Effectiveness Evaluation Of Water-flood Development And Research On Regulate Strategy Of Carboniferous Oil Reservoir In Donghetang Oil Field

The Carboniferous oil reservoir in Donghetang oil field was located on Ku che County in Xinjiang. It was a massiveness basal water reservoir and was controlled by an abnormal fault in the north. The geological characteristics of Donghe sandstone include largely thickness and seriously heterogeneity. The physical property of reservoir was better at the middle of reservoir and other was worse. A large number of inter-layers were shaped in the reservoir, and one can never underestimate the influence of interlayer on movement of oil and water. Since the oil reservoir of Carboniferous was developed, it gone through some stages of development adjustment. At present, the degree of reserve recovery is 33.52%, and water cut is 54%. However, some problems, which including how does effectiveness of development in earlier days, whether the relationship of water flooding regime can acquire the requirement of fast acting extract remaining oil or not, the pressure coefficient of flooding network can be established or not at present well pattern and present well spacing, are being confronted for the development of reservoir.In the paper, on the basis of the current situation of the reservoir, the results of reservoir geological research and the fundamental principle of reservoir engineering, the dynamic analysis and the numerical simulation as two useful means were used to allocate reasonably optimal adjustment scheme. The data of drilling core, well logging and seism was applied to research geological characteristic and stochastic geologic model of the reservoir. The performance data was applied to evaluate effectiveness of water-flood development and to research of reservoir engineering. Finally, the optimal adjustment schemes were designed and were optimized for guiding later stage development of reservoir by numerical simulation. In this thesis, the author has obtained the following understandings:(1) The relational expression between water cut and degree of reserve recovery of reservoir was advanced for accurately understand the regular pattern of water cut, on the basis of the relational expression, Some indicators were selected to evaluate development effectiveness of water-flood and concluded that the reservoir has been acquired a satisfactory development result. The condition of reservoir water-flood is better, the increase of water cut is slowly, the factor of the rate of water cut is -4.32, the water cut-recovery percent ratio of reservoir is 0.97, the formation pressure was advanced and sustained after flood development. But the rate of water storage is 0.47, the injection-production ratio is 0.89, the poor tendency of water-flood is being occurred at present.(2) The recoverable reserves of reservoir is 1033.18×10~4 ton by calculation. The forecastly ultimate water drive recovery factor is 44.1%.(3) The bottom water coning was restrained owing to the development and distribution of interlayer, the existence of heavy oil section at the bottom of reservoir and the difference of rock formation by numerical simulation. The producing water of production wells mainly comes from injecting water which was moved along the layers to production wells. The remaining oil was fundamentally distributed in all area on the top of two zones. Residual OOIP is 614.91×10~4ton.So the top of two zones can be as superior zones for later adjustment. The remaining oil was distributed in partial area on the bottom of horizons.(4) The reasonable well spacing density is 18.2 hectare per well by several different methods, the rational injection to producing well ratio is Cm =1:1.084, but the actual well spacing density is 25.625 hectare per well and the actual injection to producing well ratio is Ca =1:0.47. So the adjustment of infill well pattern and injection-production pattern can be applied to regulate the reservoir. The present well pattern and present production means can not carry out the requirement of accelerating oil production rate by calculating present scheme.On the basis of the development effectiveness of water-flood, dynamic analysis and the distribution of remaining oil, the regulation schemes of injection-production were designed and were optimized. The scheme can enhance oil recovery rate, control water cut of reservoir, maintain formational pressure and enhance efficiency of inject water by simulation calculation. At the end of 2020, the degree of reserve recovery of ultimate scheme of adjustment will raise 2.71% and will reach 43.13%.More than 63.58×10~4ton crude oil was recovered by comparing with present executing scheme.