基于修正Bowers法的地层压力检测方法——以白云凹陷为例

Formation Pressure Detection Method Based on Modified Bowers Method——Taking Baiyun Sag as an Example

目前,地质研究普遍认为白云凹陷深水区域的异常高压来源于生烃增压,但缺乏定量化的论证研究。融合循环逼近思想,提出基于修正Bowers法的地层压力检测方法。针对修正Bowers法在实测压力数据不充足时难以精准确定模型参数的瓶颈,提出先采用Eaton法试算,再代入修正Bowers模型进行循环逼近的研究思路。利用声波速度—密度等交汇曲线对白云凹陷BY井的测井数据进行分析,确定了不同深度范围地层的异常高压形成机制。白云凹陷的异常高压来自欠压实和流体膨胀两方面,流体膨胀部分存在着烃源岩层,具有一定的生烃能力,生烃增压确凿是异常高压形成的主要原因。分别采用Eaton法、Bowers法和修正Bowers法对模型参数进行求取,相对误差分别为10%、3%和0.5%,表明提出的方法和思路适用于同时存在欠压实和流体膨胀异常高压成因地质条件的地层压力检测。

At present,geological research generally believes that the abnormal high pressure in the deep water area of Baiyun sag comes from hydrocarbon generation and pressurization,but it is not a quantitative demonstration study.Combined with the idea of circular approximation,the formation pressure detection method based on modified Bowers method was proposed.In view of the bottleneck that the modified Bowers method was difficult to accurately determine the model parameters when the measured pressure data were insufficient,the research idea of using Eaton method for trial calculationfirst and then substituting the modified Bowers model for circular approximation was put forward.The logging data of BY well in Baiyun sag were analyzed by using the intersection curve of acoustic velocity and density,and the formation mechanism of abnormal high pressure in different depth ranges was determined.The abnormal high pressure in Baiyun sag is caused by undercompaction andfluid expansion at the same time.There are source rocks in the fluid expansion part,which have certain hydrocarbon generation capacity.The hydrocarbon generation pressurization is certainly the main reason for the formation of abnormal high pressure.Eaton method,Bowers method and modified Bowers method were used to calculate the model parameters,and the relative errors are 10%,3%and 0.5%,respectively,which indicates that the proposed method and idea are suitable for the formation pressure detection with the geological conditions of undercompaction and abnormal high pressure offluid expansion.