致密储层孔隙度测定参数优化

孔隙度是评价储层物性、计算原始油气储量的重要参数,致密储层孔隙度一般小于10%,页岩储层普遍小于5%,常规波义尔定律双室法孔隙度测定仪器很难满足精度要求。为了提高致密储层孔隙度测定精度,建立了孔隙度压力区分度目标函数,区分度越大,测定精度越高。通过数值模拟,对孔隙度测定仪器进行了参数优化,结果表明,欲使得区分度增大,需要满足3个条件:(1)平衡前参考室压力、平衡前样品室压力尽量大;(2)取出的标准块体积、样品体积尽量小;(3)标准块体积尽量与样品体积相等。参数优化后孔隙度为5.0%的标准样品测定值相对误差最大可降低14%,绝对误差最大可降低0.7%,通过参数优化为致密储层孔隙度测定提供了技术支持。 

Parameter optimization of tight reservoir porosity determination

The porosity is an important parameter to evaluate reservoir physical properties and calculate petroleum reserves.The porosity of tight reservoir is less than 10%,and that of gas shale is usually less than 5%,which is a great challenge of porosity determination apparatuses.Currently the Boyle’s Law Double-Cell(Matrix Cup) Method is widely used.The porosity determination for gas shale and tight sandstone needs ultra high accuracy,and it is necessary to carry theory analysis and optimize determination parameters.The objective pressure distinction function is established and numerical simulation is carried out.To obtain higher accuracy,it is necessary to set higher reference cell primary pressure,higher sample cell primary pressure,lower standard bulk volume and lower sample bulk volume.The relative error of experimental porosity of the standard sample of 5.0% can decline as much as 14%,and the absolute error can decline by 0.7%.This study developed a theory calculation model,which will be useful for technical support for tight reservoir porosity determination.