碳酸盐岩缝洞型储层有效性评价新方法

碳酸盐岩储层孔隙类型多样,孔隙结构复杂,单一的孔隙度难以描述储层的有效性。以四川盆地高石梯磨溪地区龙王庙组缝洞型储层为例,优选出胶结指数m和基质孔隙度占比2个参数建立了储层有效性评价方法,胶结指数m采用新提出的基于裂缝形态的多孔介质模型计算得到,该模型可以计算出随深度变化的胶结指数m值,且精度高。研究发现,产层胶结指数m通常小于2.25,基质孔隙度占比大于44%;差产层胶结指数m通常小于2.25,基质孔隙度占比小于44%,或者,胶结指数m大于2.25,基质孔隙度占比大于44%;干层胶结指数m通常大于2.25且基质孔隙度占比小于44%。应用结果表明,该方法显著提高了研究区储层有效性评价精度。

A New Method for Evaluating the Effectiveness of Fractured-vuggy Carbonate Reservoirs

Due to various pore types and complex pore structures, it is difficult to describe the effectiveness of carbonate reservoirs with a single porosity. Taking the fractured-vuggy reservoir of Longwangmiao Formation in Gaoshiti-Moxi area of Sichuan Basin as an example, two parameters, cementation index m and the ratio of matrix porosity, were selected to establish an evaluation method for evaluating reservoir effectiveness. Cementation index m was calculated by a new porous medium model based on fracture morphology. Using the model, the cementation index is very precise and can vary with depth. It is found that for high-quality reservoirs, the cementation index m is usually less than 2.25 and the ratio of matrix porosity is more than 44%;for poor reservoirs, the cementation index m is usually less than 2.25 and the matrix porosity ratio is less than 44%, or the cementation index m is more than 2.25 and the matrix porosity ratio is more than 44%;for dry layers, the cementation index m is usually more than 2.25 and the matrix porosity ratio is less than 44%. The application results show that the method can significantly improve the accuracy of reservoir evaluation in the study area.