Cheng Dao

Location and Geology

The Chengdao oil field is situated in the shallow sea area on the northern margin of the Yellow River Delta and the south coast of Bohai Bay. It is part of the Shengli Oilfield, which is the second largest oil industry base in China.

Geological Setting

The area is characterized by shallow water depths of about 0~18 meters. The surface sediments in the Chengdao Oilfield are predominantly silt, which is prone to liquefaction damage due to its high water content. This geological condition makes the area susceptible to various types of geological disasters, including seabed erosion and sediment liquefaction under the influence of waves, currents, and storm surges.

Oil Field Characteristics

• The Chengdao oil field is a major production area, with over 100 platforms of various types built since its development began in 1993. These platforms are connected by submarine cables and pipelines, forming a comprehensive system for oil and gas transportation, water injection, power transmission, and mixed oil and gas transportation to shore.
• The field is part of the Chengbei Sag, located on the northeastern edge of the Chengning Uplift, and is surrounded by the oil-rich Chengbei Depression, Shanan Depression, and Bozhong Depression.

Reservoir Architecture

• The reservoir architecture in the Chengdao oil field is complex, particularly in the meander-river reservoirs of the Guantao Formation. Studies using seismic sedimentology and seismic geomorphology have identified six meandering belts, highlighting the transformation from braided to meandering river deposits. This complexity is crucial for understanding the distribution of remaining oil and for enhancing oil recovery.

Production Challenges

• The Chengdao oil field faces significant pressure to maintain stable production. As of January 2021, the average water cut in the study area was more than 82%, indicating a high level of water intrusion into the oil reservoirs. This makes it challenging to establish a dense production well pattern similar to onshore fields.

Geological Hazards

• The area is prone to geological hazards such as seabed erosion, sediment liquefaction, and the breakdown of submarine cables and pipelines. For instance, in 2003, ocean dynamics caused the liquefaction and disturbance of seabed sediment near an oil production platform, leading to the breakdown of two submarine cables.

Environmental and Safety Concerns

• The field is at risk of oil spills, which can have significant environmental impacts. Numerical simulations have been conducted to model oil spill trajectories and assess the environmental vulnerability of the area. These studies are crucial for developing strategies to mitigate and respond to oil spills in the Bohai Sea.

Research and Development

• Extensive research has been conducted on the geological hazards and reservoir architecture of the Chengdao oil field. This includes risk zonation studies using the analytical hierarchy process (AHP) and detailed assessments of hydrodynamic conditions, engineering geological environments, disaster geological conditions, and human engineering activities.
• Advanced technologies such as Schlumberger steering drilling and logging while drilling (LWD) are used to characterize the lithologic properties of the reservoirs and adjust borehole trajectories in real-time.

Operational Overview

• The field is operated by various entities, including Sinopec's Marine Oil Production Company. The operational activities include oil and gas production, water injection, and power transmission, all of which are integrated through a network of submarine infrastructure.

In summary, the Chengdao oil field is a critical oil production area in China, facing unique geological and environmental challenges. Ongoing research and technological advancements are essential for managing these challenges and ensuring the safe and efficient operation of the field.