海上底水油藏水平井水驱波及系数定量表征

Quantitative characterization of sweep coefficient of water drive in horizontal well for offshore bottom water reservoir

海上底水油藏开发中后期面临着水驱油规律认识不清及水平井井间水驱波及系数定量描述难的问题。以渤海Q油田为例,利用室内一维长岩心水驱油实验、油藏数值模拟方法,建立了底水油藏精细数值模型,研究了底水油藏长期水驱后驱油效率和水平井井间水驱波及系数变化规律。结果表明:水驱油实验中驱替倍数提高至2000 PV,驱替速度由1 m L/min提高至5 m L/min,驱油效率较常规水驱驱替倍数为100 PV时提高了15%~20%;基于数值模拟的水平井水驱波及体积研究,通过引入高倍水驱后相渗曲线,并将模型网格精度提高至长×宽×高为10.0 m×10.0 m×0.3 m时,实现了对水驱波及体积的精细刻画,计算出的波及系数由原始模型的66.7%降低为54.6%,提高了模型计算精度;水平井布井油柱高度和井距均是影响井间水驱波及系数的主控因素,水平段油柱高度越低,井距越大,井间水驱波及系数越低。基于以上研究结果,建立了海上底水油藏井间水驱波及系数图版,明确了底水油藏水平井布井界限参数:布井井距100~150 m,油柱高度6~8 m,井控储量(15~25)万m^3,水平井最大提液幅度2000 m^3/d,极限经济产油量10 m^3/d,水平井累计产油量大于5万m^3。该研究成果成功指导了海上Q油田底水油藏21口加密水平井的实施,可为底水油藏中后期高效挖潜提供借鉴。

In the middle and late stage of the development of offshore bottom water reservoir,there are some problems,such as unclear understanding of water drive oil law and difficulty in quantitative description of water drive sweep coefficient between horizontal wells.Taking Q oilfield in Bohai Sea as an example,the fine numerical model of bottom water reservoir was established by using indoor one-dimensional long core water flooding experiment and reservoir numerical simulation method,the variation law of flooding efficiency and cross-well water flooding sweep coefficient between horizontal wells after long-term water flooding in bottom water reservoir was carried out.The results show that the displacement multiple in the water displacement experiment was increased to 2000 PV and the displacement speed was increased from 1 m L/min to 5 m L/min,and the displacement efficiency was increased by 15%-20%when the displacement efficiency is more than 100 PV.Based on the numerical simulation of horizontal well water drive sweep volume,the phase permeability curve after high-power water drive was introduced,and the grid accuracy of the model was improved to 10.0 m×10.0 m×0.3 m,realizing the fine characterization of water drive sweep volume.The calculated sweep coefficient was reduced from66.7%of the original model to 54.6%,which improves the calculation accuracy of the model.The height and spacing of oil string in horizontal well distribution are the main control factors affecting cross-hole water drive sweep coefficient.The lower the oil column height in horizontal section is,the larger the well spacing is,and the lower the sweep coefficient of cross-hole water drive is.Based on the research results,the cross-well water drive sweep coefficient chart of offshore bottom water reservoir was established,and the boundary parameters of horizontal well layout in bottom water reservoir were defined.The well distance of the well is 100-150 m,the height of the oil column is 6-8m,the well control reserve is(15-25)×10^4m^3,the maximum extraction of the horizontal well is 2000 m^3/d,the limit economic oil production is 10 m^3/d,and the accumulated oil production of the horizontal well can reach more than 50000 m^3.The research results have successfully guided the implementation of21 infill horizontal wells in bottom water reservoir of offshore Q oilfield,and can provide reference for high efficiency potential tapping in the middle and late stage of the bottom water reservoir.