CN-121995521-A - Bedrock lithology recognition method based on normalized curve reconstruction amplitude difference

CN121995521ACN 121995521 ACN121995521 ACN 121995521ACN-121995521-A

Abstract

The invention discloses a bedrock lithology recognition method based on a normalized curve reconstruction amplitude difference, which comprises the steps of carrying out normalization processing on four logging curves of acoustic time difference AC, neutron porosity CNL, stratum density DEN and natural gamma GR, calculating the amplitude difference between any two normalized logging curves, defining the amplitude difference curve between any two logging curves as DIFF RCD 、DIFF CD 、DIFF CG 、DIFF DG , analyzing each lithology response characteristic according to different lithology characteristic parameters and logging curves, selecting a discrimination logging curve as a main discrimination curve and a plurality of secondary discrimination curves, optimizing the discrimination logging curve cut-off value based on any two discrimination logging curve intersection graphs, and carrying out lithology recognition. The method can successfully identify various lithologies of the bedrock, improves the accuracy of identifying the lithology of the bedrock, and has low logging cost and wider applicability.

Inventors

MA YUANKUN
WANG HAICHENG
LI JIYONG
WEN ZHONGLIN
CHEN FANGFANG
XU YU
ZHANG LEI
Tu Jiasha
JIA ZHENGLIANG

Assignees

中国石油天然气股份有限公司

Dates

Publication Date: 20260508
Application Date: 20241107

Claims (9)

1. The bedrock lithology recognition method based on the normalized curve reconstructed amplitude difference is characterized by comprising the following specific operation steps: Step 1, normalizing four logging curves of acoustic time difference AC, neutron porosity CNL, stratum density DEN and natural gamma GR, wherein the value interval of the logging curves is 0-1; step 2, calculating the amplitude difference among three logging curves of neutron porosity CNL, stratum density DEN and natural gamma GR and obtaining an amplitude difference curve; Step 3, analyzing each lithology response characteristic according to different lithology characteristic parameters and logging curves, and selecting and judging the logging curves; And 4, drawing an intersection chart according to any two discrimination log curves, further selecting a discrimination log curve cut-off value, distinguishing different lithology, and repeating the operation until all lithology is identified.
2. The bedrock lithology recognition method based on the normalized curve reconstruction amplitude difference according to claim 1 is characterized in that in the step 1, the maximum value of the acoustic time difference AC, the neutron porosity CNL, the formation density DEN and the natural gamma GR log curve is marked as AC max 、CNL max 、DEN max 、GR max , the minimum value is marked as AC min 、CNL min 、DEN min 、GR min , and the normalized results of the acoustic time difference AC, the neutron porosity CNL, the formation density DEN and the natural gamma GR log curve are specifically expressed as follows: Wherein, the Is that Is a reverse scale of (c).
3. The bedrock lithology recognition method based on the normalized curve reconstruction amplitude difference according to claim 2, wherein the step 2 is specifically as follows: Defining the difference between any two normalized log curves as an amplitude difference curve, namely, the inverse neutron-density amplitude difference Neutron-density amplitude difference Neutron-gamma amplitude difference , The density-gamma amplitude difference is specifically as follows: 。
4. the bedrock lithology recognition method based on the normalized curve reconstruction amplitude difference of claim 3, wherein the step 3 is specifically as follows: Firstly, carrying out lithology logging response characteristic analysis on bedrock, and selecting a first logging curve as a main discrimination curve; When the logging curve or amplitude difference curve of a certain lithology is obviously different from the logging curve or amplitude difference curve of other lithology, the curve is used as a first discrimination logging curve, namely a main discrimination logging curve, then the next discrimination logging curve, namely a primary discrimination curve, is found out from the residual lithology, and the operation is repeated until all lithology can be identified.
5. The method for identifying bedrock lithology based on the reconstructed amplitude differences of the normalized curves according to claim 4, wherein if a certain log or amplitude difference curve can divide lithology into two categories, each category can identify each lithology according to other log or amplitude difference curves, such curve can also be used as a discriminating log.
6. The bedrock lithology recognition method based on the normalized curve reconstruction amplitude difference of claim 4, wherein in step 4: The method comprises the steps of selecting a main discrimination log and a primary discrimination log to draw an intersection chart, selecting a corresponding discrimination log cut-off value A, identifying main lithology, selecting a primary discrimination log and a secondary discrimination log to draw an intersection chart, selecting a corresponding discrimination log cut-off value B, identifying residual lithology, and repeating the operation until all lithology is correctly identified.
7. The bedrock lithology recognition method based on the normalized curve reconstruction amplitude difference of claim 4, wherein the step 4 is specifically as follows: step 4.1, selecting CNL and GR logging curves to draw an intersection graph, wherein CNL is used as a main judgment logging curve, judging that a cut-off value A of the CNL logging curve is 10 according to the intersection graph, namely CNL >10 is quartz schist, and continuing to judge for the 2 nd time when CNL is less than or equal to 10; And 4.2, taking the GR log curve as a primary discrimination curve, discriminating the GR log curve cut-off value B according to the intersection map to obtain 120, wherein GR >120 is granite and gneiss, and the GR is less than or equal to 120, and continuing to perform the 3 rd discrimination.
8. The bedrock lithology recognition method based on the normalized curve reconstruction amplitude difference of claim 7, wherein the 2 nd discrimination method of step 4.1 is specifically as follows: In the 2 nd discrimination, the granite and the gneiss also need to be discriminated once to distinguish the two lithology, select An intersection graph is drawn by an amplitude difference curve and a GR logging curve, and selection is carried out As a five-level discrimination curve, according to the intersection graph, a cut-off value A is selected to be 0.35, 0.35 Is granite and gneiss, and vice versa.
9. The bedrock lithology recognition method based on the normalized curve reconstruction amplitude difference of claim 7, wherein the 3 rd discrimination method of step 4.2 is specifically as follows: The GR log curve is used as a primary discrimination curve, and the DEN log curve are selected again Drawing an intersection graph by an amplitude difference curve, selecting DEN as a secondary discrimination curve, and discriminating a logging curve cut-off value A according to the intersection graph, wherein DEN is 2.78, DEN is 2.78 which is amphibole and longite, and DEN is less than or equal to 2.78 which is amphibole and granite amphibole; When DEN is more than 2.78, DEN is continuously selected as a third-level secondary discrimination curve, the discrimination log curve cut-off value A takes 3, DEN >3 is amphibole, otherwise, DEN is amphibole, and when DEN is less than or equal to 2.78, DEN is selected As a four-level discrimination curve, the discrimination log curve cutoff value B takes 0, And >0 is clinopodium rock, otherwise is granite amphibole.

Description

Bedrock lithology recognition method based on normalized curve reconstruction amplitude difference Technical Field The invention belongs to the technical field of logging lithology identification and evaluation, and relates to a bedrock lithology identification method based on a normalized curve reconstruction amplitude difference. Background With the global increase of oil and gas resource demands, bedrock reservoirs become one of the main objects of current oil and gas resource exploration and development. Bedrock type oil and gas reservoirs are found in the basins such as Pascal, bohai Bay, huanghua depression, two-way, tarim, songliao, and Qidamu in recent years. Compared with clastic sandstone and carbonate rock, bedrock lithology is complex, igneous rock and metamorphic rock are usually developed at the same time, reservoir heterogeneity is strong, and lithology identification difficulty is high. The accuracy of lithology recognition is a key for guaranteeing the logging interpretation coincidence rate of hydrocarbon reservoirs. The method is influenced by the complex structure of the lithology components and the pores of the bedrock, and the conventional clastic rock lithology recognition method has poor adaptability to the bedrock reservoir. The current lithology recognition method mainly comprises an imaging logging technology, an element logging technology, a conventional log intersection graph plate method, a mathematical method and the like. The imaging and element logging technology can analyze structural characteristics, element content, mineral components and the like, but has higher cost and is difficult to widely popularize and apply. Deep learning techniques, particularly DenseCap networks and RNN language models, are also used to identify lithology. The method comprises the steps of collecting rock core image data, constructing a lithology intelligent identification tag database, predicting lithology tags through a training model, and combining the prediction results with lithology classification results of a logging curve to obtain a final lithology identification result, wherein the method is complex in process, high in identification cost and unfavorable for popularization and application. Disclosure of Invention The invention aims to provide a bedrock lithology recognition method based on a normalized curve reconstruction amplitude difference, which solves the problems that the existing lithology recognition analysis method is high in cost and difficult to popularize and apply widely. The invention adopts the technical scheme that the bedrock lithology recognition method based on the normalized curve reconstructed amplitude difference comprises the following specific operation steps: Step 1, normalizing four logging curves of acoustic time difference AC, neutron porosity CNL, stratum density DEN and natural gamma GR, wherein the value interval of the logging curves is 0-1; step 2, calculating the amplitude difference among three logging curves of neutron porosity CNL, stratum density DEN and natural gamma GR and obtaining an amplitude difference curve; Step 3, analyzing each lithology response characteristic according to different lithology characteristic parameters and logging curves, and selecting and judging the logging curves; And 4, drawing an intersection chart according to any two discrimination log curves, further selecting a discrimination log curve cut-off value, distinguishing different lithology, and repeating the operation until all lithology is identified. In the step 1, the maximum value of the acoustic time difference AC, the neutron porosity CNL, the formation density DEN and the natural gamma GR logging curve is recorded as AC max、CNLmax、DENmax、GRmax, the minimum value is recorded as AC min、CNLmin、DENmin、GRmin, and the normalization results of the acoustic time difference AC, the neutron porosity CNL, the formation density DEN and the natural gamma GR logging curve are specifically shown as follows: Wherein, the Is thatIs a reverse scale of (c). The step 2 is specifically as follows: Defining the difference between any two normalized log curves as an amplitude difference curve, namely, the inverse neutron-density amplitude difference Neutron-density amplitude differenceNeutron-gamma amplitude difference,The density-gamma amplitude difference is specifically as follows: 。 The step 3 is specifically as follows: Firstly, carrying out lithology logging response characteristic analysis on bedrock, and selecting a first logging curve as a main discrimination curve; When the logging curve or amplitude difference curve of a certain lithology is obviously different from the logging curve or amplitude difference curve of other lithology, the curve is used as a first discrimination logging curve, namely a main discrimination logging curve, then the next discrimination logging curve, namely a primary discrimination curve, is found out from the residual lithology, and the operat