渤海河流相底水稠油油藏特高含水期极限驱油效率认识

围绕渤海底水稠油油藏在特高含水阶段剩余油挖潜机理认识不清、渗流特征认识不深的难点问题，以典型河流相Q油田主力砂体为例，开展不同类型储层样品在2 000 PV高倍数水驱下的极限水驱油效率实验研究。实验结果显示，在经过2 000 PV高倍数水驱后，稀油、普1类稠油和普2类稠油的极限驱油效率分别为76.5%、75.5%和72.5%。在相同的高倍数水驱条件下，稀油样品驱油效率在100 PV处出现拐点，普1类稠油样品在300 PV处出现拐点，普2类稠油样品驱油效率在1 000 PV处出现拐点。地层原油黏度越大，拐点出现的时机越晚，揭示水驱至残余油状态的废弃时机越晚。普2类稠油样品在100～1 000 PV的高倍数驱替过程中，单位PV数下驱油效率要高于稀油样品和普1类稠油样品，在2 000 PV的高倍数水驱条件下驱油效率最终可高达72.5%。实验结论可为底水稠油特高含水期大液量提液挖潜提供机理支撑。

Ultimate Displacement Efficiency of Heavy Oil Reservoir with Bottom Water Formed by Fluvial Deposition in Bohai Oilfiled at Ultra-high Water Cut Stage

Focusing on the difficult problems of unclear understanding of the mechanism of tapping the potential of remaining oil and the seepage characteristics in the ultra-high water cut stage of the bottom water heavy oil reservoir in Bohai Oilfield, this paper takes the main sand body of typical fluvial facies in Q oilfield as an example to carry out the experimental study on the ultimate water displacement efficiency of different types of reservoir samples under 2 000 PV high-multiple water displacement. The experimental results show that after high multiple water flooding at 2 000 PV, the maximum displacement efficiency of thin oil, common type 1 heavy oil and common type 2 heavy oil is 76.5%, 75.5% and 72.5% respectively. Under the same high-multiple water flooding conditions, the inflection point of the oil displacement efficiency of thin oil samples appeared at 100 PV, the inflection point of the common type 1 heavy oil samples appeared at 300 PV, and the common type 2 heavy oil samples appeared at 1000 PV. The greater the viscosity of formation crude oil, the later the inflection point appears, and the later the abandonment time of water flooding to the residual oil state. In the high multiple displacement process of 100～1000 PV, the oil displacement efficiency per PV of the common type 2 heavy oil samples, is higher than that of thin oil samples and the common type 1 heavy oil samples. Under the high multiple water displacement condition of 2 000 PV, the oil displacement efficiency can finally reach up to 72.5%. The experimental results can provide mechanism support for large liquid extraction and tapping potential of heavy oil with bottom water in the ultra-high water cut stage.