Research On Reservoir Classification And The Potential Of Improved Water Drive Recovery In Huabei Oilfield

At present, the development of Huabei oilfield has entered into high water cut stage. The main problem of the oilfield development is the gradual reduction of remaining recoverable reserves, increasing water cut of the oilfield, increasing difficulty of comprehensive management and the worsening effect of implementation. Therefore, to further improve the effect of water flooding, various scientific and effective measures should be adopted for improving oil recovery. Before the implementation of improved oil recovery measures, analysis regarding to the potential of improved oil recovery and evaluation of improved oil recovery methods should be conducted in order to provide a sound direction for improved oil recovery as well as scientific base for the future deployment and adjustment of the oilfield.This paper firstly reviewed the improved water drive recovery methods of the domestic oilfield as well as its future development trends and then summarized growth process and the growth paths of recoverable reserves of Huabei oilfield. It theoretically analyzed the main influence factors of water drive recovery and identified possible measures for increasing recoverable reserves of Huabei oilfield. For the reservoirs which have geologic reserve more than 500 thousand tons, the recoverable reserves more than 150 thousand tons and has been developed for more than 3 years, we classified them into I-type and II-type based on the comparative and comprehensive methods.Y1-type water drive curve was used to judge whether the I-type reservoir, heavy oil reservoir, special lithology reservoir and buried hill reservoir have the potential to improve water drive recovery. The increase curves were used to confirm whether II- type reservoir and the reservoir that cannot meet the recovery calibration have the potential to improved water drive recovery. The evaluation of infill well potential as well as injection-production well number ratio adjustment was conducted for the reservoirs which have the potential of improving oil recovery in order to identify the target reservoirs, the measures of increasing recoverable reserves and improving oil recovery was identified.In Huabei oilfield, 67 reservoirs have potential of improved water drive recovery amongst which oil recovery can be improved in 52 reservoirs by the methods such as well patterns thickening, increasing injection well, local perfect well network, changing direction injection water and adjustable flooding. Through the implementation of adjustment measures, the recoverable reserves can increase by 1166.1 million tons, and the oil recovery can improve 5.3%. The identified evaluation methods can be effectively used for various evaluation and calculation. Among them, straight line of Y1-type water flooding curve appeared earlier and when optimized fitting it can be used for forecast of max recoverable reserves, calibration of recoverable reserves and prediction of the water cut; increase curve can not only be used for calculating recoverable reserves and recovery, but also evaluate intuitively the development effect; method of oilfield trend maximum well number can effectively evaluate the potential of well net adjustment.