as follows: ρ′(Z)＝f(Z) (3)。 Step six, calculating the recovery pressure P b generated by the assumed formation recovery erosion amount H on the destination group section by utilizing the functional relation rho' (Z) in the step five, taking absolute value of the recovery pressure P b, calculating the present pressure P x generated by the destinati