| Hai31 block is a complex small block located in the middle of Haiwaihe oilfield.The block was formally put into development in May 1990 and experienced three development stages,including natural energy,water flooding.Until now,Hai31 block has entered”double high,stage with high recovery degree and high water cut.Aiming at these problems,such as poor performance of conventional water flooding,low sweeping coefficient,high dispersion of remaining oil,it is necessary to carry out the research of replacement technology to slow down the production decline.Since 1960s,many oil fields at home and abroad have carried out the experiment and research after water injection.In this paper,the producing characteristics of common heavy oil reservoirs in Hai31 block after entering the high water cut development stage are discussed.Through the comprehensive evaluation of the water flooding,the existing development problems of the block are deeply analyzed.It is clarified that Weak gel flooding can continue to be used as a replacement technology for block development,so as to further study the performance and driving mechanism of weak gel.According to the results of the study,it can.be concluded that the dispersion characteristics of the weak gel in the porous medium have good oil displacement effect,and can effectively relieve the contradiction between the heterogeneity and the uneven reserves on hold in Hai31 reservoir.Basis on the above analysis,the well group is optimized to conduct and the scheme design is completed.At present,4 well groups have been implemented with accumulative injection agent of 209195m3,and the injection volume of 0.2PV.The percentage of effective well is 77%with total number of corresponding wells is 17.The average validity period of weak gel flooding reaches 762 days and the accumulative oil increases 36200t.The recovery factor increases by 3.55%,the natural decline rate drops by 15.2%,and the comprehensive decline does not decrease progressively. |
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