水平井地层电阻率各向异性研究及应用

Research on anisotropy of horizontal well formation resistivity and its application

1. 长江大学地球物理与石油资源学院，湖北荆州434023;2. 中国地质大学地球物理与信息技术学院，北京100083;3. 中国石油天然气股份有限公司塔里木油田分公司勘探开发研究院，新疆库尔勒841000

Yangtze University, Jingzhou 434023, China

水平井井眼轨迹与地层的相对位置经常变化,造成常规测井仪器在水平井中的响应机理发生改变,地层电阻率测井响应表现出各向异性特征,测井解释模型也因井眼位置不同而复杂化。因此,在进行水平井测井资料解释时,应考虑地层各向异性对测井响应的影响和地层非均质性对测井解释模型选择的影响。首先利用水平井井眼轨迹在钻出和钻回同一地层界面时的测井响应镜像特征提取地层界面点,用多项式趋势面分析方法确定水平井井眼轨迹的三维空间展布与地层之间的关系,确定井眼轨迹与地层的相对位置;然后通过研究水平井测井电阻率随水平井井眼轨迹与地层相对位置的变化规律,总结出油、水层的评价标准;最后采用3层水平层状模型对水平井地层电阻率的各向异性进行了研究,准确计算了地层水平电阻率和地层含油饱和度。将以上方法应用于塔里木油田水平井测井解释中,确定了井眼轨迹与地层的相对位置,计算了地层水平电阻率的大小。对油层和水层的电阻率各向异性进行了分析,认为地层电阻率如果表现为各向异性,就不能将水平井测量电阻率直接用于油水层的识别,但利用计算的水平电阻率能很好地使用垂直井的成熟研究成果进行油水层识别和地层含油饱和度计算。

In horizontal well logging, the relative position between well track of horizontal wells and strata often changes, resulting in changes of response mechanism of conventional logging instrument in horizontal wells, making the strata resistivity logging response an anisotropy characteristic and the logging interpretation model become more complex because of different positions of well bores. So, the influence of strata's anisotropy on logging response and the heterogeneity of strata on the choice of logging interpretation model should be taken into consideration in logging data interpretation. First, the interface point features are extracted by using the logging response images of horizontal well trace when it drills out of and into the same formation interface, and the polynomial trend surface analysis method is used to determine the relationship between 3-D distribution of horizontal well trace and strata, which has ascertained the relative position between well track and strata. Then, the changing rules of horizontal well logging resistivity with the relative position between well track of horizontal wells and strata are analyzed and the water-oil layer's evaluation criterion is summarized. Finally, the anisotropy of horizontal well strata resistivity is studied by using three-layer horizontal stratified model, and the horizontal resistivity and oil saturation of formation are calculated accurately. This method has been used in the horizontal well logging interpretation in Tarim oilfield to identify the relative position between well track and strata and to calculate the horizontal resistivity. The analysis of anisotropy of resistivity in oil reservoir and water layer shows that, if the resistivity of formation presents anisotropy, then the measured resistivity of horizontal well can't be directly used in oil-gas recognition. However, if the calculated horizontal resistivity is used, the research result on vertical well becomes very good in recognizing water-oil layer and in calculating the oil saturation.