Basic idea of section modeling

In the traditional geological analysis, people obtain geological information by means of drilling, geophysical exploration and exploration, and then use geological profiles to reflect the local stratigraphic structure and structural characteristics, and use the combination of multiple profiles to understand the macro-geological characteristics of the study area. The idea of profile modeling comes from the geological profile analysis method. The basic idea is: firstly, build a group of parallel geological sections, draw a section line profile composed of stratum boundary and fault boundary on each section, and then reconstruct the three-dimensional shape with two-dimensional contour lines, and connect all sections with triangulation to form a solid model. Like seamless geological modeling method, the geological model constructed by profile modeling method can also be represented by boundary representation, and each block in the model is surrounded by triangular surfaces.

7.2. Applicability of1.2 section modeling

If the fault system in the modeling area is simple, the strike of multiple faults is close, and there is no mutual cutting between faults, the solid model can be established by profile modeling method. When the strike of multiple faults in the modeling area is close, if a group of sections are drawn along the direction almost perpendicular to the average strike of faults, the line outline structure on the sections will be similar, which is convenient to connect the contour lines of adjacent sections. However, if the fault system is complex, there are many groups of faults with different strike and crossing each other, and the structure of different profile lines is quite different, it is difficult to use profile modeling method.

7.2. 1.3 modeling steps

Section modeling includes the following basic steps:

(1) Create an abstract geological profile. Geological section is a virtual section reflecting the stratigraphic structure and structural characteristics of the modeling area, which can be used to help establish the corresponding relationship between adjacent section lines.

(2) Create a section line profile. The section line section is formed by the intersection of stratum, fault interface and section. In order to facilitate the contour connection of adjacent sections, the boundary lines on each section are intersected first, and each boundary line is dispersed into a simple arc, and then each simple arc is given certain attributes according to the strata on both sides of the simple arc.

(3) Connection of line profiles of adjacent sections, that is, connecting line profiles with triangular surfaces between all adjacent sections. If the line profiles on two adjacent sections have the same structure and the simple arcs have a one-to-one correspondence, the corresponding simple arcs can be connected by the synchronous advancing method of the adjacent profiles. However, due to the phenomena of stratum pinch-out and fault pinch-out, and the different fault distances of strata on different sections, it is difficult to ensure the same structure of adjacent section lines. This book will introduce a method of connecting fault boundaries first and then connecting stratigraphic boundaries in blocks.

(4) Triangulation of model boundary. After connecting all adjacent sections, the fault interface and stratigraphic interface of the model will be obtained, but the model is not closed and the model boundary needs to be divided into triangular surfaces.

(5) Simple block search. A simple block search is carried out by using the connection relationship of triangles, and then a solid model is formed by endowing strata with attributes.