近临界蒸汽驱技术在低渗透油藏中的应用

Application of near-critical steam flooding technology in low permeability reservoir

针对大庆朝阳沟低渗透油田在注水开发过程中注采能力差等问题,应用室内实验、油藏工程分析及数值模拟手段,研究了低渗透油藏蒸汽驱提高采收率机理、不同注入介质的注采能力、裂缝系统对蒸汽驱波及效果的影响,以及适合该低渗透裂缝性油藏蒸汽驱的最优井网、井距及蒸汽驱注采参数。研究表明,与稠油蒸汽驱不同,低渗透油藏蒸汽驱过程中,注入蒸汽是一种近临界状态的高温、高压、高热焓、低比容、低干度的蒸汽,注入蒸汽显著降低了原油黏度、改变了岩石的润湿性、提高了原油蒸馏率、降低了启动压力梯度,大幅度提高了开发效果。目前该油田已开展了3个井组的注蒸汽矿场试验,开发效果显著。

The low-permeability reservoir in Daqing Chaoyanggou oilfield has the problem of low injection-production capability during water flooding process.This paper studies the mechanism of enhancing oil recovery by steam flooding,the injection-production capability of different injected media,the effect of fracture system on steam sweep efficiency,and the optimal parameters of well pattern,spacing,steam injection and production for low permeability fractured reservoirs through laboratory experiment,reservoir engineering analysis and numerical simulation.The study shows that the injected steam in low permeability reservoir is different from that in heavy oil reservoir.The steam is in a near-critical state of high temperature,high pressure,high enthalpy,low specific volume,and low steam quality.It can significantly reduce oil viscosity,alter rock wettability,enhance oil distillation ratio,reduce threshold pressure gradient,and greatly improve production performance of steam flooding.At present,steam injection pilot test has been carried out for 3 well groups and achieved remarkable effect.