The complex fault-block and multilayered reservoir with edge water, also known as the toothbrush-shaped reservoir, features in multiple oil layers, long narrow oil-bearing belts and the sufficient natural energy. Jin-94 block of Checheng oilfield is a typical toothbrush-shaped reservoir, where upward layer-by-layer production method has been implemented for dozen years. Nowadays, given that 78.2% of water cut and few oil layers that remain undeveloped, the sustainable production for a long term can’t be achieved anymore. However, only 14.2% of the original oil in place (OOIP) has been produced, indicating tremendous potential for the improvement of oil recovery.

The development method plays a dominative and decisive role in recovery efficiency. In order to comprehensively understand the characteristics of the development method, we studied the performance of two alternative methods on the basis of the current development technique in Jin-94. Numerical simulation is applied to production dynamic and comparative analysis of every method. Our simulations show that the optimizing methods exert better effects on oil production, which may serve as an efficient approach to the primary development of other similar fault-block.

To further improve the development performance, the distribution of residual oil in Jin-94 block is also analyzed via numerical simulation. Keeping the current development method of Jin-94 block unchanged, we coupled reservoir simulation with an optimization algorithm to study the capabilities of improved oil recovery (IOR) techniques for this block, i.e., reproduction of obsolete wells, feasibility of water injection, location of new oil wells and optimization of produced fluid intension. Simulation demonstrates that the degree of reserve recovery after optimization increases by over 5%.

This work will not only provide important and specific guidance for the improved oil recovery of the toothbrush-shaped reservoir, but also can improve economic benefits of the oilfield to cope with the challenges of low oil prices.