Preparation and Evaluation of Artificial Cores of Unconsolidated Sandstone Considering the Effect of Formation Water

Abstract

Unconsolidated sandstone has the characteristics of poor cementation, loose structure, and low intensity. It is difficult to obtain representative cores, and coring from reservoirs is expensive. Thus, artificial cores have been widely used in core flooding experiments instead of natural cores. We found that, during the process of making artificial cores, formation water has an important influence on the physical properties of artificial cores; this factor has been neglected in making of artificial cores thus far. This study investigated the influence of formation water on the cementation and pore throats of artificial cores. In this research, river sand with a similar size distribution to the reservoir samples was chosen as the granule of framework. The results show that the addition of a certain amount of formation water better controls the degree of cementation of artificial cores, and the cores do not need to expand the pores and are relatively easy to mould under the same size composition and dosage of cementing agent. This research demonstrates that formation water is a main factor in making artificial cores of unconsolidated sandstone by comparing parameters such as the porosity, permeability, method of cementing, cementation exponent, and seepage characteristics of natural and artificial cores. The cementation, porosity, and permeability of artificial cores with formation water are better, and the cores have high similarity with natural cores. Consequently, the artificial cores can be used in laboratory experiments instead of natural cores.