Sinopec sees the FULL-WAVE DIFFERENCE in their reservoirs in China

VectorSeis is a digital, 3C, single-point sensor that measures true 3D ground motion and records the full seismic wavefield. When VectorSeis is used to acquire seismic data, geophysicists obtain enhanced subsurface images that allow them to better plan their exploration and development drilling programs.

Regional context
As China becomes the ‘factory to the world,’ both its economy and its thirst for energy are growing at a double-digit clip. Over the last several years, Chinese oil & gas companies have embarked on a strategic quest for hydrocarbons, striking mega-deals with leading resource holders in the Middle East, West Africa, Central Asia, and Canada. Nonetheless, China has a sizeable domestic resource base (roughly half the size of that of the United States) that has yet to be fully exploited.

Sinopec is one of three quasi-national oil companies under the ownership and control of the Chinese government. Sinopec’s mandate includes the exploration and production of oil and natural gas, oil refining, and the production and sale of petrochemicals. Sinopec is the second largest crude oil producer in China. One of the main areas of production for Sinopec is the Sichuan Province, an area expected to receive 70 billion Yuan (nearly $9 billion) in new capital investment over the next three years.

Imaging and operational challenges
While Sichuan is a known gas-producing region, the productivity of individual wells can vary significantly, even within the same field and geologic horizon. This variation is often driven by natural fracturing within the reservoir rocks; increased fracturing generally correlates with higher well productivity, while well productivity falls as fracturing decreases.

Subsurface fractures aren’t the only challenge in Sichuan. One of the larger structures – known as XinChang – sits beneath an area having significant natural and man-made obstructions. The area is densely populated. Several highways and railways, as well as a network of pipelines and rivers, cut across the field. As a result, seismic acquisition systems must be flexible and reliable to ensure the health, safety, and environmental requirements of both seismic field workers and nearby residents.

The ION solution
In 2003, Sinopec tested the viability of full-wave imaging by conducting a 2D pilot test in a small area of the Zhongyuan oil field. Full-wave techniques are often useful in fracture detection and mapping, since the down-going acoustic energy will often split when it hits a natural fracture in the subsurface. Conventional seismic techniques are less effective in fracture detection. However, by using a three-component, full-wave sensor like VectorSeis, and by applying specialized seismic data processing techniques like AZIM, this shear-wave splitting can be characterized and mapped. The results of the 2003 pilot test were encouraging; areas with significant shearwave splitting correlated with existing wells having better historical productivity.

In 2005, a full-scale seismic program was acquired over a 529 square kilometre area in the Sichuan Province. It was one of the largest onshore full-wave imaging programs ever designed, with 10,400 shots and 3,168 live recording stations. ION’s System Four served as the acquisition platform for our three-component, digital full-wave VectorSeis sensor. Ultimately, nearly 100 million traces of data were acquired. Since the survey was designed with high-station density, the recorded full-wave data was well sampled, which makes it more valuable as an input in seismic data processing.

In 2006, ION’s GX Technology subsidiary (GXT) was awarded the processing contract for XinChang in a competitive tender against other seismic imaging companies. A full suite of processing and interpretation steps are currently being applied to extract high resolution seismic images and to resolve subtle properties within the reservoir zones, including an analysis of shear-wave splitting.

“We are convinced of the benefits of full-wave imaging in this area. The ION family of companies has the type of cutting-edge toolkit, the experienced personnel, and the collaborative approach we require. The raw data looks promising. I look forward to our ongoing cooperation on this imaging program and on other opportunities that may emerge in the future.” XU XIANGRONG, President of Southwest Gas Company at Sinopec

The emerging results
While the processing and interpretation stage of the project is ongoing, the early results are exceptionally promising. The seismic data contains broad bandwidth, which makes it well suited to resolving thin bedding layers within the reservoir and to detecting subtle structural features in the subsurface such as faulting. In addition, the shear-wave data recorded by VectorSeis is proving to be highly useful in detecting natural fracture patterns and intensity, as well as the distribution of gas saturation in the reservoir. The combination of these measurements, made possible through an integrated approach to full-wave seismic survey design, acquisition, and processing, is allowing ION and Sinopec personnel to identify the next round of highly prospective drilling targets in the XinChang structure.

Extending the success
The XinChang project is proving the value of full-wave imaging in fractured reservoirs. Given the importance of this reservoir type in China and many other regions – including the Americas, Middle East, and Russia – we anticipate being able to conduct a significant number of similar projects for oil & gas producers throughout the world. In the near-term, the results have provided such insight to Sinopec that we have begun discussions with them about a regional partnership to unlock the resource potential in the Sichuan Province and at other Sinopec assets worldwide.