稠油油藏水平井火驱技术风险与对策探讨

Risk and Countermeasure Discussion of Horizontal-Well Fire-Flooding in Heavy Oil Reservoir

针对新疆油田风城重18井区稠油油藏水平井火驱出现气窜、井底高温、氧气超标等问题,运用稠油燃烧理论方程,研究了水平井火驱技术存在的风险。利用自主研制的三维火驱物理模拟实验装置,通过室内实验研究了不同直井水平井距离、注采参数对水平井火驱稳定燃烧的影响,并给出了最佳调控参数。研究表明:预热阶段形成均匀的蒸汽腔和泄油通道,点火初期保持燃烧前缘结焦带和"油墙"连续封闭且形成超覆燃烧特征,是水平井火驱稳定燃烧的重要条件。通过上部射孔方式增加直井与水平井垂直距离,实现初期超覆燃烧;现场注气速度为4 000 m^3/d、生产压差为1 MPa左右时,可保持注采平衡,防止气窜。通过调控,风城重18井区空气油比降至1 000 m^3/m^3,水平井段温度控制在200℃左右,成功避免了水平井的气窜,实现了水平井火驱的稳定驱油,为稠油油藏开发提供了新的技术手段。

Gas channeling, downhole high-temperature and excessive oxygen concentration are usually encountered in the heavy oil reservoir horizontal-well fire-flooding in Fengcheng Wellblock Zhongl8 of Xinjiang Oilfield. The theoretical heavy oil combustion equation is used to study the risks in horizontal-well fire-flooding. A self-devel- oped physical 3D fire-flooding simulation equipment is applied to gain the effects of vertical-horizontal well dis- tance and injection-production parameters on the stable combustion in horizontal-well fire-flooding and provide the optimal parameter values. Research demonstrates that stable combustion in horizontal-well fire-flooding can be a- chieved by uniform steam chamber and drainage channels in the preheating stage, continuous coke zone of combus- tion front and closed ＂oil-wall＂ in the beginning of ignition and overlap combustion. The vertical distance between vertical and horizontal wells can be increased by upper perforation to achieve overlap combustion in the initial stage. 4 000 m^3/d gas injection rate and 1 MPa producing pressure drawdown could maintain injection-production balance and prevent gas channeling. After field adjustment, the air-oil ratio in Fengcheng Wellblock Zhongl8 is reduced to 1 000 m^3/m^3 and the temperature of lateral section is kept around 200 ℃, which effectively avoid gas channeling and realize stable fire-flooding in horizontal-well and provide a new technical means for heavy oil reservoir develop- ment.