| Popis: |
Qin Huang Dao 32–6 (QHD32–6) oil field located at Bohai Bay of China is a large heavy oil (74–260mPa.s) field with flat structure, multi-pay zone, complex oil and water contact system discovered by CNOOC (Fig. 1). The development plan is drilling vertical wells to penetrate multi zones with large well space (350-400m) in 3 blocks (North, South, and West). Due to comingle production pattern and quickly coning of the bottom water, the wells became mainly water producer and faced to be shut-down after a short period of the first oil.Measurement like water zone isolation and water injection optimization has been conducted to improve the production for short time. However, it is still not feasible in a long run to enhance oil recovery based on the research of water sweeping condition and remaining oil distribution. We faced a number of challenges, such as low oil production (35m3/d), high water cut of the field(86.6%) and low recovery factor(11.3%). A quick implementation of field comprehensive adjustment plan is needed to arrest the quickly water coning and fast production decline. While designing, a workflow integrating geological, well log, seismic and dynamic production data was developed to optimize the oilfield recovery factor.Following the workflow, we started with detailed reservoir description of sandbodies and systematically analyzed the remaining oil distribution mode. Then the comprehensive adjustment plan focus on develop from separate zones was carried out and the first batch of infill horizontal pilots was implemented. The responses from pilots were very positive resulting in better oil productivity (64m3/d) and longer low water-cut period.Finally, the comprehensive adjustment plan put forward 101 new infill wells and converted some part of old vertical wells to inject water for separate zones production, which resulting in 10% recovery factor enhancement. The oil recovery rate is raised from 0.8% to 1.7%. Our experiences showed that such comprehensive adjustment techniques based on detailed oil distribution is crucial to achieve better water-flooding development efficiency for offshore reservoir. |
