Study On Factors Of Production Decline And Treatment Measures After Polymer Flooding For XX Oilfield

XX oilfied started polymer flooding when the water cut was 10%,which is the first and only offshore oilfield that operated polymer flooding at early stage.The initial development effect of the oilfield was good,along with deep development,various development contradictions gradually appeared,which resulted in sharp oil production reduction.Because most polymer flooding oilfields were onshore and began polymer injection at later period of development and there were few offshore oilfields that adopted mode of polymer flooding at early stage,it was difffcult to analysis the factors infucing the production decline through research of other polymer flooding oilfields,and even further propose countermeasures.Thus,it is urgent to research causes of liquid production decline,determine current treatment measures and later reasonable development mode of XX oilfield,which provides decion-making tenique for early stage’s polymer flooding.Based on the former research,development effect evaluation system of polymer flooding at early stage of XX oilfield was eatablished,and suitability of polymer flooding was researched through various methods.It was shown that early stage’s polymer flooding of XX oilfields enhanced oil recovery ratio 3.83%,and generally,it is suitable for XX oilfields to inject polymer,but there are still needs to avoid adverse factors in the process of oil development.On the basis of above research,research on factors resulting in production decline is carried out,and put forward theory that judges whether the liquid production reduction is normal or not.Using polymer flooding relative peameability curves,mechanism of liquid production enhancement is researched;it is shown that liquid production enhancement mainly depends on increase of production pressure drop rather than water cut rise.As for two main factors influcing liquid production decline(polymer plugging and sand production),detailed research is done and propose feasible treatment measures.According to remaining oil distribution of XX oilfields,feasibility of tertiary polymer flooding is dicussed by using CMG software.The results desmontrate that extending polymer injection years doesn’t contribute to lasting good development effect,so it is advisable to shift to water flooding after the second polymer flooding period.At last,development parameters of subsequent waterflooding are optimized,it is recommended that effective injection production ratio is 0.9;well patten form is changed to line type;enhance production and injection simultaneously as much as possible within platform processing capacity;coordinate profile control measures to high water cut well group in the process of development.