鄂尔多斯盆地NNW油区再开发潜力分析

Redevelopment potential of NNW oil field,Ordos Basin—an analysis

鄂尔多斯盆地NNW油区主力油层为三叠系延长组长6和长4+5层段,为河流相和湖相三角洲透镜状和部分席状砂体叠加而成,属于超低渗透率的致密砂岩非常规油藏。NNW油区老井侧重于单个砂体的开发,油层打开程度不完善大大降低了采油速度。通过使用椭圆锥泄油模型模拟,发现油井泄油半径小于50 m,井间存在大量剩余储量。研究提出使用多油层组合、分段压裂取代单个砂体开发模式,将全井段油层及油水同层一次压裂完井。同时提出利用水平井开发方式对NNW油区进行再次开发,水平井及分段压裂具有成倍提高油区产量和经济效益的潜力。通过分析发现油区具有再次开发的良好资源条件。

The main producing zones of NNW oil field,Ordos Basin,are the Chang 6 and Chang 4+5 members of the Triassic Yanchang Formation,which consist numerous amalgamated lenticular and some sheet sands of fluvial and lacustrine deltaic facies and are classified as unconventional tight sand reservoirs.Past well completion was geared toward completing only a single pay sand in each well,however,such insufficient reservoir opening greatly suppressed daily production rate.Through modeling using an elliptoconic drainage model we found there is still a large quantity of oil left between the existing vertical wells that have a drainage radius seldom beyond 50 m.We propose to replace the single pay mining practice with multistage fracking aiming toward completing all pay sands simultaneously.We further suggest that oil field redevelopment using horizontal wells presents the most important future development opportunity,as horizontal drilling and multistage fracking has the potential to multiply oil field production and economic profit.According to our analysis the NNW oil field has sufficient resource base for redevelopment.