Analysis of the influence of thin interbed interference on prestack AVO attributes

doi:10.13745/j.esf.sf.2020.4.26

Abstract

Abstract:

Conventional AVO analysis method based on single interface can result in errors in thin layer AVO response characteristics. The Brekhovski layered propagation matrix equation takes into account reflection and transmission of layer wave and thickness, therefore it is more suitable for discussing the seismic response characteristics of thin interbeds. We conducted Brekhovski forward modeling on thin layer and found different relationship between amplitude and thickness using different offsets. The results indicate that pitch attribute has stronger linear relationship with thickness comparing with post stack, full stack amplitude, and can be a good indicator for thin interbed thickness. In different thin interbed model tests by Brekhovski forward modeling, net thickness and Poisson's ratio are two main factors affecting AVO curve characters. Poisson's ratio has less influence on pitch and gradient attributes for small net thickness. While Poisson's ratio is constant, net thickness shows near linear relationship with pitch and gradient attributes, with pitch attribute more sensitive to net thickness, which means pitch attribute could be used for net thickness prediction. Testing results demonstrated that in thin interbed area, pitch attribute is promising for sandstone percentage prediction, whereas accuracy of net thickness prediction by poststack amplitude or prestack elastic impedance inversion is poor.

Key words: thin interbed, Brekhovski forward modeling, AVO attribute, net thickness, Poisson's ratio, elastic impedance

CLC Number:

CHEN Shan, LU Rong, LIU Lihui, XU Xingyou, LIU Weibin, BAI Jing. Analysis of the influence of thin interbed interference on prestack AVO attributes[J]. Earth Science Frontiers, 2020, 27(4): 98-109.

Figures/Tables 13

Fig.1 Reflection and transmission in thin layer media

Fig.2 AVO characteristic curve analysis of thin layer by sandwich model

Fig.3 AVO curve graph with different wavelength (a) and offset (b) in sandwich model 1

Fig.4 AVO curve graph with different wavelength (a) and offset (b) in sandwich model 2

Fig.5 Relationship of pitch or gradient attribute and thickness in models 1 (P1, G1) and 2 (P2, G2) using different three-parameter set

Fig.6 Relation schema of AVO curve and thickness

Fig.7 Thin interbed models

Fig.8 Relation schema of AVO curve and sandstone percentage

Fig.9 Comparison of pitch attribute (a) and poststack (b) sections

Fig.10 Comparison of poststack amplitude slice (a), pitch attribute (b), sandstone percentage (c) and gradient attribute (d)

Fig.11 Relationship of poststack (a) or pitch (b) attribute and sandstone percentage

Fig.12 Relationship of pitch attribute and sandstone thickness

Table 1 Sandstone accumulation thickness predicted by pitch attribute

井名	砂岩累加厚度/m	P属性值	P属性预测砂岩累加厚度/m	阻抗反演预测砂岩累加厚度/m
A	42.8	52 867	43.9	40.3
B	35	45 324.5	43.3	34.5
C	68	358 420	67.5	22.7
1	6.7	-457 119	4.5	2.5
2	43	303 637	63.3	22.5
3	36	-236 707	21.5	11.5
4	22	-672 598	12.2	2.4
5	13	-187 532	25.3	2.2
6	34.5	852	39.9	18.5
7	11	-146 285	28.5	4.8
8	47	140 567	50.7	17.5
9	36.4	-218 334	22.9	23.4
10	6.5	-462 139	4.1	19.8

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