一种双泵联控联测的异常高压深层油气藏的孔隙度的实验测量方法

Measurement method of porosity for overpressure deep reservoir with double high precision constant pressure and speed pumps

高孔隙压力条件下的孔隙度实验测量对于异常高压深层油气藏的物性表征以及储层预测具有重要意义.目前,主要采用回压阀来控制孔隙压力以实现孔隙度的测量,存在孔隙压力控制精度低、孔隙体积计量不准确的不足.为此,研发了一种双泵联控联测的异常高压深层油气藏的孔隙度的实验测量方法.首先,在岩心的进口端和出口段布设两个高精度恒速恒压泵取代回压阀快速建立孔隙压力.其次,采用孔隙体积为0 mL的钢块作为刻度块,使用高精度计量泵得到了管线死体积变化量与有效压力的统计关系式.再次,测量常规条件的孔隙体积作为参考体积.最后,对岩样施加上覆地层压力、孔隙压力,得到该压力条件下计量泵的进液、退液体积变化量,减去该压力条件下的管线死体积变化量得到孔隙体积变化量,加上基准孔隙体积最终得到了该压力条件下的孔隙体积(孔隙度).对5块岩样的高孔隙压力的孔隙度的实验测量发现:不同上覆压力和孔隙压力条件下的孔隙度测量的重复性好,并且在低压段的孔隙度测量结果与相同有效压力的覆压孔隙度结果吻合得较好.

It is very important to measure the porosity in situ of overpressure deep reservoir for characterization and prediction.The normal method with back-pressure valve technology for exerting pore pressure and measurement of flow was not able to gain ideal porosity precision because of low control precision of pore pressure and low measurement precision of pore volume.A new measurement method for overpressure porosity was developed with the employment of double high precision constant pressure and speed pumps to exert pore pressure and measurement the increment of the pore volume.Firstly,the pore pressure was built by the double high precision constant pressure and speed pumps located both sides of rock sample.Secondly,an empirical relation between volume variation of dead volume and effective pressure was gotten through a set of calibration measurement with the employment of steel plug.Thirdly,the pore volume measured under the normal condition was adopt as basic pore volume.At last,the pore volume/porosity can be measured by the basic pore volume and the increment between the volume variation of bump and dead volume calculated through the empirical relation.The measurement results of 5 rock samples shows that the new method has good repeatability and matches the porosity measured under overburden pressure good.