Making deep geological formations clearly visible: a complex mountain full-waveform inversion technology at the Institute of Geophysical Prospecting of Crude Oil Fields

Recently, at the acceptance meeting of the oil and gas exploration project of China Crude Oil Field, the research and development results of the innovation research team of the Institute of Geophysical Research of China Crude Oil Field - complex mountain full waveform inversion technology were affirmed
by the judges and experts attending the meeting.
Experts at the meeting unanimously agreed that the technology has reached the domestic leading level
.
This is Sinopec's first industrial application case
of full-waveform inversion technology in the field of high-precision seismic data imaging processing in complex mountains.

The geology is complex and the existing technology cannot focus the imaging

The increasingly complex geological exploration environment puts forward higher requirements
for the resolution and focus of seismic imaging.
However, conventional seismic imaging techniques are limited by theoretical assumptions, and cannot achieve ideal high resolution, and can only obtain fuzzy imaging maps
of the subsurface.

"Sichuan Tongnan Ba is located in lofty mountains, surface ravines and valleys are longitudinal, underground structures change horizontally, and there are various structural reversals
.
Existing technology does not allow high-precision imaging
of the subsurface situation in the area.
Just like using a camera that is not in focus, the person photo taken can only see the outline and the facial features
are not clear.
Guo Yundong, the project leader and postdoctoral fellow in the oil field, said
.

At present, the internationally recognized speed modeling technology based on full waveform inversion is the best solution
to solve the problem of "unclear shooting".
Although the full waveform inversion technology seems to be quite perfect in theory, there are many bottlenecks in large-scale industrial production applications, especially for complex terrestrial seismic data, and the quality of field seismic data and the accuracy of the initial background field are very high
.

The Tongnamba area belongs to a complex mountainous terrain, the underground structure is extremely complex, and the seismic data collected in the field have many missing low-frequency components and strong signal noise, which is not conducive to the construction of the background velocity field and cannot meet the requirements
of high-precision speed modeling.

Eliminate "roadblocks" and strive to see deeply and clearly

How can accurate focused imaging of such complex structures be achieved? The Institute of Geophysical Prospecting of China Crude Oil Field set up an innovative research team to carry out special scientific research
.
Researchers use various methods of breaking to encircle, pursue, and intercept the "roadblockers"
.

In view of the actual situation of complex mountain surface undulation, drastic lateral changes in the surface layer and complex underground structure in the Tongnamba area, researchers have developed a series
of depth shift technology that approximates the real surface before stacking.
"If the previous technique was to perform surgery on massive amounts of data, now it is a minimally invasive method to solve the problem
of seismic data distortion caused by traditional methods.
" Li Qingyang, an expert in the research and development direction of geophysical software in China Crude Oil Field, said
.

On the basis of ensuring the authenticity and accuracy of the data, it is also necessary to solve the problem
of "focus".
Speed renewal is at the heart of
tectonic "focus".
In view of the difficulty of severe transverse velocity conversion in the underground exploration area of Tongnamba, the researchers further deepened the multi-information constrained velocity modeling strategy
from shallow to deep, layer by layer, and gradually iterative.

After a series of "debugging" and "focusing", how effective is the imaging of geological structures? Li Chuanqiang, deputy manager of the oilfield oil and gas exploration and management department, gave the answer: "The project has completed the prestack depth offset imaging processing of 3D seismic data covering 580 square kilometers in the Tongnamba area with high quality, with clear overall section structure, clear geological interface features, accurate offset homing, clear imaging of the fault system, and clear
fracture section.
”

Self-developed application software to achieve breakthrough from "0" to "1"

Geological modeling and imaging based on massive data puts forward very high requirements
for hardware and software technology.

For high-end seismic imaging technologies such as full waveform inversion technology, foreign research institutes have long implemented hardware graphics processing units (GPUs) and software technology monopolies
.
"On the one hand, there is an urgent domestic technology demand, and on the other hand, there is a foreign technology blockade, which makes us have to accelerate the pace
of independent development of corresponding software.
" Li Qingyang said
.

Zhongyuan Geophysical Research Institute reached a strategic cooperation with the National Supercomputing Center Zhengzhou to develop software on
the domestic hardware Haiguang Domain Controller (DCU).
At present, the relevant program modules developed by researchers on DCU have been tested and passed by the National Supercomputing Center, and the seismic data processing software independently developed by China Crude Oil Field with domestic hardware as the carrier has achieved a breakthrough
from "0" to "1".

"In the next step, we will continue to improve the operation efficiency and accuracy of independent software, and form independent property rights software
that adapts to domestic hardware.
" At the same time, we will increase the promotion of full-waveform inversion and other related technologies to provide more accurate seismic data support
for breakthroughs and discoveries in oil and gas exploration.
Li Qingyang said
with confidence.