海陆过渡相致密砂岩储层Biot系数自适应预测方法研究

A new prediction method of Biot coefficient for marine-land transition phase tight sandstone reservoir based on the self-adapt method

沁水盆地石炭—二叠系海陆过渡相致密砂岩气测异常极为普遍,具有致密气勘探、开发潜力,但目前该地层致密砂岩缺少Biot系数的相关研究。Biot系数(α)的准确预测对地震反演、压裂设计、出砂趋势预测、储层应力敏感性、井眼轨迹优化及井壁稳定性分析等方面均具有重要参考价值。为了弥补该不足,以海陆过渡相致密砂岩储层为研究对象,结合Gassman-Biot-Geertsma方程,提出基于自适应方法的Biot系数预测方法。研究结果表明,利用自适应方法能有效提取目的层致密砂岩的基质矿物体积模量(Ko)和干岩石体积模量(Kd)。Ko与Kd均与纵波速度(vP)具有较好的正相关性。该致密砂岩的孔隙度φ平均值为4.11%,α平均值为0.179。α较低的原因与致密砂岩所经历的强压实及胶结作用相关。将提出的Biot系数预测新方法分别与孔隙度方法、声学参数方法及考虑孔隙空间变形3种方法进行了对比,结果表明,利用孔隙度和声学参数方法计算所获得的α与本文结果具有较好的对应关系,验证了本文方法的有效性。

The gas logging anomalies are extremely common in the Permo-Carboniferous marine-land transition phase tight sandstone reservoir of Oinshui Basin. This shows great potential of tight gas exploration and development in this area, but there＇s no study on Biot cofficient of the tight sandstone at present. The accurate prediction of Biot coefficient （α） has impor- tant reference value for seismic irrversion, fracturing design, sand production trend prediction, reservoir stress sensitivity eval- uation, borehole trajectory optimization, borehole stability analysis and so on. In order to overcome this shortage, in this pa- per,we take the marine-land transition phase tight sandstone reservoir as the research target, combining the Gassman-Biot- Geertsma equation. A new method of calculating Biot coefficient based on the adaptive method is put forward. The results show that this method can effectively extract the matrix mineral modulus （Ko） and dry rock modulus （Ka） of the tight sand- stone reservoir. There is a good positive correlation among Ko, Kd and vp. For this tight sandstone, the average value of its porosity is 4.11 %, and the average value of its α is 0. 179. The lower value of α is associated with strong compaction and ce-mentation. We compare the proposed method in this paper with three other methods about porosity, acoustic parameter and pore space deformation. The results show that the calculated a using the former two methods both have a good corresponding relationship with the results obtained using our method. By comparing of the three methods, we demonstrate that our method is effective.