均质砂岩底水油藏含水上升影响因素综合评价:以珠江口盆地W油田Z2油组为例

Comprehensive Evaluation of Factors Affecting Water Cut Rise in Homogeneous Sandstone Reservoir with Bottom Water:Taking Z2 Oil Group of Oilfield W in Zhujiangkou Basin as an Example

国内外大量底水油藏生产实践表明,其水驱规律为见水早,见水后含水上升快,中高含水期采出程度高。而Z2油组见水时间长达680 d,见水后含水上升缓慢,常规认识无法解释这一现象。根据油藏生产动态数据,结合数值模拟及油藏工程方法,对影响底水油藏水驱规律的地质因素和油藏因素进行了分析。通过地质因素分析表明,Z2油组储层均质,无隔夹层,原油黏度低,底水驱替均匀。运用“数值模拟+正交试验设计”定量综合评价技术分析表明,影响因素的主次顺序为:原油黏度、采油速度、驱油效率、油层厚度、避水高度、Kv/Kh、水平段长度。并提出一种利用水脊体积计算驱油效率新方法,计算证实该油组驱油效率高。综合分析表明,该油藏无水采出程度高、含水上升慢的主要原因是原油黏度低、采油速度适当、驱油效率高。研究成果可为同类底水油藏的合理开发提供指导意义。

The production practice of a large number of bottom water reservoirs at home and abroad shows the following water flooding law:water breakthrough occurs early,water cut rises rapidly,and the recovery degree is high in middle and high water cut stage.However,the water breakthrough time of Z2 Oil Group is as long as 680 days,and the water cut rises slowly after breakthrough,which can not be explained by conventional rules.Based on reservoir production performance data,com-bined with numerical simulation and reservoir engineering method,this paper analyzes the geological factors and reservoir factors affecting water flooding law in bottom water reservoirs.The analysis of geological factors shows that Z2 reservoir is homogeneous without intercalation,the viscosity of crude oil is low,and the bottom water is uniform displacement.The quantitative comprehensive evaluation technology of“numerical simulation+orthogonal test design”shows that the main and secondary or-der of influencing factors are:crude oil viscosity,oil recovery rate,oil displacement efficiency,res-ervoir thickness,water avoidance height,Kv/Kh,horizontal section length.A new method for calcu-lating oil displacement efficiency is proposed by using ridge volume.The calculation proves that the oil displacement efficiency of this oil group is high.Comprehensive analysis shows that the high de-gree of anhydrous recovery and the slow increase of water cut in this reservoir are mainly due to low viscosity of crude oil,appropriate recovery rate and high displacement efficiency.The research re-sults can provide guidance for rational development of similar bottom water reservoirs.