BZ28-2S油田Cr^(3+)聚合物凝胶渗流特征及其调驱效果研究

Study on the Percolation Property of Cr^(3+) Polymer Gel and Profile Controlling Effect in BZ28-2S Oilfield

渤海BZ28-2S油田具有油藏厚度大、平均渗透率高、非均质性严重、溶剂水矿化度较高和原油黏度较低等特点,注水开发过程中水窜现象比较严重,进而影响水驱开发效果,亟待采取调剖技术措施来改善水驱开发效果。针对BZ28-2S油藏储层特征、流体性质和及其井网特点,以黏度、阻力系数、残余阻力系数和采收率为评价指标,开展了Cr^(3+)聚合物凝胶配方优选和调驱注入参数优化实验研究。结果表明,在目标油藏储层和流体条件下,交联剂Cr^(3+)与聚合物分子链间可以发生交联反应,形成具有"分子内"交联结构特征、独特渗流特性和与储层适应性良好的Cr^(3+)聚合物凝胶体系。与聚合物溶液相比较,在段塞相同条件下,Cr^(3+)聚合物凝胶调驱效果较好。从技术经济效果考虑,推荐Cr^(3+)聚合物凝胶体系组成:C_P=1 200~1 600 mg/L,m(Pol):m(Cr^(3+))=180:1~270:1,段塞尺寸为0.075~0.125 PV,预计采收率增幅1.6%~2.5%。在室内研究基础上,2012年12月开始在渤海BZ28-2S油田进行了矿场试验。目前矿场调驱施工正在进行之中,截止到2013年5月,由于调驱时间较短,部分油井已经见效。

Bohai BZ28-2S oilfield is characterized by large reservoir thickness, high average permeability, serious heterogeneity, high water salinity and low viscosity of crude oil, and water channeling phenomenon occurred seriously during water flooding, which influenced greatly the oilfield development results. Therefore, it is urgent to take technical measures for profile controlling in order to improve water flooding effect. In view of reservoir characteristics, fluid properties and well pattern of BZ28-2S Oilfield, optimization for Cr^3＋ polymer gel composition has been conducted and study on injection parameters for profile controlling has been carried out through testing viscosity, resistance coefficient, residual resistance coefficient and recovery efficiency. The study results showed that crosslinking reaction might occur between crosslinking agent Cr^3＋ and polymer molecular chains, forming Cr^3＋ polymer gel system, which has intramolecular crosslinking structure, unique percolation property and excellent adaptability to reservoirs under the condition of target reservoir and formation fluids. Compared with polymer solution, Cr^3＋ polymer gel has better effect in profile controlling and flooding effect when the slug size is the same. From economical and technical point of view, it is recommended that the composition of Cr^3＋ polymer gel system should be as follows： Cp is 1 200 mg/L to 1 600 mg/L, m（Pol） ： m（Cr^3＋）=180 ： 1 to 270 ： 1, and slug size is 0.075 to 0.125 PV, the recovery is expected to increase by 1.6% to 2.5%. On the basis of laboratory experiment results, pilot tests have been carried out in Bohai BZ28-2S Oilfield since December 2013. Currently, Cr^3＋ polymer gel flooding is underway in the pilot. As of May 2013, effect of enhancing oil production has already been obtained during short time.