Abstract: As the economic threshold of offshore oilfield development is high,selecting the reasonable production technique to enhance productivity and economic benefit is of the highest importance for heavy oil reservoir.Through the analysis of heavy oil characteristics,densification environment and densification factcors of PLA oil-bearing structures in the water area of Bohai,the crude oil is summarized to be of the characteristics of "three-low and three-high",belonging to conventional heavy and extra-high reservoir.The densification factors are found to be shallow buried depth,low temperature,poor preserving conditions,strong biodegradation and water washing,which provides good guidance for heavy oil reservoir development and thermal production technology of heavy oil.