Porosity Evolution Model Analysis of Sandstones in Sedimentary Basins: A Case Study from Ordos Basin
Hui Shi; Zhen Liu
Formation porosity evolution rule is not only one of the basic geological law, but is also the indispensably important theory to many geological applications , such as burial history analysis, paleostructure recovery and ancient formation pressure forecasting and so on. In addtion, it is one of the main control factors to hydrocarbon migration, accumulation and preservation.
This study takes the Member-8 sandstones, Yanchang Formation in Zhenjing Area of Ordos Basin as the research object, and has established a mathematical model for the sandstone porosity evolution with current porosity characteristics as the entry point and geologic time as the principal line, combining with researches on the burial and diagenetic history. The sandstone porosity evolution can be divided to a continuous decreased-porosity model mainly due to the mechanical compaction and cementation and a regional enhanced-porosity model mainly due to the dissolution.
Multiple regression analysis about the porosity of fine sandstones, buried depth and age of 13 wells in Area Zhenjing, decreased-porosity can be induced into a dual function about time and depth. Enhanced-porosity model is an piecewise equation about the time when disslolution begins and the abnormal high value.The total porosity model is a three separate function about depth and time, as well as a superposition of those two models in time-domain.
Results derived from the total porosity model have been validated to be reliable in the study area. The proposal method is relatively simple to operate and can be applied to other regions.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013