裂缝性低渗油藏复合体系协同驱油适应性研究

Adaptability study on a compound system for cooperative oil displacement in fractured low-permeability reservoir

针对低渗油藏注水开发过程中对储层微裂缝简单调驱后,注入水易沿高渗条带发生绕流造成开发效果严重受限的问题,评价了泡沫体系起泡、稳泡性能和一种改性淀粉凝胶成胶性能,开展了泡沫微观调驱和裂缝性低渗岩心复合体系协同驱油实验,并利用径向流模型模拟油藏实际井网对复合体系协同驱油适应性进行了验证。实验结果表明:起泡剂和稳泡剂最佳质量分数分别为0.5%和0.1%,改性淀粉凝胶体系成胶后具有较高强度和突破压力;注入泡沫体系后水驱,小孔隙微观驱油效果较前期水驱提高14.21%,其在渗透率级差约为30时具有更好的调剖性能;裂缝性低渗油藏水驱过程中,采用改性淀粉凝胶联合泡沫协同驱油效果最佳,其较注入单一改性淀粉凝胶或泡沫体系后水驱采收率可分别提高22.17%和46.07%,且径向流模型验证实验表明该协同驱油方法在裂缝性低渗油藏的适应性较好。

In the low-permeability reservoir, injection water is easy to flow along the high-permeability strips after simply profile control on the micro-fractures, which induces severe problems in the reservoir development. In this work, the foaming and stabilizing performance of a foam system and the gelling properties of a modified starch gel were evaluated. Then, the microadjustment and flooding of the foam and the collaborative oil displacement experiment of this compound system with fractured low-permeability core were carried out. The adaptability of collaborative oil displacement was verified with radial flow model, and the actual reservoir pattern was simulated. The experimental results show that the optimal mass concentrations of foaming agent and foam stabilizer are 0.5% and 0.1%, respectively. The strength and breakthrough pressure of starch gel system is high. After foam injection, the micro oil displacement efficiency of small pores during further water flooding is 14.21% higher than that of previous water flooding. And when the permeability ratio is approximately 30, its profile control performance is better. In the process of water flooding in fractured low-permeability reservoir, the collaborative oil displacement efficiency of modified starch gel combined with foam is best, which can increase the recovery by 22.17% and 46.07% as respectively compared with that of single use of modified starch gel or foam system. Moreover, the radial flow model validation experiment shows that the adaptability of this method is good in fractured low-permeability reservoir.