SAGD蒸汽腔扩展阶段电加热机理及操作参数优化

为进一步提高风城油田已进入蒸汽腔扩展阶段的SAGD井组水平段动用程度,利用典型储层参数建立电加热辅助SAGD一体化数值模型,开展井下电加热的渗流特征研究和操作参数优化设计。结果表明:SAGD扩展阶段实施井下电加热,具有定点升温、促进蒸汽腔发育、定点泄油和提高低渗段有效渗透率等4项重要机理;其合理注汽速度为158~171m³/d,蒸汽腔操作压力为4.9~5.4 MPa,注采井间压差为0.4～0.5 MPa,相邻井组井间压差需小于0.5 MPa;合理电加热时间为2.0～3.0 a,电加热器最高表面温度为250 ℃,每米功率为800～1 000 W;典型井组电加热3.0 a后水平段动用程度从67%提高至100%,日产油提高2~4 m³,累计油汽比从0.15提高至0.24,最终采收率达51.3%,提高8.1个百分点。该研究成果对改善SAGD开发效果具有一定指导意义。

Electric Heating Mechanism and Operating Parameter Optimization in the Expansion Stage of SAGD Steam Chamber

To further improve the productivity of the horizontal intervals in SAGD well cluster that has entered the steam chamber expansion stage in Fengcheng Oilfield, an integrated numerical model of electric heating-assisted SAGD was established with typical reservoir parameters to study the seepage characteristics of downhole electric heating and optimize the design of operating parameters. The results showed that, downhole electric heating performed in the SAGD expansion stage had four important mechanisms: fixed-point heating, promotion of steam chamber development, fixed-point oil drainage, and improvement of effective permeability in low-permeability intervals; the reasonable steam injection rate was 158-171 m³/d, the steam chamber operating pressure was 4.9-5.4 MPa, the pressure difference between injection and production wells was 0.4-0.5 MPa, and the inter-well pressure difference between adjacent well clusters was less than 0.5 MPa; the reasonable electric heating duration was 2.0-3.0 years, the maximum surface temperature of the electric heater was 250 ℃, and the power was 800-1 000 W/m; the productivity of horizontal interval was increased from 67% to 100% after the typical well cluster was electrically heated for 3.0a, the daily oil production was increased by 2-4 m³/d,Accamulative oil-steam ratio in creased from 0.15 to 0.24, and the final recovery efficiency reached 51.3%, an increase of 8.1 percentage points. The study results can be used as a guidance for improving the development effect of SAGD.