复杂断块超低渗油气藏试采动态评价与开发对策——以松辽盆地南部十屋油田营城组及沙河子组一段油藏为例

Performance evaluation on production tests in the extra-low permeability reservoirs of complex fault-blocks and development strategies——examples from oil reservoirs in the Yingcheng Formation and the first member of the Shahezi Formation in Shiwu oilfiel

松辽盆地南部十屋油田营城组及沙河子组油气藏属于特低渗-超低渗复杂断块油气藏。单薄层砂体的平面分布稳定性差,展布规模小且受断层切割,油气藏内类型丰富的流体受构造和岩性共同控制。研究区内绝大多数井需要压裂投产,只有个别气井可自然投产。单井试采动态表明,地层系数小、流动启动压力梯度大决定油井产量低,弹性驱动的天然能量开发油井产量递减快;油气同出井开发效果明显好于油井,气井的开发效果最好。针对这些问题,提出综合的开发对策,即在油井分层压裂、分层测试、分层评价的基础上,开展分层油藏精细描述;对油井先分层压裂、后合层投产,提高单井产能,对注水井先笼统注水、后分层注水,补充地层能量;优选出好的断块,采取不规则井网开展超前注水先导试验,试验成功后逐步推广;对气层和含油气层考虑大规模压裂投产,对油层可考虑单井CO2吞吐,但要选低气/油比油井。

The Yingcheng Formation and the Shahezi Formation in the Shiwu oilfield harbor oil/gas reservoirs of low to ultra-low permeability in complex fault-blocks.Single thin sand bodies there distribute unevenly and are compartmentalized by faults in certain places.Fluids of various types inside the reservoirs are controlled both by structure and lithology.Most wells drilled in the field have to be fractured before production with only a few can produce by natural energy.Performance of production test in single wells shows a low formation volume factor,a bigger start-up pressure gradient（meaning a low production）,and a faster production declining rate for wells in natural depletion.The results also suggest that wells producing both oil and gas have a better performance than those produce oil only,and gas wells are the most productive ones.To tackle these problems,we proposed a comprehensive development strategy which includes the following aspects.The first is performing a separate-layer fine reservoir description based on separate-layer fracturing,testing and evaluating.The second is increa-sing single well production capacity by commingled production after separate-layer fracturing and supplementing formation energy with whole-layer water injection followed by separate-layer water injection.The third is carrying out water injection pilot with irregular well patterns in the selected favorable fault blocks at first and then implementing the successful experience to other areas.The fourth is performing large-scale fracturing in gas/oil-bearing layers and CO2 huff-n＇-puff in single oil well with low gas-oil ratio.